local copy of x/net/webdav (#438)

endpoints/drive/backend.go

@@ -5,8 +5,8 @@ import (
 	"github.com/openziti/sdk-golang/ziti"
 	"github.com/openziti/sdk-golang/ziti/edge"
 	"github.com/openziti/zrok/endpoints"
+	"github.com/openziti/zrok/endpoints/drive/webdav"
 	"github.com/pkg/errors"
-	"golang.org/x/net/webdav"
 	"net/http"
 	"time"
 )

endpoints/drive/webdav/file.go

@@ -0,0 +1,803 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"context"
+	"encoding/xml"
+	"io"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+)
+
+// slashClean is equivalent to but slightly more efficient than
+// path.Clean("/" + name).
+func slashClean(name string) string {
+	if name == "" || name[0] != '/' {
+		name = "/" + name
+	}
+	return path.Clean(name)
+}
+
+// A FileSystem implements access to a collection of named files. The elements
+// in a file path are separated by slash ('/', U+002F) characters, regardless
+// of host operating system convention.
+//
+// Each method has the same semantics as the os package's function of the same
+// name.
+//
+// Note that the os.Rename documentation says that "OS-specific restrictions
+// might apply". In particular, whether or not renaming a file or directory
+// overwriting another existing file or directory is an error is OS-dependent.
+type FileSystem interface {
+	Mkdir(ctx context.Context, name string, perm os.FileMode) error
+	OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (File, error)
+	RemoveAll(ctx context.Context, name string) error
+	Rename(ctx context.Context, oldName, newName string) error
+	Stat(ctx context.Context, name string) (os.FileInfo, error)
+}
+
+// A File is returned by a FileSystem's OpenFile method and can be served by a
+// Handler.
+//
+// A File may optionally implement the DeadPropsHolder interface, if it can
+// load and save dead properties.
+type File interface {
+	http.File
+	io.Writer
+}
+
+// A Dir implements FileSystem using the native file system restricted to a
+// specific directory tree.
+//
+// While the FileSystem.OpenFile method takes '/'-separated paths, a Dir's
+// string value is a filename on the native file system, not a URL, so it is
+// separated by filepath.Separator, which isn't necessarily '/'.
+//
+// An empty Dir is treated as ".".
+type Dir string
+
+func (d Dir) resolve(name string) string {
+	// This implementation is based on Dir.Open's code in the standard net/http package.
+	if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 ||
+		strings.Contains(name, "\x00") {
+		return ""
+	}
+	dir := string(d)
+	if dir == "" {
+		dir = "."
+	}
+	return filepath.Join(dir, filepath.FromSlash(slashClean(name)))
+}
+
+func (d Dir) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
+	if name = d.resolve(name); name == "" {
+		return os.ErrNotExist
+	}
+	return os.Mkdir(name, perm)
+}
+
+func (d Dir) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (File, error) {
+	if name = d.resolve(name); name == "" {
+		return nil, os.ErrNotExist
+	}
+	f, err := os.OpenFile(name, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+	return f, nil
+}
+
+func (d Dir) RemoveAll(ctx context.Context, name string) error {
+	if name = d.resolve(name); name == "" {
+		return os.ErrNotExist
+	}
+	if name == filepath.Clean(string(d)) {
+		// Prohibit removing the virtual root directory.
+		return os.ErrInvalid
+	}
+	return os.RemoveAll(name)
+}
+
+func (d Dir) Rename(ctx context.Context, oldName, newName string) error {
+	if oldName = d.resolve(oldName); oldName == "" {
+		return os.ErrNotExist
+	}
+	if newName = d.resolve(newName); newName == "" {
+		return os.ErrNotExist
+	}
+	if root := filepath.Clean(string(d)); root == oldName || root == newName {
+		// Prohibit renaming from or to the virtual root directory.
+		return os.ErrInvalid
+	}
+	return os.Rename(oldName, newName)
+}
+
+func (d Dir) Stat(ctx context.Context, name string) (os.FileInfo, error) {
+	if name = d.resolve(name); name == "" {
+		return nil, os.ErrNotExist
+	}
+	return os.Stat(name)
+}
+
+// NewMemFS returns a new in-memory FileSystem implementation.
+func NewMemFS() FileSystem {
+	return &memFS{
+		root: memFSNode{
+			children: make(map[string]*memFSNode),
+			mode:     0660 | os.ModeDir,
+			modTime:  time.Now(),
+		},
+	}
+}
+
+// A memFS implements FileSystem, storing all metadata and actual file data
+// in-memory. No limits on filesystem size are used, so it is not recommended
+// this be used where the clients are untrusted.
+//
+// Concurrent access is permitted. The tree structure is protected by a mutex,
+// and each node's contents and metadata are protected by a per-node mutex.
+//
+// TODO: Enforce file permissions.
+type memFS struct {
+	mu   sync.Mutex
+	root memFSNode
+}
+
+// TODO: clean up and rationalize the walk/find code.
+
+// walk walks the directory tree for the fullname, calling f at each step. If f
+// returns an error, the walk will be aborted and return that same error.
+//
+// dir is the directory at that step, frag is the name fragment, and final is
+// whether it is the final step. For example, walking "/foo/bar/x" will result
+// in 3 calls to f:
+//   - "/", "foo", false
+//   - "/foo/", "bar", false
+//   - "/foo/bar/", "x", true
+//
+// The frag argument will be empty only if dir is the root node and the walk
+// ends at that root node.
+func (fs *memFS) walk(op, fullname string, f func(dir *memFSNode, frag string, final bool) error) error {
+	original := fullname
+	fullname = slashClean(fullname)
+
+	// Strip any leading "/"s to make fullname a relative path, as the walk
+	// starts at fs.root.
+	if fullname[0] == '/' {
+		fullname = fullname[1:]
+	}
+	dir := &fs.root
+
+	for {
+		frag, remaining := fullname, ""
+		i := strings.IndexRune(fullname, '/')
+		final := i < 0
+		if !final {
+			frag, remaining = fullname[:i], fullname[i+1:]
+		}
+		if frag == "" && dir != &fs.root {
+			panic("webdav: empty path fragment for a clean path")
+		}
+		if err := f(dir, frag, final); err != nil {
+			return &os.PathError{
+				Op:   op,
+				Path: original,
+				Err:  err,
+			}
+		}
+		if final {
+			break
+		}
+		child := dir.children[frag]
+		if child == nil {
+			return &os.PathError{
+				Op:   op,
+				Path: original,
+				Err:  os.ErrNotExist,
+			}
+		}
+		if !child.mode.IsDir() {
+			return &os.PathError{
+				Op:   op,
+				Path: original,
+				Err:  os.ErrInvalid,
+			}
+		}
+		dir, fullname = child, remaining
+	}
+	return nil
+}
+
+// find returns the parent of the named node and the relative name fragment
+// from the parent to the child. For example, if finding "/foo/bar/baz" then
+// parent will be the node for "/foo/bar" and frag will be "baz".
+//
+// If the fullname names the root node, then parent, frag and err will be zero.
+//
+// find returns an error if the parent does not already exist or the parent
+// isn't a directory, but it will not return an error per se if the child does
+// not already exist. The error returned is either nil or an *os.PathError
+// whose Op is op.
+func (fs *memFS) find(op, fullname string) (parent *memFSNode, frag string, err error) {
+	err = fs.walk(op, fullname, func(parent0 *memFSNode, frag0 string, final bool) error {
+		if !final {
+			return nil
+		}
+		if frag0 != "" {
+			parent, frag = parent0, frag0
+		}
+		return nil
+	})
+	return parent, frag, err
+}
+
+func (fs *memFS) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	dir, frag, err := fs.find("mkdir", name)
+	if err != nil {
+		return err
+	}
+	if dir == nil {
+		// We can't create the root.
+		return os.ErrInvalid
+	}
+	if _, ok := dir.children[frag]; ok {
+		return os.ErrExist
+	}
+	dir.children[frag] = &memFSNode{
+		children: make(map[string]*memFSNode),
+		mode:     perm.Perm() | os.ModeDir,
+		modTime:  time.Now(),
+	}
+	return nil
+}
+
+func (fs *memFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (File, error) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	dir, frag, err := fs.find("open", name)
+	if err != nil {
+		return nil, err
+	}
+	var n *memFSNode
+	if dir == nil {
+		// We're opening the root.
+		if runtime.GOOS == "zos" {
+			if flag&os.O_WRONLY != 0 {
+				return nil, os.ErrPermission
+			}
+		} else {
+			if flag&(os.O_WRONLY|os.O_RDWR) != 0 {
+				return nil, os.ErrPermission
+			}
+		}
+		n, frag = &fs.root, "/"
+
+	} else {
+		n = dir.children[frag]
+		if flag&(os.O_SYNC|os.O_APPEND) != 0 {
+			// memFile doesn't support these flags yet.
+			return nil, os.ErrInvalid
+		}
+		if flag&os.O_CREATE != 0 {
+			if flag&os.O_EXCL != 0 && n != nil {
+				return nil, os.ErrExist
+			}
+			if n == nil {
+				n = &memFSNode{
+					mode: perm.Perm(),
+				}
+				dir.children[frag] = n
+			}
+		}
+		if n == nil {
+			return nil, os.ErrNotExist
+		}
+		if flag&(os.O_WRONLY|os.O_RDWR) != 0 && flag&os.O_TRUNC != 0 {
+			n.mu.Lock()
+			n.data = nil
+			n.mu.Unlock()
+		}
+	}
+
+	children := make([]os.FileInfo, 0, len(n.children))
+	for cName, c := range n.children {
+		children = append(children, c.stat(cName))
+	}
+	return &memFile{
+		n:                n,
+		nameSnapshot:     frag,
+		childrenSnapshot: children,
+	}, nil
+}
+
+func (fs *memFS) RemoveAll(ctx context.Context, name string) error {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	dir, frag, err := fs.find("remove", name)
+	if err != nil {
+		return err
+	}
+	if dir == nil {
+		// We can't remove the root.
+		return os.ErrInvalid
+	}
+	delete(dir.children, frag)
+	return nil
+}
+
+func (fs *memFS) Rename(ctx context.Context, oldName, newName string) error {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	oldName = slashClean(oldName)
+	newName = slashClean(newName)
+	if oldName == newName {
+		return nil
+	}
+	if strings.HasPrefix(newName, oldName+"/") {
+		// We can't rename oldName to be a sub-directory of itself.
+		return os.ErrInvalid
+	}
+
+	oDir, oFrag, err := fs.find("rename", oldName)
+	if err != nil {
+		return err
+	}
+	if oDir == nil {
+		// We can't rename from the root.
+		return os.ErrInvalid
+	}
+
+	nDir, nFrag, err := fs.find("rename", newName)
+	if err != nil {
+		return err
+	}
+	if nDir == nil {
+		// We can't rename to the root.
+		return os.ErrInvalid
+	}
+
+	oNode, ok := oDir.children[oFrag]
+	if !ok {
+		return os.ErrNotExist
+	}
+	if oNode.children != nil {
+		if nNode, ok := nDir.children[nFrag]; ok {
+			if nNode.children == nil {
+				return errNotADirectory
+			}
+			if len(nNode.children) != 0 {
+				return errDirectoryNotEmpty
+			}
+		}
+	}
+	delete(oDir.children, oFrag)
+	nDir.children[nFrag] = oNode
+	return nil
+}
+
+func (fs *memFS) Stat(ctx context.Context, name string) (os.FileInfo, error) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	dir, frag, err := fs.find("stat", name)
+	if err != nil {
+		return nil, err
+	}
+	if dir == nil {
+		// We're stat'ting the root.
+		return fs.root.stat("/"), nil
+	}
+	if n, ok := dir.children[frag]; ok {
+		return n.stat(path.Base(name)), nil
+	}
+	return nil, os.ErrNotExist
+}
+
+// A memFSNode represents a single entry in the in-memory filesystem and also
+// implements os.FileInfo.
+type memFSNode struct {
+	// children is protected by memFS.mu.
+	children map[string]*memFSNode
+
+	mu        sync.Mutex
+	data      []byte
+	mode      os.FileMode
+	modTime   time.Time
+	deadProps map[xml.Name]Property
+}
+
+func (n *memFSNode) stat(name string) *memFileInfo {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	return &memFileInfo{
+		name:    name,
+		size:    int64(len(n.data)),
+		mode:    n.mode,
+		modTime: n.modTime,
+	}
+}
+
+func (n *memFSNode) DeadProps() (map[xml.Name]Property, error) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	if len(n.deadProps) == 0 {
+		return nil, nil
+	}
+	ret := make(map[xml.Name]Property, len(n.deadProps))
+	for k, v := range n.deadProps {
+		ret[k] = v
+	}
+	return ret, nil
+}
+
+func (n *memFSNode) Patch(patches []Proppatch) ([]Propstat, error) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	pstat := Propstat{Status: http.StatusOK}
+	for _, patch := range patches {
+		for _, p := range patch.Props {
+			pstat.Props = append(pstat.Props, Property{XMLName: p.XMLName})
+			if patch.Remove {
+				delete(n.deadProps, p.XMLName)
+				continue
+			}
+			if n.deadProps == nil {
+				n.deadProps = map[xml.Name]Property{}
+			}
+			n.deadProps[p.XMLName] = p
+		}
+	}
+	return []Propstat{pstat}, nil
+}
+
+type memFileInfo struct {
+	name    string
+	size    int64
+	mode    os.FileMode
+	modTime time.Time
+}
+
+func (f *memFileInfo) Name() string       { return f.name }
+func (f *memFileInfo) Size() int64        { return f.size }
+func (f *memFileInfo) Mode() os.FileMode  { return f.mode }
+func (f *memFileInfo) ModTime() time.Time { return f.modTime }
+func (f *memFileInfo) IsDir() bool        { return f.mode.IsDir() }
+func (f *memFileInfo) Sys() interface{}   { return nil }
+
+// A memFile is a File implementation for a memFSNode. It is a per-file (not
+// per-node) read/write position, and a snapshot of the memFS' tree structure
+// (a node's name and children) for that node.
+type memFile struct {
+	n                *memFSNode
+	nameSnapshot     string
+	childrenSnapshot []os.FileInfo
+	// pos is protected by n.mu.
+	pos int
+}
+
+// A *memFile implements the optional DeadPropsHolder interface.
+var _ DeadPropsHolder = (*memFile)(nil)
+
+func (f *memFile) DeadProps() (map[xml.Name]Property, error)     { return f.n.DeadProps() }
+func (f *memFile) Patch(patches []Proppatch) ([]Propstat, error) { return f.n.Patch(patches) }
+
+func (f *memFile) Close() error {
+	return nil
+}
+
+func (f *memFile) Read(p []byte) (int, error) {
+	f.n.mu.Lock()
+	defer f.n.mu.Unlock()
+	if f.n.mode.IsDir() {
+		return 0, os.ErrInvalid
+	}
+	if f.pos >= len(f.n.data) {
+		return 0, io.EOF
+	}
+	n := copy(p, f.n.data[f.pos:])
+	f.pos += n
+	return n, nil
+}
+
+func (f *memFile) Readdir(count int) ([]os.FileInfo, error) {
+	f.n.mu.Lock()
+	defer f.n.mu.Unlock()
+	if !f.n.mode.IsDir() {
+		return nil, os.ErrInvalid
+	}
+	old := f.pos
+	if old >= len(f.childrenSnapshot) {
+		// The os.File Readdir docs say that at the end of a directory,
+		// the error is io.EOF if count > 0 and nil if count <= 0.
+		if count > 0 {
+			return nil, io.EOF
+		}
+		return nil, nil
+	}
+	if count > 0 {
+		f.pos += count
+		if f.pos > len(f.childrenSnapshot) {
+			f.pos = len(f.childrenSnapshot)
+		}
+	} else {
+		f.pos = len(f.childrenSnapshot)
+		old = 0
+	}
+	return f.childrenSnapshot[old:f.pos], nil
+}
+
+func (f *memFile) Seek(offset int64, whence int) (int64, error) {
+	f.n.mu.Lock()
+	defer f.n.mu.Unlock()
+	npos := f.pos
+	// TODO: How to handle offsets greater than the size of system int?
+	switch whence {
+	case io.SeekStart:
+		npos = int(offset)
+	case io.SeekCurrent:
+		npos += int(offset)
+	case io.SeekEnd:
+		npos = len(f.n.data) + int(offset)
+	default:
+		npos = -1
+	}
+	if npos < 0 {
+		return 0, os.ErrInvalid
+	}
+	f.pos = npos
+	return int64(f.pos), nil
+}
+
+func (f *memFile) Stat() (os.FileInfo, error) {
+	return f.n.stat(f.nameSnapshot), nil
+}
+
+func (f *memFile) Write(p []byte) (int, error) {
+	lenp := len(p)
+	f.n.mu.Lock()
+	defer f.n.mu.Unlock()
+
+	if f.n.mode.IsDir() {
+		return 0, os.ErrInvalid
+	}
+	if f.pos < len(f.n.data) {
+		n := copy(f.n.data[f.pos:], p)
+		f.pos += n
+		p = p[n:]
+	} else if f.pos > len(f.n.data) {
+		// Write permits the creation of holes, if we've seek'ed past the
+		// existing end of file.
+		if f.pos <= cap(f.n.data) {
+			oldLen := len(f.n.data)
+			f.n.data = f.n.data[:f.pos]
+			hole := f.n.data[oldLen:]
+			for i := range hole {
+				hole[i] = 0
+			}
+		} else {
+			d := make([]byte, f.pos, f.pos+len(p))
+			copy(d, f.n.data)
+			f.n.data = d
+		}
+	}
+
+	if len(p) > 0 {
+		// We should only get here if f.pos == len(f.n.data).
+		f.n.data = append(f.n.data, p...)
+		f.pos = len(f.n.data)
+	}
+	f.n.modTime = time.Now()
+	return lenp, nil
+}
+
+// moveFiles moves files and/or directories from src to dst.
+//
+// See section 9.9.4 for when various HTTP status codes apply.
+func moveFiles(ctx context.Context, fs FileSystem, src, dst string, overwrite bool) (status int, err error) {
+	created := false
+	if _, err := fs.Stat(ctx, dst); err != nil {
+		if !os.IsNotExist(err) {
+			return http.StatusForbidden, err
+		}
+		created = true
+	} else if overwrite {
+		// Section 9.9.3 says that "If a resource exists at the destination
+		// and the Overwrite header is "T", then prior to performing the move,
+		// the server must perform a DELETE with "Depth: infinity" on the
+		// destination resource.
+		if err := fs.RemoveAll(ctx, dst); err != nil {
+			return http.StatusForbidden, err
+		}
+	} else {
+		return http.StatusPreconditionFailed, os.ErrExist
+	}
+	if err := fs.Rename(ctx, src, dst); err != nil {
+		return http.StatusForbidden, err
+	}
+	if created {
+		return http.StatusCreated, nil
+	}
+	return http.StatusNoContent, nil
+}
+
+func copyProps(dst, src File) error {
+	d, ok := dst.(DeadPropsHolder)
+	if !ok {
+		return nil
+	}
+	s, ok := src.(DeadPropsHolder)
+	if !ok {
+		return nil
+	}
+	m, err := s.DeadProps()
+	if err != nil {
+		return err
+	}
+	props := make([]Property, 0, len(m))
+	for _, prop := range m {
+		props = append(props, prop)
+	}
+	_, err = d.Patch([]Proppatch{{Props: props}})
+	return err
+}
+
+// copyFiles copies files and/or directories from src to dst.
+//
+// See section 9.8.5 for when various HTTP status codes apply.
+func copyFiles(ctx context.Context, fs FileSystem, src, dst string, overwrite bool, depth int, recursion int) (status int, err error) {
+	if recursion == 1000 {
+		return http.StatusInternalServerError, errRecursionTooDeep
+	}
+	recursion++
+
+	// TODO: section 9.8.3 says that "Note that an infinite-depth COPY of /A/
+	// into /A/B/ could lead to infinite recursion if not handled correctly."
+
+	srcFile, err := fs.OpenFile(ctx, src, os.O_RDONLY, 0)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return http.StatusNotFound, err
+		}
+		return http.StatusInternalServerError, err
+	}
+	defer srcFile.Close()
+	srcStat, err := srcFile.Stat()
+	if err != nil {
+		if os.IsNotExist(err) {
+			return http.StatusNotFound, err
+		}
+		return http.StatusInternalServerError, err
+	}
+	srcPerm := srcStat.Mode() & os.ModePerm
+
+	created := false
+	if _, err := fs.Stat(ctx, dst); err != nil {
+		if os.IsNotExist(err) {
+			created = true
+		} else {
+			return http.StatusForbidden, err
+		}
+	} else {
+		if !overwrite {
+			return http.StatusPreconditionFailed, os.ErrExist
+		}
+		if err := fs.RemoveAll(ctx, dst); err != nil && !os.IsNotExist(err) {
+			return http.StatusForbidden, err
+		}
+	}
+
+	if srcStat.IsDir() {
+		if err := fs.Mkdir(ctx, dst, srcPerm); err != nil {
+			return http.StatusForbidden, err
+		}
+		if depth == infiniteDepth {
+			children, err := srcFile.Readdir(-1)
+			if err != nil {
+				return http.StatusForbidden, err
+			}
+			for _, c := range children {
+				name := c.Name()
+				s := path.Join(src, name)
+				d := path.Join(dst, name)
+				cStatus, cErr := copyFiles(ctx, fs, s, d, overwrite, depth, recursion)
+				if cErr != nil {
+					// TODO: MultiStatus.
+					return cStatus, cErr
+				}
+			}
+		}
+
+	} else {
+		dstFile, err := fs.OpenFile(ctx, dst, os.O_RDWR|os.O_CREATE|os.O_TRUNC, srcPerm)
+		if err != nil {
+			if os.IsNotExist(err) {
+				return http.StatusConflict, err
+			}
+			return http.StatusForbidden, err
+
+		}
+		_, copyErr := io.Copy(dstFile, srcFile)
+		propsErr := copyProps(dstFile, srcFile)
+		closeErr := dstFile.Close()
+		if copyErr != nil {
+			return http.StatusInternalServerError, copyErr
+		}
+		if propsErr != nil {
+			return http.StatusInternalServerError, propsErr
+		}
+		if closeErr != nil {
+			return http.StatusInternalServerError, closeErr
+		}
+	}
+
+	if created {
+		return http.StatusCreated, nil
+	}
+	return http.StatusNoContent, nil
+}
+
+// walkFS traverses filesystem fs starting at name up to depth levels.
+//
+// Allowed values for depth are 0, 1 or infiniteDepth. For each visited node,
+// walkFS calls walkFn. If a visited file system node is a directory and
+// walkFn returns filepath.SkipDir, walkFS will skip traversal of this node.
+func walkFS(ctx context.Context, fs FileSystem, depth int, name string, info os.FileInfo, walkFn filepath.WalkFunc) error {
+	// This implementation is based on Walk's code in the standard path/filepath package.
+	err := walkFn(name, info, nil)
+	if err != nil {
+		if info.IsDir() && err == filepath.SkipDir {
+			return nil
+		}
+		return err
+	}
+	if !info.IsDir() || depth == 0 {
+		return nil
+	}
+	if depth == 1 {
+		depth = 0
+	}
+
+	// Read directory names.
+	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
+	if err != nil {
+		return walkFn(name, info, err)
+	}
+	fileInfos, err := f.Readdir(0)
+	f.Close()
+	if err != nil {
+		return walkFn(name, info, err)
+	}
+
+	for _, fileInfo := range fileInfos {
+		filename := path.Join(name, fileInfo.Name())
+		fileInfo, err := fs.Stat(ctx, filename)
+		if err != nil {
+			if err := walkFn(filename, fileInfo, err); err != nil && err != filepath.SkipDir {
+				return err
+			}
+		} else {
+			err = walkFS(ctx, fs, depth, filename, fileInfo, walkFn)
+			if err != nil {
+				if !fileInfo.IsDir() || err != filepath.SkipDir {
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}

endpoints/drive/webdav/if.go

@@ -0,0 +1,173 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+// The If header is covered by Section 10.4.
+// http://www.webdav.org/specs/rfc4918.html#HEADER_If
+
+import (
+	"strings"
+)
+
+// ifHeader is a disjunction (OR) of ifLists.
+type ifHeader struct {
+	lists []ifList
+}
+
+// ifList is a conjunction (AND) of Conditions, and an optional resource tag.
+type ifList struct {
+	resourceTag string
+	conditions  []Condition
+}
+
+// parseIfHeader parses the "If: foo bar" HTTP header. The httpHeader string
+// should omit the "If:" prefix and have any "\r\n"s collapsed to a " ", as is
+// returned by req.Header.Get("If") for an http.Request req.
+func parseIfHeader(httpHeader string) (h ifHeader, ok bool) {
+	s := strings.TrimSpace(httpHeader)
+	switch tokenType, _, _ := lex(s); tokenType {
+	case '(':
+		return parseNoTagLists(s)
+	case angleTokenType:
+		return parseTaggedLists(s)
+	default:
+		return ifHeader{}, false
+	}
+}
+
+func parseNoTagLists(s string) (h ifHeader, ok bool) {
+	for {
+		l, remaining, ok := parseList(s)
+		if !ok {
+			return ifHeader{}, false
+		}
+		h.lists = append(h.lists, l)
+		if remaining == "" {
+			return h, true
+		}
+		s = remaining
+	}
+}
+
+func parseTaggedLists(s string) (h ifHeader, ok bool) {
+	resourceTag, n := "", 0
+	for first := true; ; first = false {
+		tokenType, tokenStr, remaining := lex(s)
+		switch tokenType {
+		case angleTokenType:
+			if !first && n == 0 {
+				return ifHeader{}, false
+			}
+			resourceTag, n = tokenStr, 0
+			s = remaining
+		case '(':
+			n++
+			l, remaining, ok := parseList(s)
+			if !ok {
+				return ifHeader{}, false
+			}
+			l.resourceTag = resourceTag
+			h.lists = append(h.lists, l)
+			if remaining == "" {
+				return h, true
+			}
+			s = remaining
+		default:
+			return ifHeader{}, false
+		}
+	}
+}
+
+func parseList(s string) (l ifList, remaining string, ok bool) {
+	tokenType, _, s := lex(s)
+	if tokenType != '(' {
+		return ifList{}, "", false
+	}
+	for {
+		tokenType, _, remaining = lex(s)
+		if tokenType == ')' {
+			if len(l.conditions) == 0 {
+				return ifList{}, "", false
+			}
+			return l, remaining, true
+		}
+		c, remaining, ok := parseCondition(s)
+		if !ok {
+			return ifList{}, "", false
+		}
+		l.conditions = append(l.conditions, c)
+		s = remaining
+	}
+}
+
+func parseCondition(s string) (c Condition, remaining string, ok bool) {
+	tokenType, tokenStr, s := lex(s)
+	if tokenType == notTokenType {
+		c.Not = true
+		tokenType, tokenStr, s = lex(s)
+	}
+	switch tokenType {
+	case strTokenType, angleTokenType:
+		c.Token = tokenStr
+	case squareTokenType:
+		c.ETag = tokenStr
+	default:
+		return Condition{}, "", false
+	}
+	return c, s, true
+}
+
+// Single-rune tokens like '(' or ')' have a token type equal to their rune.
+// All other tokens have a negative token type.
+const (
+	errTokenType    = rune(-1)
+	eofTokenType    = rune(-2)
+	strTokenType    = rune(-3)
+	notTokenType    = rune(-4)
+	angleTokenType  = rune(-5)
+	squareTokenType = rune(-6)
+)
+
+func lex(s string) (tokenType rune, tokenStr string, remaining string) {
+	// The net/textproto Reader that parses the HTTP header will collapse
+	// Linear White Space that spans multiple "\r\n" lines to a single " ",
+	// so we don't need to look for '\r' or '\n'.
+	for len(s) > 0 && (s[0] == '\t' || s[0] == ' ') {
+		s = s[1:]
+	}
+	if len(s) == 0 {
+		return eofTokenType, "", ""
+	}
+	i := 0
+loop:
+	for ; i < len(s); i++ {
+		switch s[i] {
+		case '\t', ' ', '(', ')', '<', '>', '[', ']':
+			break loop
+		}
+	}
+
+	if i != 0 {
+		tokenStr, remaining = s[:i], s[i:]
+		if tokenStr == "Not" {
+			return notTokenType, "", remaining
+		}
+		return strTokenType, tokenStr, remaining
+	}
+
+	j := 0
+	switch s[0] {
+	case '<':
+		j, tokenType = strings.IndexByte(s, '>'), angleTokenType
+	case '[':
+		j, tokenType = strings.IndexByte(s, ']'), squareTokenType
+	default:
+		return rune(s[0]), "", s[1:]
+	}
+	if j < 0 {
+		return errTokenType, "", ""
+	}
+	return tokenType, s[1:j], s[j+1:]
+}

endpoints/drive/webdav/if_test.go

@@ -0,0 +1,322 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestParseIfHeader(t *testing.T) {
+	// The "section x.y.z" test cases come from section x.y.z of the spec at
+	// http://www.webdav.org/specs/rfc4918.html
+	testCases := []struct {
+		desc  string
+		input string
+		want  ifHeader
+	}{{
+		"bad: empty",
+		``,
+		ifHeader{},
+	}, {
+		"bad: no parens",
+		`foobar`,
+		ifHeader{},
+	}, {
+		"bad: empty list #1",
+		`()`,
+		ifHeader{},
+	}, {
+		"bad: empty list #2",
+		`(a) (b c) () (d)`,
+		ifHeader{},
+	}, {
+		"bad: no list after resource #1",
+		`<foo>`,
+		ifHeader{},
+	}, {
+		"bad: no list after resource #2",
+		`<foo> <bar> (a)`,
+		ifHeader{},
+	}, {
+		"bad: no list after resource #3",
+		`<foo> (a) (b) <bar>`,
+		ifHeader{},
+	}, {
+		"bad: no-tag-list followed by tagged-list",
+		`(a) (b) <foo> (c)`,
+		ifHeader{},
+	}, {
+		"bad: unfinished list",
+		`(a`,
+		ifHeader{},
+	}, {
+		"bad: unfinished ETag",
+		`([b`,
+		ifHeader{},
+	}, {
+		"bad: unfinished Notted list",
+		`(Not a`,
+		ifHeader{},
+	}, {
+		"bad: double Not",
+		`(Not Not a)`,
+		ifHeader{},
+	}, {
+		"good: one list with a Token",
+		`(a)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `a`,
+				}},
+			}},
+		},
+	}, {
+		"good: one list with an ETag",
+		`([a])`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					ETag: `a`,
+				}},
+			}},
+		},
+	}, {
+		"good: one list with three Nots",
+		`(Not a Not b Not [d])`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Not:   true,
+					Token: `a`,
+				}, {
+					Not:   true,
+					Token: `b`,
+				}, {
+					Not:  true,
+					ETag: `d`,
+				}},
+			}},
+		},
+	}, {
+		"good: two lists",
+		`(a) (b)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `a`,
+				}},
+			}, {
+				conditions: []Condition{{
+					Token: `b`,
+				}},
+			}},
+		},
+	}, {
+		"good: two Notted lists",
+		`(Not a) (Not b)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Not:   true,
+					Token: `a`,
+				}},
+			}, {
+				conditions: []Condition{{
+					Not:   true,
+					Token: `b`,
+				}},
+			}},
+		},
+	}, {
+		"section 7.5.1",
+		`<http://www.example.com/users/f/fielding/index.html> 
+			(<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>)`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `http://www.example.com/users/f/fielding/index.html`,
+				conditions: []Condition{{
+					Token: `urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6`,
+				}},
+			}},
+		},
+	}, {
+		"section 7.5.2 #1",
+		`(<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf`,
+				}},
+			}},
+		},
+	}, {
+		"section 7.5.2 #2",
+		`<http://example.com/locked/>
+			(<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `http://example.com/locked/`,
+				conditions: []Condition{{
+					Token: `urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf`,
+				}},
+			}},
+		},
+	}, {
+		"section 7.5.2 #3",
+		`<http://example.com/locked/member>
+			(<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `http://example.com/locked/member`,
+				conditions: []Condition{{
+					Token: `urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf`,
+				}},
+			}},
+		},
+	}, {
+		"section 9.9.6",
+		`(<urn:uuid:fe184f2e-6eec-41d0-c765-01adc56e6bb4>) 
+			(<urn:uuid:e454f3f3-acdc-452a-56c7-00a5c91e4b77>)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `urn:uuid:fe184f2e-6eec-41d0-c765-01adc56e6bb4`,
+				}},
+			}, {
+				conditions: []Condition{{
+					Token: `urn:uuid:e454f3f3-acdc-452a-56c7-00a5c91e4b77`,
+				}},
+			}},
+		},
+	}, {
+		"section 9.10.8",
+		`(<urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4>)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.6",
+		`(<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> 
+			["I am an ETag"])
+			(["I am another ETag"])`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2`,
+				}, {
+					ETag: `"I am an ETag"`,
+				}},
+			}, {
+				conditions: []Condition{{
+					ETag: `"I am another ETag"`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.7",
+		`(Not <urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> 
+			<urn:uuid:58f202ac-22cf-11d1-b12d-002035b29092>)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Not:   true,
+					Token: `urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2`,
+				}, {
+					Token: `urn:uuid:58f202ac-22cf-11d1-b12d-002035b29092`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.8",
+		`(<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2>) 
+			(Not <DAV:no-lock>)`,
+		ifHeader{
+			lists: []ifList{{
+				conditions: []Condition{{
+					Token: `urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2`,
+				}},
+			}, {
+				conditions: []Condition{{
+					Not:   true,
+					Token: `DAV:no-lock`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.9",
+		`</resource1> 
+			(<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> 
+			[W/"A weak ETag"]) (["strong ETag"])`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `/resource1`,
+				conditions: []Condition{{
+					Token: `urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2`,
+				}, {
+					ETag: `W/"A weak ETag"`,
+				}},
+			}, {
+				resourceTag: `/resource1`,
+				conditions: []Condition{{
+					ETag: `"strong ETag"`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.10",
+		`<http://www.example.com/specs/> 
+			(<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2>)`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `http://www.example.com/specs/`,
+				conditions: []Condition{{
+					Token: `urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.11 #1",
+		`</specs/rfc2518.doc> (["4217"])`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `/specs/rfc2518.doc`,
+				conditions: []Condition{{
+					ETag: `"4217"`,
+				}},
+			}},
+		},
+	}, {
+		"section 10.4.11 #2",
+		`</specs/rfc2518.doc> (Not ["4217"])`,
+		ifHeader{
+			lists: []ifList{{
+				resourceTag: `/specs/rfc2518.doc`,
+				conditions: []Condition{{
+					Not:  true,
+					ETag: `"4217"`,
+				}},
+			}},
+		},
+	}}
+
+	for _, tc := range testCases {
+		got, ok := parseIfHeader(strings.Replace(tc.input, "\n", "", -1))
+		if gotEmpty := reflect.DeepEqual(got, ifHeader{}); gotEmpty == ok {
+			t.Errorf("%s: should be different: empty header == %t, ok == %t", tc.desc, gotEmpty, ok)
+			continue
+		}
+		if !reflect.DeepEqual(got, tc.want) {
+			t.Errorf("%s:\ngot  %v\nwant %v", tc.desc, got, tc.want)
+			continue
+		}
+	}
+}

endpoints/drive/webdav/internal/xml/README

@@ -0,0 +1,11 @@
+This is a fork of the encoding/xml package at ca1d6c4, the last commit before
+https://go.googlesource.com/go/+/c0d6d33 "encoding/xml: restore Go 1.4 name
+space behavior" made late in the lead-up to the Go 1.5 release.
+
+The list of encoding/xml changes is at
+https://go.googlesource.com/go/+log/master/src/encoding/xml
+
+This fork is temporary, and I (nigeltao) expect to revert it after Go 1.6 is
+released.
+
+See http://golang.org/issue/11841

endpoints/drive/webdav/internal/xml/atom_test.go

@@ -0,0 +1,56 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import "time"
+
+var atomValue = &Feed{
+	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
+	Title:   "Example Feed",
+	Link:    []Link{{Href: "http://example.org/"}},
+	Updated: ParseTime("2003-12-13T18:30:02Z"),
+	Author:  Person{Name: "John Doe"},
+	Id:      "urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6",
+
+	Entry: []Entry{
+		{
+			Title:   "Atom-Powered Robots Run Amok",
+			Link:    []Link{{Href: "http://example.org/2003/12/13/atom03"}},
+			Id:      "urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a",
+			Updated: ParseTime("2003-12-13T18:30:02Z"),
+			Summary: NewText("Some text."),
+		},
+	},
+}
+
+var atomXml = `` +
+	`<feed xmlns="http://www.w3.org/2005/Atom" updated="2003-12-13T18:30:02Z">` +
+	`<title>Example Feed</title>` +
+	`<id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>` +
+	`<link href="http://example.org/"></link>` +
+	`<author><name>John Doe</name><uri></uri><email></email></author>` +
+	`<entry>` +
+	`<title>Atom-Powered Robots Run Amok</title>` +
+	`<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>` +
+	`<link href="http://example.org/2003/12/13/atom03"></link>` +
+	`<updated>2003-12-13T18:30:02Z</updated>` +
+	`<author><name></name><uri></uri><email></email></author>` +
+	`<summary>Some text.</summary>` +
+	`</entry>` +
+	`</feed>`
+
+func ParseTime(str string) time.Time {
+	t, err := time.Parse(time.RFC3339, str)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+func NewText(text string) Text {
+	return Text{
+		Body: text,
+	}
+}

endpoints/drive/webdav/internal/xml/example_test.go

@@ -0,0 +1,151 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml_test
+
+import (
+	"encoding/xml"
+	"fmt"
+	"os"
+)
+
+func ExampleMarshalIndent() {
+	type Address struct {
+		City, State string
+	}
+	type Person struct {
+		XMLName   xml.Name `xml:"person"`
+		Id        int      `xml:"id,attr"`
+		FirstName string   `xml:"name>first"`
+		LastName  string   `xml:"name>last"`
+		Age       int      `xml:"age"`
+		Height    float32  `xml:"height,omitempty"`
+		Married   bool
+		Address
+		Comment string `xml:",comment"`
+	}
+
+	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
+	v.Comment = " Need more details. "
+	v.Address = Address{"Hanga Roa", "Easter Island"}
+
+	output, err := xml.MarshalIndent(v, "  ", "    ")
+	if err != nil {
+		fmt.Printf("error: %v\n", err)
+	}
+
+	os.Stdout.Write(output)
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <City>Hanga Roa</City>
+	//       <State>Easter Island</State>
+	//       <!-- Need more details. -->
+	//   </person>
+}
+
+func ExampleEncoder() {
+	type Address struct {
+		City, State string
+	}
+	type Person struct {
+		XMLName   xml.Name `xml:"person"`
+		Id        int      `xml:"id,attr"`
+		FirstName string   `xml:"name>first"`
+		LastName  string   `xml:"name>last"`
+		Age       int      `xml:"age"`
+		Height    float32  `xml:"height,omitempty"`
+		Married   bool
+		Address
+		Comment string `xml:",comment"`
+	}
+
+	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
+	v.Comment = " Need more details. "
+	v.Address = Address{"Hanga Roa", "Easter Island"}
+
+	enc := xml.NewEncoder(os.Stdout)
+	enc.Indent("  ", "    ")
+	if err := enc.Encode(v); err != nil {
+		fmt.Printf("error: %v\n", err)
+	}
+
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <City>Hanga Roa</City>
+	//       <State>Easter Island</State>
+	//       <!-- Need more details. -->
+	//   </person>
+}
+
+// This example demonstrates unmarshaling an XML excerpt into a value with
+// some preset fields. Note that the Phone field isn't modified and that
+// the XML <Company> element is ignored. Also, the Groups field is assigned
+// considering the element path provided in its tag.
+func ExampleUnmarshal() {
+	type Email struct {
+		Where string `xml:"where,attr"`
+		Addr  string
+	}
+	type Address struct {
+		City, State string
+	}
+	type Result struct {
+		XMLName xml.Name `xml:"Person"`
+		Name    string   `xml:"FullName"`
+		Phone   string
+		Email   []Email
+		Groups  []string `xml:"Group>Value"`
+		Address
+	}
+	v := Result{Name: "none", Phone: "none"}
+
+	data := `
+		<Person>
+			<FullName>Grace R. Emlin</FullName>
+			<Company>Example Inc.</Company>
+			<Email where="home">
+				<Addr>gre@example.com</Addr>
+			</Email>
+			<Email where='work'>
+				<Addr>gre@work.com</Addr>
+			</Email>
+			<Group>
+				<Value>Friends</Value>
+				<Value>Squash</Value>
+			</Group>
+			<City>Hanga Roa</City>
+			<State>Easter Island</State>
+		</Person>
+	`
+	err := xml.Unmarshal([]byte(data), &v)
+	if err != nil {
+		fmt.Printf("error: %v", err)
+		return
+	}
+	fmt.Printf("XMLName: %#v\n", v.XMLName)
+	fmt.Printf("Name: %q\n", v.Name)
+	fmt.Printf("Phone: %q\n", v.Phone)
+	fmt.Printf("Email: %v\n", v.Email)
+	fmt.Printf("Groups: %v\n", v.Groups)
+	fmt.Printf("Address: %v\n", v.Address)
+	// Output:
+	// XMLName: xml.Name{Space:"", Local:"Person"}
+	// Name: "Grace R. Emlin"
+	// Phone: "none"
+	// Email: [{home gre@example.com} {work gre@work.com}]
+	// Groups: [Friends Squash]
+	// Address: {Hanga Roa Easter Island}
+}

endpoints/drive/webdav/internal/xml/read.go

@@ -0,0 +1,691 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"encoding"
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
+// an XML element is an order-dependent collection of anonymous
+// values, while a data structure is an order-independent collection
+// of named values.
+// See package json for a textual representation more suitable
+// to data structures.
+
+// Unmarshal parses the XML-encoded data and stores the result in
+// the value pointed to by v, which must be an arbitrary struct,
+// slice, or string. Well-formed data that does not fit into v is
+// discarded.
+//
+// Because Unmarshal uses the reflect package, it can only assign
+// to exported (upper case) fields. Unmarshal uses a case-sensitive
+// comparison to match XML element names to tag values and struct
+// field names.
+//
+// Unmarshal maps an XML element to a struct using the following rules.
+// In the rules, the tag of a field refers to the value associated with the
+// key 'xml' in the struct field's tag (see the example above).
+//
+//   - If the struct has a field of type []byte or string with tag
+//     ",innerxml", Unmarshal accumulates the raw XML nested inside the
+//     element in that field. The rest of the rules still apply.
+//
+//   - If the struct has a field named XMLName of type xml.Name,
+//     Unmarshal records the element name in that field.
+//
+//   - If the XMLName field has an associated tag of the form
+//     "name" or "namespace-URL name", the XML element must have
+//     the given name (and, optionally, name space) or else Unmarshal
+//     returns an error.
+//
+//   - If the XML element has an attribute whose name matches a
+//     struct field name with an associated tag containing ",attr" or
+//     the explicit name in a struct field tag of the form "name,attr",
+//     Unmarshal records the attribute value in that field.
+//
+//   - If the XML element contains character data, that data is
+//     accumulated in the first struct field that has tag ",chardata".
+//     The struct field may have type []byte or string.
+//     If there is no such field, the character data is discarded.
+//
+//   - If the XML element contains comments, they are accumulated in
+//     the first struct field that has tag ",comment".  The struct
+//     field may have type []byte or string. If there is no such
+//     field, the comments are discarded.
+//
+//   - If the XML element contains a sub-element whose name matches
+//     the prefix of a tag formatted as "a" or "a>b>c", unmarshal
+//     will descend into the XML structure looking for elements with the
+//     given names, and will map the innermost elements to that struct
+//     field. A tag starting with ">" is equivalent to one starting
+//     with the field name followed by ">".
+//
+//   - If the XML element contains a sub-element whose name matches
+//     a struct field's XMLName tag and the struct field has no
+//     explicit name tag as per the previous rule, unmarshal maps
+//     the sub-element to that struct field.
+//
+//   - If the XML element contains a sub-element whose name matches a
+//     field without any mode flags (",attr", ",chardata", etc), Unmarshal
+//     maps the sub-element to that struct field.
+//
+//   - If the XML element contains a sub-element that hasn't matched any
+//     of the above rules and the struct has a field with tag ",any",
+//     unmarshal maps the sub-element to that struct field.
+//
+//   - An anonymous struct field is handled as if the fields of its
+//     value were part of the outer struct.
+//
+//   - A struct field with tag "-" is never unmarshalled into.
+//
+// Unmarshal maps an XML element to a string or []byte by saving the
+// concatenation of that element's character data in the string or
+// []byte. The saved []byte is never nil.
+//
+// Unmarshal maps an attribute value to a string or []byte by saving
+// the value in the string or slice.
+//
+// Unmarshal maps an XML element to a slice by extending the length of
+// the slice and mapping the element to the newly created value.
+//
+// Unmarshal maps an XML element or attribute value to a bool by
+// setting it to the boolean value represented by the string.
+//
+// Unmarshal maps an XML element or attribute value to an integer or
+// floating-point field by setting the field to the result of
+// interpreting the string value in decimal. There is no check for
+// overflow.
+//
+// Unmarshal maps an XML element to an xml.Name by recording the
+// element name.
+//
+// Unmarshal maps an XML element to a pointer by setting the pointer
+// to a freshly allocated value and then mapping the element to that value.
+func Unmarshal(data []byte, v interface{}) error {
+	return NewDecoder(bytes.NewReader(data)).Decode(v)
+}
+
+// Decode works like xml.Unmarshal, except it reads the decoder
+// stream to find the start element.
+func (d *Decoder) Decode(v interface{}) error {
+	return d.DecodeElement(v, nil)
+}
+
+// DecodeElement works like xml.Unmarshal except that it takes
+// a pointer to the start XML element to decode into v.
+// It is useful when a client reads some raw XML tokens itself
+// but also wants to defer to Unmarshal for some elements.
+func (d *Decoder) DecodeElement(v interface{}, start *StartElement) error {
+	val := reflect.ValueOf(v)
+	if val.Kind() != reflect.Ptr {
+		return errors.New("non-pointer passed to Unmarshal")
+	}
+	return d.unmarshal(val.Elem(), start)
+}
+
+// An UnmarshalError represents an error in the unmarshalling process.
+type UnmarshalError string
+
+func (e UnmarshalError) Error() string { return string(e) }
+
+// Unmarshaler is the interface implemented by objects that can unmarshal
+// an XML element description of themselves.
+//
+// UnmarshalXML decodes a single XML element
+// beginning with the given start element.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXML must consume exactly one XML element.
+// One common implementation strategy is to unmarshal into
+// a separate value with a layout matching the expected XML
+// using d.DecodeElement,  and then to copy the data from
+// that value into the receiver.
+// Another common strategy is to use d.Token to process the
+// XML object one token at a time.
+// UnmarshalXML may not use d.RawToken.
+type Unmarshaler interface {
+	UnmarshalXML(d *Decoder, start StartElement) error
+}
+
+// UnmarshalerAttr is the interface implemented by objects that can unmarshal
+// an XML attribute description of themselves.
+//
+// UnmarshalXMLAttr decodes a single XML attribute.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXMLAttr is used only for struct fields with the
+// "attr" option in the field tag.
+type UnmarshalerAttr interface {
+	UnmarshalXMLAttr(attr Attr) error
+}
+
+// receiverType returns the receiver type to use in an expression like "%s.MethodName".
+func receiverType(val interface{}) string {
+	t := reflect.TypeOf(val)
+	if t.Name() != "" {
+		return t.String()
+	}
+	return "(" + t.String() + ")"
+}
+
+// unmarshalInterface unmarshals a single XML element into val.
+// start is the opening tag of the element.
+func (p *Decoder) unmarshalInterface(val Unmarshaler, start *StartElement) error {
+	// Record that decoder must stop at end tag corresponding to start.
+	p.pushEOF()
+
+	p.unmarshalDepth++
+	err := val.UnmarshalXML(p, *start)
+	p.unmarshalDepth--
+	if err != nil {
+		p.popEOF()
+		return err
+	}
+
+	if !p.popEOF() {
+		return fmt.Errorf("xml: %s.UnmarshalXML did not consume entire <%s> element", receiverType(val), start.Name.Local)
+	}
+
+	return nil
+}
+
+// unmarshalTextInterface unmarshals a single XML element into val.
+// The chardata contained in the element (but not its children)
+// is passed to the text unmarshaler.
+func (p *Decoder) unmarshalTextInterface(val encoding.TextUnmarshaler, start *StartElement) error {
+	var buf []byte
+	depth := 1
+	for depth > 0 {
+		t, err := p.Token()
+		if err != nil {
+			return err
+		}
+		switch t := t.(type) {
+		case CharData:
+			if depth == 1 {
+				buf = append(buf, t...)
+			}
+		case StartElement:
+			depth++
+		case EndElement:
+			depth--
+		}
+	}
+	return val.UnmarshalText(buf)
+}
+
+// unmarshalAttr unmarshals a single XML attribute into val.
+func (p *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
+	if val.Kind() == reflect.Ptr {
+		if val.IsNil() {
+			val.Set(reflect.New(val.Type().Elem()))
+		}
+		val = val.Elem()
+	}
+
+	if val.CanInterface() && val.Type().Implements(unmarshalerAttrType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return val.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(unmarshalerAttrType) {
+			return pv.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
+		}
+	}
+
+	// Not an UnmarshalerAttr; try encoding.TextUnmarshaler.
+	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return val.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			return pv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
+		}
+	}
+
+	copyValue(val, []byte(attr.Value))
+	return nil
+}
+
+var (
+	unmarshalerType     = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
+	unmarshalerAttrType = reflect.TypeOf((*UnmarshalerAttr)(nil)).Elem()
+	textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+)
+
+// Unmarshal a single XML element into val.
+func (p *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
+	// Find start element if we need it.
+	if start == nil {
+		for {
+			tok, err := p.Token()
+			if err != nil {
+				return err
+			}
+			if t, ok := tok.(StartElement); ok {
+				start = &t
+				break
+			}
+		}
+	}
+
+	// Load value from interface, but only if the result will be
+	// usefully addressable.
+	if val.Kind() == reflect.Interface && !val.IsNil() {
+		e := val.Elem()
+		if e.Kind() == reflect.Ptr && !e.IsNil() {
+			val = e
+		}
+	}
+
+	if val.Kind() == reflect.Ptr {
+		if val.IsNil() {
+			val.Set(reflect.New(val.Type().Elem()))
+		}
+		val = val.Elem()
+	}
+
+	if val.CanInterface() && val.Type().Implements(unmarshalerType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return p.unmarshalInterface(val.Interface().(Unmarshaler), start)
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(unmarshalerType) {
+			return p.unmarshalInterface(pv.Interface().(Unmarshaler), start)
+		}
+	}
+
+	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
+		return p.unmarshalTextInterface(val.Interface().(encoding.TextUnmarshaler), start)
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			return p.unmarshalTextInterface(pv.Interface().(encoding.TextUnmarshaler), start)
+		}
+	}
+
+	var (
+		data         []byte
+		saveData     reflect.Value
+		comment      []byte
+		saveComment  reflect.Value
+		saveXML      reflect.Value
+		saveXMLIndex int
+		saveXMLData  []byte
+		saveAny      reflect.Value
+		sv           reflect.Value
+		tinfo        *typeInfo
+		err          error
+	)
+
+	switch v := val; v.Kind() {
+	default:
+		return errors.New("unknown type " + v.Type().String())
+
+	case reflect.Interface:
+		// TODO: For now, simply ignore the field. In the near
+		//       future we may choose to unmarshal the start
+		//       element on it, if not nil.
+		return p.Skip()
+
+	case reflect.Slice:
+		typ := v.Type()
+		if typ.Elem().Kind() == reflect.Uint8 {
+			// []byte
+			saveData = v
+			break
+		}
+
+		// Slice of element values.
+		// Grow slice.
+		n := v.Len()
+		if n >= v.Cap() {
+			ncap := 2 * n
+			if ncap < 4 {
+				ncap = 4
+			}
+			new := reflect.MakeSlice(typ, n, ncap)
+			reflect.Copy(new, v)
+			v.Set(new)
+		}
+		v.SetLen(n + 1)
+
+		// Recur to read element into slice.
+		if err := p.unmarshal(v.Index(n), start); err != nil {
+			v.SetLen(n)
+			return err
+		}
+		return nil
+
+	case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.String:
+		saveData = v
+
+	case reflect.Struct:
+		typ := v.Type()
+		if typ == nameType {
+			v.Set(reflect.ValueOf(start.Name))
+			break
+		}
+
+		sv = v
+		tinfo, err = getTypeInfo(typ)
+		if err != nil {
+			return err
+		}
+
+		// Validate and assign element name.
+		if tinfo.xmlname != nil {
+			finfo := tinfo.xmlname
+			if finfo.name != "" && finfo.name != start.Name.Local {
+				return UnmarshalError("expected element type <" + finfo.name + "> but have <" + start.Name.Local + ">")
+			}
+			if finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
+				e := "expected element <" + finfo.name + "> in name space " + finfo.xmlns + " but have "
+				if start.Name.Space == "" {
+					e += "no name space"
+				} else {
+					e += start.Name.Space
+				}
+				return UnmarshalError(e)
+			}
+			fv := finfo.value(sv)
+			if _, ok := fv.Interface().(Name); ok {
+				fv.Set(reflect.ValueOf(start.Name))
+			}
+		}
+
+		// Assign attributes.
+		// Also, determine whether we need to save character data or comments.
+		for i := range tinfo.fields {
+			finfo := &tinfo.fields[i]
+			switch finfo.flags & fMode {
+			case fAttr:
+				strv := finfo.value(sv)
+				// Look for attribute.
+				for _, a := range start.Attr {
+					if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
+						if err := p.unmarshalAttr(strv, a); err != nil {
+							return err
+						}
+						break
+					}
+				}
+
+			case fCharData:
+				if !saveData.IsValid() {
+					saveData = finfo.value(sv)
+				}
+
+			case fComment:
+				if !saveComment.IsValid() {
+					saveComment = finfo.value(sv)
+				}
+
+			case fAny, fAny | fElement:
+				if !saveAny.IsValid() {
+					saveAny = finfo.value(sv)
+				}
+
+			case fInnerXml:
+				if !saveXML.IsValid() {
+					saveXML = finfo.value(sv)
+					if p.saved == nil {
+						saveXMLIndex = 0
+						p.saved = new(bytes.Buffer)
+					} else {
+						saveXMLIndex = p.savedOffset()
+					}
+				}
+			}
+		}
+	}
+
+	// Find end element.
+	// Process sub-elements along the way.
+Loop:
+	for {
+		var savedOffset int
+		if saveXML.IsValid() {
+			savedOffset = p.savedOffset()
+		}
+		tok, err := p.Token()
+		if err != nil {
+			return err
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			consumed := false
+			if sv.IsValid() {
+				consumed, err = p.unmarshalPath(tinfo, sv, nil, &t)
+				if err != nil {
+					return err
+				}
+				if !consumed && saveAny.IsValid() {
+					consumed = true
+					if err := p.unmarshal(saveAny, &t); err != nil {
+						return err
+					}
+				}
+			}
+			if !consumed {
+				if err := p.Skip(); err != nil {
+					return err
+				}
+			}
+
+		case EndElement:
+			if saveXML.IsValid() {
+				saveXMLData = p.saved.Bytes()[saveXMLIndex:savedOffset]
+				if saveXMLIndex == 0 {
+					p.saved = nil
+				}
+			}
+			break Loop
+
+		case CharData:
+			if saveData.IsValid() {
+				data = append(data, t...)
+			}
+
+		case Comment:
+			if saveComment.IsValid() {
+				comment = append(comment, t...)
+			}
+		}
+	}
+
+	if saveData.IsValid() && saveData.CanInterface() && saveData.Type().Implements(textUnmarshalerType) {
+		if err := saveData.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+			return err
+		}
+		saveData = reflect.Value{}
+	}
+
+	if saveData.IsValid() && saveData.CanAddr() {
+		pv := saveData.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			if err := pv.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+				return err
+			}
+			saveData = reflect.Value{}
+		}
+	}
+
+	if err := copyValue(saveData, data); err != nil {
+		return err
+	}
+
+	switch t := saveComment; t.Kind() {
+	case reflect.String:
+		t.SetString(string(comment))
+	case reflect.Slice:
+		t.Set(reflect.ValueOf(comment))
+	}
+
+	switch t := saveXML; t.Kind() {
+	case reflect.String:
+		t.SetString(string(saveXMLData))
+	case reflect.Slice:
+		t.Set(reflect.ValueOf(saveXMLData))
+	}
+
+	return nil
+}
+
+func copyValue(dst reflect.Value, src []byte) (err error) {
+	dst0 := dst
+
+	if dst.Kind() == reflect.Ptr {
+		if dst.IsNil() {
+			dst.Set(reflect.New(dst.Type().Elem()))
+		}
+		dst = dst.Elem()
+	}
+
+	// Save accumulated data.
+	switch dst.Kind() {
+	case reflect.Invalid:
+		// Probably a comment.
+	default:
+		return errors.New("cannot unmarshal into " + dst0.Type().String())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		itmp, err := strconv.ParseInt(string(src), 10, dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetInt(itmp)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		utmp, err := strconv.ParseUint(string(src), 10, dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetUint(utmp)
+	case reflect.Float32, reflect.Float64:
+		ftmp, err := strconv.ParseFloat(string(src), dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetFloat(ftmp)
+	case reflect.Bool:
+		value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
+		if err != nil {
+			return err
+		}
+		dst.SetBool(value)
+	case reflect.String:
+		dst.SetString(string(src))
+	case reflect.Slice:
+		if len(src) == 0 {
+			// non-nil to flag presence
+			src = []byte{}
+		}
+		dst.SetBytes(src)
+	}
+	return nil
+}
+
+// unmarshalPath walks down an XML structure looking for wanted
+// paths, and calls unmarshal on them.
+// The consumed result tells whether XML elements have been consumed
+// from the Decoder until start's matching end element, or if it's
+// still untouched because start is uninteresting for sv's fields.
+func (p *Decoder) unmarshalPath(tinfo *typeInfo, sv reflect.Value, parents []string, start *StartElement) (consumed bool, err error) {
+	recurse := false
+Loop:
+	for i := range tinfo.fields {
+		finfo := &tinfo.fields[i]
+		if finfo.flags&fElement == 0 || len(finfo.parents) < len(parents) || finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
+			continue
+		}
+		for j := range parents {
+			if parents[j] != finfo.parents[j] {
+				continue Loop
+			}
+		}
+		if len(finfo.parents) == len(parents) && finfo.name == start.Name.Local {
+			// It's a perfect match, unmarshal the field.
+			return true, p.unmarshal(finfo.value(sv), start)
+		}
+		if len(finfo.parents) > len(parents) && finfo.parents[len(parents)] == start.Name.Local {
+			// It's a prefix for the field. Break and recurse
+			// since it's not ok for one field path to be itself
+			// the prefix for another field path.
+			recurse = true
+
+			// We can reuse the same slice as long as we
+			// don't try to append to it.
+			parents = finfo.parents[:len(parents)+1]
+			break
+		}
+	}
+	if !recurse {
+		// We have no business with this element.
+		return false, nil
+	}
+	// The element is not a perfect match for any field, but one
+	// or more fields have the path to this element as a parent
+	// prefix. Recurse and attempt to match these.
+	for {
+		var tok Token
+		tok, err = p.Token()
+		if err != nil {
+			return true, err
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			consumed2, err := p.unmarshalPath(tinfo, sv, parents, &t)
+			if err != nil {
+				return true, err
+			}
+			if !consumed2 {
+				if err := p.Skip(); err != nil {
+					return true, err
+				}
+			}
+		case EndElement:
+			return true, nil
+		}
+	}
+}
+
+// Skip reads tokens until it has consumed the end element
+// matching the most recent start element already consumed.
+// It recurs if it encounters a start element, so it can be used to
+// skip nested structures.
+// It returns nil if it finds an end element matching the start
+// element; otherwise it returns an error describing the problem.
+func (d *Decoder) Skip() error {
+	for {
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch tok.(type) {
+		case StartElement:
+			if err := d.Skip(); err != nil {
+				return err
+			}
+		case EndElement:
+			return nil
+		}
+	}
+}

endpoints/drive/webdav/internal/xml/read_test.go

@@ -0,0 +1,744 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Stripped down Atom feed data structures.
+
+func TestUnmarshalFeed(t *testing.T) {
+	var f Feed
+	if err := Unmarshal([]byte(atomFeedString), &f); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if !reflect.DeepEqual(f, atomFeed) {
+		t.Fatalf("have %#v\nwant %#v", f, atomFeed)
+	}
+}
+
+// hget http://codereview.appspot.com/rss/mine/rsc
+const atomFeedString = `
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en-us" updated="2009-10-04T01:35:58+00:00"><title>Code Review - My issues</title><link href="http://codereview.appspot.com/" rel="alternate"></link><link href="http://codereview.appspot.com/rss/mine/rsc" rel="self"></link><id>http://codereview.appspot.com/</id><author><name>rietveld&lt;&gt;</name></author><entry><title>rietveld: an attempt at pubsubhubbub
+</title><link href="http://codereview.appspot.com/126085" rel="alternate"></link><updated>2009-10-04T01:35:58+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:134d9179c41f806be79b3a5f7877d19a</id><summary type="html">
+  An attempt at adding pubsubhubbub support to Rietveld.
+http://code.google.com/p/pubsubhubbub
+http://code.google.com/p/rietveld/issues/detail?id=155
+
+The server side of the protocol is trivial:
+  1. add a &amp;lt;link rel=&amp;quot;hub&amp;quot; href=&amp;quot;hub-server&amp;quot;&amp;gt; tag to all
+     feeds that will be pubsubhubbubbed.
+  2. every time one of those feeds changes, tell the hub
+     with a simple POST request.
+
+I have tested this by adding debug prints to a local hub
+server and checking that the server got the right publish
+requests.
+
+I can&amp;#39;t quite get the server to work, but I think the bug
+is not in my code.  I think that the server expects to be
+able to grab the feed and see the feed&amp;#39;s actual URL in
+the link rel=&amp;quot;self&amp;quot;, but the default value for that drops
+the :port from the URL, and I cannot for the life of me
+figure out how to get the Atom generator deep inside
+django not to do that, or even where it is doing that,
+or even what code is running to generate the Atom feed.
+(I thought I knew but I added some assert False statements
+and it kept running!)
+
+Ignoring that particular problem, I would appreciate
+feedback on the right way to get the two values at
+the top of feeds.py marked NOTE(rsc).
+
+
+</summary></entry><entry><title>rietveld: correct tab handling
+</title><link href="http://codereview.appspot.com/124106" rel="alternate"></link><updated>2009-10-03T23:02:17+00:00</updated><author><name>email-address-removed</name></author><id>urn:md5:0a2a4f19bb815101f0ba2904aed7c35a</id><summary type="html">
+  This fixes the buggy tab rendering that can be seen at
+http://codereview.appspot.com/116075/diff/1/2
+
+The fundamental problem was that the tab code was
+not being told what column the text began in, so it
+didn&amp;#39;t know where to put the tab stops.  Another problem
+was that some of the code assumed that string byte
+offsets were the same as column offsets, which is only
+true if there are no tabs.
+
+In the process of fixing this, I cleaned up the arguments
+to Fold and ExpandTabs and renamed them Break and
+_ExpandTabs so that I could be sure that I found all the
+call sites.  I also wanted to verify that ExpandTabs was
+not being used from outside intra_region_diff.py.
+
+
+</summary></entry></feed> 	   `
+
+type Feed struct {
+	XMLName Name      `xml:"http://www.w3.org/2005/Atom feed"`
+	Title   string    `xml:"title"`
+	Id      string    `xml:"id"`
+	Link    []Link    `xml:"link"`
+	Updated time.Time `xml:"updated,attr"`
+	Author  Person    `xml:"author"`
+	Entry   []Entry   `xml:"entry"`
+}
+
+type Entry struct {
+	Title   string    `xml:"title"`
+	Id      string    `xml:"id"`
+	Link    []Link    `xml:"link"`
+	Updated time.Time `xml:"updated"`
+	Author  Person    `xml:"author"`
+	Summary Text      `xml:"summary"`
+}
+
+type Link struct {
+	Rel  string `xml:"rel,attr,omitempty"`
+	Href string `xml:"href,attr"`
+}
+
+type Person struct {
+	Name     string `xml:"name"`
+	URI      string `xml:"uri"`
+	Email    string `xml:"email"`
+	InnerXML string `xml:",innerxml"`
+}
+
+type Text struct {
+	Type string `xml:"type,attr,omitempty"`
+	Body string `xml:",chardata"`
+}
+
+var atomFeed = Feed{
+	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
+	Title:   "Code Review - My issues",
+	Link: []Link{
+		{Rel: "alternate", Href: "http://codereview.appspot.com/"},
+		{Rel: "self", Href: "http://codereview.appspot.com/rss/mine/rsc"},
+	},
+	Id:      "http://codereview.appspot.com/",
+	Updated: ParseTime("2009-10-04T01:35:58+00:00"),
+	Author: Person{
+		Name:     "rietveld<>",
+		InnerXML: "<name>rietveld&lt;&gt;</name>",
+	},
+	Entry: []Entry{
+		{
+			Title: "rietveld: an attempt at pubsubhubbub\n",
+			Link: []Link{
+				{Rel: "alternate", Href: "http://codereview.appspot.com/126085"},
+			},
+			Updated: ParseTime("2009-10-04T01:35:58+00:00"),
+			Author: Person{
+				Name:     "email-address-removed",
+				InnerXML: "<name>email-address-removed</name>",
+			},
+			Id: "urn:md5:134d9179c41f806be79b3a5f7877d19a",
+			Summary: Text{
+				Type: "html",
+				Body: `
+  An attempt at adding pubsubhubbub support to Rietveld.
+http://code.google.com/p/pubsubhubbub
+http://code.google.com/p/rietveld/issues/detail?id=155
+
+The server side of the protocol is trivial:
+  1. add a &lt;link rel=&quot;hub&quot; href=&quot;hub-server&quot;&gt; tag to all
+     feeds that will be pubsubhubbubbed.
+  2. every time one of those feeds changes, tell the hub
+     with a simple POST request.
+
+I have tested this by adding debug prints to a local hub
+server and checking that the server got the right publish
+requests.
+
+I can&#39;t quite get the server to work, but I think the bug
+is not in my code.  I think that the server expects to be
+able to grab the feed and see the feed&#39;s actual URL in
+the link rel=&quot;self&quot;, but the default value for that drops
+the :port from the URL, and I cannot for the life of me
+figure out how to get the Atom generator deep inside
+django not to do that, or even where it is doing that,
+or even what code is running to generate the Atom feed.
+(I thought I knew but I added some assert False statements
+and it kept running!)
+
+Ignoring that particular problem, I would appreciate
+feedback on the right way to get the two values at
+the top of feeds.py marked NOTE(rsc).
+
+
+`,
+			},
+		},
+		{
+			Title: "rietveld: correct tab handling\n",
+			Link: []Link{
+				{Rel: "alternate", Href: "http://codereview.appspot.com/124106"},
+			},
+			Updated: ParseTime("2009-10-03T23:02:17+00:00"),
+			Author: Person{
+				Name:     "email-address-removed",
+				InnerXML: "<name>email-address-removed</name>",
+			},
+			Id: "urn:md5:0a2a4f19bb815101f0ba2904aed7c35a",
+			Summary: Text{
+				Type: "html",
+				Body: `
+  This fixes the buggy tab rendering that can be seen at
+http://codereview.appspot.com/116075/diff/1/2
+
+The fundamental problem was that the tab code was
+not being told what column the text began in, so it
+didn&#39;t know where to put the tab stops.  Another problem
+was that some of the code assumed that string byte
+offsets were the same as column offsets, which is only
+true if there are no tabs.
+
+In the process of fixing this, I cleaned up the arguments
+to Fold and ExpandTabs and renamed them Break and
+_ExpandTabs so that I could be sure that I found all the
+call sites.  I also wanted to verify that ExpandTabs was
+not being used from outside intra_region_diff.py.
+
+
+`,
+			},
+		},
+	},
+}
+
+const pathTestString = `
+<Result>
+    <Before>1</Before>
+    <Items>
+        <Item1>
+            <Value>A</Value>
+        </Item1>
+        <Item2>
+            <Value>B</Value>
+        </Item2>
+        <Item1>
+            <Value>C</Value>
+            <Value>D</Value>
+        </Item1>
+        <_>
+            <Value>E</Value>
+        </_>
+    </Items>
+    <After>2</After>
+</Result>
+`
+
+type PathTestItem struct {
+	Value string
+}
+
+type PathTestA struct {
+	Items         []PathTestItem `xml:">Item1"`
+	Before, After string
+}
+
+type PathTestB struct {
+	Other         []PathTestItem `xml:"Items>Item1"`
+	Before, After string
+}
+
+type PathTestC struct {
+	Values1       []string `xml:"Items>Item1>Value"`
+	Values2       []string `xml:"Items>Item2>Value"`
+	Before, After string
+}
+
+type PathTestSet struct {
+	Item1 []PathTestItem
+}
+
+type PathTestD struct {
+	Other         PathTestSet `xml:"Items"`
+	Before, After string
+}
+
+type PathTestE struct {
+	Underline     string `xml:"Items>_>Value"`
+	Before, After string
+}
+
+var pathTests = []interface{}{
+	&PathTestA{Items: []PathTestItem{{"A"}, {"D"}}, Before: "1", After: "2"},
+	&PathTestB{Other: []PathTestItem{{"A"}, {"D"}}, Before: "1", After: "2"},
+	&PathTestC{Values1: []string{"A", "C", "D"}, Values2: []string{"B"}, Before: "1", After: "2"},
+	&PathTestD{Other: PathTestSet{Item1: []PathTestItem{{"A"}, {"D"}}}, Before: "1", After: "2"},
+	&PathTestE{Underline: "E", Before: "1", After: "2"},
+}
+
+func TestUnmarshalPaths(t *testing.T) {
+	for _, pt := range pathTests {
+		v := reflect.New(reflect.TypeOf(pt).Elem()).Interface()
+		if err := Unmarshal([]byte(pathTestString), v); err != nil {
+			t.Fatalf("Unmarshal: %s", err)
+		}
+		if !reflect.DeepEqual(v, pt) {
+			t.Fatalf("have %#v\nwant %#v", v, pt)
+		}
+	}
+}
+
+type BadPathTestA struct {
+	First  string `xml:"items>item1"`
+	Other  string `xml:"items>item2"`
+	Second string `xml:"items"`
+}
+
+type BadPathTestB struct {
+	Other  string `xml:"items>item2>value"`
+	First  string `xml:"items>item1"`
+	Second string `xml:"items>item1>value"`
+}
+
+type BadPathTestC struct {
+	First  string
+	Second string `xml:"First"`
+}
+
+type BadPathTestD struct {
+	BadPathEmbeddedA
+	BadPathEmbeddedB
+}
+
+type BadPathEmbeddedA struct {
+	First string
+}
+
+type BadPathEmbeddedB struct {
+	Second string `xml:"First"`
+}
+
+var badPathTests = []struct {
+	v, e interface{}
+}{
+	{&BadPathTestA{}, &TagPathError{reflect.TypeOf(BadPathTestA{}), "First", "items>item1", "Second", "items"}},
+	{&BadPathTestB{}, &TagPathError{reflect.TypeOf(BadPathTestB{}), "First", "items>item1", "Second", "items>item1>value"}},
+	{&BadPathTestC{}, &TagPathError{reflect.TypeOf(BadPathTestC{}), "First", "", "Second", "First"}},
+	{&BadPathTestD{}, &TagPathError{reflect.TypeOf(BadPathTestD{}), "First", "", "Second", "First"}},
+}
+
+func TestUnmarshalBadPaths(t *testing.T) {
+	for _, tt := range badPathTests {
+		err := Unmarshal([]byte(pathTestString), tt.v)
+		if !reflect.DeepEqual(err, tt.e) {
+			t.Fatalf("Unmarshal with %#v didn't fail properly:\nhave %#v,\nwant %#v", tt.v, err, tt.e)
+		}
+	}
+}
+
+const OK = "OK"
+const withoutNameTypeData = `
+<?xml version="1.0" charset="utf-8"?>
+<Test3 Attr="OK" />`
+
+type TestThree struct {
+	XMLName Name   `xml:"Test3"`
+	Attr    string `xml:",attr"`
+}
+
+func TestUnmarshalWithoutNameType(t *testing.T) {
+	var x TestThree
+	if err := Unmarshal([]byte(withoutNameTypeData), &x); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if x.Attr != OK {
+		t.Fatalf("have %v\nwant %v", x.Attr, OK)
+	}
+}
+
+func TestUnmarshalAttr(t *testing.T) {
+	type ParamVal struct {
+		Int int `xml:"int,attr"`
+	}
+
+	type ParamPtr struct {
+		Int *int `xml:"int,attr"`
+	}
+
+	type ParamStringPtr struct {
+		Int *string `xml:"int,attr"`
+	}
+
+	x := []byte(`<Param int="1" />`)
+
+	p1 := &ParamPtr{}
+	if err := Unmarshal(x, p1); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if p1.Int == nil {
+		t.Fatalf("Unmarshal failed in to *int field")
+	} else if *p1.Int != 1 {
+		t.Fatalf("Unmarshal with %s failed:\nhave %#v,\n want %#v", x, p1.Int, 1)
+	}
+
+	p2 := &ParamVal{}
+	if err := Unmarshal(x, p2); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if p2.Int != 1 {
+		t.Fatalf("Unmarshal with %s failed:\nhave %#v,\n want %#v", x, p2.Int, 1)
+	}
+
+	p3 := &ParamStringPtr{}
+	if err := Unmarshal(x, p3); err != nil {
+		t.Fatalf("Unmarshal: %s", err)
+	}
+	if p3.Int == nil {
+		t.Fatalf("Unmarshal failed in to *string field")
+	} else if *p3.Int != "1" {
+		t.Fatalf("Unmarshal with %s failed:\nhave %#v,\n want %#v", x, p3.Int, 1)
+	}
+}
+
+type Tables struct {
+	HTable string `xml:"http://www.w3.org/TR/html4/ table"`
+	FTable string `xml:"http://www.w3schools.com/furniture table"`
+}
+
+var tables = []struct {
+	xml string
+	tab Tables
+	ns  string
+}{
+	{
+		xml: `<Tables>` +
+			`<table xmlns="http://www.w3.org/TR/html4/">hello</table>` +
+			`<table xmlns="http://www.w3schools.com/furniture">world</table>` +
+			`</Tables>`,
+		tab: Tables{"hello", "world"},
+	},
+	{
+		xml: `<Tables>` +
+			`<table xmlns="http://www.w3schools.com/furniture">world</table>` +
+			`<table xmlns="http://www.w3.org/TR/html4/">hello</table>` +
+			`</Tables>`,
+		tab: Tables{"hello", "world"},
+	},
+	{
+		xml: `<Tables xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/">` +
+			`<f:table>world</f:table>` +
+			`<h:table>hello</h:table>` +
+			`</Tables>`,
+		tab: Tables{"hello", "world"},
+	},
+	{
+		xml: `<Tables>` +
+			`<table>bogus</table>` +
+			`</Tables>`,
+		tab: Tables{},
+	},
+	{
+		xml: `<Tables>` +
+			`<table>only</table>` +
+			`</Tables>`,
+		tab: Tables{HTable: "only"},
+		ns:  "http://www.w3.org/TR/html4/",
+	},
+	{
+		xml: `<Tables>` +
+			`<table>only</table>` +
+			`</Tables>`,
+		tab: Tables{FTable: "only"},
+		ns:  "http://www.w3schools.com/furniture",
+	},
+	{
+		xml: `<Tables>` +
+			`<table>only</table>` +
+			`</Tables>`,
+		tab: Tables{},
+		ns:  "something else entirely",
+	},
+}
+
+func TestUnmarshalNS(t *testing.T) {
+	for i, tt := range tables {
+		var dst Tables
+		var err error
+		if tt.ns != "" {
+			d := NewDecoder(strings.NewReader(tt.xml))
+			d.DefaultSpace = tt.ns
+			err = d.Decode(&dst)
+		} else {
+			err = Unmarshal([]byte(tt.xml), &dst)
+		}
+		if err != nil {
+			t.Errorf("#%d: Unmarshal: %v", i, err)
+			continue
+		}
+		want := tt.tab
+		if dst != want {
+			t.Errorf("#%d: dst=%+v, want %+v", i, dst, want)
+		}
+	}
+}
+
+func TestRoundTrip(t *testing.T) {
+	// From issue 7535
+	const s = `<ex:element xmlns:ex="http://example.com/schema"></ex:element>`
+	in := bytes.NewBufferString(s)
+	for i := 0; i < 10; i++ {
+		out := &bytes.Buffer{}
+		d := NewDecoder(in)
+		e := NewEncoder(out)
+
+		for {
+			t, err := d.Token()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				fmt.Println("failed:", err)
+				return
+			}
+			e.EncodeToken(t)
+		}
+		e.Flush()
+		in = out
+	}
+	if got := in.String(); got != s {
+		t.Errorf("have: %q\nwant: %q\n", got, s)
+	}
+}
+
+func TestMarshalNS(t *testing.T) {
+	dst := Tables{"hello", "world"}
+	data, err := Marshal(&dst)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	want := `<Tables><table xmlns="http://www.w3.org/TR/html4/">hello</table><table xmlns="http://www.w3schools.com/furniture">world</table></Tables>`
+	str := string(data)
+	if str != want {
+		t.Errorf("have: %q\nwant: %q\n", str, want)
+	}
+}
+
+type TableAttrs struct {
+	TAttr TAttr
+}
+
+type TAttr struct {
+	HTable string `xml:"http://www.w3.org/TR/html4/ table,attr"`
+	FTable string `xml:"http://www.w3schools.com/furniture table,attr"`
+	Lang   string `xml:"http://www.w3.org/XML/1998/namespace lang,attr,omitempty"`
+	Other1 string `xml:"http://golang.org/xml/ other,attr,omitempty"`
+	Other2 string `xml:"http://golang.org/xmlfoo/ other,attr,omitempty"`
+	Other3 string `xml:"http://golang.org/json/ other,attr,omitempty"`
+	Other4 string `xml:"http://golang.org/2/json/ other,attr,omitempty"`
+}
+
+var tableAttrs = []struct {
+	xml string
+	tab TableAttrs
+	ns  string
+}{
+	{
+		xml: `<TableAttrs xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/"><TAttr ` +
+			`h:table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: "world"}},
+	},
+	{
+		xml: `<TableAttrs><TAttr xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/" ` +
+			`h:table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: "world"}},
+	},
+	{
+		xml: `<TableAttrs><TAttr ` +
+			`h:table="hello" f:table="world" xmlns:f="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: "world"}},
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns="http://www.w3schools.com/furniture" xmlns:h="http://www.w3.org/TR/html4/"><TAttr ` +
+			`h:table="hello" table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: ""}},
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns:f="http://www.w3schools.com/furniture"><TAttr xmlns="http://www.w3.org/TR/html4/" ` +
+			`table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "", FTable: "world"}},
+	},
+	{
+		xml: `<TableAttrs><TAttr ` +
+			`table="bogus" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{},
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns:h="http://www.w3.org/TR/html4/"><TAttr ` +
+			`h:table="hello" table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "hello", FTable: ""}},
+		ns:  "http://www.w3schools.com/furniture",
+	},
+	{
+		// Default space does not apply to attribute names.
+		xml: `<TableAttrs xmlns:f="http://www.w3schools.com/furniture"><TAttr ` +
+			`table="hello" f:table="world" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{TAttr{HTable: "", FTable: "world"}},
+		ns:  "http://www.w3.org/TR/html4/",
+	},
+	{
+		xml: `<TableAttrs><TAttr ` +
+			`table="bogus" ` +
+			`/></TableAttrs>`,
+		tab: TableAttrs{},
+		ns:  "something else entirely",
+	},
+}
+
+func TestUnmarshalNSAttr(t *testing.T) {
+	for i, tt := range tableAttrs {
+		var dst TableAttrs
+		var err error
+		if tt.ns != "" {
+			d := NewDecoder(strings.NewReader(tt.xml))
+			d.DefaultSpace = tt.ns
+			err = d.Decode(&dst)
+		} else {
+			err = Unmarshal([]byte(tt.xml), &dst)
+		}
+		if err != nil {
+			t.Errorf("#%d: Unmarshal: %v", i, err)
+			continue
+		}
+		want := tt.tab
+		if dst != want {
+			t.Errorf("#%d: dst=%+v, want %+v", i, dst, want)
+		}
+	}
+}
+
+func TestMarshalNSAttr(t *testing.T) {
+	src := TableAttrs{TAttr{"hello", "world", "en_US", "other1", "other2", "other3", "other4"}}
+	data, err := Marshal(&src)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	want := `<TableAttrs><TAttr xmlns:json_1="http://golang.org/2/json/" xmlns:json="http://golang.org/json/" xmlns:_xmlfoo="http://golang.org/xmlfoo/" xmlns:_xml="http://golang.org/xml/" xmlns:furniture="http://www.w3schools.com/furniture" xmlns:html4="http://www.w3.org/TR/html4/" html4:table="hello" furniture:table="world" xml:lang="en_US" _xml:other="other1" _xmlfoo:other="other2" json:other="other3" json_1:other="other4"></TAttr></TableAttrs>`
+	str := string(data)
+	if str != want {
+		t.Errorf("Marshal:\nhave: %#q\nwant: %#q\n", str, want)
+	}
+
+	var dst TableAttrs
+	if err := Unmarshal(data, &dst); err != nil {
+		t.Errorf("Unmarshal: %v", err)
+	}
+
+	if dst != src {
+		t.Errorf("Unmarshal = %q, want %q", dst, src)
+	}
+}
+
+type MyCharData struct {
+	body string
+}
+
+func (m *MyCharData) UnmarshalXML(d *Decoder, start StartElement) error {
+	for {
+		t, err := d.Token()
+		if err == io.EOF { // found end of element
+			break
+		}
+		if err != nil {
+			return err
+		}
+		if char, ok := t.(CharData); ok {
+			m.body += string(char)
+		}
+	}
+	return nil
+}
+
+var _ Unmarshaler = (*MyCharData)(nil)
+
+func (m *MyCharData) UnmarshalXMLAttr(attr Attr) error {
+	panic("must not call")
+}
+
+type MyAttr struct {
+	attr string
+}
+
+func (m *MyAttr) UnmarshalXMLAttr(attr Attr) error {
+	m.attr = attr.Value
+	return nil
+}
+
+var _ UnmarshalerAttr = (*MyAttr)(nil)
+
+type MyStruct struct {
+	Data *MyCharData
+	Attr *MyAttr `xml:",attr"`
+
+	Data2 MyCharData
+	Attr2 MyAttr `xml:",attr"`
+}
+
+func TestUnmarshaler(t *testing.T) {
+	xml := `<?xml version="1.0" encoding="utf-8"?>
+		<MyStruct Attr="attr1" Attr2="attr2">
+		<Data>hello <!-- comment -->world</Data>
+		<Data2>howdy <!-- comment -->world</Data2>
+		</MyStruct>
+	`
+
+	var m MyStruct
+	if err := Unmarshal([]byte(xml), &m); err != nil {
+		t.Fatal(err)
+	}
+
+	if m.Data == nil || m.Attr == nil || m.Data.body != "hello world" || m.Attr.attr != "attr1" || m.Data2.body != "howdy world" || m.Attr2.attr != "attr2" {
+		t.Errorf("m=%#+v\n", m)
+	}
+}
+
+type Pea struct {
+	Cotelydon string
+}
+
+type Pod struct {
+	Pea interface{} `xml:"Pea"`
+}
+
+// https://golang.org/issue/6836
+func TestUnmarshalIntoInterface(t *testing.T) {
+	pod := new(Pod)
+	pod.Pea = new(Pea)
+	xml := `<Pod><Pea><Cotelydon>Green stuff</Cotelydon></Pea></Pod>`
+	err := Unmarshal([]byte(xml), pod)
+	if err != nil {
+		t.Fatalf("failed to unmarshal %q: %v", xml, err)
+	}
+	pea, ok := pod.Pea.(*Pea)
+	if !ok {
+		t.Fatalf("unmarshalled into wrong type: have %T want *Pea", pod.Pea)
+	}
+	have, want := pea.Cotelydon, "Green stuff"
+	if have != want {
+		t.Errorf("failed to unmarshal into interface, have %q want %q", have, want)
+	}
+}

endpoints/drive/webdav/internal/xml/typeinfo.go

@@ -0,0 +1,371 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"sync"
+)
+
+// typeInfo holds details for the xml representation of a type.
+type typeInfo struct {
+	xmlname *fieldInfo
+	fields  []fieldInfo
+}
+
+// fieldInfo holds details for the xml representation of a single field.
+type fieldInfo struct {
+	idx     []int
+	name    string
+	xmlns   string
+	flags   fieldFlags
+	parents []string
+}
+
+type fieldFlags int
+
+const (
+	fElement fieldFlags = 1 << iota
+	fAttr
+	fCharData
+	fInnerXml
+	fComment
+	fAny
+
+	fOmitEmpty
+
+	fMode = fElement | fAttr | fCharData | fInnerXml | fComment | fAny
+)
+
+var tinfoMap = make(map[reflect.Type]*typeInfo)
+var tinfoLock sync.RWMutex
+
+var nameType = reflect.TypeOf(Name{})
+
+// getTypeInfo returns the typeInfo structure with details necessary
+// for marshalling and unmarshalling typ.
+func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
+	tinfoLock.RLock()
+	tinfo, ok := tinfoMap[typ]
+	tinfoLock.RUnlock()
+	if ok {
+		return tinfo, nil
+	}
+	tinfo = &typeInfo{}
+	if typ.Kind() == reflect.Struct && typ != nameType {
+		n := typ.NumField()
+		for i := 0; i < n; i++ {
+			f := typ.Field(i)
+			if f.PkgPath != "" || f.Tag.Get("xml") == "-" {
+				continue // Private field
+			}
+
+			// For embedded structs, embed its fields.
+			if f.Anonymous {
+				t := f.Type
+				if t.Kind() == reflect.Ptr {
+					t = t.Elem()
+				}
+				if t.Kind() == reflect.Struct {
+					inner, err := getTypeInfo(t)
+					if err != nil {
+						return nil, err
+					}
+					if tinfo.xmlname == nil {
+						tinfo.xmlname = inner.xmlname
+					}
+					for _, finfo := range inner.fields {
+						finfo.idx = append([]int{i}, finfo.idx...)
+						if err := addFieldInfo(typ, tinfo, &finfo); err != nil {
+							return nil, err
+						}
+					}
+					continue
+				}
+			}
+
+			finfo, err := structFieldInfo(typ, &f)
+			if err != nil {
+				return nil, err
+			}
+
+			if f.Name == "XMLName" {
+				tinfo.xmlname = finfo
+				continue
+			}
+
+			// Add the field if it doesn't conflict with other fields.
+			if err := addFieldInfo(typ, tinfo, finfo); err != nil {
+				return nil, err
+			}
+		}
+	}
+	tinfoLock.Lock()
+	tinfoMap[typ] = tinfo
+	tinfoLock.Unlock()
+	return tinfo, nil
+}
+
+// structFieldInfo builds and returns a fieldInfo for f.
+func structFieldInfo(typ reflect.Type, f *reflect.StructField) (*fieldInfo, error) {
+	finfo := &fieldInfo{idx: f.Index}
+
+	// Split the tag from the xml namespace if necessary.
+	tag := f.Tag.Get("xml")
+	if i := strings.Index(tag, " "); i >= 0 {
+		finfo.xmlns, tag = tag[:i], tag[i+1:]
+	}
+
+	// Parse flags.
+	tokens := strings.Split(tag, ",")
+	if len(tokens) == 1 {
+		finfo.flags = fElement
+	} else {
+		tag = tokens[0]
+		for _, flag := range tokens[1:] {
+			switch flag {
+			case "attr":
+				finfo.flags |= fAttr
+			case "chardata":
+				finfo.flags |= fCharData
+			case "innerxml":
+				finfo.flags |= fInnerXml
+			case "comment":
+				finfo.flags |= fComment
+			case "any":
+				finfo.flags |= fAny
+			case "omitempty":
+				finfo.flags |= fOmitEmpty
+			}
+		}
+
+		// Validate the flags used.
+		valid := true
+		switch mode := finfo.flags & fMode; mode {
+		case 0:
+			finfo.flags |= fElement
+		case fAttr, fCharData, fInnerXml, fComment, fAny:
+			if f.Name == "XMLName" || tag != "" && mode != fAttr {
+				valid = false
+			}
+		default:
+			// This will also catch multiple modes in a single field.
+			valid = false
+		}
+		if finfo.flags&fMode == fAny {
+			finfo.flags |= fElement
+		}
+		if finfo.flags&fOmitEmpty != 0 && finfo.flags&(fElement|fAttr) == 0 {
+			valid = false
+		}
+		if !valid {
+			return nil, fmt.Errorf("xml: invalid tag in field %s of type %s: %q",
+				f.Name, typ, f.Tag.Get("xml"))
+		}
+	}
+
+	// Use of xmlns without a name is not allowed.
+	if finfo.xmlns != "" && tag == "" {
+		return nil, fmt.Errorf("xml: namespace without name in field %s of type %s: %q",
+			f.Name, typ, f.Tag.Get("xml"))
+	}
+
+	if f.Name == "XMLName" {
+		// The XMLName field records the XML element name. Don't
+		// process it as usual because its name should default to
+		// empty rather than to the field name.
+		finfo.name = tag
+		return finfo, nil
+	}
+
+	if tag == "" {
+		// If the name part of the tag is completely empty, get
+		// default from XMLName of underlying struct if feasible,
+		// or field name otherwise.
+		if xmlname := lookupXMLName(f.Type); xmlname != nil {
+			finfo.xmlns, finfo.name = xmlname.xmlns, xmlname.name
+		} else {
+			finfo.name = f.Name
+		}
+		return finfo, nil
+	}
+
+	if finfo.xmlns == "" && finfo.flags&fAttr == 0 {
+		// If it's an element no namespace specified, get the default
+		// from the XMLName of enclosing struct if possible.
+		if xmlname := lookupXMLName(typ); xmlname != nil {
+			finfo.xmlns = xmlname.xmlns
+		}
+	}
+
+	// Prepare field name and parents.
+	parents := strings.Split(tag, ">")
+	if parents[0] == "" {
+		parents[0] = f.Name
+	}
+	if parents[len(parents)-1] == "" {
+		return nil, fmt.Errorf("xml: trailing '>' in field %s of type %s", f.Name, typ)
+	}
+	finfo.name = parents[len(parents)-1]
+	if len(parents) > 1 {
+		if (finfo.flags & fElement) == 0 {
+			return nil, fmt.Errorf("xml: %s chain not valid with %s flag", tag, strings.Join(tokens[1:], ","))
+		}
+		finfo.parents = parents[:len(parents)-1]
+	}
+
+	// If the field type has an XMLName field, the names must match
+	// so that the behavior of both marshalling and unmarshalling
+	// is straightforward and unambiguous.
+	if finfo.flags&fElement != 0 {
+		ftyp := f.Type
+		xmlname := lookupXMLName(ftyp)
+		if xmlname != nil && xmlname.name != finfo.name {
+			return nil, fmt.Errorf("xml: name %q in tag of %s.%s conflicts with name %q in %s.XMLName",
+				finfo.name, typ, f.Name, xmlname.name, ftyp)
+		}
+	}
+	return finfo, nil
+}
+
+// lookupXMLName returns the fieldInfo for typ's XMLName field
+// in case it exists and has a valid xml field tag, otherwise
+// it returns nil.
+func lookupXMLName(typ reflect.Type) (xmlname *fieldInfo) {
+	for typ.Kind() == reflect.Ptr {
+		typ = typ.Elem()
+	}
+	if typ.Kind() != reflect.Struct {
+		return nil
+	}
+	for i, n := 0, typ.NumField(); i < n; i++ {
+		f := typ.Field(i)
+		if f.Name != "XMLName" {
+			continue
+		}
+		finfo, err := structFieldInfo(typ, &f)
+		if finfo.name != "" && err == nil {
+			return finfo
+		}
+		// Also consider errors as a non-existent field tag
+		// and let getTypeInfo itself report the error.
+		break
+	}
+	return nil
+}
+
+func min(a, b int) int {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+// addFieldInfo adds finfo to tinfo.fields if there are no
+// conflicts, or if conflicts arise from previous fields that were
+// obtained from deeper embedded structures than finfo. In the latter
+// case, the conflicting entries are dropped.
+// A conflict occurs when the path (parent + name) to a field is
+// itself a prefix of another path, or when two paths match exactly.
+// It is okay for field paths to share a common, shorter prefix.
+func addFieldInfo(typ reflect.Type, tinfo *typeInfo, newf *fieldInfo) error {
+	var conflicts []int
+Loop:
+	// First, figure all conflicts. Most working code will have none.
+	for i := range tinfo.fields {
+		oldf := &tinfo.fields[i]
+		if oldf.flags&fMode != newf.flags&fMode {
+			continue
+		}
+		if oldf.xmlns != "" && newf.xmlns != "" && oldf.xmlns != newf.xmlns {
+			continue
+		}
+		minl := min(len(newf.parents), len(oldf.parents))
+		for p := 0; p < minl; p++ {
+			if oldf.parents[p] != newf.parents[p] {
+				continue Loop
+			}
+		}
+		if len(oldf.parents) > len(newf.parents) {
+			if oldf.parents[len(newf.parents)] == newf.name {
+				conflicts = append(conflicts, i)
+			}
+		} else if len(oldf.parents) < len(newf.parents) {
+			if newf.parents[len(oldf.parents)] == oldf.name {
+				conflicts = append(conflicts, i)
+			}
+		} else {
+			if newf.name == oldf.name {
+				conflicts = append(conflicts, i)
+			}
+		}
+	}
+	// Without conflicts, add the new field and return.
+	if conflicts == nil {
+		tinfo.fields = append(tinfo.fields, *newf)
+		return nil
+	}
+
+	// If any conflict is shallower, ignore the new field.
+	// This matches the Go field resolution on embedding.
+	for _, i := range conflicts {
+		if len(tinfo.fields[i].idx) < len(newf.idx) {
+			return nil
+		}
+	}
+
+	// Otherwise, if any of them is at the same depth level, it's an error.
+	for _, i := range conflicts {
+		oldf := &tinfo.fields[i]
+		if len(oldf.idx) == len(newf.idx) {
+			f1 := typ.FieldByIndex(oldf.idx)
+			f2 := typ.FieldByIndex(newf.idx)
+			return &TagPathError{typ, f1.Name, f1.Tag.Get("xml"), f2.Name, f2.Tag.Get("xml")}
+		}
+	}
+
+	// Otherwise, the new field is shallower, and thus takes precedence,
+	// so drop the conflicting fields from tinfo and append the new one.
+	for c := len(conflicts) - 1; c >= 0; c-- {
+		i := conflicts[c]
+		copy(tinfo.fields[i:], tinfo.fields[i+1:])
+		tinfo.fields = tinfo.fields[:len(tinfo.fields)-1]
+	}
+	tinfo.fields = append(tinfo.fields, *newf)
+	return nil
+}
+
+// A TagPathError represents an error in the unmarshalling process
+// caused by the use of field tags with conflicting paths.
+type TagPathError struct {
+	Struct       reflect.Type
+	Field1, Tag1 string
+	Field2, Tag2 string
+}
+
+func (e *TagPathError) Error() string {
+	return fmt.Sprintf("%s field %q with tag %q conflicts with field %q with tag %q", e.Struct, e.Field1, e.Tag1, e.Field2, e.Tag2)
+}
+
+// value returns v's field value corresponding to finfo.
+// It's equivalent to v.FieldByIndex(finfo.idx), but initializes
+// and dereferences pointers as necessary.
+func (finfo *fieldInfo) value(v reflect.Value) reflect.Value {
+	for i, x := range finfo.idx {
+		if i > 0 {
+			t := v.Type()
+			if t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Struct {
+				if v.IsNil() {
+					v.Set(reflect.New(v.Type().Elem()))
+				}
+				v = v.Elem()
+			}
+		}
+		v = v.Field(x)
+	}
+	return v
+}

endpoints/drive/webdav/internal/xml/xml_test.go

@@ -0,0 +1,752 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xml
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+const testInput = `
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<body xmlns:foo="ns1" xmlns="ns2" xmlns:tag="ns3" ` +
+	"\r\n\t" + `  >
+  <hello lang="en">World &lt;&gt;&apos;&quot; &#x767d;&#40300;翔</hello>
+  <query>&何; &is-it;</query>
+  <goodbye />
+  <outer foo:attr="value" xmlns:tag="ns4">
+    <inner/>
+  </outer>
+  <tag:name>
+    <![CDATA[Some text here.]]>
+  </tag:name>
+</body><!-- missing final newline -->`
+
+var testEntity = map[string]string{"何": "What", "is-it": "is it?"}
+
+var rawTokens = []Token{
+	CharData("\n"),
+	ProcInst{"xml", []byte(`version="1.0" encoding="UTF-8"`)},
+	CharData("\n"),
+	Directive(`DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"`),
+	CharData("\n"),
+	StartElement{Name{"", "body"}, []Attr{{Name{"xmlns", "foo"}, "ns1"}, {Name{"", "xmlns"}, "ns2"}, {Name{"xmlns", "tag"}, "ns3"}}},
+	CharData("\n  "),
+	StartElement{Name{"", "hello"}, []Attr{{Name{"", "lang"}, "en"}}},
+	CharData("World <>'\" 白鵬翔"),
+	EndElement{Name{"", "hello"}},
+	CharData("\n  "),
+	StartElement{Name{"", "query"}, []Attr{}},
+	CharData("What is it?"),
+	EndElement{Name{"", "query"}},
+	CharData("\n  "),
+	StartElement{Name{"", "goodbye"}, []Attr{}},
+	EndElement{Name{"", "goodbye"}},
+	CharData("\n  "),
+	StartElement{Name{"", "outer"}, []Attr{{Name{"foo", "attr"}, "value"}, {Name{"xmlns", "tag"}, "ns4"}}},
+	CharData("\n    "),
+	StartElement{Name{"", "inner"}, []Attr{}},
+	EndElement{Name{"", "inner"}},
+	CharData("\n  "),
+	EndElement{Name{"", "outer"}},
+	CharData("\n  "),
+	StartElement{Name{"tag", "name"}, []Attr{}},
+	CharData("\n    "),
+	CharData("Some text here."),
+	CharData("\n  "),
+	EndElement{Name{"tag", "name"}},
+	CharData("\n"),
+	EndElement{Name{"", "body"}},
+	Comment(" missing final newline "),
+}
+
+var cookedTokens = []Token{
+	CharData("\n"),
+	ProcInst{"xml", []byte(`version="1.0" encoding="UTF-8"`)},
+	CharData("\n"),
+	Directive(`DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"`),
+	CharData("\n"),
+	StartElement{Name{"ns2", "body"}, []Attr{{Name{"xmlns", "foo"}, "ns1"}, {Name{"", "xmlns"}, "ns2"}, {Name{"xmlns", "tag"}, "ns3"}}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "hello"}, []Attr{{Name{"", "lang"}, "en"}}},
+	CharData("World <>'\" 白鵬翔"),
+	EndElement{Name{"ns2", "hello"}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "query"}, []Attr{}},
+	CharData("What is it?"),
+	EndElement{Name{"ns2", "query"}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "goodbye"}, []Attr{}},
+	EndElement{Name{"ns2", "goodbye"}},
+	CharData("\n  "),
+	StartElement{Name{"ns2", "outer"}, []Attr{{Name{"ns1", "attr"}, "value"}, {Name{"xmlns", "tag"}, "ns4"}}},
+	CharData("\n    "),
+	StartElement{Name{"ns2", "inner"}, []Attr{}},
+	EndElement{Name{"ns2", "inner"}},
+	CharData("\n  "),
+	EndElement{Name{"ns2", "outer"}},
+	CharData("\n  "),
+	StartElement{Name{"ns3", "name"}, []Attr{}},
+	CharData("\n    "),
+	CharData("Some text here."),
+	CharData("\n  "),
+	EndElement{Name{"ns3", "name"}},
+	CharData("\n"),
+	EndElement{Name{"ns2", "body"}},
+	Comment(" missing final newline "),
+}
+
+const testInputAltEncoding = `
+<?xml version="1.0" encoding="x-testing-uppercase"?>
+<TAG>VALUE</TAG>`
+
+var rawTokensAltEncoding = []Token{
+	CharData("\n"),
+	ProcInst{"xml", []byte(`version="1.0" encoding="x-testing-uppercase"`)},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("value"),
+	EndElement{Name{"", "tag"}},
+}
+
+var xmlInput = []string{
+	// unexpected EOF cases
+	"<",
+	"<t",
+	"<t ",
+	"<t/",
+	"<!",
+	"<!-",
+	"<!--",
+	"<!--c-",
+	"<!--c--",
+	"<!d",
+	"<t></",
+	"<t></t",
+	"<?",
+	"<?p",
+	"<t a",
+	"<t a=",
+	"<t a='",
+	"<t a=''",
+	"<t/><![",
+	"<t/><![C",
+	"<t/><![CDATA[d",
+	"<t/><![CDATA[d]",
+	"<t/><![CDATA[d]]",
+
+	// other Syntax errors
+	"<>",
+	"<t/a",
+	"<0 />",
+	"<?0 >",
+	//	"<!0 >",	// let the Token() caller handle
+	"</0>",
+	"<t 0=''>",
+	"<t a='&'>",
+	"<t a='<'>",
+	"<t>&nbspc;</t>",
+	"<t a>",
+	"<t a=>",
+	"<t a=v>",
+	//	"<![CDATA[d]]>",	// let the Token() caller handle
+	"<t></e>",
+	"<t></>",
+	"<t></t!",
+	"<t>cdata]]></t>",
+}
+
+func TestRawToken(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInput))
+	d.Entity = testEntity
+	testRawToken(t, d, testInput, rawTokens)
+}
+
+const nonStrictInput = `
+<tag>non&entity</tag>
+<tag>&unknown;entity</tag>
+<tag>&#123</tag>
+<tag>&#zzz;</tag>
+<tag>&なまえ3;</tag>
+<tag>&lt-gt;</tag>
+<tag>&;</tag>
+<tag>&0a;</tag>
+`
+
+var nonStringEntity = map[string]string{"": "oops!", "0a": "oops!"}
+
+var nonStrictTokens = []Token{
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("non&entity"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&unknown;entity"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&#123"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&#zzz;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&なまえ3;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&lt-gt;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+	StartElement{Name{"", "tag"}, []Attr{}},
+	CharData("&0a;"),
+	EndElement{Name{"", "tag"}},
+	CharData("\n"),
+}
+
+func TestNonStrictRawToken(t *testing.T) {
+	d := NewDecoder(strings.NewReader(nonStrictInput))
+	d.Strict = false
+	testRawToken(t, d, nonStrictInput, nonStrictTokens)
+}
+
+type downCaser struct {
+	t *testing.T
+	r io.ByteReader
+}
+
+func (d *downCaser) ReadByte() (c byte, err error) {
+	c, err = d.r.ReadByte()
+	if c >= 'A' && c <= 'Z' {
+		c += 'a' - 'A'
+	}
+	return
+}
+
+func (d *downCaser) Read(p []byte) (int, error) {
+	d.t.Fatalf("unexpected Read call on downCaser reader")
+	panic("unreachable")
+}
+
+func TestRawTokenAltEncoding(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInputAltEncoding))
+	d.CharsetReader = func(charset string, input io.Reader) (io.Reader, error) {
+		if charset != "x-testing-uppercase" {
+			t.Fatalf("unexpected charset %q", charset)
+		}
+		return &downCaser{t, input.(io.ByteReader)}, nil
+	}
+	testRawToken(t, d, testInputAltEncoding, rawTokensAltEncoding)
+}
+
+func TestRawTokenAltEncodingNoConverter(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInputAltEncoding))
+	token, err := d.RawToken()
+	if token == nil {
+		t.Fatalf("expected a token on first RawToken call")
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	token, err = d.RawToken()
+	if token != nil {
+		t.Errorf("expected a nil token; got %#v", token)
+	}
+	if err == nil {
+		t.Fatalf("expected an error on second RawToken call")
+	}
+	const encoding = "x-testing-uppercase"
+	if !strings.Contains(err.Error(), encoding) {
+		t.Errorf("expected error to contain %q; got error: %v",
+			encoding, err)
+	}
+}
+
+func testRawToken(t *testing.T, d *Decoder, raw string, rawTokens []Token) {
+	lastEnd := int64(0)
+	for i, want := range rawTokens {
+		start := d.InputOffset()
+		have, err := d.RawToken()
+		end := d.InputOffset()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			var shave, swant string
+			if _, ok := have.(CharData); ok {
+				shave = fmt.Sprintf("CharData(%q)", have)
+			} else {
+				shave = fmt.Sprintf("%#v", have)
+			}
+			if _, ok := want.(CharData); ok {
+				swant = fmt.Sprintf("CharData(%q)", want)
+			} else {
+				swant = fmt.Sprintf("%#v", want)
+			}
+			t.Errorf("token %d = %s, want %s", i, shave, swant)
+		}
+
+		// Check that InputOffset returned actual token.
+		switch {
+		case start < lastEnd:
+			t.Errorf("token %d: position [%d,%d) for %T is before previous token", i, start, end, have)
+		case start >= end:
+			// Special case: EndElement can be synthesized.
+			if start == end && end == lastEnd {
+				break
+			}
+			t.Errorf("token %d: position [%d,%d) for %T is empty", i, start, end, have)
+		case end > int64(len(raw)):
+			t.Errorf("token %d: position [%d,%d) for %T extends beyond input", i, start, end, have)
+		default:
+			text := raw[start:end]
+			if strings.ContainsAny(text, "<>") && (!strings.HasPrefix(text, "<") || !strings.HasSuffix(text, ">")) {
+				t.Errorf("token %d: misaligned raw token %#q for %T", i, text, have)
+			}
+		}
+		lastEnd = end
+	}
+}
+
+// Ensure that directives (specifically !DOCTYPE) include the complete
+// text of any nested directives, noting that < and > do not change
+// nesting depth if they are in single or double quotes.
+
+var nestedDirectivesInput = `
+<!DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]>
+<!DOCTYPE [<!ENTITY xlt ">">]>
+<!DOCTYPE [<!ENTITY xlt "<">]>
+<!DOCTYPE [<!ENTITY xlt '>'>]>
+<!DOCTYPE [<!ENTITY xlt '<'>]>
+<!DOCTYPE [<!ENTITY xlt '">'>]>
+<!DOCTYPE [<!ENTITY xlt "'<">]>
+`
+
+var nestedDirectivesTokens = []Token{
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt ">">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt "<">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt '>'>]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt '<'>]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt '">'>]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY xlt "'<">]`),
+	CharData("\n"),
+}
+
+func TestNestedDirectives(t *testing.T) {
+	d := NewDecoder(strings.NewReader(nestedDirectivesInput))
+
+	for i, want := range nestedDirectivesTokens {
+		have, err := d.Token()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("token %d = %#v want %#v", i, have, want)
+		}
+	}
+}
+
+func TestToken(t *testing.T) {
+	d := NewDecoder(strings.NewReader(testInput))
+	d.Entity = testEntity
+
+	for i, want := range cookedTokens {
+		have, err := d.Token()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("token %d = %#v want %#v", i, have, want)
+		}
+	}
+}
+
+func TestSyntax(t *testing.T) {
+	for i := range xmlInput {
+		d := NewDecoder(strings.NewReader(xmlInput[i]))
+		var err error
+		for _, err = d.Token(); err == nil; _, err = d.Token() {
+		}
+		if _, ok := err.(*SyntaxError); !ok {
+			t.Fatalf(`xmlInput "%s": expected SyntaxError not received`, xmlInput[i])
+		}
+	}
+}
+
+type allScalars struct {
+	True1     bool
+	True2     bool
+	False1    bool
+	False2    bool
+	Int       int
+	Int8      int8
+	Int16     int16
+	Int32     int32
+	Int64     int64
+	Uint      int
+	Uint8     uint8
+	Uint16    uint16
+	Uint32    uint32
+	Uint64    uint64
+	Uintptr   uintptr
+	Float32   float32
+	Float64   float64
+	String    string
+	PtrString *string
+}
+
+var all = allScalars{
+	True1:     true,
+	True2:     true,
+	False1:    false,
+	False2:    false,
+	Int:       1,
+	Int8:      -2,
+	Int16:     3,
+	Int32:     -4,
+	Int64:     5,
+	Uint:      6,
+	Uint8:     7,
+	Uint16:    8,
+	Uint32:    9,
+	Uint64:    10,
+	Uintptr:   11,
+	Float32:   13.0,
+	Float64:   14.0,
+	String:    "15",
+	PtrString: &sixteen,
+}
+
+var sixteen = "16"
+
+const testScalarsInput = `<allscalars>
+	<True1>true</True1>
+	<True2>1</True2>
+	<False1>false</False1>
+	<False2>0</False2>
+	<Int>1</Int>
+	<Int8>-2</Int8>
+	<Int16>3</Int16>
+	<Int32>-4</Int32>
+	<Int64>5</Int64>
+	<Uint>6</Uint>
+	<Uint8>7</Uint8>
+	<Uint16>8</Uint16>
+	<Uint32>9</Uint32>
+	<Uint64>10</Uint64>
+	<Uintptr>11</Uintptr>
+	<Float>12.0</Float>
+	<Float32>13.0</Float32>
+	<Float64>14.0</Float64>
+	<String>15</String>
+	<PtrString>16</PtrString>
+</allscalars>`
+
+func TestAllScalars(t *testing.T) {
+	var a allScalars
+	err := Unmarshal([]byte(testScalarsInput), &a)
+
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(a, all) {
+		t.Errorf("have %+v want %+v", a, all)
+	}
+}
+
+type item struct {
+	Field_a string
+}
+
+func TestIssue569(t *testing.T) {
+	data := `<item><Field_a>abcd</Field_a></item>`
+	var i item
+	err := Unmarshal([]byte(data), &i)
+
+	if err != nil || i.Field_a != "abcd" {
+		t.Fatal("Expecting abcd")
+	}
+}
+
+func TestUnquotedAttrs(t *testing.T) {
+	data := "<tag attr=azAZ09:-_\t>"
+	d := NewDecoder(strings.NewReader(data))
+	d.Strict = false
+	token, err := d.Token()
+	if _, ok := err.(*SyntaxError); ok {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if token.(StartElement).Name.Local != "tag" {
+		t.Errorf("Unexpected tag name: %v", token.(StartElement).Name.Local)
+	}
+	attr := token.(StartElement).Attr[0]
+	if attr.Value != "azAZ09:-_" {
+		t.Errorf("Unexpected attribute value: %v", attr.Value)
+	}
+	if attr.Name.Local != "attr" {
+		t.Errorf("Unexpected attribute name: %v", attr.Name.Local)
+	}
+}
+
+func TestValuelessAttrs(t *testing.T) {
+	tests := [][3]string{
+		{"<p nowrap>", "p", "nowrap"},
+		{"<p nowrap >", "p", "nowrap"},
+		{"<input checked/>", "input", "checked"},
+		{"<input checked />", "input", "checked"},
+	}
+	for _, test := range tests {
+		d := NewDecoder(strings.NewReader(test[0]))
+		d.Strict = false
+		token, err := d.Token()
+		if _, ok := err.(*SyntaxError); ok {
+			t.Errorf("Unexpected error: %v", err)
+		}
+		if token.(StartElement).Name.Local != test[1] {
+			t.Errorf("Unexpected tag name: %v", token.(StartElement).Name.Local)
+		}
+		attr := token.(StartElement).Attr[0]
+		if attr.Value != test[2] {
+			t.Errorf("Unexpected attribute value: %v", attr.Value)
+		}
+		if attr.Name.Local != test[2] {
+			t.Errorf("Unexpected attribute name: %v", attr.Name.Local)
+		}
+	}
+}
+
+func TestCopyTokenCharData(t *testing.T) {
+	data := []byte("same data")
+	var tok1 Token = CharData(data)
+	tok2 := CopyToken(tok1)
+	if !reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(CharData) != CharData")
+	}
+	data[1] = 'o'
+	if reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(CharData) uses same buffer.")
+	}
+}
+
+func TestCopyTokenStartElement(t *testing.T) {
+	elt := StartElement{Name{"", "hello"}, []Attr{{Name{"", "lang"}, "en"}}}
+	var tok1 Token = elt
+	tok2 := CopyToken(tok1)
+	if tok1.(StartElement).Attr[0].Value != "en" {
+		t.Error("CopyToken overwrote Attr[0]")
+	}
+	if !reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(StartElement) != StartElement")
+	}
+	tok1.(StartElement).Attr[0] = Attr{Name{"", "lang"}, "de"}
+	if reflect.DeepEqual(tok1, tok2) {
+		t.Error("CopyToken(CharData) uses same buffer.")
+	}
+}
+
+func TestSyntaxErrorLineNum(t *testing.T) {
+	testInput := "<P>Foo<P>\n\n<P>Bar</>\n"
+	d := NewDecoder(strings.NewReader(testInput))
+	var err error
+	for _, err = d.Token(); err == nil; _, err = d.Token() {
+	}
+	synerr, ok := err.(*SyntaxError)
+	if !ok {
+		t.Error("Expected SyntaxError.")
+	}
+	if synerr.Line != 3 {
+		t.Error("SyntaxError didn't have correct line number.")
+	}
+}
+
+func TestTrailingRawToken(t *testing.T) {
+	input := `<FOO></FOO>  `
+	d := NewDecoder(strings.NewReader(input))
+	var err error
+	for _, err = d.RawToken(); err == nil; _, err = d.RawToken() {
+	}
+	if err != io.EOF {
+		t.Fatalf("d.RawToken() = _, %v, want _, io.EOF", err)
+	}
+}
+
+func TestTrailingToken(t *testing.T) {
+	input := `<FOO></FOO>  `
+	d := NewDecoder(strings.NewReader(input))
+	var err error
+	for _, err = d.Token(); err == nil; _, err = d.Token() {
+	}
+	if err != io.EOF {
+		t.Fatalf("d.Token() = _, %v, want _, io.EOF", err)
+	}
+}
+
+func TestEntityInsideCDATA(t *testing.T) {
+	input := `<test><![CDATA[ &val=foo ]]></test>`
+	d := NewDecoder(strings.NewReader(input))
+	var err error
+	for _, err = d.Token(); err == nil; _, err = d.Token() {
+	}
+	if err != io.EOF {
+		t.Fatalf("d.Token() = _, %v, want _, io.EOF", err)
+	}
+}
+
+var characterTests = []struct {
+	in  string
+	err string
+}{
+	{"\x12<doc/>", "illegal character code U+0012"},
+	{"<?xml version=\"1.0\"?>\x0b<doc/>", "illegal character code U+000B"},
+	{"\xef\xbf\xbe<doc/>", "illegal character code U+FFFE"},
+	{"<?xml version=\"1.0\"?><doc>\r\n<hiya/>\x07<toots/></doc>", "illegal character code U+0007"},
+	{"<?xml version=\"1.0\"?><doc \x12='value'>what's up</doc>", "expected attribute name in element"},
+	{"<doc>&abc\x01;</doc>", "invalid character entity &abc (no semicolon)"},
+	{"<doc>&\x01;</doc>", "invalid character entity & (no semicolon)"},
+	{"<doc>&\xef\xbf\xbe;</doc>", "invalid character entity &\uFFFE;"},
+	{"<doc>&hello;</doc>", "invalid character entity &hello;"},
+}
+
+func TestDisallowedCharacters(t *testing.T) {
+
+	for i, tt := range characterTests {
+		d := NewDecoder(strings.NewReader(tt.in))
+		var err error
+
+		for err == nil {
+			_, err = d.Token()
+		}
+		synerr, ok := err.(*SyntaxError)
+		if !ok {
+			t.Fatalf("input %d d.Token() = _, %v, want _, *SyntaxError", i, err)
+		}
+		if synerr.Msg != tt.err {
+			t.Fatalf("input %d synerr.Msg wrong: want %q, got %q", i, tt.err, synerr.Msg)
+		}
+	}
+}
+
+type procInstEncodingTest struct {
+	expect, got string
+}
+
+var procInstTests = []struct {
+	input  string
+	expect [2]string
+}{
+	{`version="1.0" encoding="utf-8"`, [2]string{"1.0", "utf-8"}},
+	{`version="1.0" encoding='utf-8'`, [2]string{"1.0", "utf-8"}},
+	{`version="1.0" encoding='utf-8' `, [2]string{"1.0", "utf-8"}},
+	{`version="1.0" encoding=utf-8`, [2]string{"1.0", ""}},
+	{`encoding="FOO" `, [2]string{"", "FOO"}},
+}
+
+func TestProcInstEncoding(t *testing.T) {
+	for _, test := range procInstTests {
+		if got := procInst("version", test.input); got != test.expect[0] {
+			t.Errorf("procInst(version, %q) = %q; want %q", test.input, got, test.expect[0])
+		}
+		if got := procInst("encoding", test.input); got != test.expect[1] {
+			t.Errorf("procInst(encoding, %q) = %q; want %q", test.input, got, test.expect[1])
+		}
+	}
+}
+
+// Ensure that directives with comments include the complete
+// text of any nested directives.
+
+var directivesWithCommentsInput = `
+<!DOCTYPE [<!-- a comment --><!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]>
+<!DOCTYPE [<!ENTITY go "Golang"><!-- a comment-->]>
+<!DOCTYPE <!-> <!> <!----> <!-->--> <!--->--> [<!ENTITY go "Golang"><!-- a comment-->]>
+`
+
+var directivesWithCommentsTokens = []Token{
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE [<!ENTITY go "Golang">]`),
+	CharData("\n"),
+	Directive(`DOCTYPE <!-> <!>    [<!ENTITY go "Golang">]`),
+	CharData("\n"),
+}
+
+func TestDirectivesWithComments(t *testing.T) {
+	d := NewDecoder(strings.NewReader(directivesWithCommentsInput))
+
+	for i, want := range directivesWithCommentsTokens {
+		have, err := d.Token()
+		if err != nil {
+			t.Fatalf("token %d: unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(have, want) {
+			t.Errorf("token %d = %#v want %#v", i, have, want)
+		}
+	}
+}
+
+// Writer whose Write method always returns an error.
+type errWriter struct{}
+
+func (errWriter) Write(p []byte) (n int, err error) { return 0, fmt.Errorf("unwritable") }
+
+func TestEscapeTextIOErrors(t *testing.T) {
+	expectErr := "unwritable"
+	err := EscapeText(errWriter{}, []byte{'A'})
+
+	if err == nil || err.Error() != expectErr {
+		t.Errorf("have %v, want %v", err, expectErr)
+	}
+}
+
+func TestEscapeTextInvalidChar(t *testing.T) {
+	input := []byte("A \x00 terminated string.")
+	expected := "A \uFFFD terminated string."
+
+	buff := new(bytes.Buffer)
+	if err := EscapeText(buff, input); err != nil {
+		t.Fatalf("have %v, want nil", err)
+	}
+	text := buff.String()
+
+	if text != expected {
+		t.Errorf("have %v, want %v", text, expected)
+	}
+}
+
+func TestIssue5880(t *testing.T) {
+	type T []byte
+	data, err := Marshal(T{192, 168, 0, 1})
+	if err != nil {
+		t.Errorf("Marshal error: %v", err)
+	}
+	if !utf8.Valid(data) {
+		t.Errorf("Marshal generated invalid UTF-8: %x", data)
+	}
+}

endpoints/drive/webdav/litmus_test_server.go

@@ -0,0 +1,94 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+// +build ignore
+
+/*
+This program is a server for the WebDAV 'litmus' compliance test at
+http://www.webdav.org/neon/litmus/
+To run the test:
+
+go run litmus_test_server.go
+
+and separately, from the downloaded litmus-xxx directory:
+
+make URL=http://localhost:9999/ check
+*/
+package main
+
+import (
+	"flag"
+	"fmt"
+	"golang.org/x/net/webdav"
+	"log"
+	"net/http"
+	"net/url"
+)
+
+var port = flag.Int("port", 9999, "server port")
+
+func main() {
+	flag.Parse()
+	log.SetFlags(0)
+	h := &webdav.Handler{
+		FileSystem: webdav.NewMemFS(),
+		LockSystem: webdav.NewMemLS(),
+		Logger: func(r *http.Request, err error) {
+			litmus := r.Header.Get("X-Litmus")
+			if len(litmus) > 19 {
+				litmus = litmus[:16] + "..."
+			}
+
+			switch r.Method {
+			case "COPY", "MOVE":
+				dst := ""
+				if u, err := url.Parse(r.Header.Get("Destination")); err == nil {
+					dst = u.Path
+				}
+				o := r.Header.Get("Overwrite")
+				log.Printf("%-20s%-10s%-30s%-30so=%-2s%v", litmus, r.Method, r.URL.Path, dst, o, err)
+			default:
+				log.Printf("%-20s%-10s%-30s%v", litmus, r.Method, r.URL.Path, err)
+			}
+		},
+	}
+
+	// The next line would normally be:
+	//	http.Handle("/", h)
+	// but we wrap that HTTP handler h to cater for a special case.
+	//
+	// The propfind_invalid2 litmus test case expects an empty namespace prefix
+	// declaration to be an error. The FAQ in the webdav litmus test says:
+	//
+	// "What does the "propfind_invalid2" test check for?...
+	//
+	// If a request was sent with an XML body which included an empty namespace
+	// prefix declaration (xmlns:ns1=""), then the server must reject that with
+	// a "400 Bad Request" response, as it is invalid according to the XML
+	// Namespace specification."
+	//
+	// On the other hand, the Go standard library's encoding/xml package
+	// accepts an empty xmlns namespace, as per the discussion at
+	// https://github.com/golang/go/issues/8068
+	//
+	// Empty namespaces seem disallowed in the second (2006) edition of the XML
+	// standard, but allowed in a later edition. The grammar differs between
+	// http://www.w3.org/TR/2006/REC-xml-names-20060816/#ns-decl and
+	// http://www.w3.org/TR/REC-xml-names/#dt-prefix
+	//
+	// Thus, we assume that the propfind_invalid2 test is obsolete, and
+	// hard-code the 400 Bad Request response that the test expects.
+	http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("X-Litmus") == "props: 3 (propfind_invalid2)" {
+			http.Error(w, "400 Bad Request", http.StatusBadRequest)
+			return
+		}
+		h.ServeHTTP(w, r)
+	}))
+
+	addr := fmt.Sprintf(":%d", *port)
+	log.Printf("Serving %v", addr)
+	log.Fatal(http.ListenAndServe(addr, nil))
+}

endpoints/drive/webdav/lock.go

@@ -0,0 +1,445 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"container/heap"
+	"errors"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	// ErrConfirmationFailed is returned by a LockSystem's Confirm method.
+	ErrConfirmationFailed = errors.New("webdav: confirmation failed")
+	// ErrForbidden is returned by a LockSystem's Unlock method.
+	ErrForbidden = errors.New("webdav: forbidden")
+	// ErrLocked is returned by a LockSystem's Create, Refresh and Unlock methods.
+	ErrLocked = errors.New("webdav: locked")
+	// ErrNoSuchLock is returned by a LockSystem's Refresh and Unlock methods.
+	ErrNoSuchLock = errors.New("webdav: no such lock")
+)
+
+// Condition can match a WebDAV resource, based on a token or ETag.
+// Exactly one of Token and ETag should be non-empty.
+type Condition struct {
+	Not   bool
+	Token string
+	ETag  string
+}
+
+// LockSystem manages access to a collection of named resources. The elements
+// in a lock name are separated by slash ('/', U+002F) characters, regardless
+// of host operating system convention.
+type LockSystem interface {
+	// Confirm confirms that the caller can claim all of the locks specified by
+	// the given conditions, and that holding the union of all of those locks
+	// gives exclusive access to all of the named resources. Up to two resources
+	// can be named. Empty names are ignored.
+	//
+	// Exactly one of release and err will be non-nil. If release is non-nil,
+	// all of the requested locks are held until release is called. Calling
+	// release does not unlock the lock, in the WebDAV UNLOCK sense, but once
+	// Confirm has confirmed that a lock claim is valid, that lock cannot be
+	// Confirmed again until it has been released.
+	//
+	// If Confirm returns ErrConfirmationFailed then the Handler will continue
+	// to try any other set of locks presented (a WebDAV HTTP request can
+	// present more than one set of locks). If it returns any other non-nil
+	// error, the Handler will write a "500 Internal Server Error" HTTP status.
+	Confirm(now time.Time, name0, name1 string, conditions ...Condition) (release func(), err error)
+
+	// Create creates a lock with the given depth, duration, owner and root
+	// (name). The depth will either be negative (meaning infinite) or zero.
+	//
+	// If Create returns ErrLocked then the Handler will write a "423 Locked"
+	// HTTP status. If it returns any other non-nil error, the Handler will
+	// write a "500 Internal Server Error" HTTP status.
+	//
+	// See http://www.webdav.org/specs/rfc4918.html#rfc.section.9.10.6 for
+	// when to use each error.
+	//
+	// The token returned identifies the created lock. It should be an absolute
+	// URI as defined by RFC 3986, Section 4.3. In particular, it should not
+	// contain whitespace.
+	Create(now time.Time, details LockDetails) (token string, err error)
+
+	// Refresh refreshes the lock with the given token.
+	//
+	// If Refresh returns ErrLocked then the Handler will write a "423 Locked"
+	// HTTP Status. If Refresh returns ErrNoSuchLock then the Handler will write
+	// a "412 Precondition Failed" HTTP Status. If it returns any other non-nil
+	// error, the Handler will write a "500 Internal Server Error" HTTP status.
+	//
+	// See http://www.webdav.org/specs/rfc4918.html#rfc.section.9.10.6 for
+	// when to use each error.
+	Refresh(now time.Time, token string, duration time.Duration) (LockDetails, error)
+
+	// Unlock unlocks the lock with the given token.
+	//
+	// If Unlock returns ErrForbidden then the Handler will write a "403
+	// Forbidden" HTTP Status. If Unlock returns ErrLocked then the Handler
+	// will write a "423 Locked" HTTP status. If Unlock returns ErrNoSuchLock
+	// then the Handler will write a "409 Conflict" HTTP Status. If it returns
+	// any other non-nil error, the Handler will write a "500 Internal Server
+	// Error" HTTP status.
+	//
+	// See http://www.webdav.org/specs/rfc4918.html#rfc.section.9.11.1 for
+	// when to use each error.
+	Unlock(now time.Time, token string) error
+}
+
+// LockDetails are a lock's metadata.
+type LockDetails struct {
+	// Root is the root resource name being locked. For a zero-depth lock, the
+	// root is the only resource being locked.
+	Root string
+	// Duration is the lock timeout. A negative duration means infinite.
+	Duration time.Duration
+	// OwnerXML is the verbatim <owner> XML given in a LOCK HTTP request.
+	//
+	// TODO: does the "verbatim" nature play well with XML namespaces?
+	// Does the OwnerXML field need to have more structure? See
+	// https://codereview.appspot.com/175140043/#msg2
+	OwnerXML string
+	// ZeroDepth is whether the lock has zero depth. If it does not have zero
+	// depth, it has infinite depth.
+	ZeroDepth bool
+}
+
+// NewMemLS returns a new in-memory LockSystem.
+func NewMemLS() LockSystem {
+	return &memLS{
+		byName:  make(map[string]*memLSNode),
+		byToken: make(map[string]*memLSNode),
+		gen:     uint64(time.Now().Unix()),
+	}
+}
+
+type memLS struct {
+	mu      sync.Mutex
+	byName  map[string]*memLSNode
+	byToken map[string]*memLSNode
+	gen     uint64
+	// byExpiry only contains those nodes whose LockDetails have a finite
+	// Duration and are yet to expire.
+	byExpiry byExpiry
+}
+
+func (m *memLS) nextToken() string {
+	m.gen++
+	return strconv.FormatUint(m.gen, 10)
+}
+
+func (m *memLS) collectExpiredNodes(now time.Time) {
+	for len(m.byExpiry) > 0 {
+		if now.Before(m.byExpiry[0].expiry) {
+			break
+		}
+		m.remove(m.byExpiry[0])
+	}
+}
+
+func (m *memLS) Confirm(now time.Time, name0, name1 string, conditions ...Condition) (func(), error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.collectExpiredNodes(now)
+
+	var n0, n1 *memLSNode
+	if name0 != "" {
+		if n0 = m.lookup(slashClean(name0), conditions...); n0 == nil {
+			return nil, ErrConfirmationFailed
+		}
+	}
+	if name1 != "" {
+		if n1 = m.lookup(slashClean(name1), conditions...); n1 == nil {
+			return nil, ErrConfirmationFailed
+		}
+	}
+
+	// Don't hold the same node twice.
+	if n1 == n0 {
+		n1 = nil
+	}
+
+	if n0 != nil {
+		m.hold(n0)
+	}
+	if n1 != nil {
+		m.hold(n1)
+	}
+	return func() {
+		m.mu.Lock()
+		defer m.mu.Unlock()
+		if n1 != nil {
+			m.unhold(n1)
+		}
+		if n0 != nil {
+			m.unhold(n0)
+		}
+	}, nil
+}
+
+// lookup returns the node n that locks the named resource, provided that n
+// matches at least one of the given conditions and that lock isn't held by
+// another party. Otherwise, it returns nil.
+//
+// n may be a parent of the named resource, if n is an infinite depth lock.
+func (m *memLS) lookup(name string, conditions ...Condition) (n *memLSNode) {
+	// TODO: support Condition.Not and Condition.ETag.
+	for _, c := range conditions {
+		n = m.byToken[c.Token]
+		if n == nil || n.held {
+			continue
+		}
+		if name == n.details.Root {
+			return n
+		}
+		if n.details.ZeroDepth {
+			continue
+		}
+		if n.details.Root == "/" || strings.HasPrefix(name, n.details.Root+"/") {
+			return n
+		}
+	}
+	return nil
+}
+
+func (m *memLS) hold(n *memLSNode) {
+	if n.held {
+		panic("webdav: memLS inconsistent held state")
+	}
+	n.held = true
+	if n.details.Duration >= 0 && n.byExpiryIndex >= 0 {
+		heap.Remove(&m.byExpiry, n.byExpiryIndex)
+	}
+}
+
+func (m *memLS) unhold(n *memLSNode) {
+	if !n.held {
+		panic("webdav: memLS inconsistent held state")
+	}
+	n.held = false
+	if n.details.Duration >= 0 {
+		heap.Push(&m.byExpiry, n)
+	}
+}
+
+func (m *memLS) Create(now time.Time, details LockDetails) (string, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.collectExpiredNodes(now)
+	details.Root = slashClean(details.Root)
+
+	if !m.canCreate(details.Root, details.ZeroDepth) {
+		return "", ErrLocked
+	}
+	n := m.create(details.Root)
+	n.token = m.nextToken()
+	m.byToken[n.token] = n
+	n.details = details
+	if n.details.Duration >= 0 {
+		n.expiry = now.Add(n.details.Duration)
+		heap.Push(&m.byExpiry, n)
+	}
+	return n.token, nil
+}
+
+func (m *memLS) Refresh(now time.Time, token string, duration time.Duration) (LockDetails, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.collectExpiredNodes(now)
+
+	n := m.byToken[token]
+	if n == nil {
+		return LockDetails{}, ErrNoSuchLock
+	}
+	if n.held {
+		return LockDetails{}, ErrLocked
+	}
+	if n.byExpiryIndex >= 0 {
+		heap.Remove(&m.byExpiry, n.byExpiryIndex)
+	}
+	n.details.Duration = duration
+	if n.details.Duration >= 0 {
+		n.expiry = now.Add(n.details.Duration)
+		heap.Push(&m.byExpiry, n)
+	}
+	return n.details, nil
+}
+
+func (m *memLS) Unlock(now time.Time, token string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.collectExpiredNodes(now)
+
+	n := m.byToken[token]
+	if n == nil {
+		return ErrNoSuchLock
+	}
+	if n.held {
+		return ErrLocked
+	}
+	m.remove(n)
+	return nil
+}
+
+func (m *memLS) canCreate(name string, zeroDepth bool) bool {
+	return walkToRoot(name, func(name0 string, first bool) bool {
+		n := m.byName[name0]
+		if n == nil {
+			return true
+		}
+		if first {
+			if n.token != "" {
+				// The target node is already locked.
+				return false
+			}
+			if !zeroDepth {
+				// The requested lock depth is infinite, and the fact that n exists
+				// (n != nil) means that a descendent of the target node is locked.
+				return false
+			}
+		} else if n.token != "" && !n.details.ZeroDepth {
+			// An ancestor of the target node is locked with infinite depth.
+			return false
+		}
+		return true
+	})
+}
+
+func (m *memLS) create(name string) (ret *memLSNode) {
+	walkToRoot(name, func(name0 string, first bool) bool {
+		n := m.byName[name0]
+		if n == nil {
+			n = &memLSNode{
+				details: LockDetails{
+					Root: name0,
+				},
+				byExpiryIndex: -1,
+			}
+			m.byName[name0] = n
+		}
+		n.refCount++
+		if first {
+			ret = n
+		}
+		return true
+	})
+	return ret
+}
+
+func (m *memLS) remove(n *memLSNode) {
+	delete(m.byToken, n.token)
+	n.token = ""
+	walkToRoot(n.details.Root, func(name0 string, first bool) bool {
+		x := m.byName[name0]
+		x.refCount--
+		if x.refCount == 0 {
+			delete(m.byName, name0)
+		}
+		return true
+	})
+	if n.byExpiryIndex >= 0 {
+		heap.Remove(&m.byExpiry, n.byExpiryIndex)
+	}
+}
+
+func walkToRoot(name string, f func(name0 string, first bool) bool) bool {
+	for first := true; ; first = false {
+		if !f(name, first) {
+			return false
+		}
+		if name == "/" {
+			break
+		}
+		name = name[:strings.LastIndex(name, "/")]
+		if name == "" {
+			name = "/"
+		}
+	}
+	return true
+}
+
+type memLSNode struct {
+	// details are the lock metadata. Even if this node's name is not explicitly locked,
+	// details.Root will still equal the node's name.
+	details LockDetails
+	// token is the unique identifier for this node's lock. An empty token means that
+	// this node is not explicitly locked.
+	token string
+	// refCount is the number of self-or-descendent nodes that are explicitly locked.
+	refCount int
+	// expiry is when this node's lock expires.
+	expiry time.Time
+	// byExpiryIndex is the index of this node in memLS.byExpiry. It is -1
+	// if this node does not expire, or has expired.
+	byExpiryIndex int
+	// held is whether this node's lock is actively held by a Confirm call.
+	held bool
+}
+
+type byExpiry []*memLSNode
+
+func (b *byExpiry) Len() int {
+	return len(*b)
+}
+
+func (b *byExpiry) Less(i, j int) bool {
+	return (*b)[i].expiry.Before((*b)[j].expiry)
+}
+
+func (b *byExpiry) Swap(i, j int) {
+	(*b)[i], (*b)[j] = (*b)[j], (*b)[i]
+	(*b)[i].byExpiryIndex = i
+	(*b)[j].byExpiryIndex = j
+}
+
+func (b *byExpiry) Push(x interface{}) {
+	n := x.(*memLSNode)
+	n.byExpiryIndex = len(*b)
+	*b = append(*b, n)
+}
+
+func (b *byExpiry) Pop() interface{} {
+	i := len(*b) - 1
+	n := (*b)[i]
+	(*b)[i] = nil
+	n.byExpiryIndex = -1
+	*b = (*b)[:i]
+	return n
+}
+
+const infiniteTimeout = -1
+
+// parseTimeout parses the Timeout HTTP header, as per section 10.7. If s is
+// empty, an infiniteTimeout is returned.
+func parseTimeout(s string) (time.Duration, error) {
+	if s == "" {
+		return infiniteTimeout, nil
+	}
+	if i := strings.IndexByte(s, ','); i >= 0 {
+		s = s[:i]
+	}
+	s = strings.TrimSpace(s)
+	if s == "Infinite" {
+		return infiniteTimeout, nil
+	}
+	const pre = "Second-"
+	if !strings.HasPrefix(s, pre) {
+		return 0, errInvalidTimeout
+	}
+	s = s[len(pre):]
+	if s == "" || s[0] < '0' || '9' < s[0] {
+		return 0, errInvalidTimeout
+	}
+	n, err := strconv.ParseInt(s, 10, 64)
+	if err != nil || 1<<32-1 < n {
+		return 0, errInvalidTimeout
+	}
+	return time.Duration(n) * time.Second, nil
+}

endpoints/drive/webdav/lock_test.go

@@ -0,0 +1,735 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"fmt"
+	"math/rand"
+	"path"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestWalkToRoot(t *testing.T) {
+	testCases := []struct {
+		name string
+		want []string
+	}{{
+		"/a/b/c/d",
+		[]string{
+			"/a/b/c/d",
+			"/a/b/c",
+			"/a/b",
+			"/a",
+			"/",
+		},
+	}, {
+		"/a",
+		[]string{
+			"/a",
+			"/",
+		},
+	}, {
+		"/",
+		[]string{
+			"/",
+		},
+	}}
+
+	for _, tc := range testCases {
+		var got []string
+		if !walkToRoot(tc.name, func(name0 string, first bool) bool {
+			if first != (len(got) == 0) {
+				t.Errorf("name=%q: first=%t but len(got)==%d", tc.name, first, len(got))
+				return false
+			}
+			got = append(got, name0)
+			return true
+		}) {
+			continue
+		}
+		if !reflect.DeepEqual(got, tc.want) {
+			t.Errorf("name=%q:\ngot  %q\nwant %q", tc.name, got, tc.want)
+		}
+	}
+}
+
+var lockTestDurations = []time.Duration{
+	infiniteTimeout, // infiniteTimeout means to never expire.
+	0,               // A zero duration means to expire immediately.
+	100 * time.Hour, // A very large duration will not expire in these tests.
+}
+
+// lockTestNames are the names of a set of mutually compatible locks. For each
+// name fragment:
+//   - _ means no explicit lock.
+//   - i means an infinite-depth lock,
+//   - z means a zero-depth lock,
+var lockTestNames = []string{
+	"/_/_/_/_/z",
+	"/_/_/i",
+	"/_/z",
+	"/_/z/i",
+	"/_/z/z",
+	"/_/z/_/i",
+	"/_/z/_/z",
+	"/i",
+	"/z",
+	"/z/_/i",
+	"/z/_/z",
+}
+
+func lockTestZeroDepth(name string) bool {
+	switch name[len(name)-1] {
+	case 'i':
+		return false
+	case 'z':
+		return true
+	}
+	panic(fmt.Sprintf("lock name %q did not end with 'i' or 'z'", name))
+}
+
+func TestMemLSCanCreate(t *testing.T) {
+	now := time.Unix(0, 0)
+	m := NewMemLS().(*memLS)
+
+	for _, name := range lockTestNames {
+		_, err := m.Create(now, LockDetails{
+			Root:      name,
+			Duration:  infiniteTimeout,
+			ZeroDepth: lockTestZeroDepth(name),
+		})
+		if err != nil {
+			t.Fatalf("creating lock for %q: %v", name, err)
+		}
+	}
+
+	wantCanCreate := func(name string, zeroDepth bool) bool {
+		for _, n := range lockTestNames {
+			switch {
+			case n == name:
+				// An existing lock has the same name as the proposed lock.
+				return false
+			case strings.HasPrefix(n, name):
+				// An existing lock would be a child of the proposed lock,
+				// which conflicts if the proposed lock has infinite depth.
+				if !zeroDepth {
+					return false
+				}
+			case strings.HasPrefix(name, n):
+				// An existing lock would be an ancestor of the proposed lock,
+				// which conflicts if the ancestor has infinite depth.
+				if n[len(n)-1] == 'i' {
+					return false
+				}
+			}
+		}
+		return true
+	}
+
+	var check func(int, string)
+	check = func(recursion int, name string) {
+		for _, zeroDepth := range []bool{false, true} {
+			got := m.canCreate(name, zeroDepth)
+			want := wantCanCreate(name, zeroDepth)
+			if got != want {
+				t.Errorf("canCreate name=%q zeroDepth=%t: got %t, want %t", name, zeroDepth, got, want)
+			}
+		}
+		if recursion == 6 {
+			return
+		}
+		if name != "/" {
+			name += "/"
+		}
+		for _, c := range "_iz" {
+			check(recursion+1, name+string(c))
+		}
+	}
+	check(0, "/")
+}
+
+func TestMemLSLookup(t *testing.T) {
+	now := time.Unix(0, 0)
+	m := NewMemLS().(*memLS)
+
+	badToken := m.nextToken()
+	t.Logf("badToken=%q", badToken)
+
+	for _, name := range lockTestNames {
+		token, err := m.Create(now, LockDetails{
+			Root:      name,
+			Duration:  infiniteTimeout,
+			ZeroDepth: lockTestZeroDepth(name),
+		})
+		if err != nil {
+			t.Fatalf("creating lock for %q: %v", name, err)
+		}
+		t.Logf("%-15q -> node=%p token=%q", name, m.byName[name], token)
+	}
+
+	baseNames := append([]string{"/a", "/b/c"}, lockTestNames...)
+	for _, baseName := range baseNames {
+		for _, suffix := range []string{"", "/0", "/1/2/3"} {
+			name := baseName + suffix
+
+			goodToken := ""
+			base := m.byName[baseName]
+			if base != nil && (suffix == "" || !lockTestZeroDepth(baseName)) {
+				goodToken = base.token
+			}
+
+			for _, token := range []string{badToken, goodToken} {
+				if token == "" {
+					continue
+				}
+
+				got := m.lookup(name, Condition{Token: token})
+				want := base
+				if token == badToken {
+					want = nil
+				}
+				if got != want {
+					t.Errorf("name=%-20qtoken=%q (bad=%t): got %p, want %p",
+						name, token, token == badToken, got, want)
+				}
+			}
+		}
+	}
+}
+
+func TestMemLSConfirm(t *testing.T) {
+	now := time.Unix(0, 0)
+	m := NewMemLS().(*memLS)
+	alice, err := m.Create(now, LockDetails{
+		Root:      "/alice",
+		Duration:  infiniteTimeout,
+		ZeroDepth: false,
+	})
+	if err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+
+	tweedle, err := m.Create(now, LockDetails{
+		Root:      "/tweedle",
+		Duration:  infiniteTimeout,
+		ZeroDepth: false,
+	})
+	if err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Create: inconsistent state: %v", err)
+	}
+
+	// Test a mismatch between name and condition.
+	_, err = m.Confirm(now, "/tweedle/dee", "", Condition{Token: alice})
+	if err != ErrConfirmationFailed {
+		t.Fatalf("Confirm (mismatch): got %v, want ErrConfirmationFailed", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Confirm (mismatch): inconsistent state: %v", err)
+	}
+
+	// Test two names (that fall under the same lock) in the one Confirm call.
+	release, err := m.Confirm(now, "/tweedle/dee", "/tweedle/dum", Condition{Token: tweedle})
+	if err != nil {
+		t.Fatalf("Confirm (twins): %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Confirm (twins): inconsistent state: %v", err)
+	}
+	release()
+	if err := m.consistent(); err != nil {
+		t.Fatalf("release (twins): inconsistent state: %v", err)
+	}
+
+	// Test the same two names in overlapping Confirm / release calls.
+	releaseDee, err := m.Confirm(now, "/tweedle/dee", "", Condition{Token: tweedle})
+	if err != nil {
+		t.Fatalf("Confirm (sequence #0): %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Confirm (sequence #0): inconsistent state: %v", err)
+	}
+
+	_, err = m.Confirm(now, "/tweedle/dum", "", Condition{Token: tweedle})
+	if err != ErrConfirmationFailed {
+		t.Fatalf("Confirm (sequence #1): got %v, want ErrConfirmationFailed", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Confirm (sequence #1): inconsistent state: %v", err)
+	}
+
+	releaseDee()
+	if err := m.consistent(); err != nil {
+		t.Fatalf("release (sequence #2): inconsistent state: %v", err)
+	}
+
+	releaseDum, err := m.Confirm(now, "/tweedle/dum", "", Condition{Token: tweedle})
+	if err != nil {
+		t.Fatalf("Confirm (sequence #3): %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Confirm (sequence #3): inconsistent state: %v", err)
+	}
+
+	// Test that you can't unlock a held lock.
+	err = m.Unlock(now, tweedle)
+	if err != ErrLocked {
+		t.Fatalf("Unlock (sequence #4): got %v, want ErrLocked", err)
+	}
+
+	releaseDum()
+	if err := m.consistent(); err != nil {
+		t.Fatalf("release (sequence #5): inconsistent state: %v", err)
+	}
+
+	err = m.Unlock(now, tweedle)
+	if err != nil {
+		t.Fatalf("Unlock (sequence #6): %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Unlock (sequence #6): inconsistent state: %v", err)
+	}
+}
+
+func TestMemLSNonCanonicalRoot(t *testing.T) {
+	now := time.Unix(0, 0)
+	m := NewMemLS().(*memLS)
+	token, err := m.Create(now, LockDetails{
+		Root:     "/foo/./bar//",
+		Duration: 1 * time.Second,
+	})
+	if err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Create: inconsistent state: %v", err)
+	}
+	if err := m.Unlock(now, token); err != nil {
+		t.Fatalf("Unlock: %v", err)
+	}
+	if err := m.consistent(); err != nil {
+		t.Fatalf("Unlock: inconsistent state: %v", err)
+	}
+}
+
+func TestMemLSExpiry(t *testing.T) {
+	m := NewMemLS().(*memLS)
+	testCases := []string{
+		"setNow 0",
+		"create /a.5",
+		"want /a.5",
+		"create /c.6",
+		"want /a.5 /c.6",
+		"create /a/b.7",
+		"want /a.5 /a/b.7 /c.6",
+		"setNow 4",
+		"want /a.5 /a/b.7 /c.6",
+		"setNow 5",
+		"want /a/b.7 /c.6",
+		"setNow 6",
+		"want /a/b.7",
+		"setNow 7",
+		"want ",
+		"setNow 8",
+		"want ",
+		"create /a.12",
+		"create /b.13",
+		"create /c.15",
+		"create /a/d.16",
+		"want /a.12 /a/d.16 /b.13 /c.15",
+		"refresh /a.14",
+		"want /a.14 /a/d.16 /b.13 /c.15",
+		"setNow 12",
+		"want /a.14 /a/d.16 /b.13 /c.15",
+		"setNow 13",
+		"want /a.14 /a/d.16 /c.15",
+		"setNow 14",
+		"want /a/d.16 /c.15",
+		"refresh /a/d.20",
+		"refresh /c.20",
+		"want /a/d.20 /c.20",
+		"setNow 20",
+		"want ",
+	}
+
+	tokens := map[string]string{}
+	zTime := time.Unix(0, 0)
+	now := zTime
+	for i, tc := range testCases {
+		j := strings.IndexByte(tc, ' ')
+		if j < 0 {
+			t.Fatalf("test case #%d %q: invalid command", i, tc)
+		}
+		op, arg := tc[:j], tc[j+1:]
+		switch op {
+		default:
+			t.Fatalf("test case #%d %q: invalid operation %q", i, tc, op)
+
+		case "create", "refresh":
+			parts := strings.Split(arg, ".")
+			if len(parts) != 2 {
+				t.Fatalf("test case #%d %q: invalid create", i, tc)
+			}
+			root := parts[0]
+			d, err := strconv.Atoi(parts[1])
+			if err != nil {
+				t.Fatalf("test case #%d %q: invalid duration", i, tc)
+			}
+			dur := time.Unix(0, 0).Add(time.Duration(d) * time.Second).Sub(now)
+
+			switch op {
+			case "create":
+				token, err := m.Create(now, LockDetails{
+					Root:      root,
+					Duration:  dur,
+					ZeroDepth: true,
+				})
+				if err != nil {
+					t.Fatalf("test case #%d %q: Create: %v", i, tc, err)
+				}
+				tokens[root] = token
+
+			case "refresh":
+				token := tokens[root]
+				if token == "" {
+					t.Fatalf("test case #%d %q: no token for %q", i, tc, root)
+				}
+				got, err := m.Refresh(now, token, dur)
+				if err != nil {
+					t.Fatalf("test case #%d %q: Refresh: %v", i, tc, err)
+				}
+				want := LockDetails{
+					Root:      root,
+					Duration:  dur,
+					ZeroDepth: true,
+				}
+				if got != want {
+					t.Fatalf("test case #%d %q:\ngot  %v\nwant %v", i, tc, got, want)
+				}
+			}
+
+		case "setNow":
+			d, err := strconv.Atoi(arg)
+			if err != nil {
+				t.Fatalf("test case #%d %q: invalid duration", i, tc)
+			}
+			now = time.Unix(0, 0).Add(time.Duration(d) * time.Second)
+
+		case "want":
+			m.mu.Lock()
+			m.collectExpiredNodes(now)
+			got := make([]string, 0, len(m.byToken))
+			for _, n := range m.byToken {
+				got = append(got, fmt.Sprintf("%s.%d",
+					n.details.Root, n.expiry.Sub(zTime)/time.Second))
+			}
+			m.mu.Unlock()
+			sort.Strings(got)
+			want := []string{}
+			if arg != "" {
+				want = strings.Split(arg, " ")
+			}
+			if !reflect.DeepEqual(got, want) {
+				t.Fatalf("test case #%d %q:\ngot  %q\nwant %q", i, tc, got, want)
+			}
+		}
+
+		if err := m.consistent(); err != nil {
+			t.Fatalf("test case #%d %q: inconsistent state: %v", i, tc, err)
+		}
+	}
+}
+
+func TestMemLS(t *testing.T) {
+	now := time.Unix(0, 0)
+	m := NewMemLS().(*memLS)
+	rng := rand.New(rand.NewSource(0))
+	tokens := map[string]string{}
+	nConfirm, nCreate, nRefresh, nUnlock := 0, 0, 0, 0
+	const N = 2000
+
+	for i := 0; i < N; i++ {
+		name := lockTestNames[rng.Intn(len(lockTestNames))]
+		duration := lockTestDurations[rng.Intn(len(lockTestDurations))]
+		confirmed, unlocked := false, false
+
+		// If the name was already locked, we randomly confirm/release, refresh
+		// or unlock it. Otherwise, we create a lock.
+		token := tokens[name]
+		if token != "" {
+			switch rng.Intn(3) {
+			case 0:
+				confirmed = true
+				nConfirm++
+				release, err := m.Confirm(now, name, "", Condition{Token: token})
+				if err != nil {
+					t.Fatalf("iteration #%d: Confirm %q: %v", i, name, err)
+				}
+				if err := m.consistent(); err != nil {
+					t.Fatalf("iteration #%d: inconsistent state: %v", i, err)
+				}
+				release()
+
+			case 1:
+				nRefresh++
+				if _, err := m.Refresh(now, token, duration); err != nil {
+					t.Fatalf("iteration #%d: Refresh %q: %v", i, name, err)
+				}
+
+			case 2:
+				unlocked = true
+				nUnlock++
+				if err := m.Unlock(now, token); err != nil {
+					t.Fatalf("iteration #%d: Unlock %q: %v", i, name, err)
+				}
+			}
+
+		} else {
+			nCreate++
+			var err error
+			token, err = m.Create(now, LockDetails{
+				Root:      name,
+				Duration:  duration,
+				ZeroDepth: lockTestZeroDepth(name),
+			})
+			if err != nil {
+				t.Fatalf("iteration #%d: Create %q: %v", i, name, err)
+			}
+		}
+
+		if !confirmed {
+			if duration == 0 || unlocked {
+				// A zero-duration lock should expire immediately and is
+				// effectively equivalent to being unlocked.
+				tokens[name] = ""
+			} else {
+				tokens[name] = token
+			}
+		}
+
+		if err := m.consistent(); err != nil {
+			t.Fatalf("iteration #%d: inconsistent state: %v", i, err)
+		}
+	}
+
+	if nConfirm < N/10 {
+		t.Fatalf("too few Confirm calls: got %d, want >= %d", nConfirm, N/10)
+	}
+	if nCreate < N/10 {
+		t.Fatalf("too few Create calls: got %d, want >= %d", nCreate, N/10)
+	}
+	if nRefresh < N/10 {
+		t.Fatalf("too few Refresh calls: got %d, want >= %d", nRefresh, N/10)
+	}
+	if nUnlock < N/10 {
+		t.Fatalf("too few Unlock calls: got %d, want >= %d", nUnlock, N/10)
+	}
+}
+
+func (m *memLS) consistent() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// If m.byName is non-empty, then it must contain an entry for the root "/",
+	// and its refCount should equal the number of locked nodes.
+	if len(m.byName) > 0 {
+		n := m.byName["/"]
+		if n == nil {
+			return fmt.Errorf(`non-empty m.byName does not contain the root "/"`)
+		}
+		if n.refCount != len(m.byToken) {
+			return fmt.Errorf("root node refCount=%d, differs from len(m.byToken)=%d", n.refCount, len(m.byToken))
+		}
+	}
+
+	for name, n := range m.byName {
+		// The map keys should be consistent with the node's copy of the key.
+		if n.details.Root != name {
+			return fmt.Errorf("node name %q != byName map key %q", n.details.Root, name)
+		}
+
+		// A name must be clean, and start with a "/".
+		if len(name) == 0 || name[0] != '/' {
+			return fmt.Errorf(`node name %q does not start with "/"`, name)
+		}
+		if name != path.Clean(name) {
+			return fmt.Errorf(`node name %q is not clean`, name)
+		}
+
+		// A node's refCount should be positive.
+		if n.refCount <= 0 {
+			return fmt.Errorf("non-positive refCount for node at name %q", name)
+		}
+
+		// A node's refCount should be the number of self-or-descendents that
+		// are locked (i.e. have a non-empty token).
+		var list []string
+		for name0, n0 := range m.byName {
+			// All of lockTestNames' name fragments are one byte long: '_', 'i' or 'z',
+			// so strings.HasPrefix is equivalent to self-or-descendent name match.
+			// We don't have to worry about "/foo/bar" being a false positive match
+			// for "/foo/b".
+			if strings.HasPrefix(name0, name) && n0.token != "" {
+				list = append(list, name0)
+			}
+		}
+		if n.refCount != len(list) {
+			sort.Strings(list)
+			return fmt.Errorf("node at name %q has refCount %d but locked self-or-descendents are %q (len=%d)",
+				name, n.refCount, list, len(list))
+		}
+
+		// A node n is in m.byToken if it has a non-empty token.
+		if n.token != "" {
+			if _, ok := m.byToken[n.token]; !ok {
+				return fmt.Errorf("node at name %q has token %q but not in m.byToken", name, n.token)
+			}
+		}
+
+		// A node n is in m.byExpiry if it has a non-negative byExpiryIndex.
+		if n.byExpiryIndex >= 0 {
+			if n.byExpiryIndex >= len(m.byExpiry) {
+				return fmt.Errorf("node at name %q has byExpiryIndex %d but m.byExpiry has length %d", name, n.byExpiryIndex, len(m.byExpiry))
+			}
+			if n != m.byExpiry[n.byExpiryIndex] {
+				return fmt.Errorf("node at name %q has byExpiryIndex %d but that indexes a different node", name, n.byExpiryIndex)
+			}
+		}
+	}
+
+	for token, n := range m.byToken {
+		// The map keys should be consistent with the node's copy of the key.
+		if n.token != token {
+			return fmt.Errorf("node token %q != byToken map key %q", n.token, token)
+		}
+
+		// Every node in m.byToken is in m.byName.
+		if _, ok := m.byName[n.details.Root]; !ok {
+			return fmt.Errorf("node at name %q in m.byToken but not in m.byName", n.details.Root)
+		}
+	}
+
+	for i, n := range m.byExpiry {
+		// The slice indices should be consistent with the node's copy of the index.
+		if n.byExpiryIndex != i {
+			return fmt.Errorf("node byExpiryIndex %d != byExpiry slice index %d", n.byExpiryIndex, i)
+		}
+
+		// Every node in m.byExpiry is in m.byName.
+		if _, ok := m.byName[n.details.Root]; !ok {
+			return fmt.Errorf("node at name %q in m.byExpiry but not in m.byName", n.details.Root)
+		}
+
+		// No node in m.byExpiry should be held.
+		if n.held {
+			return fmt.Errorf("node at name %q in m.byExpiry is held", n.details.Root)
+		}
+	}
+	return nil
+}
+
+func TestParseTimeout(t *testing.T) {
+	testCases := []struct {
+		s       string
+		want    time.Duration
+		wantErr error
+	}{{
+		"",
+		infiniteTimeout,
+		nil,
+	}, {
+		"Infinite",
+		infiniteTimeout,
+		nil,
+	}, {
+		"Infinitesimal",
+		0,
+		errInvalidTimeout,
+	}, {
+		"infinite",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second-0",
+		0 * time.Second,
+		nil,
+	}, {
+		"Second-123",
+		123 * time.Second,
+		nil,
+	}, {
+		"  Second-456    ",
+		456 * time.Second,
+		nil,
+	}, {
+		"Second-4100000000",
+		4100000000 * time.Second,
+		nil,
+	}, {
+		"junk",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second-",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second--1",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second--123",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second-+123",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second-0x123",
+		0,
+		errInvalidTimeout,
+	}, {
+		"second-123",
+		0,
+		errInvalidTimeout,
+	}, {
+		"Second-4294967295",
+		4294967295 * time.Second,
+		nil,
+	}, {
+		// Section 10.7 says that "The timeout value for TimeType "Second"
+		// must not be greater than 2^32-1."
+		"Second-4294967296",
+		0,
+		errInvalidTimeout,
+	}, {
+		// This test case comes from section 9.10.9 of the spec. It says,
+		//
+		// "In this request, the client has specified that it desires an
+		// infinite-length lock, if available, otherwise a timeout of 4.1
+		// billion seconds, if available."
+		//
+		// The Go WebDAV package always supports infinite length locks,
+		// and ignores the fallback after the comma.
+		"Infinite, Second-4100000000",
+		infiniteTimeout,
+		nil,
+	}}
+
+	for _, tc := range testCases {
+		got, gotErr := parseTimeout(tc.s)
+		if got != tc.want || gotErr != tc.wantErr {
+			t.Errorf("parsing %q:\ngot  %v, %v\nwant %v, %v", tc.s, got, gotErr, tc.want, tc.wantErr)
+		}
+	}
+}

endpoints/drive/webdav/prop.go

@@ -0,0 +1,469 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"bytes"
+	"context"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"io"
+	"mime"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+// Proppatch describes a property update instruction as defined in RFC 4918.
+// See http://www.webdav.org/specs/rfc4918.html#METHOD_PROPPATCH
+type Proppatch struct {
+	// Remove specifies whether this patch removes properties. If it does not
+	// remove them, it sets them.
+	Remove bool
+	// Props contains the properties to be set or removed.
+	Props []Property
+}
+
+// Propstat describes a XML propstat element as defined in RFC 4918.
+// See http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat
+type Propstat struct {
+	// Props contains the properties for which Status applies.
+	Props []Property
+
+	// Status defines the HTTP status code of the properties in Prop.
+	// Allowed values include, but are not limited to the WebDAV status
+	// code extensions for HTTP/1.1.
+	// http://www.webdav.org/specs/rfc4918.html#status.code.extensions.to.http11
+	Status int
+
+	// XMLError contains the XML representation of the optional error element.
+	// XML content within this field must not rely on any predefined
+	// namespace declarations or prefixes. If empty, the XML error element
+	// is omitted.
+	XMLError string
+
+	// ResponseDescription contains the contents of the optional
+	// responsedescription field. If empty, the XML element is omitted.
+	ResponseDescription string
+}
+
+// makePropstats returns a slice containing those of x and y whose Props slice
+// is non-empty. If both are empty, it returns a slice containing an otherwise
+// zero Propstat whose HTTP status code is 200 OK.
+func makePropstats(x, y Propstat) []Propstat {
+	pstats := make([]Propstat, 0, 2)
+	if len(x.Props) != 0 {
+		pstats = append(pstats, x)
+	}
+	if len(y.Props) != 0 {
+		pstats = append(pstats, y)
+	}
+	if len(pstats) == 0 {
+		pstats = append(pstats, Propstat{
+			Status: http.StatusOK,
+		})
+	}
+	return pstats
+}
+
+// DeadPropsHolder holds the dead properties of a resource.
+//
+// Dead properties are those properties that are explicitly defined. In
+// comparison, live properties, such as DAV:getcontentlength, are implicitly
+// defined by the underlying resource, and cannot be explicitly overridden or
+// removed. See the Terminology section of
+// http://www.webdav.org/specs/rfc4918.html#rfc.section.3
+//
+// There is a whitelist of the names of live properties. This package handles
+// all live properties, and will only pass non-whitelisted names to the Patch
+// method of DeadPropsHolder implementations.
+type DeadPropsHolder interface {
+	// DeadProps returns a copy of the dead properties held.
+	DeadProps() (map[xml.Name]Property, error)
+
+	// Patch patches the dead properties held.
+	//
+	// Patching is atomic; either all or no patches succeed. It returns (nil,
+	// non-nil) if an internal server error occurred, otherwise the Propstats
+	// collectively contain one Property for each proposed patch Property. If
+	// all patches succeed, Patch returns a slice of length one and a Propstat
+	// element with a 200 OK HTTP status code. If none succeed, for reasons
+	// other than an internal server error, no Propstat has status 200 OK.
+	//
+	// For more details on when various HTTP status codes apply, see
+	// http://www.webdav.org/specs/rfc4918.html#PROPPATCH-status
+	Patch([]Proppatch) ([]Propstat, error)
+}
+
+// liveProps contains all supported, protected DAV: properties.
+var liveProps = map[xml.Name]struct {
+	// findFn implements the propfind function of this property. If nil,
+	// it indicates a hidden property.
+	findFn func(context.Context, FileSystem, LockSystem, string, os.FileInfo) (string, error)
+	// dir is true if the property applies to directories.
+	dir bool
+}{
+	{Space: "DAV:", Local: "resourcetype"}: {
+		findFn: findResourceType,
+		dir:    true,
+	},
+	{Space: "DAV:", Local: "displayname"}: {
+		findFn: findDisplayName,
+		dir:    true,
+	},
+	{Space: "DAV:", Local: "getcontentlength"}: {
+		findFn: findContentLength,
+		dir:    false,
+	},
+	{Space: "DAV:", Local: "getlastmodified"}: {
+		findFn: findLastModified,
+		// http://webdav.org/specs/rfc4918.html#PROPERTY_getlastmodified
+		// suggests that getlastmodified should only apply to GETable
+		// resources, and this package does not support GET on directories.
+		//
+		// Nonetheless, some WebDAV clients expect child directories to be
+		// sortable by getlastmodified date, so this value is true, not false.
+		// See golang.org/issue/15334.
+		dir: true,
+	},
+	{Space: "DAV:", Local: "creationdate"}: {
+		findFn: nil,
+		dir:    false,
+	},
+	{Space: "DAV:", Local: "getcontentlanguage"}: {
+		findFn: nil,
+		dir:    false,
+	},
+	{Space: "DAV:", Local: "getcontenttype"}: {
+		findFn: findContentType,
+		dir:    false,
+	},
+	{Space: "DAV:", Local: "getetag"}: {
+		findFn: findETag,
+		// findETag implements ETag as the concatenated hex values of a file's
+		// modification time and size. This is not a reliable synchronization
+		// mechanism for directories, so we do not advertise getetag for DAV
+		// collections.
+		dir: false,
+	},
+
+	// TODO: The lockdiscovery property requires LockSystem to list the
+	// active locks on a resource.
+	{Space: "DAV:", Local: "lockdiscovery"}: {},
+	{Space: "DAV:", Local: "supportedlock"}: {
+		findFn: findSupportedLock,
+		dir:    true,
+	},
+}
+
+// TODO(nigeltao) merge props and allprop?
+
+// props returns the status of the properties named pnames for resource name.
+//
+// Each Propstat has a unique status and each property name will only be part
+// of one Propstat element.
+func props(ctx context.Context, fs FileSystem, ls LockSystem, name string, pnames []xml.Name) ([]Propstat, error) {
+	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	fi, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+	isDir := fi.IsDir()
+
+	var deadProps map[xml.Name]Property
+	if dph, ok := f.(DeadPropsHolder); ok {
+		deadProps, err = dph.DeadProps()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	pstatOK := Propstat{Status: http.StatusOK}
+	pstatNotFound := Propstat{Status: http.StatusNotFound}
+	for _, pn := range pnames {
+		// If this file has dead properties, check if they contain pn.
+		if dp, ok := deadProps[pn]; ok {
+			pstatOK.Props = append(pstatOK.Props, dp)
+			continue
+		}
+		// Otherwise, it must either be a live property or we don't know it.
+		if prop := liveProps[pn]; prop.findFn != nil && (prop.dir || !isDir) {
+			innerXML, err := prop.findFn(ctx, fs, ls, name, fi)
+			if err != nil {
+				return nil, err
+			}
+			pstatOK.Props = append(pstatOK.Props, Property{
+				XMLName:  pn,
+				InnerXML: []byte(innerXML),
+			})
+		} else {
+			pstatNotFound.Props = append(pstatNotFound.Props, Property{
+				XMLName: pn,
+			})
+		}
+	}
+	return makePropstats(pstatOK, pstatNotFound), nil
+}
+
+// propnames returns the property names defined for resource name.
+func propnames(ctx context.Context, fs FileSystem, ls LockSystem, name string) ([]xml.Name, error) {
+	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	fi, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+	isDir := fi.IsDir()
+
+	var deadProps map[xml.Name]Property
+	if dph, ok := f.(DeadPropsHolder); ok {
+		deadProps, err = dph.DeadProps()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	pnames := make([]xml.Name, 0, len(liveProps)+len(deadProps))
+	for pn, prop := range liveProps {
+		if prop.findFn != nil && (prop.dir || !isDir) {
+			pnames = append(pnames, pn)
+		}
+	}
+	for pn := range deadProps {
+		pnames = append(pnames, pn)
+	}
+	return pnames, nil
+}
+
+// allprop returns the properties defined for resource name and the properties
+// named in include.
+//
+// Note that RFC 4918 defines 'allprop' to return the DAV: properties defined
+// within the RFC plus dead properties. Other live properties should only be
+// returned if they are named in 'include'.
+//
+// See http://www.webdav.org/specs/rfc4918.html#METHOD_PROPFIND
+func allprop(ctx context.Context, fs FileSystem, ls LockSystem, name string, include []xml.Name) ([]Propstat, error) {
+	pnames, err := propnames(ctx, fs, ls, name)
+	if err != nil {
+		return nil, err
+	}
+	// Add names from include if they are not already covered in pnames.
+	nameset := make(map[xml.Name]bool)
+	for _, pn := range pnames {
+		nameset[pn] = true
+	}
+	for _, pn := range include {
+		if !nameset[pn] {
+			pnames = append(pnames, pn)
+		}
+	}
+	return props(ctx, fs, ls, name, pnames)
+}
+
+// patch patches the properties of resource name. The return values are
+// constrained in the same manner as DeadPropsHolder.Patch.
+func patch(ctx context.Context, fs FileSystem, ls LockSystem, name string, patches []Proppatch) ([]Propstat, error) {
+	conflict := false
+loop:
+	for _, patch := range patches {
+		for _, p := range patch.Props {
+			if _, ok := liveProps[p.XMLName]; ok {
+				conflict = true
+				break loop
+			}
+		}
+	}
+	if conflict {
+		pstatForbidden := Propstat{
+			Status:   http.StatusForbidden,
+			XMLError: `<D:cannot-modify-protected-property xmlns:D="DAV:"/>`,
+		}
+		pstatFailedDep := Propstat{
+			Status: StatusFailedDependency,
+		}
+		for _, patch := range patches {
+			for _, p := range patch.Props {
+				if _, ok := liveProps[p.XMLName]; ok {
+					pstatForbidden.Props = append(pstatForbidden.Props, Property{XMLName: p.XMLName})
+				} else {
+					pstatFailedDep.Props = append(pstatFailedDep.Props, Property{XMLName: p.XMLName})
+				}
+			}
+		}
+		return makePropstats(pstatForbidden, pstatFailedDep), nil
+	}
+
+	f, err := fs.OpenFile(ctx, name, os.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	if dph, ok := f.(DeadPropsHolder); ok {
+		ret, err := dph.Patch(patches)
+		if err != nil {
+			return nil, err
+		}
+		// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat says that
+		// "The contents of the prop XML element must only list the names of
+		// properties to which the result in the status element applies."
+		for _, pstat := range ret {
+			for i, p := range pstat.Props {
+				pstat.Props[i] = Property{XMLName: p.XMLName}
+			}
+		}
+		return ret, nil
+	}
+	// The file doesn't implement the optional DeadPropsHolder interface, so
+	// all patches are forbidden.
+	pstat := Propstat{Status: http.StatusForbidden}
+	for _, patch := range patches {
+		for _, p := range patch.Props {
+			pstat.Props = append(pstat.Props, Property{XMLName: p.XMLName})
+		}
+	}
+	return []Propstat{pstat}, nil
+}
+
+func escapeXML(s string) string {
+	for i := 0; i < len(s); i++ {
+		// As an optimization, if s contains only ASCII letters, digits or a
+		// few special characters, the escaped value is s itself and we don't
+		// need to allocate a buffer and convert between string and []byte.
+		switch c := s[i]; {
+		case c == ' ' || c == '_' ||
+			('+' <= c && c <= '9') || // Digits as well as + , - . and /
+			('A' <= c && c <= 'Z') ||
+			('a' <= c && c <= 'z'):
+			continue
+		}
+		// Otherwise, go through the full escaping process.
+		var buf bytes.Buffer
+		xml.EscapeText(&buf, []byte(s))
+		return buf.String()
+	}
+	return s
+}
+
+func findResourceType(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	if fi.IsDir() {
+		return `<D:collection xmlns:D="DAV:"/>`, nil
+	}
+	return "", nil
+}
+
+func findDisplayName(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	if slashClean(name) == "/" {
+		// Hide the real name of a possibly prefixed root directory.
+		return "", nil
+	}
+	return escapeXML(fi.Name()), nil
+}
+
+func findContentLength(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	return strconv.FormatInt(fi.Size(), 10), nil
+}
+
+func findLastModified(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	return fi.ModTime().UTC().Format(http.TimeFormat), nil
+}
+
+// ErrNotImplemented should be returned by optional interfaces if they
+// want the original implementation to be used.
+var ErrNotImplemented = errors.New("not implemented")
+
+// ContentTyper is an optional interface for the os.FileInfo
+// objects returned by the FileSystem.
+//
+// If this interface is defined then it will be used to read the
+// content type from the object.
+//
+// If this interface is not defined the file will be opened and the
+// content type will be guessed from the initial contents of the file.
+type ContentTyper interface {
+	// ContentType returns the content type for the file.
+	//
+	// If this returns error ErrNotImplemented then the error will
+	// be ignored and the base implementation will be used
+	// instead.
+	ContentType(ctx context.Context) (string, error)
+}
+
+func findContentType(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	if do, ok := fi.(ContentTyper); ok {
+		ctype, err := do.ContentType(ctx)
+		if err != ErrNotImplemented {
+			return ctype, err
+		}
+	}
+	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	// This implementation is based on serveContent's code in the standard net/http package.
+	ctype := mime.TypeByExtension(filepath.Ext(name))
+	if ctype != "" {
+		return ctype, nil
+	}
+	// Read a chunk to decide between utf-8 text and binary.
+	var buf [512]byte
+	n, err := io.ReadFull(f, buf[:])
+	if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
+		return "", err
+	}
+	ctype = http.DetectContentType(buf[:n])
+	// Rewind file.
+	_, err = f.Seek(0, io.SeekStart)
+	return ctype, err
+}
+
+// ETager is an optional interface for the os.FileInfo objects
+// returned by the FileSystem.
+//
+// If this interface is defined then it will be used to read the ETag
+// for the object.
+//
+// If this interface is not defined an ETag will be computed using the
+// ModTime() and the Size() methods of the os.FileInfo object.
+type ETager interface {
+	// ETag returns an ETag for the file.  This should be of the
+	// form "value" or W/"value"
+	//
+	// If this returns error ErrNotImplemented then the error will
+	// be ignored and the base implementation will be used
+	// instead.
+	ETag(ctx context.Context) (string, error)
+}
+
+func findETag(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	if do, ok := fi.(ETager); ok {
+		etag, err := do.ETag(ctx)
+		if err != ErrNotImplemented {
+			return etag, err
+		}
+	}
+	// The Apache http 2.4 web server by default concatenates the
+	// modification time and size of a file. We replicate the heuristic
+	// with nanosecond granularity.
+	return fmt.Sprintf(`"%x%x"`, fi.ModTime().UnixNano(), fi.Size()), nil
+}
+
+func findSupportedLock(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
+	return `` +
+		`<D:lockentry xmlns:D="DAV:">` +
+		`<D:lockscope><D:exclusive/></D:lockscope>` +
+		`<D:locktype><D:write/></D:locktype>` +
+		`</D:lockentry>`, nil
+}

endpoints/drive/webdav/prop_test.go

@@ -0,0 +1,716 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"context"
+	"encoding/xml"
+	"fmt"
+	"net/http"
+	"os"
+	"reflect"
+	"regexp"
+	"sort"
+	"testing"
+)
+
+func TestMemPS(t *testing.T) {
+	ctx := context.Background()
+	// calcProps calculates the getlastmodified and getetag DAV: property
+	// values in pstats for resource name in file-system fs.
+	calcProps := func(name string, fs FileSystem, ls LockSystem, pstats []Propstat) error {
+		fi, err := fs.Stat(ctx, name)
+		if err != nil {
+			return err
+		}
+		for _, pst := range pstats {
+			for i, p := range pst.Props {
+				switch p.XMLName {
+				case xml.Name{Space: "DAV:", Local: "getlastmodified"}:
+					p.InnerXML = []byte(fi.ModTime().UTC().Format(http.TimeFormat))
+					pst.Props[i] = p
+				case xml.Name{Space: "DAV:", Local: "getetag"}:
+					if fi.IsDir() {
+						continue
+					}
+					etag, err := findETag(ctx, fs, ls, name, fi)
+					if err != nil {
+						return err
+					}
+					p.InnerXML = []byte(etag)
+					pst.Props[i] = p
+				}
+			}
+		}
+		return nil
+	}
+
+	const (
+		lockEntry = `` +
+			`<D:lockentry xmlns:D="DAV:">` +
+			`<D:lockscope><D:exclusive/></D:lockscope>` +
+			`<D:locktype><D:write/></D:locktype>` +
+			`</D:lockentry>`
+		statForbiddenError = `<D:cannot-modify-protected-property xmlns:D="DAV:"/>`
+	)
+
+	type propOp struct {
+		op            string
+		name          string
+		pnames        []xml.Name
+		patches       []Proppatch
+		wantPnames    []xml.Name
+		wantPropstats []Propstat
+	}
+
+	testCases := []struct {
+		desc        string
+		noDeadProps bool
+		buildfs     []string
+		propOp      []propOp
+	}{{
+		desc:    "propname",
+		buildfs: []string{"mkdir /dir", "touch /file"},
+		propOp: []propOp{{
+			op:   "propname",
+			name: "/dir",
+			wantPnames: []xml.Name{
+				{Space: "DAV:", Local: "resourcetype"},
+				{Space: "DAV:", Local: "displayname"},
+				{Space: "DAV:", Local: "supportedlock"},
+				{Space: "DAV:", Local: "getlastmodified"},
+			},
+		}, {
+			op:   "propname",
+			name: "/file",
+			wantPnames: []xml.Name{
+				{Space: "DAV:", Local: "resourcetype"},
+				{Space: "DAV:", Local: "displayname"},
+				{Space: "DAV:", Local: "getcontentlength"},
+				{Space: "DAV:", Local: "getlastmodified"},
+				{Space: "DAV:", Local: "getcontenttype"},
+				{Space: "DAV:", Local: "getetag"},
+				{Space: "DAV:", Local: "supportedlock"},
+			},
+		}},
+	}, {
+		desc:    "allprop dir and file",
+		buildfs: []string{"mkdir /dir", "write /file foobarbaz"},
+		propOp: []propOp{{
+			op:   "allprop",
+			name: "/dir",
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "resourcetype"},
+					InnerXML: []byte(`<D:collection xmlns:D="DAV:"/>`),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "displayname"},
+					InnerXML: []byte("dir"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getlastmodified"},
+					InnerXML: nil, // Calculated during test.
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "supportedlock"},
+					InnerXML: []byte(lockEntry),
+				}},
+			}},
+		}, {
+			op:   "allprop",
+			name: "/file",
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "resourcetype"},
+					InnerXML: []byte(""),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "displayname"},
+					InnerXML: []byte("file"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getcontentlength"},
+					InnerXML: []byte("9"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getlastmodified"},
+					InnerXML: nil, // Calculated during test.
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getcontenttype"},
+					InnerXML: []byte("text/plain; charset=utf-8"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getetag"},
+					InnerXML: nil, // Calculated during test.
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "supportedlock"},
+					InnerXML: []byte(lockEntry),
+				}},
+			}},
+		}, {
+			op:   "allprop",
+			name: "/file",
+			pnames: []xml.Name{
+				{Space: "DAV:", Local: "resourcetype"},
+				{Space: "foo", Local: "bar"},
+			},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "resourcetype"},
+					InnerXML: []byte(""),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "displayname"},
+					InnerXML: []byte("file"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getcontentlength"},
+					InnerXML: []byte("9"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getlastmodified"},
+					InnerXML: nil, // Calculated during test.
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getcontenttype"},
+					InnerXML: []byte("text/plain; charset=utf-8"),
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "getetag"},
+					InnerXML: nil, // Calculated during test.
+				}, {
+					XMLName:  xml.Name{Space: "DAV:", Local: "supportedlock"},
+					InnerXML: []byte(lockEntry),
+				}}}, {
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}}},
+			},
+		}},
+	}, {
+		desc:    "propfind DAV:resourcetype",
+		buildfs: []string{"mkdir /dir", "touch /file"},
+		propOp: []propOp{{
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "DAV:", Local: "resourcetype"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "resourcetype"},
+					InnerXML: []byte(`<D:collection xmlns:D="DAV:"/>`),
+				}},
+			}},
+		}, {
+			op:     "propfind",
+			name:   "/file",
+			pnames: []xml.Name{{Space: "DAV:", Local: "resourcetype"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "resourcetype"},
+					InnerXML: []byte(""),
+				}},
+			}},
+		}},
+	}, {
+		desc:    "propfind unsupported DAV properties",
+		buildfs: []string{"mkdir /dir"},
+		propOp: []propOp{{
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "DAV:", Local: "getcontentlanguage"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "DAV:", Local: "getcontentlanguage"},
+				}},
+			}},
+		}, {
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "DAV:", Local: "creationdate"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "DAV:", Local: "creationdate"},
+				}},
+			}},
+		}},
+	}, {
+		desc:    "propfind getetag for files but not for directories",
+		buildfs: []string{"mkdir /dir", "touch /file"},
+		propOp: []propOp{{
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "DAV:", Local: "getetag"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "DAV:", Local: "getetag"},
+				}},
+			}},
+		}, {
+			op:     "propfind",
+			name:   "/file",
+			pnames: []xml.Name{{Space: "DAV:", Local: "getetag"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "getetag"},
+					InnerXML: nil, // Calculated during test.
+				}},
+			}},
+		}},
+	}, {
+		desc:        "proppatch property on no-dead-properties file system",
+		buildfs:     []string{"mkdir /dir"},
+		noDeadProps: true,
+		propOp: []propOp{{
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusForbidden,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}, {
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Props: []Property{{
+					XMLName: xml.Name{Space: "DAV:", Local: "getetag"},
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status:   http.StatusForbidden,
+				XMLError: statForbiddenError,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "DAV:", Local: "getetag"},
+				}},
+			}},
+		}},
+	}, {
+		desc:    "proppatch dead property",
+		buildfs: []string{"mkdir /dir"},
+		propOp: []propOp{{
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "foo", Local: "bar"},
+					InnerXML: []byte("baz"),
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}, {
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "foo", Local: "bar"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "foo", Local: "bar"},
+					InnerXML: []byte("baz"),
+				}},
+			}},
+		}},
+	}, {
+		desc:    "proppatch dead property with failed dependency",
+		buildfs: []string{"mkdir /dir"},
+		propOp: []propOp{{
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "foo", Local: "bar"},
+					InnerXML: []byte("baz"),
+				}},
+			}, {
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "DAV:", Local: "displayname"},
+					InnerXML: []byte("xxx"),
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status:   http.StatusForbidden,
+				XMLError: statForbiddenError,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "DAV:", Local: "displayname"},
+				}},
+			}, {
+				Status: StatusFailedDependency,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}, {
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "foo", Local: "bar"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}},
+	}, {
+		desc:    "proppatch remove dead property",
+		buildfs: []string{"mkdir /dir"},
+		propOp: []propOp{{
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "foo", Local: "bar"},
+					InnerXML: []byte("baz"),
+				}, {
+					XMLName:  xml.Name{Space: "spam", Local: "ham"},
+					InnerXML: []byte("eggs"),
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}, {
+					XMLName: xml.Name{Space: "spam", Local: "ham"},
+				}},
+			}},
+		}, {
+			op:   "propfind",
+			name: "/dir",
+			pnames: []xml.Name{
+				{Space: "foo", Local: "bar"},
+				{Space: "spam", Local: "ham"},
+			},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "foo", Local: "bar"},
+					InnerXML: []byte("baz"),
+				}, {
+					XMLName:  xml.Name{Space: "spam", Local: "ham"},
+					InnerXML: []byte("eggs"),
+				}},
+			}},
+		}, {
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Remove: true,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}, {
+			op:   "propfind",
+			name: "/dir",
+			pnames: []xml.Name{
+				{Space: "foo", Local: "bar"},
+				{Space: "spam", Local: "ham"},
+			},
+			wantPropstats: []Propstat{{
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}, {
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "spam", Local: "ham"},
+					InnerXML: []byte("eggs"),
+				}},
+			}},
+		}},
+	}, {
+		desc:    "propname with dead property",
+		buildfs: []string{"touch /file"},
+		propOp: []propOp{{
+			op:   "proppatch",
+			name: "/file",
+			patches: []Proppatch{{
+				Props: []Property{{
+					XMLName:  xml.Name{Space: "foo", Local: "bar"},
+					InnerXML: []byte("baz"),
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}, {
+			op:   "propname",
+			name: "/file",
+			wantPnames: []xml.Name{
+				{Space: "DAV:", Local: "resourcetype"},
+				{Space: "DAV:", Local: "displayname"},
+				{Space: "DAV:", Local: "getcontentlength"},
+				{Space: "DAV:", Local: "getlastmodified"},
+				{Space: "DAV:", Local: "getcontenttype"},
+				{Space: "DAV:", Local: "getetag"},
+				{Space: "DAV:", Local: "supportedlock"},
+				{Space: "foo", Local: "bar"},
+			},
+		}},
+	}, {
+		desc:    "proppatch remove unknown dead property",
+		buildfs: []string{"mkdir /dir"},
+		propOp: []propOp{{
+			op:   "proppatch",
+			name: "/dir",
+			patches: []Proppatch{{
+				Remove: true,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusOK,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo", Local: "bar"},
+				}},
+			}},
+		}},
+	}, {
+		desc:    "bad: propfind unknown property",
+		buildfs: []string{"mkdir /dir"},
+		propOp: []propOp{{
+			op:     "propfind",
+			name:   "/dir",
+			pnames: []xml.Name{{Space: "foo:", Local: "bar"}},
+			wantPropstats: []Propstat{{
+				Status: http.StatusNotFound,
+				Props: []Property{{
+					XMLName: xml.Name{Space: "foo:", Local: "bar"},
+				}},
+			}},
+		}},
+	}}
+
+	for _, tc := range testCases {
+		fs, err := buildTestFS(tc.buildfs)
+		if err != nil {
+			t.Fatalf("%s: cannot create test filesystem: %v", tc.desc, err)
+		}
+		if tc.noDeadProps {
+			fs = noDeadPropsFS{fs}
+		}
+		ls := NewMemLS()
+		for _, op := range tc.propOp {
+			desc := fmt.Sprintf("%s: %s %s", tc.desc, op.op, op.name)
+			if err = calcProps(op.name, fs, ls, op.wantPropstats); err != nil {
+				t.Fatalf("%s: calcProps: %v", desc, err)
+			}
+
+			// Call property system.
+			var propstats []Propstat
+			switch op.op {
+			case "propname":
+				pnames, err := propnames(ctx, fs, ls, op.name)
+				if err != nil {
+					t.Errorf("%s: got error %v, want nil", desc, err)
+					continue
+				}
+				sort.Sort(byXMLName(pnames))
+				sort.Sort(byXMLName(op.wantPnames))
+				if !reflect.DeepEqual(pnames, op.wantPnames) {
+					t.Errorf("%s: pnames\ngot  %q\nwant %q", desc, pnames, op.wantPnames)
+				}
+				continue
+			case "allprop":
+				propstats, err = allprop(ctx, fs, ls, op.name, op.pnames)
+			case "propfind":
+				propstats, err = props(ctx, fs, ls, op.name, op.pnames)
+			case "proppatch":
+				propstats, err = patch(ctx, fs, ls, op.name, op.patches)
+			default:
+				t.Fatalf("%s: %s not implemented", desc, op.op)
+			}
+			if err != nil {
+				t.Errorf("%s: got error %v, want nil", desc, err)
+				continue
+			}
+			// Compare return values from allprop, propfind or proppatch.
+			for _, pst := range propstats {
+				sort.Sort(byPropname(pst.Props))
+			}
+			for _, pst := range op.wantPropstats {
+				sort.Sort(byPropname(pst.Props))
+			}
+			sort.Sort(byStatus(propstats))
+			sort.Sort(byStatus(op.wantPropstats))
+			if !reflect.DeepEqual(propstats, op.wantPropstats) {
+				t.Errorf("%s: propstat\ngot  %q\nwant %q", desc, propstats, op.wantPropstats)
+			}
+		}
+	}
+}
+
+func cmpXMLName(a, b xml.Name) bool {
+	if a.Space != b.Space {
+		return a.Space < b.Space
+	}
+	return a.Local < b.Local
+}
+
+type byXMLName []xml.Name
+
+func (b byXMLName) Len() int           { return len(b) }
+func (b byXMLName) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+func (b byXMLName) Less(i, j int) bool { return cmpXMLName(b[i], b[j]) }
+
+type byPropname []Property
+
+func (b byPropname) Len() int           { return len(b) }
+func (b byPropname) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+func (b byPropname) Less(i, j int) bool { return cmpXMLName(b[i].XMLName, b[j].XMLName) }
+
+type byStatus []Propstat
+
+func (b byStatus) Len() int           { return len(b) }
+func (b byStatus) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+func (b byStatus) Less(i, j int) bool { return b[i].Status < b[j].Status }
+
+type noDeadPropsFS struct {
+	FileSystem
+}
+
+func (fs noDeadPropsFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (File, error) {
+	f, err := fs.FileSystem.OpenFile(ctx, name, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+	return noDeadPropsFile{f}, nil
+}
+
+// noDeadPropsFile wraps a File but strips any optional DeadPropsHolder methods
+// provided by the underlying File implementation.
+type noDeadPropsFile struct {
+	f File
+}
+
+func (f noDeadPropsFile) Close() error                              { return f.f.Close() }
+func (f noDeadPropsFile) Read(p []byte) (int, error)                { return f.f.Read(p) }
+func (f noDeadPropsFile) Readdir(count int) ([]os.FileInfo, error)  { return f.f.Readdir(count) }
+func (f noDeadPropsFile) Seek(off int64, whence int) (int64, error) { return f.f.Seek(off, whence) }
+func (f noDeadPropsFile) Stat() (os.FileInfo, error)                { return f.f.Stat() }
+func (f noDeadPropsFile) Write(p []byte) (int, error)               { return f.f.Write(p) }
+
+type overrideContentType struct {
+	os.FileInfo
+	contentType string
+	err         error
+}
+
+func (o *overrideContentType) ContentType(ctx context.Context) (string, error) {
+	return o.contentType, o.err
+}
+
+func TestFindContentTypeOverride(t *testing.T) {
+	fs, err := buildTestFS([]string{"touch /file"})
+	if err != nil {
+		t.Fatalf("cannot create test filesystem: %v", err)
+	}
+	ctx := context.Background()
+	fi, err := fs.Stat(ctx, "/file")
+	if err != nil {
+		t.Fatalf("cannot Stat /file: %v", err)
+	}
+
+	// Check non overridden case
+	originalContentType, err := findContentType(ctx, fs, nil, "/file", fi)
+	if err != nil {
+		t.Fatalf("findContentType /file failed: %v", err)
+	}
+	if originalContentType != "text/plain; charset=utf-8" {
+		t.Fatalf("ContentType wrong want %q got %q", "text/plain; charset=utf-8", originalContentType)
+	}
+
+	// Now try overriding the ContentType
+	o := &overrideContentType{fi, "OverriddenContentType", nil}
+	ContentType, err := findContentType(ctx, fs, nil, "/file", o)
+	if err != nil {
+		t.Fatalf("findContentType /file failed: %v", err)
+	}
+	if ContentType != o.contentType {
+		t.Fatalf("ContentType wrong want %q got %q", o.contentType, ContentType)
+	}
+
+	// Now return ErrNotImplemented and check we get the original content type
+	o = &overrideContentType{fi, "OverriddenContentType", ErrNotImplemented}
+	ContentType, err = findContentType(ctx, fs, nil, "/file", o)
+	if err != nil {
+		t.Fatalf("findContentType /file failed: %v", err)
+	}
+	if ContentType != originalContentType {
+		t.Fatalf("ContentType wrong want %q got %q", originalContentType, ContentType)
+	}
+}
+
+type overrideETag struct {
+	os.FileInfo
+	eTag string
+	err  error
+}
+
+func (o *overrideETag) ETag(ctx context.Context) (string, error) {
+	return o.eTag, o.err
+}
+
+func TestFindETagOverride(t *testing.T) {
+	fs, err := buildTestFS([]string{"touch /file"})
+	if err != nil {
+		t.Fatalf("cannot create test filesystem: %v", err)
+	}
+	ctx := context.Background()
+	fi, err := fs.Stat(ctx, "/file")
+	if err != nil {
+		t.Fatalf("cannot Stat /file: %v", err)
+	}
+
+	// Check non overridden case
+	originalETag, err := findETag(ctx, fs, nil, "/file", fi)
+	if err != nil {
+		t.Fatalf("findETag /file failed: %v", err)
+	}
+	matchETag := regexp.MustCompile(`^"-?[0-9a-f]{6,}"$`)
+	if !matchETag.MatchString(originalETag) {
+		t.Fatalf("ETag wrong, wanted something matching %v got %q", matchETag, originalETag)
+	}
+
+	// Now try overriding the ETag
+	o := &overrideETag{fi, `"OverriddenETag"`, nil}
+	ETag, err := findETag(ctx, fs, nil, "/file", o)
+	if err != nil {
+		t.Fatalf("findETag /file failed: %v", err)
+	}
+	if ETag != o.eTag {
+		t.Fatalf("ETag wrong want %q got %q", o.eTag, ETag)
+	}
+
+	// Now return ErrNotImplemented and check we get the original Etag
+	o = &overrideETag{fi, `"OverriddenETag"`, ErrNotImplemented}
+	ETag, err = findETag(ctx, fs, nil, "/file", o)
+	if err != nil {
+		t.Fatalf("findETag /file failed: %v", err)
+	}
+	if ETag != originalETag {
+		t.Fatalf("ETag wrong want %q got %q", originalETag, ETag)
+	}
+}

endpoints/drive/webdav/webdav.go

@@ -0,0 +1,736 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package webdav provides a WebDAV server implementation.
+package webdav // import "golang.org/x/net/webdav"
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+type Handler struct {
+	// Prefix is the URL path prefix to strip from WebDAV resource paths.
+	Prefix string
+	// FileSystem is the virtual file system.
+	FileSystem FileSystem
+	// LockSystem is the lock management system.
+	LockSystem LockSystem
+	// Logger is an optional error logger. If non-nil, it will be called
+	// for all HTTP requests.
+	Logger func(*http.Request, error)
+}
+
+func (h *Handler) stripPrefix(p string) (string, int, error) {
+	if h.Prefix == "" {
+		return p, http.StatusOK, nil
+	}
+	if r := strings.TrimPrefix(p, h.Prefix); len(r) < len(p) {
+		return r, http.StatusOK, nil
+	}
+	return p, http.StatusNotFound, errPrefixMismatch
+}
+
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	status, err := http.StatusBadRequest, errUnsupportedMethod
+	if h.FileSystem == nil {
+		status, err = http.StatusInternalServerError, errNoFileSystem
+	} else if h.LockSystem == nil {
+		status, err = http.StatusInternalServerError, errNoLockSystem
+	} else {
+		switch r.Method {
+		case "OPTIONS":
+			status, err = h.handleOptions(w, r)
+		case "GET", "HEAD", "POST":
+			status, err = h.handleGetHeadPost(w, r)
+		case "DELETE":
+			status, err = h.handleDelete(w, r)
+		case "PUT":
+			status, err = h.handlePut(w, r)
+		case "MKCOL":
+			status, err = h.handleMkcol(w, r)
+		case "COPY", "MOVE":
+			status, err = h.handleCopyMove(w, r)
+		case "LOCK":
+			status, err = h.handleLock(w, r)
+		case "UNLOCK":
+			status, err = h.handleUnlock(w, r)
+		case "PROPFIND":
+			status, err = h.handlePropfind(w, r)
+		case "PROPPATCH":
+			status, err = h.handleProppatch(w, r)
+		}
+	}
+
+	if status != 0 {
+		w.WriteHeader(status)
+		if status != http.StatusNoContent {
+			w.Write([]byte(StatusText(status)))
+		}
+	}
+	if h.Logger != nil {
+		h.Logger(r, err)
+	}
+}
+
+func (h *Handler) lock(now time.Time, root string) (token string, status int, err error) {
+	token, err = h.LockSystem.Create(now, LockDetails{
+		Root:      root,
+		Duration:  infiniteTimeout,
+		ZeroDepth: true,
+	})
+	if err != nil {
+		if err == ErrLocked {
+			return "", StatusLocked, err
+		}
+		return "", http.StatusInternalServerError, err
+	}
+	return token, 0, nil
+}
+
+func (h *Handler) confirmLocks(r *http.Request, src, dst string) (release func(), status int, err error) {
+	hdr := r.Header.Get("If")
+	if hdr == "" {
+		// An empty If header means that the client hasn't previously created locks.
+		// Even if this client doesn't care about locks, we still need to check that
+		// the resources aren't locked by another client, so we create temporary
+		// locks that would conflict with another client's locks. These temporary
+		// locks are unlocked at the end of the HTTP request.
+		now, srcToken, dstToken := time.Now(), "", ""
+		if src != "" {
+			srcToken, status, err = h.lock(now, src)
+			if err != nil {
+				return nil, status, err
+			}
+		}
+		if dst != "" {
+			dstToken, status, err = h.lock(now, dst)
+			if err != nil {
+				if srcToken != "" {
+					h.LockSystem.Unlock(now, srcToken)
+				}
+				return nil, status, err
+			}
+		}
+
+		return func() {
+			if dstToken != "" {
+				h.LockSystem.Unlock(now, dstToken)
+			}
+			if srcToken != "" {
+				h.LockSystem.Unlock(now, srcToken)
+			}
+		}, 0, nil
+	}
+
+	ih, ok := parseIfHeader(hdr)
+	if !ok {
+		return nil, http.StatusBadRequest, errInvalidIfHeader
+	}
+	// ih is a disjunction (OR) of ifLists, so any ifList will do.
+	for _, l := range ih.lists {
+		lsrc := l.resourceTag
+		if lsrc == "" {
+			lsrc = src
+		} else {
+			u, err := url.Parse(lsrc)
+			if err != nil {
+				continue
+			}
+			if u.Host != r.Host {
+				continue
+			}
+			lsrc, status, err = h.stripPrefix(u.Path)
+			if err != nil {
+				return nil, status, err
+			}
+		}
+		release, err = h.LockSystem.Confirm(time.Now(), lsrc, dst, l.conditions...)
+		if err == ErrConfirmationFailed {
+			continue
+		}
+		if err != nil {
+			return nil, http.StatusInternalServerError, err
+		}
+		return release, 0, nil
+	}
+	// Section 10.4.1 says that "If this header is evaluated and all state lists
+	// fail, then the request must fail with a 412 (Precondition Failed) status."
+	// We follow the spec even though the cond_put_corrupt_token test case from
+	// the litmus test warns on seeing a 412 instead of a 423 (Locked).
+	return nil, http.StatusPreconditionFailed, ErrLocked
+}
+
+func (h *Handler) handleOptions(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	ctx := r.Context()
+	allow := "OPTIONS, LOCK, PUT, MKCOL"
+	if fi, err := h.FileSystem.Stat(ctx, reqPath); err == nil {
+		if fi.IsDir() {
+			allow = "OPTIONS, LOCK, DELETE, PROPPATCH, COPY, MOVE, UNLOCK, PROPFIND"
+		} else {
+			allow = "OPTIONS, LOCK, GET, HEAD, POST, DELETE, PROPPATCH, COPY, MOVE, UNLOCK, PROPFIND, PUT"
+		}
+	}
+	w.Header().Set("Allow", allow)
+	// http://www.webdav.org/specs/rfc4918.html#dav.compliance.classes
+	w.Header().Set("DAV", "1, 2")
+	// http://msdn.microsoft.com/en-au/library/cc250217.aspx
+	w.Header().Set("MS-Author-Via", "DAV")
+	return 0, nil
+}
+
+func (h *Handler) handleGetHeadPost(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	// TODO: check locks for read-only access??
+	ctx := r.Context()
+	f, err := h.FileSystem.OpenFile(ctx, reqPath, os.O_RDONLY, 0)
+	if err != nil {
+		return http.StatusNotFound, err
+	}
+	defer f.Close()
+	fi, err := f.Stat()
+	if err != nil {
+		return http.StatusNotFound, err
+	}
+	if fi.IsDir() {
+		return http.StatusMethodNotAllowed, nil
+	}
+	etag, err := findETag(ctx, h.FileSystem, h.LockSystem, reqPath, fi)
+	if err != nil {
+		return http.StatusInternalServerError, err
+	}
+	w.Header().Set("ETag", etag)
+	// Let ServeContent determine the Content-Type header.
+	http.ServeContent(w, r, reqPath, fi.ModTime(), f)
+	return 0, nil
+}
+
+func (h *Handler) handleDelete(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	release, status, err := h.confirmLocks(r, reqPath, "")
+	if err != nil {
+		return status, err
+	}
+	defer release()
+
+	ctx := r.Context()
+
+	// TODO: return MultiStatus where appropriate.
+
+	// "godoc os RemoveAll" says that "If the path does not exist, RemoveAll
+	// returns nil (no error)." WebDAV semantics are that it should return a
+	// "404 Not Found". We therefore have to Stat before we RemoveAll.
+	if _, err := h.FileSystem.Stat(ctx, reqPath); err != nil {
+		if os.IsNotExist(err) {
+			return http.StatusNotFound, err
+		}
+		return http.StatusMethodNotAllowed, err
+	}
+	if err := h.FileSystem.RemoveAll(ctx, reqPath); err != nil {
+		return http.StatusMethodNotAllowed, err
+	}
+	return http.StatusNoContent, nil
+}
+
+func (h *Handler) handlePut(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	release, status, err := h.confirmLocks(r, reqPath, "")
+	if err != nil {
+		return status, err
+	}
+	defer release()
+	// TODO(rost): Support the If-Match, If-None-Match headers? See bradfitz'
+	// comments in http.checkEtag.
+	ctx := r.Context()
+
+	f, err := h.FileSystem.OpenFile(ctx, reqPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+	if err != nil {
+		return http.StatusNotFound, err
+	}
+	_, copyErr := io.Copy(f, r.Body)
+	fi, statErr := f.Stat()
+	closeErr := f.Close()
+	// TODO(rost): Returning 405 Method Not Allowed might not be appropriate.
+	if copyErr != nil {
+		return http.StatusMethodNotAllowed, copyErr
+	}
+	if statErr != nil {
+		return http.StatusMethodNotAllowed, statErr
+	}
+	if closeErr != nil {
+		return http.StatusMethodNotAllowed, closeErr
+	}
+	etag, err := findETag(ctx, h.FileSystem, h.LockSystem, reqPath, fi)
+	if err != nil {
+		return http.StatusInternalServerError, err
+	}
+	w.Header().Set("ETag", etag)
+	return http.StatusCreated, nil
+}
+
+func (h *Handler) handleMkcol(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	release, status, err := h.confirmLocks(r, reqPath, "")
+	if err != nil {
+		return status, err
+	}
+	defer release()
+
+	ctx := r.Context()
+
+	if r.ContentLength > 0 {
+		return http.StatusUnsupportedMediaType, nil
+	}
+	if err := h.FileSystem.Mkdir(ctx, reqPath, 0777); err != nil {
+		if os.IsNotExist(err) {
+			return http.StatusConflict, err
+		}
+		return http.StatusMethodNotAllowed, err
+	}
+	return http.StatusCreated, nil
+}
+
+func (h *Handler) handleCopyMove(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	hdr := r.Header.Get("Destination")
+	if hdr == "" {
+		return http.StatusBadRequest, errInvalidDestination
+	}
+	u, err := url.Parse(hdr)
+	if err != nil {
+		return http.StatusBadRequest, errInvalidDestination
+	}
+	if u.Host != "" && u.Host != r.Host {
+		return http.StatusBadGateway, errInvalidDestination
+	}
+
+	src, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+
+	dst, status, err := h.stripPrefix(u.Path)
+	if err != nil {
+		return status, err
+	}
+
+	if dst == "" {
+		return http.StatusBadGateway, errInvalidDestination
+	}
+	if dst == src {
+		return http.StatusForbidden, errDestinationEqualsSource
+	}
+
+	ctx := r.Context()
+
+	if r.Method == "COPY" {
+		// Section 7.5.1 says that a COPY only needs to lock the destination,
+		// not both destination and source. Strictly speaking, this is racy,
+		// even though a COPY doesn't modify the source, if a concurrent
+		// operation modifies the source. However, the litmus test explicitly
+		// checks that COPYing a locked-by-another source is OK.
+		release, status, err := h.confirmLocks(r, "", dst)
+		if err != nil {
+			return status, err
+		}
+		defer release()
+
+		// Section 9.8.3 says that "The COPY method on a collection without a Depth
+		// header must act as if a Depth header with value "infinity" was included".
+		depth := infiniteDepth
+		if hdr := r.Header.Get("Depth"); hdr != "" {
+			depth = parseDepth(hdr)
+			if depth != 0 && depth != infiniteDepth {
+				// Section 9.8.3 says that "A client may submit a Depth header on a
+				// COPY on a collection with a value of "0" or "infinity"."
+				return http.StatusBadRequest, errInvalidDepth
+			}
+		}
+		return copyFiles(ctx, h.FileSystem, src, dst, r.Header.Get("Overwrite") != "F", depth, 0)
+	}
+
+	release, status, err := h.confirmLocks(r, src, dst)
+	if err != nil {
+		return status, err
+	}
+	defer release()
+
+	// Section 9.9.2 says that "The MOVE method on a collection must act as if
+	// a "Depth: infinity" header was used on it. A client must not submit a
+	// Depth header on a MOVE on a collection with any value but "infinity"."
+	if hdr := r.Header.Get("Depth"); hdr != "" {
+		if parseDepth(hdr) != infiniteDepth {
+			return http.StatusBadRequest, errInvalidDepth
+		}
+	}
+	return moveFiles(ctx, h.FileSystem, src, dst, r.Header.Get("Overwrite") == "T")
+}
+
+func (h *Handler) handleLock(w http.ResponseWriter, r *http.Request) (retStatus int, retErr error) {
+	duration, err := parseTimeout(r.Header.Get("Timeout"))
+	if err != nil {
+		return http.StatusBadRequest, err
+	}
+	li, status, err := readLockInfo(r.Body)
+	if err != nil {
+		return status, err
+	}
+
+	ctx := r.Context()
+	token, ld, now, created := "", LockDetails{}, time.Now(), false
+	if li == (lockInfo{}) {
+		// An empty lockInfo means to refresh the lock.
+		ih, ok := parseIfHeader(r.Header.Get("If"))
+		if !ok {
+			return http.StatusBadRequest, errInvalidIfHeader
+		}
+		if len(ih.lists) == 1 && len(ih.lists[0].conditions) == 1 {
+			token = ih.lists[0].conditions[0].Token
+		}
+		if token == "" {
+			return http.StatusBadRequest, errInvalidLockToken
+		}
+		ld, err = h.LockSystem.Refresh(now, token, duration)
+		if err != nil {
+			if err == ErrNoSuchLock {
+				return http.StatusPreconditionFailed, err
+			}
+			return http.StatusInternalServerError, err
+		}
+
+	} else {
+		// Section 9.10.3 says that "If no Depth header is submitted on a LOCK request,
+		// then the request MUST act as if a "Depth:infinity" had been submitted."
+		depth := infiniteDepth
+		if hdr := r.Header.Get("Depth"); hdr != "" {
+			depth = parseDepth(hdr)
+			if depth != 0 && depth != infiniteDepth {
+				// Section 9.10.3 says that "Values other than 0 or infinity must not be
+				// used with the Depth header on a LOCK method".
+				return http.StatusBadRequest, errInvalidDepth
+			}
+		}
+		reqPath, status, err := h.stripPrefix(r.URL.Path)
+		if err != nil {
+			return status, err
+		}
+		ld = LockDetails{
+			Root:      reqPath,
+			Duration:  duration,
+			OwnerXML:  li.Owner.InnerXML,
+			ZeroDepth: depth == 0,
+		}
+		token, err = h.LockSystem.Create(now, ld)
+		if err != nil {
+			if err == ErrLocked {
+				return StatusLocked, err
+			}
+			return http.StatusInternalServerError, err
+		}
+		defer func() {
+			if retErr != nil {
+				h.LockSystem.Unlock(now, token)
+			}
+		}()
+
+		// Create the resource if it didn't previously exist.
+		if _, err := h.FileSystem.Stat(ctx, reqPath); err != nil {
+			f, err := h.FileSystem.OpenFile(ctx, reqPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+			if err != nil {
+				// TODO: detect missing intermediate dirs and return http.StatusConflict?
+				return http.StatusInternalServerError, err
+			}
+			f.Close()
+			created = true
+		}
+
+		// http://www.webdav.org/specs/rfc4918.html#HEADER_Lock-Token says that the
+		// Lock-Token value is a Coded-URL. We add angle brackets.
+		w.Header().Set("Lock-Token", "<"+token+">")
+	}
+
+	w.Header().Set("Content-Type", "application/xml; charset=utf-8")
+	if created {
+		// This is "w.WriteHeader(http.StatusCreated)" and not "return
+		// http.StatusCreated, nil" because we write our own (XML) response to w
+		// and Handler.ServeHTTP would otherwise write "Created".
+		w.WriteHeader(http.StatusCreated)
+	}
+	writeLockInfo(w, token, ld)
+	return 0, nil
+}
+
+func (h *Handler) handleUnlock(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	// http://www.webdav.org/specs/rfc4918.html#HEADER_Lock-Token says that the
+	// Lock-Token value is a Coded-URL. We strip its angle brackets.
+	t := r.Header.Get("Lock-Token")
+	if len(t) < 2 || t[0] != '<' || t[len(t)-1] != '>' {
+		return http.StatusBadRequest, errInvalidLockToken
+	}
+	t = t[1 : len(t)-1]
+
+	switch err = h.LockSystem.Unlock(time.Now(), t); err {
+	case nil:
+		return http.StatusNoContent, err
+	case ErrForbidden:
+		return http.StatusForbidden, err
+	case ErrLocked:
+		return StatusLocked, err
+	case ErrNoSuchLock:
+		return http.StatusConflict, err
+	default:
+		return http.StatusInternalServerError, err
+	}
+}
+
+func (h *Handler) handlePropfind(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	ctx := r.Context()
+	fi, err := h.FileSystem.Stat(ctx, reqPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return http.StatusNotFound, err
+		}
+		return http.StatusMethodNotAllowed, err
+	}
+	depth := infiniteDepth
+	if hdr := r.Header.Get("Depth"); hdr != "" {
+		depth = parseDepth(hdr)
+		if depth == invalidDepth {
+			return http.StatusBadRequest, errInvalidDepth
+		}
+	}
+	pf, status, err := readPropfind(r.Body)
+	if err != nil {
+		return status, err
+	}
+
+	mw := multistatusWriter{w: w}
+
+	walkFn := func(reqPath string, info os.FileInfo, err error) error {
+		if err != nil {
+			return handlePropfindError(err, info)
+		}
+
+		var pstats []Propstat
+		if pf.Propname != nil {
+			pnames, err := propnames(ctx, h.FileSystem, h.LockSystem, reqPath)
+			if err != nil {
+				return handlePropfindError(err, info)
+			}
+			pstat := Propstat{Status: http.StatusOK}
+			for _, xmlname := range pnames {
+				pstat.Props = append(pstat.Props, Property{XMLName: xmlname})
+			}
+			pstats = append(pstats, pstat)
+		} else if pf.Allprop != nil {
+			pstats, err = allprop(ctx, h.FileSystem, h.LockSystem, reqPath, pf.Prop)
+		} else {
+			pstats, err = props(ctx, h.FileSystem, h.LockSystem, reqPath, pf.Prop)
+		}
+		if err != nil {
+			return handlePropfindError(err, info)
+		}
+		href := path.Join(h.Prefix, reqPath)
+		if href != "/" && info.IsDir() {
+			href += "/"
+		}
+		return mw.write(makePropstatResponse(href, pstats))
+	}
+
+	walkErr := walkFS(ctx, h.FileSystem, depth, reqPath, fi, walkFn)
+	closeErr := mw.close()
+	if walkErr != nil {
+		return http.StatusInternalServerError, walkErr
+	}
+	if closeErr != nil {
+		return http.StatusInternalServerError, closeErr
+	}
+	return 0, nil
+}
+
+func (h *Handler) handleProppatch(w http.ResponseWriter, r *http.Request) (status int, err error) {
+	reqPath, status, err := h.stripPrefix(r.URL.Path)
+	if err != nil {
+		return status, err
+	}
+	release, status, err := h.confirmLocks(r, reqPath, "")
+	if err != nil {
+		return status, err
+	}
+	defer release()
+
+	ctx := r.Context()
+
+	if _, err := h.FileSystem.Stat(ctx, reqPath); err != nil {
+		if os.IsNotExist(err) {
+			return http.StatusNotFound, err
+		}
+		return http.StatusMethodNotAllowed, err
+	}
+	patches, status, err := readProppatch(r.Body)
+	if err != nil {
+		return status, err
+	}
+	pstats, err := patch(ctx, h.FileSystem, h.LockSystem, reqPath, patches)
+	if err != nil {
+		return http.StatusInternalServerError, err
+	}
+	mw := multistatusWriter{w: w}
+	writeErr := mw.write(makePropstatResponse(r.URL.Path, pstats))
+	closeErr := mw.close()
+	if writeErr != nil {
+		return http.StatusInternalServerError, writeErr
+	}
+	if closeErr != nil {
+		return http.StatusInternalServerError, closeErr
+	}
+	return 0, nil
+}
+
+func makePropstatResponse(href string, pstats []Propstat) *response {
+	resp := response{
+		Href:     []string{(&url.URL{Path: href}).EscapedPath()},
+		Propstat: make([]propstat, 0, len(pstats)),
+	}
+	for _, p := range pstats {
+		var xmlErr *xmlError
+		if p.XMLError != "" {
+			xmlErr = &xmlError{InnerXML: []byte(p.XMLError)}
+		}
+		resp.Propstat = append(resp.Propstat, propstat{
+			Status:              fmt.Sprintf("HTTP/1.1 %d %s", p.Status, StatusText(p.Status)),
+			Prop:                p.Props,
+			ResponseDescription: p.ResponseDescription,
+			Error:               xmlErr,
+		})
+	}
+	return &resp
+}
+
+func handlePropfindError(err error, info os.FileInfo) error {
+	var skipResp error = nil
+	if info != nil && info.IsDir() {
+		skipResp = filepath.SkipDir
+	}
+
+	if errors.Is(err, os.ErrPermission) {
+		// If the server cannot recurse into a directory because it is not allowed,
+		// then there is nothing more to say about it. Just skip sending anything.
+		return skipResp
+	}
+
+	if _, ok := err.(*os.PathError); ok {
+		// If the file is just bad, it couldn't be a proper WebDAV resource. Skip it.
+		return skipResp
+	}
+
+	// We need to be careful with other errors: there is no way to abort the xml stream
+	// part way through while returning a valid PROPFIND response. Returning only half
+	// the data would be misleading, but so would be returning results tainted by errors.
+	// The current behaviour by returning an error here leads to the stream being aborted,
+	// and the parent http server complaining about writing a spurious header. We should
+	// consider further enhancing this error handling to more gracefully fail, or perhaps
+	// buffer the entire response until we've walked the tree.
+	return err
+}
+
+const (
+	infiniteDepth = -1
+	invalidDepth  = -2
+)
+
+// parseDepth maps the strings "0", "1" and "infinity" to 0, 1 and
+// infiniteDepth. Parsing any other string returns invalidDepth.
+//
+// Different WebDAV methods have further constraints on valid depths:
+//   - PROPFIND has no further restrictions, as per section 9.1.
+//   - COPY accepts only "0" or "infinity", as per section 9.8.3.
+//   - MOVE accepts only "infinity", as per section 9.9.2.
+//   - LOCK accepts only "0" or "infinity", as per section 9.10.3.
+//
+// These constraints are enforced by the handleXxx methods.
+func parseDepth(s string) int {
+	switch s {
+	case "0":
+		return 0
+	case "1":
+		return 1
+	case "infinity":
+		return infiniteDepth
+	}
+	return invalidDepth
+}
+
+// http://www.webdav.org/specs/rfc4918.html#status.code.extensions.to.http11
+const (
+	StatusMulti               = 207
+	StatusUnprocessableEntity = 422
+	StatusLocked              = 423
+	StatusFailedDependency    = 424
+	StatusInsufficientStorage = 507
+)
+
+func StatusText(code int) string {
+	switch code {
+	case StatusMulti:
+		return "Multi-Status"
+	case StatusUnprocessableEntity:
+		return "Unprocessable Entity"
+	case StatusLocked:
+		return "Locked"
+	case StatusFailedDependency:
+		return "Failed Dependency"
+	case StatusInsufficientStorage:
+		return "Insufficient Storage"
+	}
+	return http.StatusText(code)
+}
+
+var (
+	errDestinationEqualsSource = errors.New("webdav: destination equals source")
+	errDirectoryNotEmpty       = errors.New("webdav: directory not empty")
+	errInvalidDepth            = errors.New("webdav: invalid depth")
+	errInvalidDestination      = errors.New("webdav: invalid destination")
+	errInvalidIfHeader         = errors.New("webdav: invalid If header")
+	errInvalidLockInfo         = errors.New("webdav: invalid lock info")
+	errInvalidLockToken        = errors.New("webdav: invalid lock token")
+	errInvalidPropfind         = errors.New("webdav: invalid propfind")
+	errInvalidProppatch        = errors.New("webdav: invalid proppatch")
+	errInvalidResponse         = errors.New("webdav: invalid response")
+	errInvalidTimeout          = errors.New("webdav: invalid timeout")
+	errNoFileSystem            = errors.New("webdav: no file system")
+	errNoLockSystem            = errors.New("webdav: no lock system")
+	errNotADirectory           = errors.New("webdav: not a directory")
+	errPrefixMismatch          = errors.New("webdav: prefix mismatch")
+	errRecursionTooDeep        = errors.New("webdav: recursion too deep")
+	errUnsupportedLockInfo     = errors.New("webdav: unsupported lock info")
+	errUnsupportedMethod       = errors.New("webdav: unsupported method")
+)

endpoints/drive/webdav/webdav_test.go

@@ -0,0 +1,349 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"reflect"
+	"regexp"
+	"sort"
+	"strings"
+	"testing"
+)
+
+// TODO: add tests to check XML responses with the expected prefix path
+func TestPrefix(t *testing.T) {
+	const dst, blah = "Destination", "blah blah blah"
+
+	// createLockBody comes from the example in Section 9.10.7.
+	const createLockBody = `<?xml version="1.0" encoding="utf-8" ?>
+		<D:lockinfo xmlns:D='DAV:'>
+			<D:lockscope><D:exclusive/></D:lockscope>
+			<D:locktype><D:write/></D:locktype>
+			<D:owner>
+				<D:href>http://example.org/~ejw/contact.html</D:href>
+			</D:owner>
+		</D:lockinfo>
+	`
+
+	do := func(method, urlStr string, body string, wantStatusCode int, headers ...string) (http.Header, error) {
+		var bodyReader io.Reader
+		if body != "" {
+			bodyReader = strings.NewReader(body)
+		}
+		req, err := http.NewRequest(method, urlStr, bodyReader)
+		if err != nil {
+			return nil, err
+		}
+		for len(headers) >= 2 {
+			req.Header.Add(headers[0], headers[1])
+			headers = headers[2:]
+		}
+		res, err := http.DefaultTransport.RoundTrip(req)
+		if err != nil {
+			return nil, err
+		}
+		defer res.Body.Close()
+		if res.StatusCode != wantStatusCode {
+			return nil, fmt.Errorf("got status code %d, want %d", res.StatusCode, wantStatusCode)
+		}
+		return res.Header, nil
+	}
+
+	prefixes := []string{
+		"/",
+		"/a/",
+		"/a/b/",
+		"/a/b/c/",
+	}
+	ctx := context.Background()
+	for _, prefix := range prefixes {
+		fs := NewMemFS()
+		h := &Handler{
+			FileSystem: fs,
+			LockSystem: NewMemLS(),
+		}
+		mux := http.NewServeMux()
+		if prefix != "/" {
+			h.Prefix = prefix
+		}
+		mux.Handle(prefix, h)
+		srv := httptest.NewServer(mux)
+		defer srv.Close()
+
+		// The script is:
+		//	MKCOL /a
+		//	MKCOL /a/b
+		//	PUT   /a/b/c
+		//	COPY  /a/b/c /a/b/d
+		//	MKCOL /a/b/e
+		//	MOVE  /a/b/d /a/b/e/f
+		//	LOCK  /a/b/e/g
+		//	PUT   /a/b/e/g
+		// which should yield the (possibly stripped) filenames /a/b/c,
+		// /a/b/e/f and /a/b/e/g, plus their parent directories.
+
+		wantA := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusMovedPermanently,
+			"/a/b/":   http.StatusNotFound,
+			"/a/b/c/": http.StatusNotFound,
+		}[prefix]
+		if _, err := do("MKCOL", srv.URL+"/a", "", wantA); err != nil {
+			t.Errorf("prefix=%-9q MKCOL /a: %v", prefix, err)
+			continue
+		}
+
+		wantB := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusMovedPermanently,
+			"/a/b/c/": http.StatusNotFound,
+		}[prefix]
+		if _, err := do("MKCOL", srv.URL+"/a/b", "", wantB); err != nil {
+			t.Errorf("prefix=%-9q MKCOL /a/b: %v", prefix, err)
+			continue
+		}
+
+		wantC := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusCreated,
+			"/a/b/c/": http.StatusMovedPermanently,
+		}[prefix]
+		if _, err := do("PUT", srv.URL+"/a/b/c", blah, wantC); err != nil {
+			t.Errorf("prefix=%-9q PUT /a/b/c: %v", prefix, err)
+			continue
+		}
+
+		wantD := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusCreated,
+			"/a/b/c/": http.StatusMovedPermanently,
+		}[prefix]
+		if _, err := do("COPY", srv.URL+"/a/b/c", "", wantD, dst, srv.URL+"/a/b/d"); err != nil {
+			t.Errorf("prefix=%-9q COPY /a/b/c /a/b/d: %v", prefix, err)
+			continue
+		}
+
+		wantE := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusCreated,
+			"/a/b/c/": http.StatusNotFound,
+		}[prefix]
+		if _, err := do("MKCOL", srv.URL+"/a/b/e", "", wantE); err != nil {
+			t.Errorf("prefix=%-9q MKCOL /a/b/e: %v", prefix, err)
+			continue
+		}
+
+		wantF := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusCreated,
+			"/a/b/c/": http.StatusNotFound,
+		}[prefix]
+		if _, err := do("MOVE", srv.URL+"/a/b/d", "", wantF, dst, srv.URL+"/a/b/e/f"); err != nil {
+			t.Errorf("prefix=%-9q MOVE /a/b/d /a/b/e/f: %v", prefix, err)
+			continue
+		}
+
+		var lockToken string
+		wantG := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusCreated,
+			"/a/b/c/": http.StatusNotFound,
+		}[prefix]
+		if h, err := do("LOCK", srv.URL+"/a/b/e/g", createLockBody, wantG); err != nil {
+			t.Errorf("prefix=%-9q LOCK /a/b/e/g: %v", prefix, err)
+			continue
+		} else {
+			lockToken = h.Get("Lock-Token")
+		}
+
+		ifHeader := fmt.Sprintf("<%s/a/b/e/g> (%s)", srv.URL, lockToken)
+		wantH := map[string]int{
+			"/":       http.StatusCreated,
+			"/a/":     http.StatusCreated,
+			"/a/b/":   http.StatusCreated,
+			"/a/b/c/": http.StatusNotFound,
+		}[prefix]
+		if _, err := do("PUT", srv.URL+"/a/b/e/g", blah, wantH, "If", ifHeader); err != nil {
+			t.Errorf("prefix=%-9q PUT /a/b/e/g: %v", prefix, err)
+			continue
+		}
+
+		got, err := find(ctx, nil, fs, "/")
+		if err != nil {
+			t.Errorf("prefix=%-9q find: %v", prefix, err)
+			continue
+		}
+		sort.Strings(got)
+		want := map[string][]string{
+			"/":       {"/", "/a", "/a/b", "/a/b/c", "/a/b/e", "/a/b/e/f", "/a/b/e/g"},
+			"/a/":     {"/", "/b", "/b/c", "/b/e", "/b/e/f", "/b/e/g"},
+			"/a/b/":   {"/", "/c", "/e", "/e/f", "/e/g"},
+			"/a/b/c/": {"/"},
+		}[prefix]
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("prefix=%-9q find:\ngot  %v\nwant %v", prefix, got, want)
+			continue
+		}
+	}
+}
+
+func TestEscapeXML(t *testing.T) {
+	// These test cases aren't exhaustive, and there is more than one way to
+	// escape e.g. a quot (as "&#34;" or "&quot;") or an apos. We presume that
+	// the encoding/xml package tests xml.EscapeText more thoroughly. This test
+	// here is just a sanity check for this package's escapeXML function, and
+	// its attempt to provide a fast path (and avoid a bytes.Buffer allocation)
+	// when escaping filenames is obviously a no-op.
+	testCases := map[string]string{
+		"":              "",
+		" ":             " ",
+		"&":             "&amp;",
+		"*":             "*",
+		"+":             "+",
+		",":             ",",
+		"-":             "-",
+		".":             ".",
+		"/":             "/",
+		"0":             "0",
+		"9":             "9",
+		":":             ":",
+		"<":             "&lt;",
+		">":             "&gt;",
+		"A":             "A",
+		"_":             "_",
+		"a":             "a",
+		"~":             "~",
+		"\u0201":        "\u0201",
+		"&amp;":         "&amp;amp;",
+		"foo&<b/ar>baz": "foo&amp;&lt;b/ar&gt;baz",
+	}
+
+	for in, want := range testCases {
+		if got := escapeXML(in); got != want {
+			t.Errorf("in=%q: got %q, want %q", in, got, want)
+		}
+	}
+}
+
+func TestFilenameEscape(t *testing.T) {
+	hrefRe := regexp.MustCompile(`<D:href>([^<]*)</D:href>`)
+	displayNameRe := regexp.MustCompile(`<D:displayname>([^<]*)</D:displayname>`)
+	do := func(method, urlStr string) (string, string, error) {
+		req, err := http.NewRequest(method, urlStr, nil)
+		if err != nil {
+			return "", "", err
+		}
+		res, err := http.DefaultClient.Do(req)
+		if err != nil {
+			return "", "", err
+		}
+		defer res.Body.Close()
+
+		b, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			return "", "", err
+		}
+		hrefMatch := hrefRe.FindStringSubmatch(string(b))
+		if len(hrefMatch) != 2 {
+			return "", "", errors.New("D:href not found")
+		}
+		displayNameMatch := displayNameRe.FindStringSubmatch(string(b))
+		if len(displayNameMatch) != 2 {
+			return "", "", errors.New("D:displayname not found")
+		}
+
+		return hrefMatch[1], displayNameMatch[1], nil
+	}
+
+	testCases := []struct {
+		name, wantHref, wantDisplayName string
+	}{{
+		name:            `/foo%bar`,
+		wantHref:        `/foo%25bar`,
+		wantDisplayName: `foo%bar`,
+	}, {
+		name:            `/こんにちわ世界`,
+		wantHref:        `/%E3%81%93%E3%82%93%E3%81%AB%E3%81%A1%E3%82%8F%E4%B8%96%E7%95%8C`,
+		wantDisplayName: `こんにちわ世界`,
+	}, {
+		name:            `/Program Files/`,
+		wantHref:        `/Program%20Files/`,
+		wantDisplayName: `Program Files`,
+	}, {
+		name:            `/go+lang`,
+		wantHref:        `/go+lang`,
+		wantDisplayName: `go+lang`,
+	}, {
+		name:            `/go&lang`,
+		wantHref:        `/go&amp;lang`,
+		wantDisplayName: `go&amp;lang`,
+	}, {
+		name:            `/go<lang`,
+		wantHref:        `/go%3Clang`,
+		wantDisplayName: `go&lt;lang`,
+	}, {
+		name:            `/`,
+		wantHref:        `/`,
+		wantDisplayName: ``,
+	}}
+	ctx := context.Background()
+	fs := NewMemFS()
+	for _, tc := range testCases {
+		if tc.name != "/" {
+			if strings.HasSuffix(tc.name, "/") {
+				if err := fs.Mkdir(ctx, tc.name, 0755); err != nil {
+					t.Fatalf("name=%q: Mkdir: %v", tc.name, err)
+				}
+			} else {
+				f, err := fs.OpenFile(ctx, tc.name, os.O_CREATE, 0644)
+				if err != nil {
+					t.Fatalf("name=%q: OpenFile: %v", tc.name, err)
+				}
+				f.Close()
+			}
+		}
+	}
+
+	srv := httptest.NewServer(&Handler{
+		FileSystem: fs,
+		LockSystem: NewMemLS(),
+	})
+	defer srv.Close()
+
+	u, err := url.Parse(srv.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, tc := range testCases {
+		u.Path = tc.name
+		gotHref, gotDisplayName, err := do("PROPFIND", u.String())
+		if err != nil {
+			t.Errorf("name=%q: PROPFIND: %v", tc.name, err)
+			continue
+		}
+		if gotHref != tc.wantHref {
+			t.Errorf("name=%q: got href %q, want %q", tc.name, gotHref, tc.wantHref)
+		}
+		if gotDisplayName != tc.wantDisplayName {
+			t.Errorf("name=%q: got dispayname %q, want %q", tc.name, gotDisplayName, tc.wantDisplayName)
+		}
+	}
+}

endpoints/drive/webdav/xml.go

@@ -0,0 +1,519 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+// The XML encoding is covered by Section 14.
+// http://www.webdav.org/specs/rfc4918.html#xml.element.definitions
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	// As of https://go-review.googlesource.com/#/c/12772/ which was submitted
+	// in July 2015, this package uses an internal fork of the standard
+	// library's encoding/xml package, due to changes in the way namespaces
+	// were encoded. Such changes were introduced in the Go 1.5 cycle, but were
+	// rolled back in response to https://github.com/golang/go/issues/11841
+	//
+	// However, this package's exported API, specifically the Property and
+	// DeadPropsHolder types, need to refer to the standard library's version
+	// of the xml.Name type, as code that imports this package cannot refer to
+	// the internal version.
+	//
+	// This file therefore imports both the internal and external versions, as
+	// ixml and xml, and converts between them.
+	//
+	// In the long term, this package should use the standard library's version
+	// only, and the internal fork deleted, once
+	// https://github.com/golang/go/issues/13400 is resolved.
+	ixml "golang.org/x/net/webdav/internal/xml"
+)
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_lockinfo
+type lockInfo struct {
+	XMLName   ixml.Name `xml:"lockinfo"`
+	Exclusive *struct{} `xml:"lockscope>exclusive"`
+	Shared    *struct{} `xml:"lockscope>shared"`
+	Write     *struct{} `xml:"locktype>write"`
+	Owner     owner     `xml:"owner"`
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_owner
+type owner struct {
+	InnerXML string `xml:",innerxml"`
+}
+
+func readLockInfo(r io.Reader) (li lockInfo, status int, err error) {
+	c := &countingReader{r: r}
+	if err = ixml.NewDecoder(c).Decode(&li); err != nil {
+		if err == io.EOF {
+			if c.n == 0 {
+				// An empty body means to refresh the lock.
+				// http://www.webdav.org/specs/rfc4918.html#refreshing-locks
+				return lockInfo{}, 0, nil
+			}
+			err = errInvalidLockInfo
+		}
+		return lockInfo{}, http.StatusBadRequest, err
+	}
+	// We only support exclusive (non-shared) write locks. In practice, these are
+	// the only types of locks that seem to matter.
+	if li.Exclusive == nil || li.Shared != nil || li.Write == nil {
+		return lockInfo{}, http.StatusNotImplemented, errUnsupportedLockInfo
+	}
+	return li, 0, nil
+}
+
+type countingReader struct {
+	n int
+	r io.Reader
+}
+
+func (c *countingReader) Read(p []byte) (int, error) {
+	n, err := c.r.Read(p)
+	c.n += n
+	return n, err
+}
+
+func writeLockInfo(w io.Writer, token string, ld LockDetails) (int, error) {
+	depth := "infinity"
+	if ld.ZeroDepth {
+		depth = "0"
+	}
+	timeout := ld.Duration / time.Second
+	return fmt.Fprintf(w, "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"+
+		"<D:prop xmlns:D=\"DAV:\"><D:lockdiscovery><D:activelock>\n"+
+		"	<D:locktype><D:write/></D:locktype>\n"+
+		"	<D:lockscope><D:exclusive/></D:lockscope>\n"+
+		"	<D:depth>%s</D:depth>\n"+
+		"	<D:owner>%s</D:owner>\n"+
+		"	<D:timeout>Second-%d</D:timeout>\n"+
+		"	<D:locktoken><D:href>%s</D:href></D:locktoken>\n"+
+		"	<D:lockroot><D:href>%s</D:href></D:lockroot>\n"+
+		"</D:activelock></D:lockdiscovery></D:prop>",
+		depth, ld.OwnerXML, timeout, escape(token), escape(ld.Root),
+	)
+}
+
+func escape(s string) string {
+	for i := 0; i < len(s); i++ {
+		switch s[i] {
+		case '"', '&', '\'', '<', '>':
+			b := bytes.NewBuffer(nil)
+			ixml.EscapeText(b, []byte(s))
+			return b.String()
+		}
+	}
+	return s
+}
+
+// next returns the next token, if any, in the XML stream of d.
+// RFC 4918 requires to ignore comments, processing instructions
+// and directives.
+// http://www.webdav.org/specs/rfc4918.html#property_values
+// http://www.webdav.org/specs/rfc4918.html#xml-extensibility
+func next(d *ixml.Decoder) (ixml.Token, error) {
+	for {
+		t, err := d.Token()
+		if err != nil {
+			return t, err
+		}
+		switch t.(type) {
+		case ixml.Comment, ixml.Directive, ixml.ProcInst:
+			continue
+		default:
+			return t, nil
+		}
+	}
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_prop (for propfind)
+type propfindProps []xml.Name
+
+// UnmarshalXML appends the property names enclosed within start to pn.
+//
+// It returns an error if start does not contain any properties or if
+// properties contain values. Character data between properties is ignored.
+func (pn *propfindProps) UnmarshalXML(d *ixml.Decoder, start ixml.StartElement) error {
+	for {
+		t, err := next(d)
+		if err != nil {
+			return err
+		}
+		switch t.(type) {
+		case ixml.EndElement:
+			if len(*pn) == 0 {
+				return fmt.Errorf("%s must not be empty", start.Name.Local)
+			}
+			return nil
+		case ixml.StartElement:
+			name := t.(ixml.StartElement).Name
+			t, err = next(d)
+			if err != nil {
+				return err
+			}
+			if _, ok := t.(ixml.EndElement); !ok {
+				return fmt.Errorf("unexpected token %T", t)
+			}
+			*pn = append(*pn, xml.Name(name))
+		}
+	}
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propfind
+type propfind struct {
+	XMLName  ixml.Name     `xml:"DAV: propfind"`
+	Allprop  *struct{}     `xml:"DAV: allprop"`
+	Propname *struct{}     `xml:"DAV: propname"`
+	Prop     propfindProps `xml:"DAV: prop"`
+	Include  propfindProps `xml:"DAV: include"`
+}
+
+func readPropfind(r io.Reader) (pf propfind, status int, err error) {
+	c := countingReader{r: r}
+	if err = ixml.NewDecoder(&c).Decode(&pf); err != nil {
+		if err == io.EOF {
+			if c.n == 0 {
+				// An empty body means to propfind allprop.
+				// http://www.webdav.org/specs/rfc4918.html#METHOD_PROPFIND
+				return propfind{Allprop: new(struct{})}, 0, nil
+			}
+			err = errInvalidPropfind
+		}
+		return propfind{}, http.StatusBadRequest, err
+	}
+
+	if pf.Allprop == nil && pf.Include != nil {
+		return propfind{}, http.StatusBadRequest, errInvalidPropfind
+	}
+	if pf.Allprop != nil && (pf.Prop != nil || pf.Propname != nil) {
+		return propfind{}, http.StatusBadRequest, errInvalidPropfind
+	}
+	if pf.Prop != nil && pf.Propname != nil {
+		return propfind{}, http.StatusBadRequest, errInvalidPropfind
+	}
+	if pf.Propname == nil && pf.Allprop == nil && pf.Prop == nil {
+		return propfind{}, http.StatusBadRequest, errInvalidPropfind
+	}
+	return pf, 0, nil
+}
+
+// Property represents a single DAV resource property as defined in RFC 4918.
+// See http://www.webdav.org/specs/rfc4918.html#data.model.for.resource.properties
+type Property struct {
+	// XMLName is the fully qualified name that identifies this property.
+	XMLName xml.Name
+
+	// Lang is an optional xml:lang attribute.
+	Lang string `xml:"xml:lang,attr,omitempty"`
+
+	// InnerXML contains the XML representation of the property value.
+	// See http://www.webdav.org/specs/rfc4918.html#property_values
+	//
+	// Property values of complex type or mixed-content must have fully
+	// expanded XML namespaces or be self-contained with according
+	// XML namespace declarations. They must not rely on any XML
+	// namespace declarations within the scope of the XML document,
+	// even including the DAV: namespace.
+	InnerXML []byte `xml:",innerxml"`
+}
+
+// ixmlProperty is the same as the Property type except it holds an ixml.Name
+// instead of an xml.Name.
+type ixmlProperty struct {
+	XMLName  ixml.Name
+	Lang     string `xml:"xml:lang,attr,omitempty"`
+	InnerXML []byte `xml:",innerxml"`
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_error
+// See multistatusWriter for the "D:" namespace prefix.
+type xmlError struct {
+	XMLName  ixml.Name `xml:"D:error"`
+	InnerXML []byte    `xml:",innerxml"`
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat
+// See multistatusWriter for the "D:" namespace prefix.
+type propstat struct {
+	Prop                []Property `xml:"D:prop>_ignored_"`
+	Status              string     `xml:"D:status"`
+	Error               *xmlError  `xml:"D:error"`
+	ResponseDescription string     `xml:"D:responsedescription,omitempty"`
+}
+
+// ixmlPropstat is the same as the propstat type except it holds an ixml.Name
+// instead of an xml.Name.
+type ixmlPropstat struct {
+	Prop                []ixmlProperty `xml:"D:prop>_ignored_"`
+	Status              string         `xml:"D:status"`
+	Error               *xmlError      `xml:"D:error"`
+	ResponseDescription string         `xml:"D:responsedescription,omitempty"`
+}
+
+// MarshalXML prepends the "D:" namespace prefix on properties in the DAV: namespace
+// before encoding. See multistatusWriter.
+func (ps propstat) MarshalXML(e *ixml.Encoder, start ixml.StartElement) error {
+	// Convert from a propstat to an ixmlPropstat.
+	ixmlPs := ixmlPropstat{
+		Prop:                make([]ixmlProperty, len(ps.Prop)),
+		Status:              ps.Status,
+		Error:               ps.Error,
+		ResponseDescription: ps.ResponseDescription,
+	}
+	for k, prop := range ps.Prop {
+		ixmlPs.Prop[k] = ixmlProperty{
+			XMLName:  ixml.Name(prop.XMLName),
+			Lang:     prop.Lang,
+			InnerXML: prop.InnerXML,
+		}
+	}
+
+	for k, prop := range ixmlPs.Prop {
+		if prop.XMLName.Space == "DAV:" {
+			prop.XMLName = ixml.Name{Space: "", Local: "D:" + prop.XMLName.Local}
+			ixmlPs.Prop[k] = prop
+		}
+	}
+	// Distinct type to avoid infinite recursion of MarshalXML.
+	type newpropstat ixmlPropstat
+	return e.EncodeElement(newpropstat(ixmlPs), start)
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_response
+// See multistatusWriter for the "D:" namespace prefix.
+type response struct {
+	XMLName             ixml.Name  `xml:"D:response"`
+	Href                []string   `xml:"D:href"`
+	Propstat            []propstat `xml:"D:propstat"`
+	Status              string     `xml:"D:status,omitempty"`
+	Error               *xmlError  `xml:"D:error"`
+	ResponseDescription string     `xml:"D:responsedescription,omitempty"`
+}
+
+// MultistatusWriter marshals one or more Responses into a XML
+// multistatus response.
+// See http://www.webdav.org/specs/rfc4918.html#ELEMENT_multistatus
+// TODO(rsto, mpl): As a workaround, the "D:" namespace prefix, defined as
+// "DAV:" on this element, is prepended on the nested response, as well as on all
+// its nested elements. All property names in the DAV: namespace are prefixed as
+// well. This is because some versions of Mini-Redirector (on windows 7) ignore
+// elements with a default namespace (no prefixed namespace). A less intrusive fix
+// should be possible after golang.org/cl/11074. See https://golang.org/issue/11177
+type multistatusWriter struct {
+	// ResponseDescription contains the optional responsedescription
+	// of the multistatus XML element. Only the latest content before
+	// close will be emitted. Empty response descriptions are not
+	// written.
+	responseDescription string
+
+	w   http.ResponseWriter
+	enc *ixml.Encoder
+}
+
+// Write validates and emits a DAV response as part of a multistatus response
+// element.
+//
+// It sets the HTTP status code of its underlying http.ResponseWriter to 207
+// (Multi-Status) and populates the Content-Type header. If r is the
+// first, valid response to be written, Write prepends the XML representation
+// of r with a multistatus tag. Callers must call close after the last response
+// has been written.
+func (w *multistatusWriter) write(r *response) error {
+	switch len(r.Href) {
+	case 0:
+		return errInvalidResponse
+	case 1:
+		if len(r.Propstat) > 0 != (r.Status == "") {
+			return errInvalidResponse
+		}
+	default:
+		if len(r.Propstat) > 0 || r.Status == "" {
+			return errInvalidResponse
+		}
+	}
+	err := w.writeHeader()
+	if err != nil {
+		return err
+	}
+	return w.enc.Encode(r)
+}
+
+// writeHeader writes a XML multistatus start element on w's underlying
+// http.ResponseWriter and returns the result of the write operation.
+// After the first write attempt, writeHeader becomes a no-op.
+func (w *multistatusWriter) writeHeader() error {
+	if w.enc != nil {
+		return nil
+	}
+	w.w.Header().Add("Content-Type", "text/xml; charset=utf-8")
+	w.w.WriteHeader(StatusMulti)
+	_, err := fmt.Fprintf(w.w, `<?xml version="1.0" encoding="UTF-8"?>`)
+	if err != nil {
+		return err
+	}
+	w.enc = ixml.NewEncoder(w.w)
+	return w.enc.EncodeToken(ixml.StartElement{
+		Name: ixml.Name{
+			Space: "DAV:",
+			Local: "multistatus",
+		},
+		Attr: []ixml.Attr{{
+			Name:  ixml.Name{Space: "xmlns", Local: "D"},
+			Value: "DAV:",
+		}},
+	})
+}
+
+// Close completes the marshalling of the multistatus response. It returns
+// an error if the multistatus response could not be completed. If both the
+// return value and field enc of w are nil, then no multistatus response has
+// been written.
+func (w *multistatusWriter) close() error {
+	if w.enc == nil {
+		return nil
+	}
+	var end []ixml.Token
+	if w.responseDescription != "" {
+		name := ixml.Name{Space: "DAV:", Local: "responsedescription"}
+		end = append(end,
+			ixml.StartElement{Name: name},
+			ixml.CharData(w.responseDescription),
+			ixml.EndElement{Name: name},
+		)
+	}
+	end = append(end, ixml.EndElement{
+		Name: ixml.Name{Space: "DAV:", Local: "multistatus"},
+	})
+	for _, t := range end {
+		err := w.enc.EncodeToken(t)
+		if err != nil {
+			return err
+		}
+	}
+	return w.enc.Flush()
+}
+
+var xmlLangName = ixml.Name{Space: "http://www.w3.org/XML/1998/namespace", Local: "lang"}
+
+func xmlLang(s ixml.StartElement, d string) string {
+	for _, attr := range s.Attr {
+		if attr.Name == xmlLangName {
+			return attr.Value
+		}
+	}
+	return d
+}
+
+type xmlValue []byte
+
+func (v *xmlValue) UnmarshalXML(d *ixml.Decoder, start ixml.StartElement) error {
+	// The XML value of a property can be arbitrary, mixed-content XML.
+	// To make sure that the unmarshalled value contains all required
+	// namespaces, we encode all the property value XML tokens into a
+	// buffer. This forces the encoder to redeclare any used namespaces.
+	var b bytes.Buffer
+	e := ixml.NewEncoder(&b)
+	for {
+		t, err := next(d)
+		if err != nil {
+			return err
+		}
+		if e, ok := t.(ixml.EndElement); ok && e.Name == start.Name {
+			break
+		}
+		if err = e.EncodeToken(t); err != nil {
+			return err
+		}
+	}
+	err := e.Flush()
+	if err != nil {
+		return err
+	}
+	*v = b.Bytes()
+	return nil
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_prop (for proppatch)
+type proppatchProps []Property
+
+// UnmarshalXML appends the property names and values enclosed within start
+// to ps.
+//
+// An xml:lang attribute that is defined either on the DAV:prop or property
+// name XML element is propagated to the property's Lang field.
+//
+// UnmarshalXML returns an error if start does not contain any properties or if
+// property values contain syntactically incorrect XML.
+func (ps *proppatchProps) UnmarshalXML(d *ixml.Decoder, start ixml.StartElement) error {
+	lang := xmlLang(start, "")
+	for {
+		t, err := next(d)
+		if err != nil {
+			return err
+		}
+		switch elem := t.(type) {
+		case ixml.EndElement:
+			if len(*ps) == 0 {
+				return fmt.Errorf("%s must not be empty", start.Name.Local)
+			}
+			return nil
+		case ixml.StartElement:
+			p := Property{
+				XMLName: xml.Name(t.(ixml.StartElement).Name),
+				Lang:    xmlLang(t.(ixml.StartElement), lang),
+			}
+			err = d.DecodeElement(((*xmlValue)(&p.InnerXML)), &elem)
+			if err != nil {
+				return err
+			}
+			*ps = append(*ps, p)
+		}
+	}
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_set
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_remove
+type setRemove struct {
+	XMLName ixml.Name
+	Lang    string         `xml:"xml:lang,attr,omitempty"`
+	Prop    proppatchProps `xml:"DAV: prop"`
+}
+
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propertyupdate
+type propertyupdate struct {
+	XMLName   ixml.Name   `xml:"DAV: propertyupdate"`
+	Lang      string      `xml:"xml:lang,attr,omitempty"`
+	SetRemove []setRemove `xml:",any"`
+}
+
+func readProppatch(r io.Reader) (patches []Proppatch, status int, err error) {
+	var pu propertyupdate
+	if err = ixml.NewDecoder(r).Decode(&pu); err != nil {
+		return nil, http.StatusBadRequest, err
+	}
+	for _, op := range pu.SetRemove {
+		remove := false
+		switch op.XMLName {
+		case ixml.Name{Space: "DAV:", Local: "set"}:
+			// No-op.
+		case ixml.Name{Space: "DAV:", Local: "remove"}:
+			for _, p := range op.Prop {
+				if len(p.InnerXML) > 0 {
+					return nil, http.StatusBadRequest, errInvalidProppatch
+				}
+			}
+			remove = true
+		default:
+			return nil, http.StatusBadRequest, errInvalidProppatch
+		}
+		patches = append(patches, Proppatch{Remove: remove, Props: op.Prop})
+	}
+	return patches, 0, nil
+}

endpoints/drive/webdav/xml_test.go

@@ -0,0 +1,905 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webdav
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"sort"
+	"strings"
+	"testing"
+
+	ixml "github.com/openziti/zrok/endpoints/drive/webdav/internal/xml"
+)
+
+func TestReadLockInfo(t *testing.T) {
+	// The "section x.y.z" test cases come from section x.y.z of the spec at
+	// http://www.webdav.org/specs/rfc4918.html
+	testCases := []struct {
+		desc       string
+		input      string
+		wantLI     lockInfo
+		wantStatus int
+	}{{
+		"bad: junk",
+		"xxx",
+		lockInfo{},
+		http.StatusBadRequest,
+	}, {
+		"bad: invalid owner XML",
+		"" +
+			"<D:lockinfo xmlns:D='DAV:'>\n" +
+			"  <D:lockscope><D:exclusive/></D:lockscope>\n" +
+			"  <D:locktype><D:write/></D:locktype>\n" +
+			"  <D:owner>\n" +
+			"    <D:href>   no end tag   \n" +
+			"  </D:owner>\n" +
+			"</D:lockinfo>",
+		lockInfo{},
+		http.StatusBadRequest,
+	}, {
+		"bad: invalid UTF-8",
+		"" +
+			"<D:lockinfo xmlns:D='DAV:'>\n" +
+			"  <D:lockscope><D:exclusive/></D:lockscope>\n" +
+			"  <D:locktype><D:write/></D:locktype>\n" +
+			"  <D:owner>\n" +
+			"    <D:href>   \xff   </D:href>\n" +
+			"  </D:owner>\n" +
+			"</D:lockinfo>",
+		lockInfo{},
+		http.StatusBadRequest,
+	}, {
+		"bad: unfinished XML #1",
+		"" +
+			"<D:lockinfo xmlns:D='DAV:'>\n" +
+			"  <D:lockscope><D:exclusive/></D:lockscope>\n" +
+			"  <D:locktype><D:write/></D:locktype>\n",
+		lockInfo{},
+		http.StatusBadRequest,
+	}, {
+		"bad: unfinished XML #2",
+		"" +
+			"<D:lockinfo xmlns:D='DAV:'>\n" +
+			"  <D:lockscope><D:exclusive/></D:lockscope>\n" +
+			"  <D:locktype><D:write/></D:locktype>\n" +
+			"  <D:owner>\n",
+		lockInfo{},
+		http.StatusBadRequest,
+	}, {
+		"good: empty",
+		"",
+		lockInfo{},
+		0,
+	}, {
+		"good: plain-text owner",
+		"" +
+			"<D:lockinfo xmlns:D='DAV:'>\n" +
+			"  <D:lockscope><D:exclusive/></D:lockscope>\n" +
+			"  <D:locktype><D:write/></D:locktype>\n" +
+			"  <D:owner>gopher</D:owner>\n" +
+			"</D:lockinfo>",
+		lockInfo{
+			XMLName:   ixml.Name{Space: "DAV:", Local: "lockinfo"},
+			Exclusive: new(struct{}),
+			Write:     new(struct{}),
+			Owner: owner{
+				InnerXML: "gopher",
+			},
+		},
+		0,
+	}, {
+		"section 9.10.7",
+		"" +
+			"<D:lockinfo xmlns:D='DAV:'>\n" +
+			"  <D:lockscope><D:exclusive/></D:lockscope>\n" +
+			"  <D:locktype><D:write/></D:locktype>\n" +
+			"  <D:owner>\n" +
+			"    <D:href>http://example.org/~ejw/contact.html</D:href>\n" +
+			"  </D:owner>\n" +
+			"</D:lockinfo>",
+		lockInfo{
+			XMLName:   ixml.Name{Space: "DAV:", Local: "lockinfo"},
+			Exclusive: new(struct{}),
+			Write:     new(struct{}),
+			Owner: owner{
+				InnerXML: "\n    <D:href>http://example.org/~ejw/contact.html</D:href>\n  ",
+			},
+		},
+		0,
+	}}
+
+	for _, tc := range testCases {
+		li, status, err := readLockInfo(strings.NewReader(tc.input))
+		if tc.wantStatus != 0 {
+			if err == nil {
+				t.Errorf("%s: got nil error, want non-nil", tc.desc)
+				continue
+			}
+		} else if err != nil {
+			t.Errorf("%s: %v", tc.desc, err)
+			continue
+		}
+		if !reflect.DeepEqual(li, tc.wantLI) || status != tc.wantStatus {
+			t.Errorf("%s:\ngot  lockInfo=%v, status=%v\nwant lockInfo=%v, status=%v",
+				tc.desc, li, status, tc.wantLI, tc.wantStatus)
+			continue
+		}
+	}
+}
+
+func TestReadPropfind(t *testing.T) {
+	testCases := []struct {
+		desc       string
+		input      string
+		wantPF     propfind
+		wantStatus int
+	}{{
+		desc: "propfind: propname",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:propname/>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName:  ixml.Name{Space: "DAV:", Local: "propfind"},
+			Propname: new(struct{}),
+		},
+	}, {
+		desc:  "propfind: empty body means allprop",
+		input: "",
+		wantPF: propfind{
+			Allprop: new(struct{}),
+		},
+	}, {
+		desc: "propfind: allprop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"   <A:allprop/>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Allprop: new(struct{}),
+		},
+	}, {
+		desc: "propfind: allprop followed by include",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:allprop/>\n" +
+			"  <A:include><A:displayname/></A:include>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Allprop: new(struct{}),
+			Include: propfindProps{xml.Name{Space: "DAV:", Local: "displayname"}},
+		},
+	}, {
+		desc: "propfind: include followed by allprop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:include><A:displayname/></A:include>\n" +
+			"  <A:allprop/>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Allprop: new(struct{}),
+			Include: propfindProps{xml.Name{Space: "DAV:", Local: "displayname"}},
+		},
+	}, {
+		desc: "propfind: propfind",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop><A:displayname/></A:prop>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Prop:    propfindProps{xml.Name{Space: "DAV:", Local: "displayname"}},
+		},
+	}, {
+		desc: "propfind: prop with ignored comments",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop>\n" +
+			"    <!-- ignore -->\n" +
+			"    <A:displayname><!-- ignore --></A:displayname>\n" +
+			"  </A:prop>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Prop:    propfindProps{xml.Name{Space: "DAV:", Local: "displayname"}},
+		},
+	}, {
+		desc: "propfind: propfind with ignored whitespace",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop>   <A:displayname/></A:prop>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Prop:    propfindProps{xml.Name{Space: "DAV:", Local: "displayname"}},
+		},
+	}, {
+		desc: "propfind: propfind with ignored mixed-content",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop>foo<A:displayname/>bar</A:prop>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName: ixml.Name{Space: "DAV:", Local: "propfind"},
+			Prop:    propfindProps{xml.Name{Space: "DAV:", Local: "displayname"}},
+		},
+	}, {
+		desc: "propfind: propname with ignored element (section A.4)",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:propname/>\n" +
+			"  <E:leave-out xmlns:E='E:'>*boss*</E:leave-out>\n" +
+			"</A:propfind>",
+		wantPF: propfind{
+			XMLName:  ixml.Name{Space: "DAV:", Local: "propfind"},
+			Propname: new(struct{}),
+		},
+	}, {
+		desc:       "propfind: bad: junk",
+		input:      "xxx",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: propname and allprop (section A.3)",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:propname/>" +
+			"  <A:allprop/>" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: propname and prop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop><A:displayname/></A:prop>\n" +
+			"  <A:propname/>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: allprop and prop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:allprop/>\n" +
+			"  <A:prop><A:foo/><A:/prop>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: empty propfind with ignored element (section A.4)",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <E:expired-props/>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: empty prop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop/>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: prop with just chardata",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop>foo</A:prop>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "bad: interrupted prop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop><A:foo></A:prop>\n",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "bad: malformed end element prop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop><A:foo/></A:bar></A:prop>\n",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: property with chardata value",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop><A:foo>bar</A:foo></A:prop>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: property with whitespace value",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:prop><A:foo> </A:foo></A:prop>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "propfind: bad: include without allprop",
+		input: "" +
+			"<A:propfind xmlns:A='DAV:'>\n" +
+			"  <A:include><A:foo/></A:include>\n" +
+			"</A:propfind>",
+		wantStatus: http.StatusBadRequest,
+	}}
+
+	for _, tc := range testCases {
+		pf, status, err := readPropfind(strings.NewReader(tc.input))
+		if tc.wantStatus != 0 {
+			if err == nil {
+				t.Errorf("%s: got nil error, want non-nil", tc.desc)
+				continue
+			}
+		} else if err != nil {
+			t.Errorf("%s: %v", tc.desc, err)
+			continue
+		}
+		if !reflect.DeepEqual(pf, tc.wantPF) || status != tc.wantStatus {
+			t.Errorf("%s:\ngot  propfind=%v, status=%v\nwant propfind=%v, status=%v",
+				tc.desc, pf, status, tc.wantPF, tc.wantStatus)
+			continue
+		}
+	}
+}
+
+func TestMultistatusWriter(t *testing.T) {
+	///The "section x.y.z" test cases come from section x.y.z of the spec at
+	// http://www.webdav.org/specs/rfc4918.html
+	testCases := []struct {
+		desc        string
+		responses   []response
+		respdesc    string
+		writeHeader bool
+		wantXML     string
+		wantCode    int
+		wantErr     error
+	}{{
+		desc: "section 9.2.2 (failed dependency)",
+		responses: []response{{
+			Href: []string{"http://example.com/foo"},
+			Propstat: []propstat{{
+				Prop: []Property{{
+					XMLName: xml.Name{
+						Space: "http://ns.example.com/",
+						Local: "Authors",
+					},
+				}},
+				Status: "HTTP/1.1 424 Failed Dependency",
+			}, {
+				Prop: []Property{{
+					XMLName: xml.Name{
+						Space: "http://ns.example.com/",
+						Local: "Copyright-Owner",
+					},
+				}},
+				Status: "HTTP/1.1 409 Conflict",
+			}},
+			ResponseDescription: "Copyright Owner cannot be deleted or altered.",
+		}},
+		wantXML: `` +
+			`<?xml version="1.0" encoding="UTF-8"?>` +
+			`<multistatus xmlns="DAV:">` +
+			`  <response>` +
+			`    <href>http://example.com/foo</href>` +
+			`    <propstat>` +
+			`      <prop>` +
+			`        <Authors xmlns="http://ns.example.com/"></Authors>` +
+			`      </prop>` +
+			`      <status>HTTP/1.1 424 Failed Dependency</status>` +
+			`    </propstat>` +
+			`    <propstat xmlns="DAV:">` +
+			`      <prop>` +
+			`        <Copyright-Owner xmlns="http://ns.example.com/"></Copyright-Owner>` +
+			`      </prop>` +
+			`      <status>HTTP/1.1 409 Conflict</status>` +
+			`    </propstat>` +
+			`  <responsedescription>Copyright Owner cannot be deleted or altered.</responsedescription>` +
+			`</response>` +
+			`</multistatus>`,
+		wantCode: StatusMulti,
+	}, {
+		desc: "section 9.6.2 (lock-token-submitted)",
+		responses: []response{{
+			Href:   []string{"http://example.com/foo"},
+			Status: "HTTP/1.1 423 Locked",
+			Error: &xmlError{
+				InnerXML: []byte(`<lock-token-submitted xmlns="DAV:"/>`),
+			},
+		}},
+		wantXML: `` +
+			`<?xml version="1.0" encoding="UTF-8"?>` +
+			`<multistatus xmlns="DAV:">` +
+			`  <response>` +
+			`    <href>http://example.com/foo</href>` +
+			`    <status>HTTP/1.1 423 Locked</status>` +
+			`    <error><lock-token-submitted xmlns="DAV:"/></error>` +
+			`  </response>` +
+			`</multistatus>`,
+		wantCode: StatusMulti,
+	}, {
+		desc: "section 9.1.3",
+		responses: []response{{
+			Href: []string{"http://example.com/foo"},
+			Propstat: []propstat{{
+				Prop: []Property{{
+					XMLName: xml.Name{Space: "http://ns.example.com/boxschema/", Local: "bigbox"},
+					InnerXML: []byte(`` +
+						`<BoxType xmlns="http://ns.example.com/boxschema/">` +
+						`Box type A` +
+						`</BoxType>`),
+				}, {
+					XMLName: xml.Name{Space: "http://ns.example.com/boxschema/", Local: "author"},
+					InnerXML: []byte(`` +
+						`<Name xmlns="http://ns.example.com/boxschema/">` +
+						`J.J. Johnson` +
+						`</Name>`),
+				}},
+				Status: "HTTP/1.1 200 OK",
+			}, {
+				Prop: []Property{{
+					XMLName: xml.Name{Space: "http://ns.example.com/boxschema/", Local: "DingALing"},
+				}, {
+					XMLName: xml.Name{Space: "http://ns.example.com/boxschema/", Local: "Random"},
+				}},
+				Status:              "HTTP/1.1 403 Forbidden",
+				ResponseDescription: "The user does not have access to the DingALing property.",
+			}},
+		}},
+		respdesc: "There has been an access violation error.",
+		wantXML: `` +
+			`<?xml version="1.0" encoding="UTF-8"?>` +
+			`<multistatus xmlns="DAV:" xmlns:B="http://ns.example.com/boxschema/">` +
+			`  <response>` +
+			`    <href>http://example.com/foo</href>` +
+			`    <propstat>` +
+			`      <prop>` +
+			`        <B:bigbox><B:BoxType>Box type A</B:BoxType></B:bigbox>` +
+			`        <B:author><B:Name>J.J. Johnson</B:Name></B:author>` +
+			`      </prop>` +
+			`      <status>HTTP/1.1 200 OK</status>` +
+			`    </propstat>` +
+			`    <propstat>` +
+			`      <prop>` +
+			`        <B:DingALing/>` +
+			`        <B:Random/>` +
+			`      </prop>` +
+			`      <status>HTTP/1.1 403 Forbidden</status>` +
+			`      <responsedescription>The user does not have access to the DingALing property.</responsedescription>` +
+			`    </propstat>` +
+			`  </response>` +
+			`  <responsedescription>There has been an access violation error.</responsedescription>` +
+			`</multistatus>`,
+		wantCode: StatusMulti,
+	}, {
+		desc: "no response written",
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}, {
+		desc:     "no response written (with description)",
+		respdesc: "too bad",
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}, {
+		desc:        "empty multistatus with header",
+		writeHeader: true,
+		wantXML:     `<multistatus xmlns="DAV:"></multistatus>`,
+		wantCode:    StatusMulti,
+	}, {
+		desc: "bad: no href",
+		responses: []response{{
+			Propstat: []propstat{{
+				Prop: []Property{{
+					XMLName: xml.Name{
+						Space: "http://example.com/",
+						Local: "foo",
+					},
+				}},
+				Status: "HTTP/1.1 200 OK",
+			}},
+		}},
+		wantErr: errInvalidResponse,
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}, {
+		desc: "bad: multiple hrefs and no status",
+		responses: []response{{
+			Href: []string{"http://example.com/foo", "http://example.com/bar"},
+		}},
+		wantErr: errInvalidResponse,
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}, {
+		desc: "bad: one href and no propstat",
+		responses: []response{{
+			Href: []string{"http://example.com/foo"},
+		}},
+		wantErr: errInvalidResponse,
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}, {
+		desc: "bad: status with one href and propstat",
+		responses: []response{{
+			Href: []string{"http://example.com/foo"},
+			Propstat: []propstat{{
+				Prop: []Property{{
+					XMLName: xml.Name{
+						Space: "http://example.com/",
+						Local: "foo",
+					},
+				}},
+				Status: "HTTP/1.1 200 OK",
+			}},
+			Status: "HTTP/1.1 200 OK",
+		}},
+		wantErr: errInvalidResponse,
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}, {
+		desc: "bad: multiple hrefs and propstat",
+		responses: []response{{
+			Href: []string{
+				"http://example.com/foo",
+				"http://example.com/bar",
+			},
+			Propstat: []propstat{{
+				Prop: []Property{{
+					XMLName: xml.Name{
+						Space: "http://example.com/",
+						Local: "foo",
+					},
+				}},
+				Status: "HTTP/1.1 200 OK",
+			}},
+		}},
+		wantErr: errInvalidResponse,
+		// default of http.responseWriter
+		wantCode: http.StatusOK,
+	}}
+
+	n := xmlNormalizer{omitWhitespace: true}
+loop:
+	for _, tc := range testCases {
+		rec := httptest.NewRecorder()
+		w := multistatusWriter{w: rec, responseDescription: tc.respdesc}
+		if tc.writeHeader {
+			if err := w.writeHeader(); err != nil {
+				t.Errorf("%s: got writeHeader error %v, want nil", tc.desc, err)
+				continue
+			}
+		}
+		for _, r := range tc.responses {
+			if err := w.write(&r); err != nil {
+				if err != tc.wantErr {
+					t.Errorf("%s: got write error %v, want %v",
+						tc.desc, err, tc.wantErr)
+				}
+				continue loop
+			}
+		}
+		if err := w.close(); err != tc.wantErr {
+			t.Errorf("%s: got close error %v, want %v",
+				tc.desc, err, tc.wantErr)
+			continue
+		}
+		if rec.Code != tc.wantCode {
+			t.Errorf("%s: got HTTP status code %d, want %d\n",
+				tc.desc, rec.Code, tc.wantCode)
+			continue
+		}
+		gotXML := rec.Body.String()
+		eq, err := n.equalXML(strings.NewReader(gotXML), strings.NewReader(tc.wantXML))
+		if err != nil {
+			t.Errorf("%s: equalXML: %v", tc.desc, err)
+			continue
+		}
+		if !eq {
+			t.Errorf("%s: XML body\ngot  %s\nwant %s", tc.desc, gotXML, tc.wantXML)
+		}
+	}
+}
+
+func TestReadProppatch(t *testing.T) {
+	ppStr := func(pps []Proppatch) string {
+		var outer []string
+		for _, pp := range pps {
+			var inner []string
+			for _, p := range pp.Props {
+				inner = append(inner, fmt.Sprintf("{XMLName: %q, Lang: %q, InnerXML: %q}",
+					p.XMLName, p.Lang, p.InnerXML))
+			}
+			outer = append(outer, fmt.Sprintf("{Remove: %t, Props: [%s]}",
+				pp.Remove, strings.Join(inner, ", ")))
+		}
+		return "[" + strings.Join(outer, ", ") + "]"
+	}
+
+	testCases := []struct {
+		desc       string
+		input      string
+		wantPP     []Proppatch
+		wantStatus int
+	}{{
+		desc: "proppatch: section 9.2 (with simple property value)",
+		input: `` +
+			`<?xml version="1.0" encoding="utf-8" ?>` +
+			`<D:propertyupdate xmlns:D="DAV:"` +
+			`                  xmlns:Z="http://ns.example.com/z/">` +
+			`    <D:set>` +
+			`         <D:prop><Z:Authors>somevalue</Z:Authors></D:prop>` +
+			`    </D:set>` +
+			`    <D:remove>` +
+			`         <D:prop><Z:Copyright-Owner/></D:prop>` +
+			`    </D:remove>` +
+			`</D:propertyupdate>`,
+		wantPP: []Proppatch{{
+			Props: []Property{{
+				xml.Name{Space: "http://ns.example.com/z/", Local: "Authors"},
+				"",
+				[]byte(`somevalue`),
+			}},
+		}, {
+			Remove: true,
+			Props: []Property{{
+				xml.Name{Space: "http://ns.example.com/z/", Local: "Copyright-Owner"},
+				"",
+				nil,
+			}},
+		}},
+	}, {
+		desc: "proppatch: lang attribute on prop",
+		input: `` +
+			`<?xml version="1.0" encoding="utf-8" ?>` +
+			`<D:propertyupdate xmlns:D="DAV:">` +
+			`    <D:set>` +
+			`         <D:prop xml:lang="en">` +
+			`              <foo xmlns="http://example.com/ns"/>` +
+			`         </D:prop>` +
+			`    </D:set>` +
+			`</D:propertyupdate>`,
+		wantPP: []Proppatch{{
+			Props: []Property{{
+				xml.Name{Space: "http://example.com/ns", Local: "foo"},
+				"en",
+				nil,
+			}},
+		}},
+	}, {
+		desc: "bad: remove with value",
+		input: `` +
+			`<?xml version="1.0" encoding="utf-8" ?>` +
+			`<D:propertyupdate xmlns:D="DAV:"` +
+			`                  xmlns:Z="http://ns.example.com/z/">` +
+			`    <D:remove>` +
+			`         <D:prop>` +
+			`              <Z:Authors>` +
+			`              <Z:Author>Jim Whitehead</Z:Author>` +
+			`              </Z:Authors>` +
+			`         </D:prop>` +
+			`    </D:remove>` +
+			`</D:propertyupdate>`,
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "bad: empty propertyupdate",
+		input: `` +
+			`<?xml version="1.0" encoding="utf-8" ?>` +
+			`<D:propertyupdate xmlns:D="DAV:"` +
+			`</D:propertyupdate>`,
+		wantStatus: http.StatusBadRequest,
+	}, {
+		desc: "bad: empty prop",
+		input: `` +
+			`<?xml version="1.0" encoding="utf-8" ?>` +
+			`<D:propertyupdate xmlns:D="DAV:"` +
+			`                  xmlns:Z="http://ns.example.com/z/">` +
+			`    <D:remove>` +
+			`        <D:prop/>` +
+			`    </D:remove>` +
+			`</D:propertyupdate>`,
+		wantStatus: http.StatusBadRequest,
+	}}
+
+	for _, tc := range testCases {
+		pp, status, err := readProppatch(strings.NewReader(tc.input))
+		if tc.wantStatus != 0 {
+			if err == nil {
+				t.Errorf("%s: got nil error, want non-nil", tc.desc)
+				continue
+			}
+		} else if err != nil {
+			t.Errorf("%s: %v", tc.desc, err)
+			continue
+		}
+		if status != tc.wantStatus {
+			t.Errorf("%s: got status %d, want %d", tc.desc, status, tc.wantStatus)
+			continue
+		}
+		if !reflect.DeepEqual(pp, tc.wantPP) || status != tc.wantStatus {
+			t.Errorf("%s: proppatch\ngot  %v\nwant %v", tc.desc, ppStr(pp), ppStr(tc.wantPP))
+		}
+	}
+}
+
+func TestUnmarshalXMLValue(t *testing.T) {
+	testCases := []struct {
+		desc    string
+		input   string
+		wantVal string
+	}{{
+		desc:    "simple char data",
+		input:   "<root>foo</root>",
+		wantVal: "foo",
+	}, {
+		desc:    "empty element",
+		input:   "<root><foo/></root>",
+		wantVal: "<foo/>",
+	}, {
+		desc:    "preserve namespace",
+		input:   `<root><foo xmlns="bar"/></root>`,
+		wantVal: `<foo xmlns="bar"/>`,
+	}, {
+		desc:    "preserve root element namespace",
+		input:   `<root xmlns:bar="bar"><bar:foo/></root>`,
+		wantVal: `<foo xmlns="bar"/>`,
+	}, {
+		desc:    "preserve whitespace",
+		input:   "<root>  \t </root>",
+		wantVal: "  \t ",
+	}, {
+		desc:    "preserve mixed content",
+		input:   `<root xmlns="bar">  <foo>a<bam xmlns="baz"/> </foo> </root>`,
+		wantVal: `  <foo xmlns="bar">a<bam xmlns="baz"/> </foo> `,
+	}, {
+		desc: "section 9.2",
+		input: `` +
+			`<Z:Authors xmlns:Z="http://ns.example.com/z/">` +
+			`  <Z:Author>Jim Whitehead</Z:Author>` +
+			`  <Z:Author>Roy Fielding</Z:Author>` +
+			`</Z:Authors>`,
+		wantVal: `` +
+			`  <Author xmlns="http://ns.example.com/z/">Jim Whitehead</Author>` +
+			`  <Author xmlns="http://ns.example.com/z/">Roy Fielding</Author>`,
+	}, {
+		desc: "section 4.3.1 (mixed content)",
+		input: `` +
+			`<x:author ` +
+			`    xmlns:x='http://example.com/ns' ` +
+			`    xmlns:D="DAV:">` +
+			`  <x:name>Jane Doe</x:name>` +
+			`  <!-- Jane's contact info -->` +
+			`  <x:uri type='email'` +
+			`         added='2005-11-26'>mailto:jane.doe@example.com</x:uri>` +
+			`  <x:uri type='web'` +
+			`         added='2005-11-27'>http://www.example.com</x:uri>` +
+			`  <x:notes xmlns:h='http://www.w3.org/1999/xhtml'>` +
+			`    Jane has been working way <h:em>too</h:em> long on the` +
+			`    long-awaited revision of <![CDATA[<RFC2518>]]>.` +
+			`  </x:notes>` +
+			`</x:author>`,
+		wantVal: `` +
+			`  <name xmlns="http://example.com/ns">Jane Doe</name>` +
+			`  ` +
+			`  <uri type='email'` +
+			`       xmlns="http://example.com/ns" ` +
+			`       added='2005-11-26'>mailto:jane.doe@example.com</uri>` +
+			`  <uri added='2005-11-27'` +
+			`       type='web'` +
+			`       xmlns="http://example.com/ns">http://www.example.com</uri>` +
+			`  <notes xmlns="http://example.com/ns" ` +
+			`         xmlns:h="http://www.w3.org/1999/xhtml">` +
+			`    Jane has been working way <h:em>too</h:em> long on the` +
+			`    long-awaited revision of &lt;RFC2518&gt;.` +
+			`  </notes>`,
+	}}
+
+	var n xmlNormalizer
+	for _, tc := range testCases {
+		d := ixml.NewDecoder(strings.NewReader(tc.input))
+		var v xmlValue
+		if err := d.Decode(&v); err != nil {
+			t.Errorf("%s: got error %v, want nil", tc.desc, err)
+			continue
+		}
+		eq, err := n.equalXML(bytes.NewReader(v), strings.NewReader(tc.wantVal))
+		if err != nil {
+			t.Errorf("%s: equalXML: %v", tc.desc, err)
+			continue
+		}
+		if !eq {
+			t.Errorf("%s:\ngot  %s\nwant %s", tc.desc, string(v), tc.wantVal)
+		}
+	}
+}
+
+// xmlNormalizer normalizes XML.
+type xmlNormalizer struct {
+	// omitWhitespace instructs to ignore whitespace between element tags.
+	omitWhitespace bool
+	// omitComments instructs to ignore XML comments.
+	omitComments bool
+}
+
+// normalize writes the normalized XML content of r to w. It applies the
+// following rules
+//
+//   - Rename namespace prefixes according to an internal heuristic.
+//   - Remove unnecessary namespace declarations.
+//   - Sort attributes in XML start elements in lexical order of their
+//     fully qualified name.
+//   - Remove XML directives and processing instructions.
+//   - Remove CDATA between XML tags that only contains whitespace, if
+//     instructed to do so.
+//   - Remove comments, if instructed to do so.
+func (n *xmlNormalizer) normalize(w io.Writer, r io.Reader) error {
+	d := ixml.NewDecoder(r)
+	e := ixml.NewEncoder(w)
+	for {
+		t, err := d.Token()
+		if err != nil {
+			if t == nil && err == io.EOF {
+				break
+			}
+			return err
+		}
+		switch val := t.(type) {
+		case ixml.Directive, ixml.ProcInst:
+			continue
+		case ixml.Comment:
+			if n.omitComments {
+				continue
+			}
+		case ixml.CharData:
+			if n.omitWhitespace && len(bytes.TrimSpace(val)) == 0 {
+				continue
+			}
+		case ixml.StartElement:
+			start, _ := ixml.CopyToken(val).(ixml.StartElement)
+			attr := start.Attr[:0]
+			for _, a := range start.Attr {
+				if a.Name.Space == "xmlns" || a.Name.Local == "xmlns" {
+					continue
+				}
+				attr = append(attr, a)
+			}
+			sort.Sort(byName(attr))
+			start.Attr = attr
+			t = start
+		}
+		err = e.EncodeToken(t)
+		if err != nil {
+			return err
+		}
+	}
+	return e.Flush()
+}
+
+// equalXML tests for equality of the normalized XML contents of a and b.
+func (n *xmlNormalizer) equalXML(a, b io.Reader) (bool, error) {
+	var buf bytes.Buffer
+	if err := n.normalize(&buf, a); err != nil {
+		return false, err
+	}
+	normA := buf.String()
+	buf.Reset()
+	if err := n.normalize(&buf, b); err != nil {
+		return false, err
+	}
+	normB := buf.String()
+	return normA == normB, nil
+}
+
+type byName []ixml.Attr
+
+func (a byName) Len() int      { return len(a) }
+func (a byName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+func (a byName) Less(i, j int) bool {
+	if a[i].Name.Space != a[j].Name.Space {
+		return a[i].Name.Space < a[j].Name.Space
+	}
+	return a[i].Name.Local < a[j].Name.Local
+}