Implement DatasetMapping + basic ZFS list functionality.

zfs/mapping.go

@@ -0,0 +1,141 @@
+package zfs
+
+import (
+	"errors"
+	"os/exec"
+	"io"
+	"bufio"
+	"fmt"
+)
+
+type DatasetMapping interface {
+	Map(source DatasetPath) (target DatasetPath, err error)
+}
+
+type GlobMapping struct {
+	PrefixPath DatasetPath
+	TargetRoot DatasetPath
+}
+
+var NoMatchError error = errors.New("no match found in mapping")
+
+func (m GlobMapping) Map(source DatasetPath) (target DatasetPath, err error) {
+
+	if len(source) < len(m.PrefixPath) {
+		err = NoMatchError
+		return
+	}
+
+	target = make([]string, 0, len(source) + len(m.TargetRoot))
+	target = append(target, m.TargetRoot...)
+
+
+	for si, sc := range source {
+		target = append(target, sc)
+		if si < len(m.PrefixPath) {
+			if sc != m.PrefixPath[si] {
+				err = NoMatchError
+				return
+			}
+			continue
+		}
+	}
+
+	return
+}
+
+type ComboMapping struct {
+	Mappings []DatasetMapping
+}
+
+func (m ComboMapping) Map(source DatasetPath) (target DatasetPath, err error) {
+	for _, sm := range m.Mappings {
+		target, err = sm.Map(source)
+		if err == nil {
+			return target, err
+		}
+	}
+	return nil, NoMatchError
+}
+
+type DirectMapping struct {
+	Source DatasetPath
+	Target DatasetPath
+}
+
+func (m DirectMapping) Map(source DatasetPath) (target DatasetPath, err error) {
+	if len(m.Source) != len(source) {
+		return nil, NoMatchError
+	}
+
+	for i, c := range source {
+		if c != m.Source[i] {
+			return nil, NoMatchError
+		}
+	}
+
+	return m.Target, nil
+}
+
+type ExecMapping struct {
+	Name string
+	Args []string
+}
+
+func NewExecMapping(name string, args... string) (m *ExecMapping) {
+	m = &ExecMapping{
+		Name: name,
+		Args: args,
+	}
+	return
+}
+
+func (m ExecMapping) Map(source DatasetPath) (target DatasetPath, err error) {
+
+	var stdin io.Writer
+	var stdout io.Reader
+
+
+	cmd := exec.Command(m.Name, m.Args...)
+
+	if stdin, err = cmd.StdinPipe(); err != nil {
+		return
+	}
+
+	if stdout, err = cmd.StdoutPipe(); err != nil {
+		return
+	}
+
+	resp := bufio.NewScanner(stdout)
+
+	if err = cmd.Start(); err != nil {
+		return
+	}
+
+	go func() {
+		err := cmd.Wait()
+		if err != nil {
+			fmt.Printf("error: %v\n", err) // TODO
+		}
+	}()
+
+	if _, err = io.WriteString(stdin, source.ToString() + "\n"); err != nil {
+		return
+	}
+
+	if !resp.Scan() {
+		err = errors.New(fmt.Sprintf("unexpected end of file: %v", resp.Err()))
+		return
+	}
+
+	t := resp.Text()
+
+	switch {
+		case t == "NOMAP":
+			return nil, NoMatchError
+	}
+
+	target = toDatasetPath(t) // TODO discover garbage?
+
+	return
+}