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310 lines
7.3 KiB
Go
310 lines
7.3 KiB
Go
// Copyright 2011 Google Inc. All rights reserved.
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// Use of this source code is governed by the Apache 2.0
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// license that can be found in the LICENSE file.
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package datastore
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import (
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"bytes"
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"encoding/base64"
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"encoding/gob"
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"errors"
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"fmt"
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"strconv"
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"strings"
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"github.com/golang/protobuf/proto"
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"golang.org/x/net/context"
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"google.golang.org/appengine/internal"
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pb "google.golang.org/appengine/internal/datastore"
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)
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// Key represents the datastore key for a stored entity, and is immutable.
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type Key struct {
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kind string
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stringID string
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intID int64
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parent *Key
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appID string
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namespace string
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}
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// Kind returns the key's kind (also known as entity type).
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func (k *Key) Kind() string {
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return k.kind
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}
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// StringID returns the key's string ID (also known as an entity name or key
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// name), which may be "".
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func (k *Key) StringID() string {
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return k.stringID
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}
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// IntID returns the key's integer ID, which may be 0.
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func (k *Key) IntID() int64 {
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return k.intID
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}
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// Parent returns the key's parent key, which may be nil.
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func (k *Key) Parent() *Key {
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return k.parent
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}
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// AppID returns the key's application ID.
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func (k *Key) AppID() string {
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return k.appID
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}
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// Namespace returns the key's namespace.
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func (k *Key) Namespace() string {
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return k.namespace
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}
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// Incomplete returns whether the key does not refer to a stored entity.
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// In particular, whether the key has a zero StringID and a zero IntID.
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func (k *Key) Incomplete() bool {
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return k.stringID == "" && k.intID == 0
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}
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// valid returns whether the key is valid.
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func (k *Key) valid() bool {
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if k == nil {
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return false
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}
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for ; k != nil; k = k.parent {
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if k.kind == "" || k.appID == "" {
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return false
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}
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if k.stringID != "" && k.intID != 0 {
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return false
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}
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if k.parent != nil {
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if k.parent.Incomplete() {
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return false
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}
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if k.parent.appID != k.appID || k.parent.namespace != k.namespace {
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return false
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}
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}
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}
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return true
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}
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// Equal returns whether two keys are equal.
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func (k *Key) Equal(o *Key) bool {
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for k != nil && o != nil {
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if k.kind != o.kind || k.stringID != o.stringID || k.intID != o.intID || k.appID != o.appID || k.namespace != o.namespace {
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return false
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}
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k, o = k.parent, o.parent
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}
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return k == o
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}
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// root returns the furthest ancestor of a key, which may be itself.
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func (k *Key) root() *Key {
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for k.parent != nil {
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k = k.parent
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}
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return k
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}
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// marshal marshals the key's string representation to the buffer.
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func (k *Key) marshal(b *bytes.Buffer) {
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if k.parent != nil {
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k.parent.marshal(b)
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}
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b.WriteByte('/')
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b.WriteString(k.kind)
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b.WriteByte(',')
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if k.stringID != "" {
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b.WriteString(k.stringID)
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} else {
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b.WriteString(strconv.FormatInt(k.intID, 10))
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}
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}
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// String returns a string representation of the key.
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func (k *Key) String() string {
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if k == nil {
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return ""
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}
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b := bytes.NewBuffer(make([]byte, 0, 512))
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k.marshal(b)
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return b.String()
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}
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type gobKey struct {
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Kind string
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StringID string
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IntID int64
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Parent *gobKey
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AppID string
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Namespace string
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}
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func keyToGobKey(k *Key) *gobKey {
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if k == nil {
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return nil
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}
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return &gobKey{
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Kind: k.kind,
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StringID: k.stringID,
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IntID: k.intID,
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Parent: keyToGobKey(k.parent),
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AppID: k.appID,
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Namespace: k.namespace,
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}
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}
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func gobKeyToKey(gk *gobKey) *Key {
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if gk == nil {
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return nil
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}
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return &Key{
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kind: gk.Kind,
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stringID: gk.StringID,
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intID: gk.IntID,
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parent: gobKeyToKey(gk.Parent),
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appID: gk.AppID,
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namespace: gk.Namespace,
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}
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}
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func (k *Key) GobEncode() ([]byte, error) {
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buf := new(bytes.Buffer)
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if err := gob.NewEncoder(buf).Encode(keyToGobKey(k)); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func (k *Key) GobDecode(buf []byte) error {
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gk := new(gobKey)
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if err := gob.NewDecoder(bytes.NewBuffer(buf)).Decode(gk); err != nil {
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return err
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}
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*k = *gobKeyToKey(gk)
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return nil
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}
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func (k *Key) MarshalJSON() ([]byte, error) {
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return []byte(`"` + k.Encode() + `"`), nil
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}
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func (k *Key) UnmarshalJSON(buf []byte) error {
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if len(buf) < 2 || buf[0] != '"' || buf[len(buf)-1] != '"' {
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return errors.New("datastore: bad JSON key")
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}
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k2, err := DecodeKey(string(buf[1 : len(buf)-1]))
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if err != nil {
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return err
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}
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*k = *k2
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return nil
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}
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// Encode returns an opaque representation of the key
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// suitable for use in HTML and URLs.
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// This is compatible with the Python and Java runtimes.
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func (k *Key) Encode() string {
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ref := keyToProto("", k)
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b, err := proto.Marshal(ref)
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if err != nil {
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panic(err)
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}
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// Trailing padding is stripped.
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return strings.TrimRight(base64.URLEncoding.EncodeToString(b), "=")
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}
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// DecodeKey decodes a key from the opaque representation returned by Encode.
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func DecodeKey(encoded string) (*Key, error) {
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// Re-add padding.
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if m := len(encoded) % 4; m != 0 {
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encoded += strings.Repeat("=", 4-m)
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}
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b, err := base64.URLEncoding.DecodeString(encoded)
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if err != nil {
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return nil, err
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}
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ref := new(pb.Reference)
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if err := proto.Unmarshal(b, ref); err != nil {
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return nil, err
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}
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return protoToKey(ref)
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}
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// NewIncompleteKey creates a new incomplete key.
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// kind cannot be empty.
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func NewIncompleteKey(c context.Context, kind string, parent *Key) *Key {
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return NewKey(c, kind, "", 0, parent)
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}
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// NewKey creates a new key.
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// kind cannot be empty.
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// Either one or both of stringID and intID must be zero. If both are zero,
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// the key returned is incomplete.
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// parent must either be a complete key or nil.
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func NewKey(c context.Context, kind, stringID string, intID int64, parent *Key) *Key {
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// If there's a parent key, use its namespace.
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// Otherwise, use any namespace attached to the context.
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var namespace string
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if parent != nil {
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namespace = parent.namespace
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} else {
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namespace = internal.NamespaceFromContext(c)
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}
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return &Key{
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kind: kind,
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stringID: stringID,
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intID: intID,
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parent: parent,
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appID: internal.FullyQualifiedAppID(c),
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namespace: namespace,
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}
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}
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// AllocateIDs returns a range of n integer IDs with the given kind and parent
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// combination. kind cannot be empty; parent may be nil. The IDs in the range
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// returned will not be used by the datastore's automatic ID sequence generator
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// and may be used with NewKey without conflict.
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//
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// The range is inclusive at the low end and exclusive at the high end. In
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// other words, valid intIDs x satisfy low <= x && x < high.
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//
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// If no error is returned, low + n == high.
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func AllocateIDs(c context.Context, kind string, parent *Key, n int) (low, high int64, err error) {
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if kind == "" {
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return 0, 0, errors.New("datastore: AllocateIDs given an empty kind")
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}
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if n < 0 {
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return 0, 0, fmt.Errorf("datastore: AllocateIDs given a negative count: %d", n)
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}
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if n == 0 {
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return 0, 0, nil
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}
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req := &pb.AllocateIdsRequest{
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ModelKey: keyToProto("", NewIncompleteKey(c, kind, parent)),
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Size: proto.Int64(int64(n)),
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}
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res := &pb.AllocateIdsResponse{}
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if err := internal.Call(c, "datastore_v3", "AllocateIds", req, res); err != nil {
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return 0, 0, err
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}
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// The protobuf is inclusive at both ends. Idiomatic Go (e.g. slices, for loops)
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// is inclusive at the low end and exclusive at the high end, so we add 1.
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low = res.GetStart()
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high = res.GetEnd() + 1
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if low+int64(n) != high {
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return 0, 0, fmt.Errorf("datastore: internal error: could not allocate %d IDs", n)
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}
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return low, high, nil
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}
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