Add testable interface for datastore.

impl/memory/datastore_data.go

 // Copyright 2015 The Chromium 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 memory
 
 import (
         "bytes"
         "fmt"
         "sync"
@@ skipping 27 matching lines @@
 }
 
 func (d *dataStoreData) Lock() {
         d.rwlock.Lock()
 }
 
 func (d *dataStoreData) Unlock() {
         d.rwlock.Unlock()
 }
 
+func (d *dataStoreData) getQuerySnaps(consistent bool) (idx, head *memStore) {
+        d.rwlock.RLock()
+        defer d.rwlock.RUnlock()
+        head = d.store.Snapshot()
+        if consistent {
+                idx = head
+        } else {
+                idx = d.snap
+        }
+        return
+}
+
+func (d *dataStoreData) takeSnapshot() *memStore {
+        d.rwlock.RLock()
+        defer d.rwlock.RUnlock()
+        return d.store.Snapshot()
+}
+
+func (d *dataStoreData) setSnapshot(snap *memStore) {
+        d.rwlock.Lock()
+        defer d.rwlock.Unlock()
+        d.snap = snap
+}
+
+func (d *dataStoreData) catchupIndexes() {
+        d.rwlock.Lock()
+        defer d.rwlock.Unlock()
+        d.snap = d.store.Snapshot()
+}
+
 /////////////////////////// indicies(dataStoreData) ////////////////////////////
 
 func groupMetaKey(key ds.Key) []byte {
         return keyBytes(ds.WithoutContext,
                 ds.NewKey("", "", "__entity_group__", "", 1, ds.KeyRoot(key)))
 }
 
 func groupIDsKey(key ds.Key) []byte {
         return keyBytes(ds.WithoutContext,
                 ds.NewKey("", "", "__entity_group_ids__", "", 1, ds.KeyRoot(key)))
@@ skipping 100 matching lines @@
                         cb(nil, ds.ErrNoSuchEntity)
                         continue
                 }
                 cb(rpmWoCtx(pdata, k.Namespace()))
         }
         return nil
 }
 
 func (d *dataStoreData) getMulti(keys []ds.Key, cb ds.GetMultiCB) error {
         getMultiInner(keys, cb, func() (*memCollection, error) {
-                d.rwlock.RLock()
-                s := d.store.Snapshot()
-                d.rwlock.RUnlock()
+                s := d.takeSnapshot()
 
                 return s.GetCollection("ents:" + keys[0].Namespace()), nil
         })
         return nil
 }
 
 func (d *dataStoreData) delMulti(keys []ds.Key, cb ds.DeleteMultiCB) {
         toDel := make([][]byte, 0, len(keys))
         for _, k := range keys {
                 toDel = append(toDel, keyBytes(ds.WithoutContext, k))
@@ skipping 231 matching lines @@
 
 func rpm(data []byte) (ds.PropertyMap, error) {
         ret := ds.PropertyMap{}
         err := ret.Read(bytes.NewBuffer(data), ds.WithContext, "", "")
         return ret, err
 }
 
 type keyitem interface {
         Key() ds.Key
 }