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// Copyright 2015 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package memory
import (
"bytes"
"go.chromium.org/gae/service/datastore"
"github.com/luci/gtreap"
"go.chromium.org/luci/common/data/treapstore"
)
type storeEntry struct {
key []byte
value []byte
}
// storeEntryCompare is a gtreap.Compare function for *storeEntry.
func storeEntryCompare(a, b interface{}) int {
// TODO(dnj): Investigate optimizing this by removing the type assertions,
// either by explicitly tailoring gtreap / treapstore to use []byte or by
// optimizing via special-case interface.
return bytes.Compare(a.(*storeEntry).key, b.(*storeEntry).key)
}
func memStoreCollide(o, n memCollection, f func(k, ov, nv []byte)) {
var oldIter, newIter memIterator
if o != nil {
if !o.IsReadOnly() {
panic("old collection is r/w")
}
oldIter = o.Iterator(nil)
} else {
oldIter = nilIterator{}
}
if n != nil {
if !n.IsReadOnly() {
panic("new collection is r/w")
}
newIter = n.Iterator(nil)
} else {
newIter = nilIterator{}
}
l, r := oldIter.Next(), newIter.Next()
for {
switch {
case l == nil:
// No more "old" items, use up the rest of "new" and finish.
for r != nil {
f(r.key, nil, r.value)
r = newIter.Next()
}
return
case r == nil:
// No more "new" items, use up the rest of "old" and finish.
for l != nil {
f(l.key, l.value, nil)
l = oldIter.Next()
}
return
default:
switch bytes.Compare(l.key, r.key) {
case -1: // l < r
f(l.key, l.value, nil)
l = oldIter.Next()
case 0: // l == r
f(l.key, l.value, r.value)
l, r = oldIter.Next(), newIter.Next()
case 1: // l > r
f(r.key, nil, r.value)
r = newIter.Next()
}
}
}
}
// memStore is a generic interface modeled after treapstore.Store.
type memStore interface {
datastore.TestingSnapshot
GetCollection(name string) memCollection
GetCollectionNames() []string
GetOrCreateCollection(name string) memCollection
Snapshot() memStore
IsReadOnly() bool
}
// memIterator is an iterator over a memStore's contents.
type memIterator interface {
Next() *storeEntry
}
// memVisitor is a callback for ForEachItem.
type memVisitor func(k, v []byte) bool
// memCollection is a generic interface modeled after treapstore.Collection.
type memCollection interface {
Name() string
Delete(k []byte)
Get(k []byte) []byte
MinItem() *storeEntry
Set(k, v []byte)
Iterator(pivot []byte) memIterator
ForEachItem(memVisitor)
IsReadOnly() bool
}
type memStoreImpl struct {
s *treapstore.Store
}
var _ memStore = (*memStoreImpl)(nil)
func (*memStoreImpl) ImATestingSnapshot() {}
func (ms *memStoreImpl) IsReadOnly() bool { return ms.s.IsReadOnly() }
func newMemStore() memStore {
ret := memStore(&memStoreImpl{treapstore.New()})
if *logMemCollectionFolder != "" {
ret = wrapTracingMemStore(ret)
}
return ret
}
func (ms *memStoreImpl) Snapshot() memStore {
if ms.s.IsReadOnly() {
return ms
}
return &memStoreImpl{ms.s.Snapshot()}
}
func (ms *memStoreImpl) GetCollection(name string) memCollection {
coll := ms.s.GetCollection(name)
if coll == nil {
return nil
}
return &memCollectionImpl{coll}
}
func (ms *memStoreImpl) GetOrCreateCollection(name string) memCollection {
coll := ms.s.GetCollection(name)
if coll == nil {
coll = ms.s.CreateCollection(name, storeEntryCompare)
}
return &memCollectionImpl{coll}
}
func (ms *memStoreImpl) GetCollectionNames() []string { return ms.s.GetCollectionNames() }
type memIteratorImpl struct {
base *gtreap.Iterator
}
func (it *memIteratorImpl) Next() *storeEntry {
v, ok := it.base.Next()
if !ok {
return nil
}
return v.(*storeEntry)
}
type memCollectionImpl struct {
c *treapstore.Collection
}
var _ memCollection = (*memCollectionImpl)(nil)
func (mc *memCollectionImpl) Name() string { return mc.c.Name() }
func (mc *memCollectionImpl) IsReadOnly() bool { return mc.c.IsReadOnly() }
func (mc *memCollectionImpl) Get(k []byte) []byte {
if ent := mc.c.Get(storeKey(k)); ent != nil {
return ent.(*storeEntry).value
}
return nil
}
func (mc *memCollectionImpl) MinItem() *storeEntry {
ent, _ := mc.c.Min().(*storeEntry)
return ent
}
func (mc *memCollectionImpl) Set(k, v []byte) { mc.c.Put(&storeEntry{k, v}) }
func (mc *memCollectionImpl) Delete(k []byte) { mc.c.Delete(storeKey(k)) }
func (mc *memCollectionImpl) Iterator(target []byte) memIterator {
if !mc.c.IsReadOnly() {
// We prevent this to ensure our internal logic, not because it's actually
// an invalid operation.
panic("attempting to get Iterator from r/w memCollection")
}
return &memIteratorImpl{mc.c.Iterator(storeKey(target))}
}
func (mc *memCollectionImpl) ForEachItem(fn memVisitor) {
mc.c.VisitAscend(storeKey(nil), func(it gtreap.Item) bool {
ent := it.(*storeEntry)
return fn(ent.key, ent.value)
})
}
func storeKey(k []byte) *storeEntry { return &storeEntry{k, nil} }
// nilIterator is a memIterator that begins in a depleted state.
type nilIterator struct{}
func (it nilIterator) Next() *storeEntry { return nil }