impl/memory: Replace gkvlite with "treapstore".

impl/memory/memstore.go

Index: impl/memory/memstore.go
diff --git a/impl/memory/memstore.go b/impl/memory/memstore.go
new file mode 100644
index 0000000000000000000000000000000000000000..b1f7c7c5820788ba8b31336bf0ae0a460043d22c
--- /dev/null
+++ b/impl/memory/memstore.go
@@ -0,0 +1,217 @@
+// Copyright 2015 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package memory
+
+import (
+	"bytes"
+
+	"github.com/luci/gae/service/datastore"
+
+	"github.com/luci/gtreap"
+	"github.com/luci/luci-go/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 }