impl/memory: Replace gkvlite with "treapstore".

impl/memory/memstore.go

+// 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 gtrea.Compare function for *storeEntry.
+func storeEntryCompare(a, b interface{}) int {
+        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 && r == nil:
+                        return
+
+                case l == nil:
+                        f(r.key, nil, r.value)

[Vadim Sh., 2016/12/28 01:57:05]

nit: this can be micro optimized by avoiding calls to oldIter.Next() and
unnecessary comparisons:

case l == nil:
  for r != nil  {
    f(r.key, nil, r.value)
    r = newIter.Next()
  }
  return

(and same for r == nil, and case l == nil && r == nil can be removed). 

IMHO, it also makes the intent cleaner.

[dnj, 2016/12/28 02:52:15]

I was initially trying to stay as close to the original function as possible,
but agreed. Done.

+                        r = newIter.Next()
+
+                case r == nil:
+                        f(l.key, l.value, nil)
+                        l = oldIter.Next()
+
+                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 treapstore.Store which will panic for anything which might
+// otherwise return an error.
+//
+// This is reasonable for in-memory Store objects, since the only errors that
+// should occur happen with file IO on the underlying file (which of course

[Vadim Sh., 2016/12/28 01:57:05]

the comment is probably stale. There should be no files involved anymore.
Mentioning file IO while none of the underlying libraries use files is
confusing.

[dnj, 2016/12/28 02:52:15]

Done.

+// doesn't exist).
+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
+}
+
+// memCollection is a treapstore.Collection which will panic for anything which
+// might otherwise return an error.
+//
+// This is reasonable for in-memory Store objects, since the only errors that
+// should occur happen with file IO on the underlying file (which of course
+// doesn't exist.
+type memCollection interface {
+        Name() string
+        Delete(k []byte)
+        Get(k []byte) []byte
+        MinItem() *storeEntry
+        Set(k, v []byte)
+        Iterator(pivot []byte) memIterator
+
+        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(storeEntryCompare)})
+        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 {
+        return &memCollectionImpl{ms.s.GetOrCreateCollection(name)}
+}
+
+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 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 }
+
+func forEachItem(mc memCollection, cb func(k, v []byte) bool) {
+        it := mc.Iterator(nil)
+        for ent := it.Next(); ent != nil; ent = it.Next() {
+                if !cb(ent.key, ent.value) {
+                        break
+                }
+        }
+}