Add "filters/count" filter.

go/src/infra/gae/libs/gae/filters/count/mc.go

Index: go/src/infra/gae/libs/gae/filters/count/mc.go
diff --git a/go/src/infra/gae/libs/gae/filters/count/mc.go b/go/src/infra/gae/libs/gae/filters/count/mc.go
new file mode 100644
index 0000000000000000000000000000000000000000..0ac3e09937f95f7612560c312966f52dfe27ea6a
--- /dev/null
+++ b/go/src/infra/gae/libs/gae/filters/count/mc.go
@@ -0,0 +1,93 @@
+// 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 count
+
+import (
+	"golang.org/x/net/context"
+
+	"infra/gae/libs/gae"
+)
+
+// MCCounter is the counter object for the Memcache service.
+type MCCounter struct {
+	NewItem             Entry
+	Add                 Entry
+	Set                 Entry
+	Get                 Entry
+	Delete              Entry
+	CompareAndSwap      Entry
+	AddMulti            Entry
+	SetMulti            Entry
+	GetMulti            Entry
+	DeleteMulti         Entry
+	CompareAndSwapMulti Entry
+	Increment           Entry
+	IncrementExisting   Entry
+	Flush               Entry
+	Stats               Entry
+}
+
+type mcCounter struct {
+	c *MCCounter
+
+	mc gae.Memcache
+}
+
+var _ gae.Memcache = (*mcCounter)(nil)
+
+func (m *mcCounter) NewItem(key string) gae.MCItem {
+	m.c.NewItem.up()
+	return m.mc.NewItem(key)
+}
+
+func (m *mcCounter) Get(key string) (gae.MCItem, error) {
+	ret, err := m.mc.Get(key)
+	return ret, m.c.Get.up(err)
+}
+
+func (m *mcCounter) GetMulti(keys []string) (map[string]gae.MCItem, error) {
+	ret, err := m.mc.GetMulti(keys)
+	return ret, m.c.GetMulti.up(err)
+}
+
+func (m *mcCounter) Add(item gae.MCItem) error { return m.c.Add.up(m.mc.Add(item)) }
+func (m *mcCounter) Set(item gae.MCItem) error { return m.c.Set.up(m.mc.Set(item)) }
+func (m *mcCounter) Delete(key string) error   { return m.c.Delete.up(m.mc.Delete(key)) }
+func (m *mcCounter) CompareAndSwap(item gae.MCItem) error {
+	return m.c.CompareAndSwap.up(m.mc.CompareAndSwap(item))
+}
+func (m *mcCounter) AddMulti(items []gae.MCItem) error { return m.c.AddMulti.up(m.mc.AddMulti(items)) }
+func (m *mcCounter) SetMulti(items []gae.MCItem) error { return m.c.SetMulti.up(m.mc.SetMulti(items)) }
+func (m *mcCounter) DeleteMulti(keys []string) error {
+	return m.c.DeleteMulti.up(m.mc.DeleteMulti(keys))
+}
+func (m *mcCounter) Flush() error { return m.c.Flush.up(m.mc.Flush()) }
+
+func (m *mcCounter) CompareAndSwapMulti(items []gae.MCItem) error {
+	return m.c.CompareAndSwapMulti.up(m.mc.CompareAndSwapMulti(items))
+}
+
+func (m *mcCounter) Increment(key string, delta int64, initialValue uint64) (newValue uint64, err error) {
+	ret, err := m.mc.Increment(key, delta, initialValue)
+	return ret, m.c.Increment.up(err)
+}
+
+func (m *mcCounter) IncrementExisting(key string, delta int64) (newValue uint64, err error) {
+	ret, err := m.mc.IncrementExisting(key, delta)
+	return ret, m.c.IncrementExisting.up(err)
+}
+
+func (m *mcCounter) Stats() (*gae.MCStatistics, error) {
+	ret, err := m.mc.Stats()
+	return ret, m.c.Stats.up(err)
+}
+
+// FilterMC installs a counter Memcache filter in the context.
+func FilterMC(c context.Context) (context.Context, *MCCounter) {
+	state := &MCCounter{}
+	return gae.AddMCFilters(c, func(ic context.Context, mc gae.Memcache) gae.Memcache {
+		return &mcCounter{state, mc}
+	}), state
+}