Better attempt at an appengine wrapper.

go/src/infra/gae/libs/wrapper/memcache.go

Index: go/src/infra/gae/libs/wrapper/memcache.go
diff --git a/go/src/infra/gae/libs/wrapper/memcache.go b/go/src/infra/gae/libs/wrapper/memcache.go
new file mode 100644
index 0000000000000000000000000000000000000000..e371d7c14caf842692bb7d6a809d644f85e286c5
--- /dev/null
+++ b/go/src/infra/gae/libs/wrapper/memcache.go
@@ -0,0 +1,107 @@
+// 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 wrapper
+
+import (
+	"golang.org/x/net/context"
+
+	"appengine/memcache"
+)
+
+// MCSingleReadWriter is the interface for interacting with a single
+// memcache.Item at a time. See appengine.memcache for more details.
+type MCSingleReadWriter interface {
+	Add(item *memcache.Item) error
+	Set(item *memcache.Item) error
+	Get(key string) (*memcache.Item, error)
+	Delete(key string) error
+	CompareAndSwap(item *memcache.Item) error
+}
+
+// MCIncrementer is the interface for atomically incrementing a numeric
+// memcache entry.  See appengine.memcache for more details.
+type MCIncrementer interface {
+	Increment(key string, delta int64, initialValue uint64) (newValue uint64, err error)
+	IncrementExisting(key string, delta int64) (newValue uint64, err error)
+}
+
+// MCMultiReadWriter is the interface for doing batched memcache
+// operations. See appengine.memcache for more details.
+type MCMultiReadWriter interface {
+	MCSingleReadWriter
+
+	AddMulti(items []*memcache.Item) error
+	SetMulti(items []*memcache.Item) error
+	GetMulti(keys []string) (map[string]*memcache.Item, error)
+	DeleteMulti(keys []string) error
+	CompareAndSwapMulti(items []*memcache.Item) error
+}
+
+// MCFlusher is the interface for wiping the whole memcache server.
+// See appengine.memcache for more details.
+type MCFlusher interface {
+	Flush() error
+}
+
+// MCStatter is the interface for gathering statistics about the
+// memcache server. See appengine.memcache for more details.
+type MCStatter interface {
+	Stats() (*memcache.Statistics, error)
+}
+
+// MCCodec is the interface representing what you can do with a memcache.Codec
+// after it's been inflated with InflateCodec. It mirrors
+// appengine.memcache.Codec.
+type MCCodec interface {
+	// would use MCSingleReadWriter, but Get has a different signature.
+	Add(item *memcache.Item) error
+	Set(item *memcache.Item) error
+	Get(key string, v interface{}) (*memcache.Item, error)
+	CompareAndSwap(item *memcache.Item) error
+
+	AddMulti(items []*memcache.Item) error
+	SetMulti(items []*memcache.Item) error
+	CompareAndSwapMulti(items []*memcache.Item) error
+}
+
+// MCCodecInflater binds a Memcache to a memcache.Codec.
+type MCCodecInflater interface {
+	InflateCodec(m memcache.Codec) MCCodec
+}
+
+// Memcache is the full interface to the memcache service.
+type Memcache interface {
+	MCMultiReadWriter
+	MCIncrementer
+	MCFlusher
+	MCStatter
+	MCCodecInflater
+}
+
+// MCFactory is the function signature for factory methods compatible with
+// SetMCFactory.
+type MCFactory func(context.Context) Memcache
+
+// GetMC gets the current memcache implementation from the context.
+func GetMC(c context.Context) Memcache {
+	obj := c.Value(memcacheKey)

[M-A Ruel, 2015/05/27 00:27:11]

line saveable

[iannucci, 2015/05/27 02:40:57]

done

+	if obj == nil || obj.(MCFactory) == nil {
+		return nil
+	}
+	return obj.(MCFactory)(c)
+}
+
+// SetMCFactory sets the function to produce Memcache instances, as returned by
+// the GetMC method.
+func SetMCFactory(c context.Context, mcf MCFactory) context.Context {
+	return context.WithValue(c, memcacheKey, mcf)
+}
+
+// SetMC sets the current Memcache object in the context. Useful for testing
+// with a quick mock. This is just a shorthand SetMCFactory invocation to set
+// a factory which always returns the same object.
+func SetMC(c context.Context, mc Memcache) context.Context {
+	return SetMCFactory(c, func(context.Context) Memcache { return mc })
+}