Reland: Refactor current GAE abstraction library to be free of the SDK*

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

-// 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 {
-        if f, ok := c.Value(memcacheKey).(MCFactory); ok && f != nil {
-                return f(c)
-        }
-        return nil
-}
-
-// 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 })
-}