Refactor a bit.

service/memcache/types.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 memcache
+
+import (
+        "time"
+)
+
+// Statistics represents a set of statistics about the memcache cache.  This
+// may include items that have expired but have not yet been removed from the
+// cache.
+type Statistics struct {
+        Hits     uint64 // Counter of cache hits
+        Misses   uint64 // Counter of cache misses
+        ByteHits uint64 // Counter of bytes transferred for gets
+
+        Items uint64 // Items currently in the cache
+        Bytes uint64 // Size of all items currently in the cache
+
+        Oldest int64 // Age of access of the oldest item, in seconds
+}
+
+// Item is a wrapper around *memcache.Item. Note that the Set* methods all
+// return the original Item (e.g. they mutate the original), due to
+// implementation constraints. They return the original item to allow easy
+// chaining, e.g.:
+//   itm := memcache.Get(c).NewItem("foo").SetValue([]byte("stuff"))
+type Item interface {
+        Key() string
+        Value() []byte
+        Object() interface{}
+        Flags() uint32
+        Expiration() time.Duration
+
+        SetKey(string) Item
+        SetValue([]byte) Item
+        SetObject(interface{}) Item
+        SetFlags(uint32) Item
+        SetExpiration(time.Duration) Item
+}