Simple memory testing for gae/wrapper

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

Index: go/src/infra/gae/libs/wrapper/unsafe/memcache.go
diff --git a/go/src/infra/gae/libs/wrapper/unsafe/memcache.go b/go/src/infra/gae/libs/wrapper/unsafe/memcache.go
new file mode 100644
index 0000000000000000000000000000000000000000..db7ad3b6f79f82c16e814e311fe9a31334d29865
--- /dev/null
+++ b/go/src/infra/gae/libs/wrapper/unsafe/memcache.go
@@ -0,0 +1,58 @@
+// 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 unsafe
+
+import (
+	"time"
+
+	"unsafe"
+
+	"appengine/memcache"
+)
+
+// Item is duplicated from appengine/memcache.
+type Item struct {
+	Key        string
+	Value      []byte
+	Object     interface{}
+	Flags      uint32
+	Expiration time.Duration
+	CasID      uint64
+}
+
+func init() {
+	// we can't actually refer to casID by name, but we can refer to everything
+	// else, and ensure that everything lines up. This should catch an api change,
+	// but wouldn't catch something like uint64 -> int64.
+	if unsafe.Sizeof(memcache.Item{}) != unsafe.Sizeof(Item{}) {
+		panic("memcache.Item and Item mismatch sizes")
+	}
+	if unsafe.Offsetof(memcache.Item{}.Key) != unsafe.Offsetof(Item{}.Key) {
+		panic("memcache.Item and Item mismatch Key")
+	}
+	if unsafe.Offsetof(memcache.Item{}.Value) != unsafe.Offsetof(Item{}.Value) {
+		panic("memcache.Item and Item mismatch Value")
+	}
+	if unsafe.Offsetof(memcache.Item{}.Object) != unsafe.Offsetof(Item{}.Object) {
+		panic("memcache.Item and Item mismatch Object")
+	}
+	if unsafe.Offsetof(memcache.Item{}.Flags) != unsafe.Offsetof(Item{}.Flags) {
+		panic("memcache.Item and Item mismatch Flags")
+	}
+	if unsafe.Offsetof(memcache.Item{}.Expiration) != unsafe.Offsetof(Item{}.Expiration) {
+		panic("memcache.Item and Item mismatch Expiration")
+	}
+}
+
+// MCSetCasID sets the private .casID field of memcache.Item.
+func MCSetCasID(i *memcache.Item, val uint64) {
+	mci := (*Item)(unsafe.Pointer(i))
+	mci.CasID = val
+}
+
+// MCGetCasID retrieves the private .casID field of memcache.Item.
+func MCGetCasID(i *memcache.Item) uint64 {
+	return (*Item)(unsafe.Pointer(i)).CasID
+}