filter/count: Fix alignment on 32-bit systems.

filter/count/count.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 count contains 'counter' filters for all the gae services. This
 // serves as a set of simple example filters, and also enables other filters
 // to test to see if certain underlying APIs are called when they should be
 // (e.g. for the datastore mcache filter, for example).
 package count
 
 import (
+        "fmt"
         "sync/atomic"
 )
 
+type Counter struct {
+        value int64
+}
+
+func (c *Counter) increment() {
+        atomic.AddInt64(&c.value, 1)

[iannucci, 2015/08/22 01:00:56]

as discussed offline, let's just change the current implementation to use 32bit
atomics, since they don't have the alignment bug/requirement.

+}
+
+func (c *Counter) Get() int64 {
+        return atomic.LoadInt64(&c.value)
+}
+
 // Entry is a success/fail pair for a single API method. It's returned
 // by the Counter interface.
 type Entry struct {
-        Successes int64
-        Errors    int64
+        Successes *Counter
+        Errors    *Counter
+}
+
+func (e *Entry) init() {
+        e.Successes = &Counter{}
+        e.Errors = &Counter{}
+}
+
+func (e *Entry) String() string {
+        return fmt.Sprintf("{Successes:%d, Errors:%d}", e.Successes.Get(), e.Errors.Get())
 }
 
 // Total is a convenience function for getting the total number of calls to
 // this API. It's Successes+Errors.
-func (e Entry) Total() int64 { return e.Successes + e.Errors }
+func (e *Entry) Total() int64 { return e.Successes.Get() + e.Errors.Get() }
 
 func (e *Entry) up(errs ...error) error {
         err := error(nil)
         if len(errs) > 0 {
                 err = errs[0]
         }
         if err == nil {
-                atomic.AddInt64(&e.Successes, 1)
+                e.Successes.increment()
         } else {
-                atomic.AddInt64(&e.Errors, 1)
+                e.Errors.increment()
         }
         return err
 }