Create rtc::AtomicInt POD struct.

webrtc/base/atomicops.h

 /*
  *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_BASE_ATOMICOPS_H_
 #define WEBRTC_BASE_ATOMICOPS_H_
 
+#include "webrtc/base/constructormagic.h"
+
 #if defined(WEBRTC_WIN)
 // Include winsock2.h before including <windows.h> to maintain consistency with
 // win32.h.  We can't include win32.h directly here since it pulls in
 // headers such as basictypes.h which causes problems in Chromium where webrtc
 // exists as two separate projects, webrtc and libjingle.
 #include <winsock2.h>
 #include <windows.h>
 #endif  // defined(WEBRTC_WIN)
 
 namespace rtc {
+
 class AtomicOps {
  public:
 #if defined(WEBRTC_WIN)
   // Assumes sizeof(int) == sizeof(LONG), which it is on Win32 and Win64.
   static int Increment(volatile int* i) {
     return ::InterlockedIncrement(reinterpret_cast<volatile LONG*>(i));
   }
   static int Decrement(volatile int* i) {
     return ::InterlockedDecrement(reinterpret_cast<volatile LONG*>(i));
   }
@@ skipping 20 matching lines @@
   }
   static void ReleaseStore(volatile int* i, int value) {
     __atomic_store_n(i, value, __ATOMIC_RELEASE);
   }
   static int CompareAndSwap(volatile int* i, int old_value, int new_value) {
     return __sync_val_compare_and_swap(i, old_value, new_value);
   }
 #endif
 };
 
+// POD struct version of AtomicOps, prevents accidental non-atomic usage (such
+// as ++, =, reads or writes). Operations are still explicit to not hide that
+// the operations are atomic.

[kwiberg-webrtc, 2015/11/02 12:41:49]

Maybe "Functions are static, so that the AtomicInt:: prefix must be present in
the code, clearly labeling the operations as being atomic." for the last
sentence?

Also, do you plan to migrate all current users of AtomicOps?

[pbos-webrtc, 2015/11/02 15:21:15]

Done, yep that's the plan. I'm not sure if that should entail removing AtomicOps
though.

+struct AtomicInt {
+  AtomicInt() = delete;
 
+  // value_ is public to permit brace initialization. Should not be accessed
+  // directly.
+  volatile int value_;
 
+  static int Increment(AtomicInt* i) {
+    return AtomicOps::Increment(&i->value_);
+  }
+  static int Decrement(AtomicInt* i) {
+    return AtomicOps::Decrement(&i->value_);
+  }
+  static int AcquireLoad(const AtomicInt* i) {
+    return AtomicOps::AcquireLoad(&i->value_);
+  }
+  static void ReleaseStore(AtomicInt* i, int value) {
+    AtomicOps::ReleaseStore(&i->value_, value);
+  }
+  static int CompareAndSwap(AtomicInt* i, int old_value, int new_value) {
+    return AtomicOps::CompareAndSwap(&i->value_, old_value, new_value);
+  }

[kwiberg-webrtc, 2015/11/02 12:41:50]

I'd like a short comment on each of these, explaining what it does and what it
returns.

[pbos-webrtc, 2015/11/02 15:21:15]

Done.

+
+  RTC_DISALLOW_COPY_AND_ASSIGN(AtomicInt);
+};
 }
 
 #endif  // WEBRTC_BASE_ATOMICOPS_H_