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      1 /*
      2  *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #ifndef WEBRTC_BASE_ATOMICOPS_H_
     12 #define WEBRTC_BASE_ATOMICOPS_H_
     13 
     14 #if defined(WEBRTC_WIN)
     15 // Include winsock2.h before including <windows.h> to maintain consistency with
     16 // win32.h.  We can't include win32.h directly here since it pulls in
     17 // headers such as basictypes.h which causes problems in Chromium where webrtc
     18 // exists as two separate projects, webrtc and libjingle.
     19 #include <winsock2.h>
     20 #include <windows.h>
     21 #endif  // defined(WEBRTC_WIN)
     22 
     23 namespace rtc {
     24 class AtomicOps {
     25  public:
     26 #if defined(WEBRTC_WIN)
     27   // Assumes sizeof(int) == sizeof(LONG), which it is on Win32 and Win64.
     28   static int Increment(volatile int* i) {
     29     return ::InterlockedIncrement(reinterpret_cast<volatile LONG*>(i));
     30   }
     31   static int Decrement(volatile int* i) {
     32     return ::InterlockedDecrement(reinterpret_cast<volatile LONG*>(i));
     33   }
     34   static int AcquireLoad(volatile const int* i) {
     35     return *i;
     36   }
     37   static void ReleaseStore(volatile int* i, int value) {
     38     *i = value;
     39   }
     40   static int CompareAndSwap(volatile int* i, int old_value, int new_value) {
     41     return ::InterlockedCompareExchange(reinterpret_cast<volatile LONG*>(i),
     42                                         new_value,
     43                                         old_value);
     44   }
     45   // Pointer variants.
     46   template <typename T>
     47   static T* AcquireLoadPtr(T* volatile* ptr) {
     48     return *ptr;
     49   }
     50   template <typename T>
     51   static T* CompareAndSwapPtr(T* volatile* ptr, T* old_value, T* new_value) {
     52     return static_cast<T*>(::InterlockedCompareExchangePointer(
     53         reinterpret_cast<PVOID volatile*>(ptr), new_value, old_value));
     54   }
     55 #else
     56   static int Increment(volatile int* i) {
     57     return __sync_add_and_fetch(i, 1);
     58   }
     59   static int Decrement(volatile int* i) {
     60     return __sync_sub_and_fetch(i, 1);
     61   }
     62   static int AcquireLoad(volatile const int* i) {
     63     return __atomic_load_n(i, __ATOMIC_ACQUIRE);
     64   }
     65   static void ReleaseStore(volatile int* i, int value) {
     66     __atomic_store_n(i, value, __ATOMIC_RELEASE);
     67   }
     68   static int CompareAndSwap(volatile int* i, int old_value, int new_value) {
     69     return __sync_val_compare_and_swap(i, old_value, new_value);
     70   }
     71   // Pointer variants.
     72   template <typename T>
     73   static T* AcquireLoadPtr(T* volatile* ptr) {
     74     return __atomic_load_n(ptr, __ATOMIC_ACQUIRE);
     75   }
     76   template <typename T>
     77   static T* CompareAndSwapPtr(T* volatile* ptr, T* old_value, T* new_value) {
     78     return __sync_val_compare_and_swap(ptr, old_value, new_value);
     79   }
     80 #endif
     81 };
     82 
     83 
     84 
     85 }
     86 
     87 #endif  // WEBRTC_BASE_ATOMICOPS_H_
     88