1 /* 2 * Copyright (c) 2012 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 // Atomic, system independent 32-bit integer. Unless you know what you're 12 // doing, use locks instead! :-) 13 // 14 // Note: assumes 32-bit (or higher) system 15 #ifndef WEBRTC_SYSTEM_WRAPPERS_INCLUDE_ATOMIC32_H_ 16 #define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_ATOMIC32_H_ 17 18 #include <stddef.h> 19 20 #include "webrtc/base/constructormagic.h" 21 #include "webrtc/common_types.h" 22 23 namespace webrtc { 24 25 // 32 bit atomic variable. Note that this class relies on the compiler to 26 // align the 32 bit value correctly (on a 32 bit boundary), so as long as you're 27 // not doing things like reinterpret_cast over some custom allocated memory 28 // without being careful with alignment, you should be fine. 29 class Atomic32 { 30 public: 31 Atomic32(int32_t initial_value = 0); 32 ~Atomic32(); 33 34 // Prefix operator! 35 int32_t operator++(); 36 int32_t operator--(); 37 38 int32_t operator+=(int32_t value); 39 int32_t operator-=(int32_t value); 40 41 // Sets the value atomically to new_value if the value equals compare value. 42 // The function returns true if the exchange happened. 43 bool CompareExchange(int32_t new_value, int32_t compare_value); 44 int32_t Value() { 45 return *this += 0; 46 } 47 48 private: 49 // Disable the + and - operator since it's unclear what these operations 50 // should do. 51 Atomic32 operator+(const Atomic32& other); 52 Atomic32 operator-(const Atomic32& other); 53 54 // Checks if |_value| is 32bit aligned. 55 inline bool Is32bitAligned() const { 56 return (reinterpret_cast<ptrdiff_t>(&value_) & 3) == 0; 57 } 58 59 RTC_DISALLOW_COPY_AND_ASSIGN(Atomic32); 60 61 int32_t value_; 62 }; 63 64 } // namespace webrtc 65 66 #endif // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_ATOMIC32_H_ 67
