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: uses full memory barriers. 15 // Note: assumes 32-bit (or higher) system 16 #ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMIC32_H_ 17 #define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMIC32_H_ 18 19 #include <cstddef> 20 21 #include "common_types.h" 22 #include "constructor_magic.h" 23 24 namespace webrtc { 25 26 // 32 bit atomic variable. Note that this class relies on the compiler to 27 // align the 32 bit value correctly (on a 32 bit boundary), so as long as you're 28 // not doing things like reinterpret_cast over some custom allocated memory 29 // without being careful with alignment, you should be fine. 30 class Atomic32 31 { 32 public: 33 Atomic32(WebRtc_Word32 initialValue = 0); 34 ~Atomic32(); 35 36 // Prefix operator! 37 WebRtc_Word32 operator++(); 38 WebRtc_Word32 operator--(); 39 40 WebRtc_Word32 operator+=(WebRtc_Word32 value); 41 WebRtc_Word32 operator-=(WebRtc_Word32 value); 42 43 // Sets the value atomically to newValue if the value equals compare value. 44 // The function returns true if the exchange happened. 45 bool CompareExchange(WebRtc_Word32 newValue, WebRtc_Word32 compareValue); 46 WebRtc_Word32 Value() const; 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. Is32bitAligned()55 inline bool Is32bitAligned() const { 56 return (reinterpret_cast<ptrdiff_t>(&_value) & 3) == 0; 57 } 58 59 DISALLOW_COPY_AND_ASSIGN(Atomic32); 60 61 WebRtc_Word32 _value; 62 }; 63 } // namespace webrtc 64 65 #endif // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMIC32_H_ 66