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_INTERFACE_ATOMIC32_H_
16#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMIC32_H_
17
18#include <stddef.h>
19
20#include "webrtc/base/constructormagic.h"
21#include "webrtc/common_types.h"
22
23namespace 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.
29class 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  DISALLOW_COPY_AND_ASSIGN(Atomic32);
60
61  int32_t value_;
62};
63
64}  // namespace webrtc
65
66#endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMIC32_H_
67