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
24namespace 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.
30class Atomic32
31{
32public:
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
48private:
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    WebRtc_Word32 _value;
62};
63}  // namespace webrtc
64
65#endif // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMIC32_H_
66