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);
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.
Is32bitAligned()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