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      1 /*
      2  *  Copyright (c) 2011 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 independant 32-bit signed integer.
     12 // Mac implementation.
     13 #ifndef WEBRTC_SYSTEM_WRAPPERS_SOURCE_ATOMIC32_MAC_H_
     14 #define WEBRTC_SYSTEM_WRAPPERS_SOURCE_ATOMIC32_MAC_H_
     15 
     16 #include <stdlib.h>
     17 #include <libkern/OSAtomic.h>
     18 
     19 #include "common_types.h"
     20 
     21 namespace webrtc {
     22 class Atomic32Impl
     23 {
     24 public:
     25     inline Atomic32Impl(WebRtc_Word32 initialValue);
     26     inline ~Atomic32Impl();
     27 
     28     inline WebRtc_Word32 operator++();
     29     inline WebRtc_Word32 operator--();
     30 
     31     inline Atomic32Impl& operator=(const Atomic32Impl& rhs);
     32     inline Atomic32Impl& operator=(WebRtc_Word32 rhs);
     33     inline WebRtc_Word32 operator+=(WebRtc_Word32 rhs);
     34     inline WebRtc_Word32 operator-=(WebRtc_Word32 rhs);
     35 
     36     inline bool CompareExchange(WebRtc_Word32 newValue,
     37                                 WebRtc_Word32 compareValue);
     38 
     39     inline WebRtc_Word32 Value() const;
     40 private:
     41     void*        _ptrMemory;
     42     // Volatile ensures full memory barriers.
     43     volatile WebRtc_Word32* _value;
     44 };
     45 
     46 // TODO (hellner) use aligned_malloc instead of doing it manually.
     47 inline Atomic32Impl::Atomic32Impl(WebRtc_Word32 initialValue)
     48     :
     49     _ptrMemory(NULL),
     50     _value(NULL)
     51 {   // Align the memory associated with _value on a 32-bit boundary. This is a
     52     // requirement for the used Mac APIs to be atomic.
     53     // Keep _ptrMemory to be able to reclaim memory.
     54     _ptrMemory = malloc(sizeof(WebRtc_Word32)*2);
     55     _value = (WebRtc_Word32*) (((uintptr_t)_ptrMemory+3)&(~0x3));
     56     *_value = initialValue;
     57 }
     58 
     59 inline Atomic32Impl::~Atomic32Impl()
     60 {
     61     if(_ptrMemory != NULL)
     62     {
     63         free(_ptrMemory);
     64     }
     65 }
     66 
     67 inline WebRtc_Word32 Atomic32Impl::operator++()
     68 {
     69     return OSAtomicIncrement32Barrier(
     70                reinterpret_cast<volatile int32_t*>(_value));
     71 }
     72 
     73 inline WebRtc_Word32 Atomic32Impl::operator--()
     74 {
     75     return OSAtomicDecrement32Barrier(
     76                reinterpret_cast<volatile int32_t*>(_value));
     77 }
     78 
     79 inline Atomic32Impl& Atomic32Impl::operator=(const Atomic32Impl& rhs)
     80 {
     81     *_value = *rhs._value;
     82     return *this;
     83 }
     84 
     85 inline Atomic32Impl& Atomic32Impl::operator=(WebRtc_Word32 rhs)
     86 {
     87     *_value = rhs;
     88     return *this;
     89 }
     90 
     91 inline WebRtc_Word32 Atomic32Impl::operator+=(WebRtc_Word32 rhs)
     92 {
     93     return OSAtomicAdd32Barrier(rhs,
     94                                 reinterpret_cast<volatile int32_t*>(_value));
     95 }
     96 
     97 inline WebRtc_Word32 Atomic32Impl::operator-=(WebRtc_Word32 rhs)
     98 {
     99     return OSAtomicAdd32Barrier(-rhs,
    100                                 reinterpret_cast<volatile int32_t*>(_value));
    101 }
    102 
    103 inline bool Atomic32Impl::CompareExchange(WebRtc_Word32 newValue,
    104                                           WebRtc_Word32 compareValue)
    105 {
    106     return OSAtomicCompareAndSwap32Barrier(
    107                compareValue,
    108                newValue,
    109                reinterpret_cast<volatile int32_t*>(_value));
    110 }
    111 
    112 inline WebRtc_Word32 Atomic32Impl::Value() const
    113 {
    114     return *_value;
    115 }
    116 } // namespace webrtc
    117 #endif // WEBRTC_SYSTEM_WRAPPERS_SOURCE_ATOMIC32_MAC_H_
    118