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// Copyright 2003, Google Inc.
//
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions are met:
//
//  1. Redistributions of source code must retain the above copyright notice, 
//     this list of conditions and the following disclaimer.
//  2. Redistributions in binary form must reproduce the above copyright notice,
//     this list of conditions and the following disclaimer in the documentation
//     and/or other materials provided with the distribution.
//  3. Neither the name of Google Inc. nor the names of its contributors may be
//     used to endorse or promote products derived from this software without
//     specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
// WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
// EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 
// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
// ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Implementation of atomic operations for Mac OS X.  This file should not be
// included directly.  Clients should instead include "atomicops.h".

#ifndef GEARS_BASE_COMMON_ATOMIC_OPS_OSX_H__
#define GEARS_BASE_COMMON_ATOMIC_OPS_OSX_H__

#include <libkern/OSAtomic.h>
#include <stdint.h>

typedef int32_t Atomic32;
typedef intptr_t AtomicWord;

#ifdef __LP64__   // Indicates 64-bit pointers under OS 
#define OSAtomicCastIntPtr(p) \
               reinterpret_cast<int64_t *>(const_cast<AtomicWord *>(p))
#define OSAtomicCompareAndSwapIntPtr OSAtomicCompareAndSwap64
#define OSAtomicAddIntPtr OSAtomicAdd64
#else
#define OSAtomicCastIntPtr(p) \
               reinterpret_cast<int32_t *>(const_cast<AtomicWord *>(p))
#define OSAtomicCompareAndSwapIntPtr OSAtomicCompareAndSwap32
#define OSAtomicAddIntPtr OSAtomicAdd32
#endif

inline AtomicWord CompareAndSwap(volatile AtomicWord *ptr,
                                 AtomicWord old_value,
                                 AtomicWord new_value) {
  AtomicWord prev_value;
  do {
    if (OSAtomicCompareAndSwapIntPtr(old_value, new_value,
                                     OSAtomicCastIntPtr(ptr))) {
      return old_value;
    }
    prev_value = *ptr;
  } while (prev_value == old_value);
  return prev_value;
}

inline AtomicWord AtomicExchange(volatile AtomicWord *ptr,
                                 AtomicWord new_value) {
  AtomicWord old_value;
  do {
    old_value = *ptr;
  } while (!OSAtomicCompareAndSwapIntPtr(old_value, new_value,
                                         OSAtomicCastIntPtr(ptr)));
  return old_value;
}


inline AtomicWord AtomicIncrement(volatile AtomicWord *ptr, AtomicWord increment) {
  return OSAtomicAddIntPtr(increment, OSAtomicCastIntPtr(ptr));
}


// MacOS uses long for intptr_t, AtomicWord and Atomic32 are always different
// on the Mac, even when they are the same size.  Thus, we always provide 
// Atomic32 versions.

inline Atomic32 CompareAndSwap(volatile Atomic32 *ptr,
                               Atomic32 old_value,
                               Atomic32 new_value) {
  Atomic32 prev_value;
  do {
    if (OSAtomicCompareAndSwap32(old_value, new_value,
                                 const_cast<Atomic32*>(ptr))) {
      return old_value;
    }
    prev_value = *ptr;
  } while (prev_value == old_value);
  return prev_value;
}

inline Atomic32 AtomicExchange(volatile Atomic32 *ptr,
                               Atomic32 new_value) {
  Atomic32 old_value;
  do {
    old_value = *ptr;
  } while (!OSAtomicCompareAndSwap32(old_value, new_value,
                                     const_cast<Atomic32*>(ptr)));
  return old_value;
}

inline Atomic32 AtomicIncrement(volatile Atomic32 *ptr, Atomic32 increment) {
  return OSAtomicAdd32(increment, const_cast<Atomic32*>(ptr));
}

#endif  // GEARS_BASE_COMMON_ATOMIC_OPS_OSX_H__