text: // Protocol Buffers - Google's data interchange format
  // Copyright 2012 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * 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.
  //     * 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 COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "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 COPYRIGHT
  // OWNER OR CONTRIBUTORS 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.
  
  // This file is an internal atomic implementation, use atomicops.h instead.
  
  #ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_MACOSX_H_
  #define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_MACOSX_H_
  
  #include <libkern/OSAtomic.h>
  
  namespace google {
  namespace protobuf {
  namespace internal {
  
  inline Atomic32 NoBarrier_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 NoBarrier_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 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
                                            Atomic32 increment) {
    return OSAtomicAdd32(increment, const_cast<Atomic32*>(ptr));
  }
  
  inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
                                            Atomic32 increment) {
    return OSAtomicAdd32Barrier(increment, const_cast<Atomic32*>(ptr));
  }
  
  inline void MemoryBarrier() {
    OSMemoryBarrier();
  }
  
  inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
                                         Atomic32 old_value,
                                         Atomic32 new_value) {
    Atomic32 prev_value;
    do {
      if (OSAtomicCompareAndSwap32Barrier(old_value, new_value,
                                          const_cast<Atomic32*>(ptr))) {
        return old_value;
      }
      prev_value = *ptr;
    } while (prev_value == old_value);
    return prev_value;
  }
  
  inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
                                         Atomic32 old_value,
                                         Atomic32 new_value) {
    return Acquire_CompareAndSwap(ptr, old_value, new_value);
  }
  
  inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
    *ptr = value;
  }
  
  inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
    *ptr = value;
    MemoryBarrier();
  }
  
  inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
    MemoryBarrier();
    *ptr = value;
  }
  
  inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
    return *ptr;
  }
  
  inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
    Atomic32 value = *ptr;
    MemoryBarrier();
    return value;
  }
  
  inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
    MemoryBarrier();
    return *ptr;
  }
  
  #ifdef __LP64__
  
  // 64-bit implementation on 64-bit platform
  
  inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
                                           Atomic64 old_value,
                                           Atomic64 new_value) {
    Atomic64 prev_value;
    do {
      if (OSAtomicCompareAndSwap64(old_value, new_value,
                                   reinterpret_cast<volatile int64_t*>(ptr))) {
        return old_value;
      }
      prev_value = *ptr;
    } while (prev_value == old_value);
    return prev_value;
  }
  
  inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
                                           Atomic64 new_value) {
    Atomic64 old_value;
    do {
      old_value = *ptr;
    } while (!OSAtomicCompareAndSwap64(old_value, new_value,
                                       reinterpret_cast<volatile int64_t*>(ptr)));
    return old_value;
  }
  
  inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
                                            Atomic64 increment) {
    return OSAtomicAdd64(increment, reinterpret_cast<volatile int64_t*>(ptr));
  }
  
  inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
                                          Atomic64 increment) {
    return OSAtomicAdd64Barrier(increment,
                                reinterpret_cast<volatile int64_t*>(ptr));
  }
  
  inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
                                         Atomic64 old_value,
                                         Atomic64 new_value) {
    Atomic64 prev_value;
    do {
      if (OSAtomicCompareAndSwap64Barrier(
          old_value, new_value, reinterpret_cast<volatile int64_t*>(ptr))) {
        return old_value;
      }
      prev_value = *ptr;
    } while (prev_value == old_value);
    return prev_value;
  }
  
  inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
                                         Atomic64 old_value,
                                         Atomic64 new_value) {
    // The lib kern interface does not distinguish between
    // Acquire and Release memory barriers; they are equivalent.
    return Acquire_CompareAndSwap(ptr, old_value, new_value);
  }
  
  inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
    *ptr = value;
  }
  
  inline void Acquire_Store(volatile Atomic64* ptr, Atomic64 value) {
    *ptr = value;
    MemoryBarrier();
  }
  
  inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
    MemoryBarrier();
    *ptr = value;
  }
  
  inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
    return *ptr;
  }
  
  inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
    Atomic64 value = *ptr;
    MemoryBarrier();
    return value;
  }
  
  inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
    MemoryBarrier();
    return *ptr;
  }
  
  #endif  // defined(__LP64__)
  
  }  // namespace internal
  }  // namespace protobuf
  }  // namespace google
  
  #endif  // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_MACOSX_H_
   