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#ifndef BASE_ATOMIC_H__
#define BASE_ATOMIC_H__

#if defined(WIN32)
#include <windows.h>
#elif defined(__APPLE__)
#include <libkern/OSAtomic.h>
#else
#error Implement atomic support on your platform
#endif

#include "base/basictypes.h"

namespace base {

///////////////////////////////////////////////////////////////////////////
//
// Forward declarations and descriptions of the functions
//
///////////////////////////////////////////////////////////////////////////

// Atomically increments *value and returns the resulting incremented value.
// This function implies no memory barriers.
int32 AtomicIncrement(volatile int32* value);

// Atomically decrements *value and returns the resulting decremented value.
// This function implies no memory barriers.
int32 AtomicDecrement(volatile int32* value);

// Atomically sets *target to new_value and returns the old value of *target.
// This function implies no memory barriers.
int32 AtomicSwap(volatile int32* target, int32 new_value);

///////////////////////////////////////////////////////////////////////////
//
// Implementations for various platforms
//
///////////////////////////////////////////////////////////////////////////

#if defined(WIN32)

inline int32 AtomicIncrement(volatile int32* value) {
  return InterlockedIncrement(reinterpret_cast<volatile LONG*>(value));
}

inline int32 AtomicDecrement(volatile int32* value) {
  return InterlockedDecrement(reinterpret_cast<volatile LONG*>(value));
}

inline int32 AtomicSwap(volatile int32* target, int32 new_value) {
  return InterlockedExchange(reinterpret_cast<volatile LONG*>(target),
                             new_value);
}

#elif defined(__APPLE__)

inline int32 AtomicIncrement(volatile int32* value) {
  return OSAtomicIncrement32(reinterpret_cast<volatile int32_t*>(value));
}

inline int32 AtomicDecrement(volatile int32* value) {
  return OSAtomicDecrement32(reinterpret_cast<volatile int32_t*>(value));
}

inline int32 AtomicSwap(volatile int32* target, int32 new_value) {
  int32 old_value;
  do {
    old_value = *target;
  } while (!OSAtomicCompareAndSwap32(old_value, new_value,
      reinterpret_cast<volatile int32_t*>(target)));
  return old_value;
}

#else

#error Implement atomic support on your platform

#endif

}  // namespace base

#endif // BASE_ATOMIC_H__