跨平台原子操作

class AtomicRefCount
{
public:
        AtomicRefCount();

        int increment();
        int decrement();
        void reset();        

private:

        AtomicRefCount& operator=( const AtomicRefCount& );

        volatile int m_count;
        Mutex m_lock;

};

#include "atomicrefcount.h"

#if defined( _WIN32 ) && !defined( __SYMBIAN32__ )
# include <windows.h>
#elif defined( __APPLE__ )
# include <libkern/OSAtomic.h>
#elif defined( HAVE_GCC_ATOMIC_BUILTINS )
 // Use intrinsic functions - no #include required.
#else
# include "mutexguard.h"
#endif


#ifdef _WIN32_WCE
# include <winbase.h>
#endif

    AtomicRefCount::AtomicRefCount()
      : m_count( 0 )
    {
    }

    int AtomicRefCount::increment()
    {
#if defined( _WIN32 ) && !defined( __SYMBIAN32__ )
      return (int) ::InterlockedIncrement( (volatile LONG*)&m_count );
#elif defined( __APPLE__ )
      return (int) OSAtomicIncrement32Barrier( (volatile int32_t*)&m_count );
#elif defined( HAVE_GCC_ATOMIC_BUILTINS )
      // Use the gcc intrinsic for atomic increment if supported.
      return (int) __sync_add_and_fetch( &m_count, 1 );
#else
      // Fallback to using a lock
      MutexGuard m( m_lock );
      return ++m_count;
#endif
    }

    int AtomicRefCount::decrement()
    {
#if defined( _WIN32 ) && !defined( __SYMBIAN32__ )
      return (int) ::InterlockedDecrement( (volatile LONG*)&m_count );
#elif defined( __APPLE__ )
      return (int) OSAtomicDecrement32Barrier( (volatile int32_t*)&m_count );
#elif defined( HAVE_GCC_ATOMIC_BUILTINS )
      // Use the gcc intrinsic for atomic decrement if supported.
      return (int) __sync_sub_and_fetch( &m_count, 1 );
#else
      // Fallback to using a lock
      MutexGuard m( m_lock );
      return --m_count;
#endif
    }

    void AtomicRefCount::reset()
    {
#if defined( _WIN32 ) && !defined( __SYMBIAN32__ )
      ::InterlockedExchange( (volatile LONG*)&m_count, (volatile LONG)0 );
#elif defined( __APPLE__ )
      OSAtomicAnd32Barrier( (int32_t)0, (volatile int32_t*)&m_count );
#elif defined( HAVE_GCC_ATOMIC_BUILTINS )
      // Use the gcc intrinsic for atomic decrement if supported.
      __sync_fetch_and_and( &m_count, 0 );
#else
      // Fallback to using a lock
      MutexGuard m( m_lock );
      m_count = 0;
#endif
    }