/*
 * Provides atomic operations for SMP/MT safety. Uses whatever OS Primitives
 * are offered.
 *
 * Current implementation should be complete on Mac OS X 10.4, but does not provide
 *  complete barriers on Linux.
 *
 * By including this file, you should have the following atomic primitives:
 * fullMemoryBarrier()
 * readMemoryBarrier()
 * writeMemoryBarrier()
 *  
 * template<class T> bool CASPointer( T oldVal, T newVal, T* Val )
 */

#ifndef ATOMIC_H
#define ATOMIC_H

using namespace std;

#if defined(__linux__) || defined(__FreeBSD__)
//extern "C" {
//#   define new nw
//#   define unlikely(a) __builtin_expect(a,false)
//#   include <asm/atomic.h>
//#   undef new
//}
//#   define fullMemoryBarrier()  do{ asm volatile("":::"memory"); smp_mb(); }while(false)
//#   define readMemoryBarrier()  do{ asm volatile("":::"memory"); smp_rmb(); }while(false)
//#   define writeMemoryBarrier() do{ asm volatile("":::"memory"); smp_wmb(); }while(false)
#   define fullMemoryBarrier()  do{ asm volatile("":::"memory"); }while(false)
#   define readMemoryBarrier()  do{ asm volatile("":::"memory"); }while(false)
#   define writeMemoryBarrier() do{ asm volatile("":::"memory"); }while(false)
#elif defined(__APPLE__)
#   include <libkern/OSAtomic.h>
#   include <stdexcept>

    /* Here are the memory barrier functions. Mac OS X only provides
       full memory barriers, so the three types of barriers are the same.
       The asm volatile may be redundant with the memory barrier, but
       until I have proof of that, I'm leaving it. The assembly calls are probably
       unnecessary */
#   define fullMemoryBarrier()  do{ asm volatile("":::"memory"); OSMemoryBarrier(); }while(false)
#   define readMemoryBarrier()  do{ asm volatile("":::"memory"); OSMemoryBarrier(); }while(false)
#   define writeMemoryBarrier() do{ asm volatile("":::"memory"); OSMemoryBarrier(); }while(false)

template<class T> bool CASPointer( T oldVal, T newVal, T* Val )
{
   if( sizeof( T ) == 4 )
      return OSAtomicCompareAndSwap32( (int32_t)oldVal, (int32_t)newVal, (int32_t *)Val );
   //else if( sizeof( T ) == 8 )
   //   return OSAtomicCompareAndSwap64( (int64_t)oldVal, (int64_t)newVal, (int64_t *)Val );
   else
      throw runtime_error( "Unkown size in comparison" );
}

#elif defined(_MSC_VER) && (_MSC_VER >= 1400)
    /* For Visual C++ 8.0 and above, use these Microsoft-specific
     * memory barriers.
     * Ref: http://msdn2.microsoft.com/en-us/library/f20w0x5e(VS.80).aspx
     */
#   include <intrin.h>
#   pragma intrinsic(_ReadWriteBarrier)
#   pragma intrinsic(_ReadBarrier)
#   pragma intrinsic(_WriteBarrier)
#   define PaUtil_FullMemoryBarrier()  _ReadWriteBarrier()
#   define PaUtil_ReadMemoryBarrier()  _ReadBarrier()
#   define PaUtil_WriteMemoryBarrier() _WriteBarrier()
#else
#   error "Memory Barriers not defined on this system or system unknown."
#endif

#endif /* ATOMIC_H */