#ifndef OSG_TIMER
#define OSG_TIMER 1

#include <osg/Export>


namespace osg {

#ifdef WIN32
    typedef __int64 Timer_t;
#elif defined(__linux) || defined(__FreeBSD__)
    typedef unsigned long long Timer_t;
#elif defined(__sgi)
    typedef unsigned long long Timer_t;
#elif defined(unix)
    typedef unsigned long long Timer_t;
#else
    #include <ctime>
    typedef std::clock_t Timer_t;
#endif

/** A high resolution, low latency time stamper.*/
class SG_EXPORT Timer {

    public:

        Timer();
        ~Timer() {}

        inline Timer_t tick();

        inline double delta_s( Timer_t t1, Timer_t t2 ) const { return (double)(t2 - t1)*_secsPerClick; }
        inline double delta_m( Timer_t t1, Timer_t t2 ) const { return delta_s(t1,t2)*1e3; }
        inline double delta_u( Timer_t t1, Timer_t t2 ) const { return delta_s(t1,t2)*1e6; }
        inline double delta_n( Timer_t t1, Timer_t t2 ) const { return delta_s(t1,t2)*1e9; }

    private :

        double                  _secsPerClick;
        bool                    _useStandardClock;
       
        #ifdef __sgi
        unsigned long*          _clockAddress;
        int                     _cycleCntrSize;
        static unsigned long    _dummy;
        #endif
        
};


#ifdef WIN32
    #include <time.h>
    #pragma optimize("",off)
    inline Timer_t Timer::tick( void )
    {
        if (_useStandardClock) return clock();
        
        volatile Timer_t ts;
        volatile unsigned int HighPart;
        volatile unsigned int LowPart;
        _asm
        {
            xor eax, eax        //  Used when QueryPerformanceCounter()
            xor edx, edx        //  not supported or minimal overhead
            _emit 0x0f          //  desired
            _emit 0x31          //
            mov HighPart,edx
            mov LowPart,eax
        }
        //ts = LowPart | HighPart >> 32;
        *((unsigned int*)&ts) = LowPart;
        *((unsigned int*)&ts+1) = HighPart;
        return ts;
    }
    #pragma optimize("",on)
    
#elif defined(__linux) || defined(__FreeBSD__)

    #include <sys/time.h>

    #define CLK(x)      __asm__ volatile (".byte 0x0f, 0x31" : "=A" (x))
    inline Timer_t Timer::tick()
    {
        if (_useStandardClock)
        {
            struct timeval tv;
            gettimeofday(&tv, NULL);
            return ((osg::Timer_t)tv.tv_sec)*1000000+(osg::Timer_t)tv.tv_usec;
        }
        else
        {
            Timer_t x;CLK(x);return x;
        }
    }
    
#elif defined(__sgi)

    #include <sys/time.h>
    inline  Timer_t Timer::tick()
    {
        if (_useStandardClock)
        {
            struct timeval tv;
            gettimeofday(&tv, NULL);
            return ((osg::Timer_t)tv.tv_sec)*1000000+(osg::Timer_t)tv.tv_usec;
        }
        else
        {
            return *_sgiClockAddress;
        }
    }
    
#elif defined(unix)

    #include <sys/time.h>
    inline  Timer_t Timer::tick()
    {
        struct timeval tv;
        gettimeofday(&tv, NULL);
        return ((osg::Timer_t)tv.tv_sec)*1000000+(osg::Timer_t)tv.tv_usec;
    }

#else

    // no choice, always use std::clock()
    inline  Timer_t Timer::tick( void ) { return std::clock(); }

#endif

};
#endif