/*
 * Author:  David Robert Nadeau
 * Site:    http://NadeauSoftware.com/
 * License: Creative Commons Attribution 3.0 Unported License
 *          http://creativecommons.org/licenses/by/3.0/deed.en_US
 */
#if defined(_WIN32)
#include <Windows.h>

#elif defined(__unix__) || defined(__unix) || defined(unix) || (defined(__APPLE__) && defined(__MACH__))
#include <unistd.h>
#include <sys/resource.h>
#include <sys/times.h>
#include <time.h>

#else
#error "Unable to define getCPUTime( ) for an unknown OS."
#endif

/**
 * Returns the amount of CPU time used by the current process,
 * in seconds, or -1.0 if an error occurred.
 */
double getCPUTime( )
{
#if defined(_WIN32)
    /* Windows -------------------------------------------------- */
    FILETIME createTime;
    FILETIME exitTime;
    FILETIME kernelTime;
    FILETIME userTime;
    if ( GetProcessTimes( GetCurrentProcess( ),
        &createTime, &exitTime, &kernelTime, &userTime ) != -1 )
    {
        SYSTEMTIME userSystemTime;
        if ( FileTimeToSystemTime( &userTime, &userSystemTime ) != -1 )
            return (double)userSystemTime.wHour * 3600.0 +
                (double)userSystemTime.wMinute * 60.0 +
                (double)userSystemTime.wSecond +
                (double)userSystemTime.wMilliseconds / 1000.0;
    }

#elif defined(__unix__) || defined(__unix) || defined(unix) || (defined(__APPLE__) && defined(__MACH__))
    /* AIX, BSD, Cygwin, HP-UX, Linux, OSX, and Solaris --------- */

#if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0)
    /* Prefer high-res POSIX timers, when available. */
    {
        clockid_t id;
        struct timespec ts;
#if _POSIX_CPUTIME > 0
        /* Clock ids vary by OS.  Query the id, if possible. */
        if ( clock_getcpuclockid( 0, &id ) == -1 )
#endif
#if defined(CLOCK_PROCESS_CPUTIME_ID)
            /* Use known clock id for AIX, Linux, or Solaris. */
            id = CLOCK_PROCESS_CPUTIME_ID;
#elif defined(CLOCK_VIRTUAL)
            /* Use known clock id for BSD or HP-UX. */
            id = CLOCK_VIRTUAL;
#else
            id = (clockid_t)-1;
#endif
        if ( id != (clockid_t)-1 && clock_gettime( id, &ts ) != -1 )
            return (double)ts.tv_sec +
                (double)ts.tv_nsec / 1000000000.0;
    }
#endif

#if defined(RUSAGE_SELF)
    {
        struct rusage rusage;
        if ( getrusage( RUSAGE_SELF, &rusage ) != -1 )
            return (double)rusage.ru_utime.tv_sec +
                (double)rusage.ru_utime.tv_usec / 1000000.0;
    }
#endif

#if defined(_SC_CLK_TCK)
    {
        const double ticks = (double)sysconf( _SC_CLK_TCK );
        struct tms tms;
        if ( times( &tms ) != (clock_t)-1 )
            return (double)tms.tms_utime / ticks;
    }
#endif

#if defined(CLOCKS_PER_SEC)
    {
        clock_t cl = clock( );
        if ( cl != (clock_t)-1 )
            return (double)cl / (double)CLOCKS_PER_SEC;
    }
#endif

#endif

    return -1;      /* Failed. */
}