mtime.c

VLC Player Source Code

/*****************************************************************************
 * mtime.c: high resolution time management functions
 * Functions are prototyped in vlc_mtime.h.
 *****************************************************************************
 * Copyright (C) 1998-2007 the VideoLAN team
 * Copyright © 2006-2007 Rémi Denis-Courmont
 * $Id: 6c13eacc49b4d578321a2d164020cf5f77d8a99d $
 *
 * Authors: Vincent Seguin <[e-mail]>
 *          Rémi Denis-Courmont <rem$videolan,org>
 *          Gisle Vanem
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <vlc_common.h>

#include <time.h>                      /* clock_gettime(), clock_nanosleep() */
#include <assert.h>
#include <errno.h>

#ifdef HAVE_UNISTD_H
#   include <unistd.h>                                           /* select() */
#endif

#ifdef HAVE_KERNEL_OS_H
#   include <kernel/OS.h>
#endif

#if defined( WIN32 ) || defined( UNDER_CE )
#   include <windows.h>
#   include <mmsystem.h>
#endif

#if defined( UNDER_CE )
#   include <windows.h>
#endif

#if defined(HAVE_SYS_TIME_H)
#   include <sys/time.h>
#endif

#if !defined(HAVE_STRUCT_TIMESPEC)
struct timespec
{
    time_t  tv_sec;
    int32_t tv_nsec;
};
#endif

#if defined(HAVE_NANOSLEEP) && !defined(HAVE_DECL_NANOSLEEP)
int nanosleep(struct timespec *, struct timespec *);
#endif

#if !defined (_POSIX_CLOCK_SELECTION)
#  define _POSIX_CLOCK_SELECTION (-1)
#endif

# if (_POSIX_CLOCK_SELECTION < 0)
/*
 * We cannot use the monotonic clock is clock selection is not available,
 * as it would screw vlc_cond_timedwait() completely. Instead, we have to
 * stick to the realtime clock. Nevermind it screws everything when ntpdate
 * warps the wall clock.
 */
#  undef CLOCK_MONOTONIC
#  define CLOCK_MONOTONIC CLOCK_REALTIME
#elif !defined (HAVE_CLOCK_NANOSLEEP)
/* Clock selection without clock in the first place, I don't think so. */
#  error We have quite a situation here! Fix me if it ever happens.
#endif

/**
 * Return a date in a readable format
 *
 * This function converts a mtime date into a string.
 * psz_buffer should be a buffer long enough to store the formatted
 * date.
 * \param date to be converted
 * \param psz_buffer should be a buffer at least MSTRTIME_MAX_SIZE characters
 * \return psz_buffer is returned so this can be used as printf parameter.
 */
char *mstrtime( char *psz_buffer, mtime_t date )
{
    static const mtime_t ll1000 = 1000, ll60 = 60, ll24 = 24;

    snprintf( psz_buffer, MSTRTIME_MAX_SIZE, "%02d:%02d:%02d-%03d.%03d",
             (int) (date / (ll1000 * ll1000 * ll60 * ll60) % ll24),
             (int) (date / (ll1000 * ll1000 * ll60) % ll60),
             (int) (date / (ll1000 * ll1000) % ll60),
             (int) (date / ll1000 % ll1000),
             (int) (date % ll1000) );
    return( psz_buffer );
}

/**
 * Convert seconds to a time in the format h:mm:ss.
 *
 * This function is provided for any interface function which need to print a
 * time string in the format h:mm:ss
 * date.
 * \param secs  the date to be converted
 * \param psz_buffer should be a buffer at least MSTRTIME_MAX_SIZE characters
 * \return psz_buffer is returned so this can be used as printf parameter.
 */
char *secstotimestr( char *psz_buffer, int i_seconds )
{
    int i_hours, i_mins;
    i_mins = i_seconds / 60;
    i_hours = i_mins / 60 ;
    if( i_hours )
    {
        snprintf( psz_buffer, MSTRTIME_MAX_SIZE, "%d:%2.2d:%2.2d",
                 (int) i_hours,
                 (int) (i_mins % 60),
                 (int) (i_seconds % 60) );
    }
    else
    {
         snprintf( psz_buffer, MSTRTIME_MAX_SIZE, "%2.2d:%2.2d",
                   (int) i_mins ,
                   (int) (i_seconds % 60) );
    }
    return( psz_buffer );
}

#if defined (HAVE_CLOCK_NANOSLEEP)
static unsigned prec = 0;

static void mprec_once( void )
{
    struct timespec ts;
    if( clock_getres( CLOCK_MONOTONIC, &ts ))
        clock_getres( CLOCK_REALTIME, &ts );

    prec = ts.tv_nsec / 1000;
}
#endif

/**
 * Return a value that is no bigger than the clock precision
 * (possibly zero).
 */
static inline unsigned mprec( void )
{
#if defined (HAVE_CLOCK_NANOSLEEP)
    static pthread_once_t once = PTHREAD_ONCE_INIT;
    pthread_once( &once, mprec_once );
    return prec;
#else
    return 0;
#endif
}

/**
 * Return high precision date
 *
 * Use a 1 MHz clock when possible, or 1 kHz
 *
 * Beware ! It doesn't reflect the actual date (since epoch), but can be the machine's uptime or anything (when monotonic clock is used)
 */
mtime_t mdate( void )
{
    mtime_t res;

#if defined (HAVE_CLOCK_NANOSLEEP)
    struct timespec ts;

    /* Try to use POSIX monotonic clock if available */
    if( clock_gettime( CLOCK_MONOTONIC, &ts ) == EINVAL )
        /* Run-time fallback to real-time clock (always available) */
        (void)clock_gettime( CLOCK_REALTIME, &ts );

    res = ((mtime_t)ts.tv_sec * (mtime_t)1000000)
           + (mtime_t)(ts.tv_nsec / 1000);

#elif defined( HAVE_KERNEL_OS_H )
    res = real_time_clock_usecs();

#elif defined( WIN32 ) || defined( UNDER_CE )
    /* We don't need the real date, just the value of a high precision timer */
    static mtime_t freq = INT64_C(-1);

    if( freq == INT64_C(-1) )
    {
        /* Extract from the Tcl source code:
         * (http://www.cs.man.ac.uk/fellowsd-bin/TIP/7.html)
         *
         * Some hardware abstraction layers use the CPU clock
         * in place of the real-time clock as a performance counter
         * reference.  This results in:
         *    - inconsistent results among the processors on
         *      multi-processor systems.
         *    - unpredictable changes in performance counter frequency
         *      on "gearshift" processors such as Transmeta and
         *      SpeedStep.
         * There seems to be no way to test whether the performance
         * counter is reliable, but a useful heuristic is that
         * if its frequency is 1.193182 MHz or 3.579545 MHz, it's
         * derived from a colorburst crystal and is therefore
         * the RTC rather than the TSC.  If it's anything else, we
         * presume that the performance counter is unreliable.
         */
        LARGE_INTEGER buf;

        freq = ( QueryPerformanceFrequency( &buf ) &&
                 (buf.QuadPart == INT64_C(1193182) || buf.QuadPart == INT64_C(3579545) ) )
               ? buf.QuadPart : 0;

#if defined( WIN32 )
        /* on windows 2000, XP and Vista detect if there are two
           cores there - that makes QueryPerformanceFrequency in
           any case not trustable?
           (may also be true, for single cores with adaptive
            CPU frequency and active power management?)
        */
        HINSTANCE h_Kernel32 = LoadLibrary(_T("kernel32.dll"));
        if(h_Kernel32)
        {
            void WINAPI (*pf_GetSystemInfo)(LPSYSTEM_INFO);
            pf_GetSystemInfo = (void WINAPI (*)(LPSYSTEM_INFO))
                                GetProcAddress(h_Kernel32, _T("GetSystemInfo"));
            if(pf_GetSystemInfo)
            {
               SYSTEM_INFO system_info;
               pf_GetSystemInfo(&system_info);
               if(system_info.dwNumberOfProcessors > 1)
                  freq = 0;
            }
            FreeLibrary(h_Kernel32);
        }
#endif
    }

    if( freq != 0 )
    {
        LARGE_INTEGER counter;
        QueryPerformanceCounter (&counter);

        /* Convert to from (1/freq) to microsecond resolution */
        /* We need to split the division to avoid 63-bits overflow */
        lldiv_t d = lldiv (counter.QuadPart, freq);

        res = (d.quot * 1000000) + ((d.rem * 1000000) / freq);
    }
    else
    {
        /* Fallback on timeGetTime() which has a milisecond resolution
         * (actually, best case is about 5 ms resolution)
         * timeGetTime() only returns a DWORD thus will wrap after
         * about 49.7 days so we try to detect the wrapping. */

        static CRITICAL_SECTION date_lock;
        static mtime_t i_previous_time = INT64_C(-1);
        static int i_wrap_counts = -1;

        if( i_wrap_counts == -1 )
        {
            /* Initialization */
#if defined( WIN32 )
            i_previous_time = INT64_C(1000) * timeGetTime();
#else
            i_previous_time = INT64_C(1000) * GetTickCount();
#endif
            InitializeCriticalSection( &date_lock );