src/misc/mtime.c

   1 /*****************************************************************************
   2  * mtime.c: high rezolution time management functions
   3  * Functions are prototyped in mtime.h.
   4  *****************************************************************************
   5  * Copyright (C) 1998-2001 VideoLAN
   6  * $Id: mtime.c,v 1.36 2003/06/05 11:52:19 gbazin Exp $
   7  *
   8  * Authors: Vincent Seguin <seguin@via.ecp.fr>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  23  *****************************************************************************/
  24
  25 /*
  26  * TODO:
  27  *  see if using Linux real-time extensions is possible and profitable
  28  */
  29
  30 /*****************************************************************************
  31  * Preamble
  32  *****************************************************************************/
  33 #include <stdio.h>                                              /* sprintf() */
  34
  35 #include <vlc/vlc.h>
  36
  37 #if defined( PTH_INIT_IN_PTH_H )                                  /* GNU Pth */
  38 #   include <pth.h>
  39 #endif
  40
  41 #ifdef HAVE_UNISTD_H
  42 #   include <unistd.h>                                           /* select() */
  43 #endif
  44
  45 #ifdef HAVE_KERNEL_OS_H
  46 #   include <kernel/OS.h>
  47 #endif
  48
  49 #if defined( WIN32 ) || defined( UNDER_CE )
  50 #   include <windows.h>
  51 #else
  52 #   include <sys/time.h>
  53 #endif
  54
  55 #if defined(HAVE_NANOSLEEP) && !defined(HAVE_STRUCT_TIMESPEC)
  56 struct timespec
  57 {
  58     time_t  tv_sec;
  59     int32_t tv_nsec;
  60 };
  61 #endif
  62
  63 #if defined(HAVE_NANOSLEEP) && !defined(HAVE_DECL_NANOSLEEP)
  64 int nanosleep(struct timespec *, struct timespec *);
  65 #endif
  66
  67 /*****************************************************************************
  68  * mstrtime: return a date in a readable format
  69  *****************************************************************************
  70  * This functions is provided for any interface function which need to print a
  71  * date. psz_buffer should be a buffer long enough to store the formatted
  72  * date.
  73  *****************************************************************************/
  74 char *mstrtime( char *psz_buffer, mtime_t date )
  75 {
  76     static mtime_t ll1000 = 1000, ll60 = 60, ll24 = 24;
  77
  78     sprintf( psz_buffer, "%02d:%02d:%02d-%03d.%03d",
  79              (int) (date / (ll1000 * ll1000 * ll60 * ll60) % ll24),
  80              (int) (date / (ll1000 * ll1000 * ll60) % ll60),
  81              (int) (date / (ll1000 * ll1000) % ll60),
  82              (int) (date / ll1000 % ll1000),
  83              (int) (date % ll1000) );
  84     return( psz_buffer );
  85 }
  86
  87 /*****************************************************************************
  88  * mdate: return high precision date
  89  *****************************************************************************
  90  * Uses the gettimeofday() function when possible (1 MHz resolution) or the
  91  * ftime() function (1 kHz resolution).
  92  *****************************************************************************/
  93 mtime_t mdate( void )
  94 {
  95 #if defined( HAVE_KERNEL_OS_H )
  96     return( real_time_clock_usecs() );
  97
  98 #elif defined( WIN32 ) || defined( UNDER_CE )
  99     /* We don't need the real date, just the value of a high precision timer */
 100     static mtime_t freq = I64C(-1);
 101     mtime_t usec_time;
 102
 103     if( freq == I64C(-1) )
 104     {
 105         /* Extract from the Tcl source code:
 106          * (http://www.cs.man.ac.uk/fellowsd-bin/TIP/7.html)
 107          *
 108          * Some hardware abstraction layers use the CPU clock
 109          * in place of the real-time clock as a performance counter
 110          * reference.  This results in:
 111          *    - inconsistent results among the processors on
 112          *      multi-processor systems.
 113          *    - unpredictable changes in performance counter frequency
 114          *      on "gearshift" processors such as Transmeta and
 115          *      SpeedStep.
 116          * There seems to be no way to test whether the performance
 117          * counter is reliable, but a useful heuristic is that
 118          * if its frequency is 1.193182 MHz or 3.579545 MHz, it's
 119          * derived from a colorburst crystal and is therefore
 120          * the RTC rather than the TSC.  If it's anything else, we
 121          * presume that the performance counter is unreliable.
 122          */
 123
 124         freq = ( QueryPerformanceFrequency( (LARGE_INTEGER *)&freq ) &&
 125                  (freq == I64C(1193182) || freq == I64C(3579545) ) )
 126                ? freq : 0;
 127     }
 128
 129     if( freq != 0 )
 130     {
 131         /* Microsecond resolution */
 132         QueryPerformanceCounter( (LARGE_INTEGER *)&usec_time );
 133         return ( usec_time * 1000000 ) / freq;
 134     }
 135
 136     /* Milisecond resolution (actually, best case is about 10 ms resolution) */
 137     return 1000 * GetTickCount();
 138
 139 #else
 140     struct timeval tv_date;
 141
 142     /* gettimeofday() could return an error, and should be tested. However, the
 143      * only possible error, according to 'man', is EFAULT, which can not happen
 144      * here, since tv is a local variable. */
 145     gettimeofday( &tv_date, NULL );
 146     return( (mtime_t) tv_date.tv_sec * 1000000 + (mtime_t) tv_date.tv_usec );
 147
 148 #endif
 149 }
 150
 151 /*****************************************************************************
 152  * mwait: wait for a date
 153  *****************************************************************************
 154  * This function uses select() and an system date function to wake up at a
 155  * precise date. It should be used for process synchronization. If current date
 156  * is posterior to wished date, the function returns immediately.
 157  *****************************************************************************/
 158 void mwait( mtime_t date )
 159 {
 160 #if defined( HAVE_KERNEL_OS_H )
 161     mtime_t delay;
 162
 163     delay = date - real_time_clock_usecs();
 164     if( delay <= 0 )
 165     {
 166         return;
 167     }
 168     snooze( delay );
 169
 170 #elif defined( WIN32 ) || defined( UNDER_CE )
 171     mtime_t usec_time, delay;
 172
 173     usec_time = mdate();
 174     delay = date - usec_time;
 175     if( delay <= 0 )
 176     {
 177         return;
 178     }
 179     msleep( delay );
 180
 181 #else
 182
 183     struct timeval tv_date;
 184     mtime_t        delay;          /* delay in msec, signed to detect errors */
 185
 186     /* see mdate() about gettimeofday() possible errors */
 187     gettimeofday( &tv_date, NULL );
 188
 189     /* calculate delay and check if current date is before wished date */
 190     delay = date - (mtime_t) tv_date.tv_sec * 1000000
 191                  - (mtime_t) tv_date.tv_usec
 192                  - 10000;
 193
 194     /* Linux/i386 has a granularity of 10 ms. It's better to be in advance
 195      * than to be late. */
 196     if( delay <= 0 )                 /* wished date is now or already passed */
 197     {
 198         return;
 199     }
 200
 201 #   if defined( PTH_INIT_IN_PTH_H )
 202     pth_usleep( delay );
 203
 204 #   elif defined( ST_INIT_IN_ST_H )
 205     st_usleep( delay );
 206
 207 #   else
 208
 209 #       if defined( HAVE_NANOSLEEP )
 210     {
 211         struct timespec ts_delay;
 212         ts_delay.tv_sec = delay / 1000000;
 213         ts_delay.tv_nsec = (delay % 1000000) * 1000;
 214
 215         nanosleep( &ts_delay, NULL );
 216     }
 217
 218 #       else
 219     tv_date.tv_sec = delay / 1000000;
 220     tv_date.tv_usec = delay % 1000000;
 221     /* see msleep() about select() errors */
 222     select( 0, NULL, NULL, NULL, &tv_date );
 223 #       endif
 224
 225 #   endif
 226
 227 #endif
 228 }
 229
 230 /*****************************************************************************
 231  * msleep: more precise sleep()
 232  *****************************************************************************
 233  * Portable usleep() function.
 234  *****************************************************************************/
 235 void msleep( mtime_t delay )
 236 {
 237 #if defined( HAVE_KERNEL_OS_H )
 238     snooze( delay );
 239
 240 #elif defined( PTH_INIT_IN_PTH_H )
 241     pth_usleep( delay );
 242
 243 #elif defined( ST_INIT_IN_ST_H )
 244     st_usleep( delay );
 245
 246 #elif defined( WIN32 ) || defined( UNDER_CE )
 247     Sleep( (int) (delay / 1000) );
 248
 249 #elif defined( HAVE_NANOSLEEP )
 250     struct timespec ts_delay;
 251
 252     ts_delay.tv_sec = delay / 1000000;
 253     ts_delay.tv_nsec = (delay % 1000000) * 1000;
 254
 255     nanosleep( &ts_delay, NULL );
 256
 257 #else
 258     struct timeval tv_delay;
 259
 260     tv_delay.tv_sec = delay / 1000000;
 261     tv_delay.tv_usec = delay % 1000000;
 262
 263     /* select() return value should be tested, since several possible errors
 264      * can occur. However, they should only happen in very particular occasions
 265      * (i.e. when a signal is sent to the thread, or when memory is full), and
 266      * can be ignored. */
 267     select( 0, NULL, NULL, NULL, &tv_delay );
 268
 269 #endif
 270 }
 271