include/vlc_mtime.h

   1 /*****************************************************************************
   2  * vlc_mtime.h: high resolution time management functions
   3  *****************************************************************************
   4  * This header provides portable high precision time management functions,
   5  * which should be the only ones used in other segments of the program, since
   6  * functions like gettimeofday() and ftime() are not always supported.
   7  * Most functions are declared as inline or as macros since they are only
   8  * interfaces to system calls and have to be called frequently.
   9  * 'm' stands for 'micro', since maximum resolution is the microsecond.
  10  * Functions prototyped are implemented in interface/mtime.c.
  11  *****************************************************************************
  12  * Copyright (C) 1996, 1997, 1998, 1999, 2000 the VideoLAN team
  13  * $Id$
  14  *
  15  * Authors: Vincent Seguin <seguin@via.ecp.fr>
  16  *
  17  * This program is free software; you can redistribute it and/or modify
  18  * it under the terms of the GNU General Public License as published by
  19  * the Free Software Foundation; either version 2 of the License, or
  20  * (at your option) any later version.
  21  *
  22  * This program is distributed in the hope that it will be useful,
  23  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  24  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25  * GNU General Public License for more details.
  26  *
  27  * You should have received a copy of the GNU General Public License
  28  * along with this program; if not, write to the Free Software
  29  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  30  *****************************************************************************/
  31
  32 #ifndef __VLC_MTIME_H
  33 # define __VLC_MTIME_H 1
  34
  35 /*****************************************************************************
  36  * LAST_MDATE: date which will never happen
  37  *****************************************************************************
  38  * This date can be used as a 'never' date, to mark missing events in a function
  39  * supposed to return a date, such as nothing to display in a function
  40  * returning the date of the first image to be displayed. It can be used in
  41  * comparaison with other values: all existing dates will be earlier.
  42  *****************************************************************************/
  43 #define LAST_MDATE ((mtime_t)((uint64_t)(-1)/2))
  44
  45 /*****************************************************************************
  46  * MSTRTIME_MAX_SIZE: maximum possible size of mstrtime
  47  *****************************************************************************
  48  * This values is the maximal possible size of the string returned by the
  49  * mstrtime() function, including '-' and the final '\0'. It should be used to
  50  * allocate the buffer.
  51  *****************************************************************************/
  52 #define MSTRTIME_MAX_SIZE 22
  53
  54 /* Well, Duh? But it does clue us in that we are converting from
  55    millisecond quantity to a second quantity or vice versa.
  56 */
  57 #define MILLISECONDS_PER_SEC 1000
  58
  59 #define msecstotimestr(psz_buffer, msecs) \
  60   secstotimestr( psz_buffer, (msecs / (int) MILLISECONDS_PER_SEC) )
  61
  62 /*****************************************************************************
  63  * Prototypes
  64  *****************************************************************************/
  65 VLC_EXPORT( char *,  mstrtime, ( char *psz_buffer, mtime_t date ) );
  66 VLC_EXPORT( mtime_t, mdate,    ( void ) );
  67 VLC_EXPORT( void,    mwait,    ( mtime_t date ) );
  68 VLC_EXPORT( void,    msleep,   ( mtime_t delay ) );
  69 VLC_EXPORT( char *,  secstotimestr, ( char *psz_buffer, int secs ) );
  70
  71 #if defined (__GNUC__) && defined (__linux__)
  72 # define VLC_HARD_MIN_SLEEP 1000 /* Linux has 100, 250, 300 or 1000Hz */
  73 # define VLC_SOFT_MIN_SLEEP 9000000
  74
  75 static
  76 __attribute__((unused))
  77 __attribute__((noinline))
  78 __attribute__((error("sorry, cannot sleep for such short a time")))
  79 mtime_t impossible_delay( mtime_t delay )
  80 {
  81     (void) delay;
  82     return VLC_HARD_MIN_SLEEP;
  83 }
  84
  85 static
  86 __attribute__((unused))
  87 __attribute__((noinline))
  88 __attribute__((warning("use proper event handling instead of short delay")))
  89 mtime_t harmful_delay( mtime_t delay )
  90 {
  91     return delay;
  92 }
  93
  94 # define check_delay( d ) \
  95     ((__builtin_constant_p(d < VLC_HARD_MIN_SLEEP) \
  96    && (d < VLC_HARD_MIN_SLEEP)) \
  97        ? impossible_delay(d) \
  98        : ((__builtin_constant_p(d < VLC_SOFT_MIN_SLEEP) \
  99        && (d < VLC_SOFT_MIN_SLEEP)) \
 100            ? harmful_delay(d) \
 101            : d))
 102
 103 static
 104 __attribute__((unused))
 105 __attribute__((noinline))
 106 __attribute__((error("deadlines can not be constant")))
 107 mtime_t impossible_deadline( mtime_t deadline )
 108 {
 109     return deadline;
 110 }
 111
 112 # define check_deadline( d ) \
 113     (__builtin_constant_p(d) ? impossible_deadline(d) : d)
 114 #else
 115 # define check_delay(d) (d)
 116 # define check_deadline(d) (d)
 117 #endif
 118
 119 #define msleep(d) msleep(check_delay(d))
 120 #define mwait(d) mwait(check_deadline(d))
 121
 122 /*****************************************************************************
 123  * date_t: date incrementation without long-term rounding errors
 124  *****************************************************************************/
 125 struct date_t
 126 {
 127     mtime_t  date;
 128     uint32_t i_divider_num;
 129     uint32_t i_divider_den;
 130     uint32_t i_remainder;
 131 };
 132
 133 VLC_EXPORT( void,    date_Init,      ( date_t *, uint32_t, uint32_t ) );
 134 VLC_EXPORT( void,    date_Change,    ( date_t *, uint32_t, uint32_t ) );
 135 VLC_EXPORT( void,    date_Set,       ( date_t *, mtime_t ) );
 136 VLC_EXPORT( mtime_t, date_Get,       ( const date_t * ) );
 137 VLC_EXPORT( void,    date_Move,      ( date_t *, mtime_t ) );
 138 VLC_EXPORT( mtime_t, date_Increment, ( date_t *, uint32_t ) );
 139 VLC_EXPORT( uint64_t, NTPtime64,     ( void ) );
 140 #endif /* !__VLC_MTIME_ */