osdep/timer-darwin.c

   1 /*
   2  * Precise timer routines using Mach kernel-space timing.
   3  *
   4  * It reports to be accurate by ~20us, unless the task is preempted.
   5  *
   6  * (C) 2003 Dan Christiansen
   7  *
   8  * Released into the public domain.
   9  */
  10
  11 #include <unistd.h>
  12 #include <stdlib.h>
  13 #include <stdio.h>
  14
  15 #include <mach/mach_time.h>
  16 #include <mach/mach.h>
  17 #include <mach/clock.h>
  18
  19 #include "../config.h"
  20 #include "../mp_msg.h"
  21 #include "timer.h"
  22
  23 /* Utility macros for mach_timespec_t - it uses nsec rather than usec */
  24
  25 /* returns time from t1 to t2, in seconds (as float) */
  26 #define diff_time(t1, t2)                                               \
  27   (((t2).tv_sec - (t1).tv_sec) +                                        \
  28    ((t2).tv_nsec - (t1).tv_nsec) / 1e9)
  29
  30 /* returns time from t1 to t2, in microseconds (as integer) */
  31 #define udiff_time(t1, t2)                                              \
  32   (((t2).tv_sec - (t1).tv_sec) * 1000000 +                              \
  33    ((t2).tv_nsec - (t1).tv_nsec) / 1000)
  34
  35 /* returns float value of t, in seconds */
  36 #define time_to_float(t)                                                \
  37   ((t).tv_sec + (t).tv_nsec / 1e9)
  38
  39 /* returns integer value of t, in microseconds */
  40 #define time_to_usec(t)                                                 \
  41   ((t).tv_sec * 1000000 + (t).tv_nsec / 1000)
  42
  43 /* sets ts to the value of f, in seconds */
  44 #define float_to_time(f, ts)                                            \
  45   do {                                                                  \
  46     (ts).tv_sec = (unsigned int)(f);                                    \
  47     (ts).tv_nsec = (int)(((f) - (ts).sec) / 1000000000.0);              \
  48   } while (0)
  49
  50 /* sets ts to the value of i, in microseconds */
  51 #define usec_to_time(i, ts)                                             \
  52   do {                                                                  \
  53     (ts).tv_sec = (i) / 1000000;                                        \
  54     (ts).tv_nsec = (i) % 1000000 * 1000;                                \
  55   } while (0)
  56
  57 #define time_uadd(i, ts)                                                \
  58   do {                                                                  \
  59     (ts).tv_sec += (i) / 1000000;                                       \
  60     (ts).tv_nsec += (i) % 1000000 * 1000;                               \
  61     while ((ts).tv_nsec > 1000000000) {                                 \
  62       (ts).tv_sec++;                                                    \
  63       (ts).tv_nsec -= 1000000000;                                       \
  64     }                                                                   \
  65   } while (0)
  66
  67
  68 /* global variables */
  69 static double relative_time, startup_time;
  70 static double timebase_ratio;
  71 static mach_port_t clock_port;
  72
  73
  74 /* sleep usec_delay microseconds */
  75 int usec_sleep(int usec_delay)
  76 {
  77   mach_timespec_t start_time, end_time;
  78
  79   clock_get_time(clock_port, &start_time);
  80
  81   end_time = start_time;
  82   time_uadd(usec_delay, end_time);
  83
  84   clock_sleep(clock_port, TIME_ABSOLUTE, end_time, NULL);
  85
  86   clock_get_time(clock_port, &end_time);
  87
  88   return usec_delay - udiff_time(start_time, end_time);
  89 }
  90
  91
  92 /* Returns current time in microseconds */
  93 unsigned int GetTimer()
  94 {
  95   return (unsigned int)((mach_absolute_time() * timebase_ratio - startup_time)
  96                         * 1e6);
  97 }
  98
  99 /* Returns current time in milliseconds */
 100 unsigned int GetTimerMS()
 101 {
 102   return (unsigned int)(GetTimer() / 1000);
 103 }
 104
 105 /* Returns time spent between now and last call in seconds */
 106 float GetRelativeTime()
 107 {
 108   double last_time;
 109
 110   last_time = relative_time;
 111
 112   relative_time = mach_absolute_time() * timebase_ratio;
 113
 114   return (float)(relative_time-last_time);
 115 }
 116
 117 /* Initialize timer, must be called at least once at start */
 118 void InitTimer()
 119 {
 120   struct mach_timebase_info timebase;
 121
 122   /* get base for mach_absolute_time() */
 123   mach_timebase_info(&timebase);
 124   timebase_ratio = (double)timebase.numer / (double)timebase.denom
 125     * (double)1e-9;
 126
 127   /* get mach port for the clock */
 128   host_get_clock_service(mach_host_self(), REALTIME_CLOCK, &clock_port);
 129
 130   /* prepare for GetRelativeTime() */
 131   relative_time = startup_time =
 132     (double)(mach_absolute_time() * timebase_ratio);
 133 }
 134
 135
 136 #if 0
 137 int main()
 138 {
 139   const long delay = 0.001*1e6;
 140   const unsigned short attempts = 100;
 141   int i,j[attempts],t[attempts],r[attempts];
 142   double sqtotal;
 143   double total;
 144
 145   InitTimer();
 146
 147   for (i = 0; i < attempts; i++) {
 148     t[i] = j[i] = GetTimer();
 149     r[i] = usec_sleep(delay);
 150       j[i] = delay-(GetTimer() - j[i]);
 151       fflush(stdout);
 152   }
 153
 154   for (i = 0; i < attempts; i++) {
 155     sqtotal += j[i]*j[i];
 156     total += j[i];
 157     printf("%2i=%0.06g  \tr: %9i\tj: %9i\tr - j:%9i\n",
 158            i, t[i] / 1e6, r[i], j[i], r[i] - j[i]);
 159   }
 160
 161   printf("attempts: %i\ttotal=%g\trms=%g\tavg=%g\n", attempts, total,
 162          sqrt(sqtotal/attempts),total/attempts);
 163
 164   return 0;
 165 }
 166 #endif