sysdeps/posix/clock_getres.c

   1 /* Copyright (C) 1999, 2000, 2001, 2003 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <stdint.h>
  21 #include <time.h>
  22 #include <unistd.h>
  23 #include <sys/param.h>
  24 #include <libc-internal.h>
  25
  26
  27 #if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME
  28 /* Clock frequency of the processor.  */
  29 static long int nsec;
  30 #endif
  31
  32
  33 /* Get resolution of clock.  */
  34 int
  35 clock_getres (clockid_t clock_id, struct timespec *res)
  36 {
  37   int retval = -1;
  38
  39   switch (clock_id)
  40     {
  41 #define HANDLE_REALTIME \
  42       do {                                                                    \
  43         long int clk_tck = sysconf (_SC_CLK_TCK);                             \
  44                                                                               \
  45         if (__builtin_expect (clk_tck != -1, 1))                              \
  46           {                                                                   \
  47             /* This implementation assumes that the realtime clock has a      \
  48                resolution higher than 1 second.  This is the case for any     \
  49                reasonable implementation.  */                                 \
  50             res->tv_sec = 0;                                                  \
  51             res->tv_nsec = 1000000000 / clk_tck;                              \
  52                                                                               \
  53             retval = 0;                                                       \
  54           }                                                                   \
  55       } while (0)
  56
  57 #ifdef SYSDEP_GETRES
  58       SYSDEP_GETRES;
  59 #endif
  60
  61 #ifndef HANDLED_REALTIME
  62     case CLOCK_REALTIME:
  63       HANDLE_REALTIME;
  64       break;
  65 #endif  /* handled REALTIME */
  66
  67     default:
  68 #if HP_TIMING_AVAIL
  69       if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1))
  70           != CLOCK_THREAD_CPUTIME_ID)
  71 #endif
  72         {
  73           __set_errno (EINVAL);
  74           break;
  75         }
  76
  77 #if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME
  78       /* FALLTHROUGH.  */
  79     case CLOCK_PROCESS_CPUTIME_ID:
  80       {
  81         if (__builtin_expect (nsec == 0, 0))
  82           {
  83             hp_timing_t freq;
  84
  85             /* This can only happen if we haven't initialized the `freq'
  86                variable yet.  Do this now. We don't have to protect this
  87                code against multiple execution since all of them should
  88                lead to the same result.  */
  89             freq = __get_clockfreq ();
  90             if (__builtin_expect (freq == 0, 0))
  91               /* Something went wrong.  */
  92               break;
  93
  94             nsec = MAX (UINT64_C (1000000000) / freq, 1);
  95           }
  96
  97         /* File in the values.  The seconds are always zero (unless we
  98            have a 1Hz machine).  */
  99         res->tv_sec = 0;
 100         res->tv_nsec = nsec;
 101
 102         retval = 0;
 103       }
 104       break;
 105 #endif
 106     }
 107
 108   return retval;
 109 }