lib/usleep.c

   1 /* Pausing execution of the current thread.
   2    Copyright (C) 2009-2019 Free Software Foundation, Inc.
   3    Written by Eric Blake <ebb9@byu.net>, 2009.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* This file is _intentionally_ light-weight.  Rather than using
  19    select or nanosleep, both of which drag in external libraries on
  20    some platforms, this merely rounds up to the nearest second if
  21    usleep() does not exist.  If sub-second resolution is important,
  22    then use a more powerful interface to begin with.  */
  23
  24 #include <config.h>
  25
  26 /* Specification.  */
  27 #include <unistd.h>
  28
  29 #include <errno.h>
  30
  31 #ifndef HAVE_USLEEP
  32 # define HAVE_USLEEP 0
  33 #endif
  34
  35 /* Sleep for MICRO microseconds, which can be greater than 1 second.
  36    Return -1 and set errno to EINVAL on range error (about 4295
  37    seconds), or 0 on success.  Interaction with SIGALARM is
  38    unspecified.  */
  39
  40 int
  41 usleep (useconds_t micro)
  42 {
  43   unsigned int seconds = micro / 1000000;
  44   if (sizeof seconds < sizeof micro && micro / 1000000 != seconds)
  45     {
  46       errno = EINVAL;
  47       return -1;
  48     }
  49   if (!HAVE_USLEEP && micro % 1000000)
  50     seconds++;
  51   while ((seconds = sleep (seconds)) != 0);
  52
  53 #undef usleep
  54 #if !HAVE_USLEEP
  55 # define usleep(x) 0
  56 #endif
  57   return usleep (micro % 1000000);
  58 }