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108 lines
3.2 KiB
C
108 lines
3.2 KiB
C
/* xnanosleep.c -- a more convenient interface to nanosleep
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Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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/* Mostly written (for sleep.c) by Paul Eggert.
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Factored out (creating this file) by Jim Meyering. */
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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include "xnanosleep.h"
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#include <limits.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <assert.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <time.h>
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#include "intprops.h"
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#ifndef TIME_T_MAX
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# define TIME_T_MAX TYPE_MAXIMUM (time_t)
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#endif
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/* Sleep until the time (call it WAKE_UP_TIME) specified as
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SECONDS seconds after the time this function is called.
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SECONDS must be non-negative. If SECONDS is so large that
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it is not representable as a `struct timespec', then use
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the maximum value for that interval. Return -1 on failure
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(setting errno), 0 on success. */
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int
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xnanosleep (double seconds)
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{
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enum { BILLION = 1000000000 };
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bool overflow = false;
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double ns;
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struct timespec ts_sleep;
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assert (0 <= seconds);
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/* Separate whole seconds from nanoseconds.
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Be careful to detect any overflow. */
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ts_sleep.tv_sec = seconds;
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ns = BILLION * (seconds - ts_sleep.tv_sec);
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overflow |= ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= BILLION);
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ts_sleep.tv_nsec = ns;
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/* Round up to the next whole number, if necessary, so that we
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always sleep for at least the requested amount of time. Assuming
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the default rounding mode, we don't have to worry about the
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rounding error when computing 'ns' above, since the error won't
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cause 'ns' to drop below an integer boundary. */
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ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
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/* Normalize the interval length. nanosleep requires this. */
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if (BILLION <= ts_sleep.tv_nsec)
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{
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time_t t = ts_sleep.tv_sec + 1;
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/* Detect integer overflow. */
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overflow |= (t < ts_sleep.tv_sec);
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ts_sleep.tv_sec = t;
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ts_sleep.tv_nsec -= BILLION;
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}
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for (;;)
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{
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if (overflow)
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{
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ts_sleep.tv_sec = TIME_T_MAX;
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ts_sleep.tv_nsec = BILLION - 1;
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}
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/* Linux-2.6.8.1's nanosleep returns -1, but doesn't set errno
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when resumed after being suspended. Earlier versions would
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set errno to EINTR. nanosleep from linux-2.6.10, as well as
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implementations by (all?) other vendors, doesn't return -1
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in that case; either it continues sleeping (if time remains)
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or it returns zero (if the wake-up time has passed). */
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errno = 0;
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if (nanosleep (&ts_sleep, NULL) == 0)
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break;
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if (errno != EINTR && errno != 0)
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return -1;
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}
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return 0;
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}
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