nanosleep.c
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nanosleep.c
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	/* Provide a replacement for the POSIX nanosleep function.

	Copyright (C) 1999, 2000, 2002, 2004, 2005, 2006 Free Software
	Foundation, Inc.

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2, or (at your option)
	any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software Foundation,
	Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */

	/* written by Jim Meyering */

	#include "defines.h"

	/* Undefine nanosleep here so any prototype is not redefined to be a
	prototype for rpl_nanosleep. (they'd conflict e.g., on alpha-dec-osf3.2) */

	#if HAVE_SYS_SELECT_H
	# include <sys/select.h>
	#endif

	#include "timespec.h"

	/* Some systems (MSDOS) don't have SIGCONT.
	Using SIGTERM here turns the signal-handling code below
	into a no-op on such systems. */
	#ifndef SIGCONT
	# define SIGCONT SIGTERM
	#endif

	#if ! HAVE_SIGINTERRUPT
	# define siginterrupt(sig, flag) /* empty */
	#endif

	static sig_atomic_t volatile suspended;

	/* Handle SIGCONT. */

	static void
	sighandler (int sig)
	{
	suspended = 1;
	}

	/* Suspend execution for at least TS_DELAY seconds. /

	static void
	my_usleep (const struct timespec *ts_delay)
	{
	struct timeval tv_delay;
	tv_delay.tv_sec = ts_delay->tv_sec;
	tv_delay.tv_usec = (ts_delay->tv_nsec + 999) / 1000;
	if (tv_delay.tv_usec == 1000000)
	{
	time_t t1 = tv_delay.tv_sec + 1;
	if (t1 < tv_delay.tv_sec)
	tv_delay.tv_usec = 1000000 - 1; /* close enough */
	else
	{
	tv_delay.tv_sec = t1;
	tv_delay.tv_usec = 0;
	}
	}
	select (0, NULL, NULL, NULL, &tv_delay);
	}

	/* Suspend execution for at least *REQUESTED_DELAY seconds. The
	REMAINING_DELAY part isn't implemented yet. /

	int
	rpl_nanosleep (const struct timespec *requested_delay,
	struct timespec *remaining_delay)
	{
	static bool initialized;

	/* set up sig handler */
	if (! initialized)
	{
	#ifdef SA_NOCLDSTOP
	struct sigaction oldact, newact;
	newact.sa_handler = sighandler;
	sigemptyset (&newact.sa_mask);
	newact.sa_flags = 0;

	sigaction (SIGCONT, NULL, &oldact);
	if (oldact.sa_handler != SIG_IGN)
	sigaction (SIGCONT, &newact, NULL);
	#else
	if (signal (SIGCONT, SIG_IGN) != SIG_IGN)
	{
	signal (SIGCONT, sighandler);
	siginterrupt (SIGCONT, 1);
	}
	#endif
	initialized = true;
	}

	suspended = 0;

	my_usleep (requested_delay);

	if (suspended)
	{
	/* Calculate time remaining. */
	/* FIXME: the code in sleep doesn't use this, so there's no
	rush to implement it. */

	errno = EINTR;
	}

	/* FIXME: Restore sig handler? */

	return suspended;
	}

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