sleepus.c

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/*
 * Copyright (c) 1996 W. Richard Stevens.  All rights reserved.
 * Permission to use or modify this software and its documentation only for
 * educational purposes and without fee is hereby granted, provided that
 * the above copyright notice appear in all copies.  The author makes no
 * representations about the suitability of this software for any purpose.
 * It is provided "as is" without express or implied warranty.
 */

#include	<sys/types.h>
#include	<sys/time.h>
#include	<errno.h>
#include	<stddef.h>

void
sleep_us(unsigned int nusecs)
{
	struct timeval	tval;

	for ( ; ; ) {
		tval.tv_sec = nusecs / 1000000;
		tval.tv_usec = nusecs % 1000000;
		if (select(0, NULL, NULL, NULL, &tval) == 0)
			break;		/* all OK */
		/*
		 * Note than on an interrupted system call (i.e, SIGIO) there's not
		 * much we can do, since the timeval{} isn't updated with the time
		 * remaining.  We could obtain the clock time before the call, and
		 * then obtain the clock time here, subtracting them to determine
		 * how long select() blocked before it was interrupted, but that
		 * seems like too much work :-)
		 */
		if (errno == EINTR)
			continue;
		err_sys("sleep_us: select error");
	}
}