/* xnanosleep.c -- a more convenient interface to nanosleep
- Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ Copyright (C) 2002-2007, 2009-2010 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.
+ the Free Software Foundation; either version 3 of the License, 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
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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Mostly written (for sleep.c) by Paul Eggert.
Factored out (creating this file) by Jim Meyering. */
-#if HAVE_CONFIG_H
-# include <config.h>
-#endif
+#include <config.h>
#include "xnanosleep.h"
#include <sys/types.h>
#include <time.h>
-/* The extra casts work around common compiler bugs. */
-#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
-/* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
- It is necessary at least when t == time_t. */
-#define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
- ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
-#define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
+#include "intprops.h"
#ifndef TIME_T_MAX
# define TIME_T_MAX TYPE_MAXIMUM (time_t)
#endif
-#include "timespec.h"
-#include "xalloc.h"
-
-/* Subtract the `struct timespec' values X and Y by computing X - Y.
- If the difference is negative or zero, return false.
- Otherwise, return true and store the difference in DIFF.
- X and Y must have valid ts_nsec values, in the range 0 to 999999999.
- If the difference would overflow, store the maximum possible difference. */
-
-static bool
-timespec_subtract (struct timespec *diff,
- struct timespec const *x, struct timespec const *y)
-{
- time_t sec = x->tv_sec - y->tv_sec;
- long int nsec = x->tv_nsec - y->tv_nsec;
-
- if (x->tv_sec < y->tv_sec)
- return false;
-
- if (sec < 0)
- {
- /* The difference has overflowed. */
- sec = TIME_T_MAX;
- nsec = 999999999;
- }
- else if (sec == 0 && nsec <= 0)
- return false;
-
- if (nsec < 0)
- {
- sec--;
- nsec += 1000000000;
- }
-
- diff->tv_sec = sec;
- diff->tv_nsec = nsec;
- return true;
-}
-
/* Sleep until the time (call it WAKE_UP_TIME) specified as
SECONDS seconds after the time this function is called.
SECONDS must be non-negative. If SECONDS is so large that
int
xnanosleep (double seconds)
{
- bool overflow;
- double ns;
- struct timespec ts_start;
+ enum { BILLION = 1000000000 };
+
+ /* For overflow checking, use naive comparison if possible, widening
+ to long double if double is not wide enough. Otherwise, use <=,
+ not <, to avoid problems when TIME_T_MAX is less than SECONDS but
+ compares equal to SECONDS after loss of precision when coercing
+ from time_t to long double. This mishandles near-maximal values
+ in some rare (perhaps theoretical) cases but that is better than
+ undefined behavior. */
+ bool overflow = ((time_t) ((double) TIME_T_MAX / 2) == TIME_T_MAX / 2
+ ? TIME_T_MAX < seconds
+ : (time_t) ((long double) TIME_T_MAX / 2) == TIME_T_MAX / 2
+ ? TIME_T_MAX < (long double) seconds
+ : TIME_T_MAX <= (long double) seconds);
+
struct timespec ts_sleep;
- struct timespec ts_stop;
assert (0 <= seconds);
- if (gettime (&ts_start) != 0)
- return -1;
-
- /* Separate whole seconds from nanoseconds.
- Be careful to detect any overflow. */
- ts_sleep.tv_sec = seconds;
- ns = 1e9 * (seconds - ts_sleep.tv_sec);
- overflow = ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= 1e9);
- ts_sleep.tv_nsec = ns;
-
- /* Round up to the next whole number, if necessary, so that we
- always sleep for at least the requested amount of time. Assuming
- the default rounding mode, we don't have to worry about the
- rounding error when computing 'ns' above, since the error won't
- cause 'ns' to drop below an integer boundary. */
- ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
-
- /* Normalize the interval length. nanosleep requires this. */
- if (1000000000 <= ts_sleep.tv_nsec)
- {
- time_t t = ts_sleep.tv_sec + 1;
-
- /* Detect integer overflow. */
- overflow |= (t < ts_sleep.tv_sec);
-
- ts_sleep.tv_sec = t;
- ts_sleep.tv_nsec -= 1000000000;
- }
-
- /* Compute the time until which we should sleep. */
- ts_stop.tv_sec = ts_start.tv_sec + ts_sleep.tv_sec;
- ts_stop.tv_nsec = ts_start.tv_nsec + ts_sleep.tv_nsec;
- if (1000000000 <= ts_stop.tv_nsec)
- {
- ++ts_stop.tv_sec;
- ts_stop.tv_nsec -= 1000000000;
- }
-
- /* Detect integer overflow. */
- overflow |= (ts_stop.tv_sec < ts_start.tv_sec
- || (ts_stop.tv_sec == ts_start.tv_sec
- && ts_stop.tv_nsec < ts_start.tv_nsec));
-
- if (overflow)
+ /* Separate whole seconds from nanoseconds. */
+ if (! overflow)
{
- /* Fix ts_sleep and ts_stop, which may be garbage due to overflow. */
- ts_sleep.tv_sec = ts_stop.tv_sec = TIME_T_MAX;
- ts_sleep.tv_nsec = ts_stop.tv_nsec = 999999999;
+ time_t floor_seconds = seconds;
+ double ns = BILLION * (seconds - floor_seconds);
+ ts_sleep.tv_sec = floor_seconds;
+
+ /* Round up to the next whole number, if necessary, so that we
+ always sleep for at least the requested amount of time. Assuming
+ the default rounding mode, we don't have to worry about the
+ rounding error when computing 'ns' above, since the error won't
+ cause 'ns' to drop below an integer boundary. */
+ ts_sleep.tv_nsec = ns;
+ ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
+
+ /* Normalize the interval length. nanosleep requires this. */
+ if (BILLION <= ts_sleep.tv_nsec)
+ {
+ if (ts_sleep.tv_sec == TIME_T_MAX)
+ overflow = true;
+ else
+ {
+ ts_sleep.tv_sec++;
+ ts_sleep.tv_nsec -= BILLION;
+ }
+ }
}
- while (nanosleep (&ts_sleep, NULL) != 0)
+ for (;;)
{
- if (errno != EINTR || gettime (&ts_start) != 0)
- return -1;
-
- /* POSIX.1-2001 requires that when a process is suspended, then
- resumed, nanosleep (A, B) returns -1, sets errno to EINTR,
- and sets *B to the time remaining at the point of resumption.
- However, some versions of the Linux kernel incorrectly return
- the time remaining at the point of suspension. Work around
- this bug by computing the remaining time here, rather than by
- relying on nanosleep's computation. */
-
- if (! timespec_subtract (&ts_sleep, &ts_stop, &ts_start))
- break;
+ if (overflow)
+ {
+ ts_sleep.tv_sec = TIME_T_MAX;
+ ts_sleep.tv_nsec = BILLION - 1;
+ }
+
+ /* Linux-2.6.8.1's nanosleep returns -1, but doesn't set errno
+ when resumed after being suspended. Earlier versions would
+ set errno to EINTR. nanosleep from linux-2.6.10, as well as
+ implementations by (all?) other vendors, doesn't return -1
+ in that case; either it continues sleeping (if time remains)
+ or it returns zero (if the wake-up time has passed). */
+ errno = 0;
+ if (nanosleep (&ts_sleep, NULL) == 0)
+ break;
+ if (errno != EINTR && errno != 0)
+ return -1;
}
return 0;
projects / gnulib.git / blobdiff