[Bug-gnulib] new module xnanosleep from coreutils

[Paul Eggert]

I installed this:

2004-08-06  Paul Eggert  <address@hidden>

        * modules/xnanosleep, lib/xnanosleep.h, lib/xnanosleep.c:
        New files.

--- /dev/null   2003-03-18 13:55:57 -0800
+++ modules/xnanosleep  2004-08-06 15:48:01 -0700
@@ -0,0 +1,22 @@
+Description:
+a more convenient interface to nanosleep
+
+Files:
+lib/xnanosleep.h
+lib/xnanosleep.c
+
+Depends-on:
+timespec
+xalloc
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += xnanosleep.h xnanosleep.c
+
+Include:
+"xnanosleep.h"
+
+Maintainer:
+Paul Eggert, Jim Meyering
+
--- /dev/null   2003-03-18 13:55:57 -0800
+++ lib/xnanosleep.h    2004-08-04 23:37:37 -0700
@@ -0,0 +1 @@
+int xnanosleep (double);
--- /dev/null   2003-03-18 13:55:57 -0800
+++ lib/xnanosleep.c    2004-08-06 15:47:52 -0700
@@ -0,0 +1,172 @@
+/* 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
+   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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* 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 "xnanosleep.h"
+
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <assert.h>
+#include <errno.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)))
+
+#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
+   it is not representable as a `struct timespec', then use
+   the maximum value for that interval.  Return -1 on failure
+   (setting errno), 0 on success.  */
+
+int
+xnanosleep (double seconds)
+{
+  bool overflow;
+  double ns;
+  struct timespec ts_start;
+  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)
+    {
+      /* 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;
+    }
+
+  while (nanosleep (&ts_sleep, NULL) != 0)
+    {
+      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;
+    }
+
+  return 0;
+}