/* Assist in file system timestamp tests.
- Copyright (C) 2009-2012 Free Software Foundation, Inc.
+ Copyright (C) 2009-2013 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
#ifndef GLTEST_NAP_H
# define GLTEST_NAP_H
+# include <limits.h>
+# include <stdbool.h>
+
+/* File descriptor used for the witness file. */
+static int nap_fd = -1;
+
+/* Return A - B, in ns.
+ Return 0 if the true result would be negative.
+ Return INT_MAX if the true result would be greater than INT_MAX. */
+static int
+diff_timespec (struct timespec a, struct timespec b)
+{
+ time_t as = a.tv_sec;
+ time_t bs = b.tv_sec;
+ int ans = a.tv_nsec;
+ int bns = b.tv_nsec;
+
+ if (! (bs < as || (bs == as && bns < ans)))
+ return 0;
+ if (as - bs <= INT_MAX / 1000000000)
+ {
+ int sdiff = (as - bs) * 1000000000;
+ int usdiff = ans - bns;
+ if (usdiff < INT_MAX - sdiff)
+ return sdiff + usdiff;
+ }
+ return INT_MAX;
+}
+
+static void
+get_stat (int fd, struct stat *st, int do_write)
+{
+ if (do_write)
+ ASSERT (write (fd, "\n", 1) == 1);
+ ASSERT (fstat (fd, st) == 0);
+}
+
+/* Given a file whose descriptor is FD, see whether delaying by DELAY
+ nanoseconds causes a change in a file's ctime and mtime.
+ OLD_ST is the file's status, recently gotten. */
+static bool
+nap_works (int fd, int delay, struct stat old_st)
+{
+ struct stat st;
+ struct timespec delay_spec;
+ delay_spec.tv_sec = delay / 1000000000;
+ delay_spec.tv_nsec = delay % 1000000000;
+ ASSERT (nanosleep (&delay_spec, 0) == 0);
+ get_stat (fd, &st, 1);
+
+ if ( diff_timespec (get_stat_ctime (&st), get_stat_ctime (&old_st))
+ && diff_timespec (get_stat_mtime (&st), get_stat_mtime (&old_st)))
+ return true;
+
+ return false;
+}
+
+#define TEMPFILE BASE "nap.tmp"
+
+static void
+clear_temp_file (void)
+{
+ if (0 <= nap_fd)
+ {
+ ASSERT (close (nap_fd) != -1);
+ ASSERT (unlink (TEMPFILE) != -1);
+ }
+}
+
/* Sleep long enough to notice a timestamp difference on the file
- system in the current directory. Assumes that BASE is defined,
- and requires that the test module depends on usleep. */
+ system in the current directory. Use an adaptive approach, trying
+ to find the smallest delay which works on the current file system
+ to make the timestamp difference appear. Assert a maximum delay of
+ ~2 seconds, more precisely sum(2^n) from 0 to 30 = 2^31 - 1 = 2.1s.
+ Assumes that BASE is defined, and requires that the test module
+ depends on nanosleep. */
static void
nap (void)
{
- static long delay;
- if (!delay)
+ struct stat old_st;
+ static int delay = 1;
+
+ if (-1 == nap_fd)
+ {
+ atexit (clear_temp_file);
+ ASSERT ((nap_fd = creat (TEMPFILE, 0600)) != -1);
+ get_stat (nap_fd, &old_st, 0);
+ }
+ else
{
- /* Initialize only once, by sleeping for 20 milliseconds (needed
- since xfs has a quantization of about 10 milliseconds, even
- though it has a granularity of 1 nanosecond, and since NTFS
- has a default quantization of 15.25 milliseconds, even though
- it has a granularity of 100 nanoseconds). If the seconds
- differ, repeat the test one more time (in case we crossed a
- quantization boundary on a file system with 1 second
- resolution). If we can't observe a difference in only the
- nanoseconds, then fall back to 1 second if the time is odd,
- and 2 seconds (needed for FAT) if time is even. */
- struct stat st1;
- struct stat st2;
- ASSERT (close (creat (BASE "tmp", 0600)) == 0);
- ASSERT (stat (BASE "tmp", &st1) == 0);
- ASSERT (unlink (BASE "tmp") == 0);
- delay = 20000;
- usleep (delay);
- ASSERT (close (creat (BASE "tmp", 0600)) == 0);
- ASSERT (stat (BASE "tmp", &st2) == 0);
- ASSERT (unlink (BASE "tmp") == 0);
- if (st1.st_mtime != st2.st_mtime)
- {
- /* Seconds differ, give it one more shot. */
- st1 = st2;
- usleep (delay);
- ASSERT (close (creat (BASE "tmp", 0600)) == 0);
- ASSERT (stat (BASE "tmp", &st2) == 0);
- ASSERT (unlink (BASE "tmp") == 0);
- }
- if (! (st1.st_mtime == st2.st_mtime
- && get_stat_mtime_ns (&st1) < get_stat_mtime_ns (&st2)))
- delay = (st1.st_mtime & 1) ? 1000000 : 2000000;
+ ASSERT (0 <= nap_fd);
+ get_stat (nap_fd, &old_st, 1);
}
- usleep (delay);
+
+ if (1 < delay)
+ delay = delay / 2; /* Try half of the previous delay. */
+ ASSERT (0 < delay);
+
+ for ( ; delay <= 2147483647; delay = delay * 2)
+ if (nap_works (nap_fd, delay, old_st))
+ return;
+
+ /* Bummer: even the highest nap delay didn't work. */
+ ASSERT (0);
}
#endif /* GLTEST_NAP_H */
projects / gnulib.git / blobdiff