summaryrefslogtreecommitdiff
path: root/tests/nap.h
diff options
context:
space:
mode:
Diffstat (limited to 'tests/nap.h')
-rw-r--r--tests/nap.h162
1 files changed, 162 insertions, 0 deletions
diff --git a/tests/nap.h b/tests/nap.h
new file mode 100644
index 0000000..2b3c1d2
--- /dev/null
+++ b/tests/nap.h
@@ -0,0 +1,162 @@
+/* Assist in file system timestamp tests.
+ Copyright (C) 2009-2022 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 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
+ 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, see <https://www.gnu.org/licenses/>. */
+
+/* Written by Eric Blake <ebb9@byu.net>, 2009. */
+
+#ifndef GLTEST_NAP_H
+# define GLTEST_NAP_H
+
+# include <limits.h>
+# include <stdbool.h>
+
+# include <intprops.h>
+
+/* Avoid a conflict with a function called nap() on UnixWare. */
+# if defined _SCO_DS || (defined __SCO_VERSION__ || defined __sysv5__) /* OpenServer, UnixWare */
+# include <unistd.h>
+# undef nap
+# define nap gl_nap
+# endif
+
+/* Name of the witness file. */
+#define TEMPFILE BASE "nap.tmp"
+
+/* 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;
+ int sdiff;
+
+ ASSERT (0 <= ans && ans < 2000000000);
+ ASSERT (0 <= bns && bns < 2000000000);
+
+ if (! (bs < as || (bs == as && bns < ans)))
+ return 0;
+
+ if (INT_SUBTRACT_WRAPV (as, bs, &sdiff)
+ || INT_MULTIPLY_WRAPV (sdiff, 1000000000, &sdiff)
+ || INT_ADD_WRAPV (sdiff, ans - bns, &sdiff))
+ return INT_MAX;
+
+ return sdiff;
+}
+
+/* If DO_WRITE, bump the modification time of the file designated by NAP_FD.
+ Then fetch the new STAT information of NAP_FD. */
+static void
+nap_get_stat (struct stat *st, int do_write)
+{
+ if (do_write)
+ {
+ ASSERT (write (nap_fd, "\n", 1) == 1);
+#if defined _WIN32 || defined __CYGWIN__
+ /* On Windows, the modification times are not changed until NAP_FD
+ is closed. See
+ <https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-writefile> */
+ close (nap_fd);
+ nap_fd = open (TEMPFILE, O_RDWR, 0600);
+ ASSERT (nap_fd != -1);
+ lseek (nap_fd, 0, SEEK_END);
+#endif
+ }
+ ASSERT (fstat (nap_fd, st) == 0);
+}
+
+/* Given a file whose descriptor is FD, see whether delaying by DELAY
+ nanoseconds causes a change in a file's mtime.
+ OLD_ST is the file's status, recently gotten. */
+static bool
+nap_works (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);
+ nap_get_stat (&st, 1);
+
+ if (diff_timespec (get_stat_mtime (&st), get_stat_mtime (&old_st)))
+ return true;
+
+ return false;
+}
+
+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. 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)
+{
+ struct stat old_st;
+ static int delay = 1;
+
+ if (-1 == nap_fd)
+ {
+ atexit (clear_temp_file);
+ ASSERT ((nap_fd = creat (TEMPFILE, 0600)) != -1);
+ nap_get_stat (&old_st, 0);
+ }
+ else
+ {
+ ASSERT (0 <= nap_fd);
+ nap_get_stat (&old_st, 1);
+ }
+
+ if (1 < delay)
+ delay = delay / 2; /* Try half of the previous delay. */
+ ASSERT (0 < delay);
+
+ for (;;)
+ {
+ if (nap_works (delay, old_st))
+ return;
+ if (delay <= (2147483647 - 1) / 2)
+ {
+ delay = delay * 2 + 1;
+ continue;
+ }
+ else
+ break;
+ }
+
+ /* Bummer: even the highest nap delay didn't work. */
+ ASSERT (0);
+}
+
+#endif /* GLTEST_NAP_H */