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Diffstat (limited to 'gnulib-tests/nap.h')
| -rw-r--r-- | gnulib-tests/nap.h | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/gnulib-tests/nap.h b/gnulib-tests/nap.h new file mode 100644 index 0000000..5dd264f --- /dev/null +++ b/gnulib-tests/nap.h @@ -0,0 +1,155 @@ +/* Assist in file system timestamp tests. + Copyright (C) 2009-2020 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> + +/* 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 */ |