134 lines
3.1 KiB
C
134 lines
3.1 KiB
C
/*
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* fspause.c: pause until a file timestamp updates
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*
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* Copyright (C) 2014 Colin Watson.
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*
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* This file is part of man-db.
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*
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* man-db is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* man-db is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with man-db; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifdef HAVE_CONFIG_H
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# include "config.h"
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#endif /* HAVE_CONFIG_H */
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <time.h>
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#include <unistd.h>
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#include <string.h>
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static char *filename;
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static int fd = -1;
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#define MUST(name, cond) \
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do { \
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if (!(cond)) { \
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fprintf (stderr, "fspause: " name " failed\n"); \
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abort (); \
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} \
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} while (0)
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struct timespec get_stat_mtime (struct stat const *st)
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{
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return st->st_mtim;
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}
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int timespec_cmp (struct timespec a, struct timespec b)
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{
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if (a.tv_sec < b.tv_sec)
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return -1;
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if (a.tv_sec > b.tv_sec)
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return 1;
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return a.tv_nsec - b.tv_nsec;
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}
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char *xstrdup (char const *string)
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{
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size_t n = strlen (string) + 1;
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void *p = malloc (n);
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if (!p && n != 0) {
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fprintf (stderr, "fspause: memory exhausted\n");
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abort ();
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}
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return memcpy (p, string, n);
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}
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static void unlink_tempfile (void)
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{
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if (fd >= 0) {
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MUST ("close", close (fd) >= 0);
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MUST ("unlink", unlink (filename) >= 0);
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}
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}
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static void delay (int delay_ns)
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{
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struct timespec delay_ts;
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delay_ts.tv_sec = delay_ns / 1000000000;
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delay_ts.tv_nsec = delay_ns % 1000000000;
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for (;;) {
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errno = 0;
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if (nanosleep (&delay_ts, NULL) == 0)
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break;
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MUST ("nanosleep", errno == 0 || errno == EINTR);
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}
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}
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static int try_delay (struct stat *st, int delay_ns)
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{
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struct timespec start_ts, end_ts;
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start_ts = get_stat_mtime (st);
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delay (delay_ns);
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MUST ("write", write (fd, "\n", 1) == 1);
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MUST ("fstat", fstat (fd, st) >= 0);
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end_ts = get_stat_mtime (st);
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return timespec_cmp (start_ts, end_ts) != 0;
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}
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int main (int argc, char **argv)
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{
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struct stat st;
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int delay_ns;
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filename = xstrdup ("fspause.tmp.XXXXXX");
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MUST ("mkstemp", (fd = mkstemp (filename)) >= 0);
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atexit (unlink_tempfile);
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MUST ("fstat", fstat (fd, &st) >= 0);
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/* 0x40000000 nanoseconds is just over a second. The effective
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* maximum delay we will allow is thus about two seconds. This
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* saves us having to keep track of anything more complicated than a
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* single signed 32-bit int.
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*/
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for (delay_ns = 1; delay_ns < 0x40000000; delay_ns *= 2) {
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if (try_delay (&st, delay_ns))
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return 0;
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}
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fprintf (stderr,
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"fspause: temporary file timestamp refuses to change!\n");
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return 1;
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}
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