74 lines
1.3 KiB
C
74 lines
1.3 KiB
C
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <errno.h>
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#include "lockfile.h"
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#define locked(x) ((x)->fd >= 0)
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int hold_lock(struct lockfile *lock, const char *filename, int force) {
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int rc, mask = O_WRONLY | O_CREAT | O_TRUNC;
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if (locked(lock))
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return -1;
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if (!force)
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mask |= O_EXCL;
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rc = snprintf(lock->name, sizeof(lock->name), "%s.lock", filename);
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if (rc > sizeof(lock->name))
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return -1;
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lock->fd = open(lock->name, mask, 0600);
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if (lock->fd < 0) {
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if (errno == EEXIST) {
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fprintf(stderr, "'%s' is locked\n", lock->name);
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} else {
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fprintf(stderr, "unable to create lockfile '%s'",
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lock->name);
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}
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return -1;
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}
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return lock->fd;
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}
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int commit_lock(struct lockfile *lock) {
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char target[4096];
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int len;
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if (!locked(lock))
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return 0;
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len = strlen(lock->name) - 5; /* .lock */
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memcpy(target, lock->name, len);
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target[len] = '\0';
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if (rename(lock->name, target))
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return -1;
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lock->name[0] = '\0';
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close(lock->fd);
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lock->fd = -1;
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return 0;
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}
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int release_lock(struct lockfile *lock) {
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int rc;
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if (!locked(lock))
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return 0;
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rc = unlink(lock->name);
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if (rc == 0) {
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lock->name[0] = '\0';
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close(lock->fd);
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lock->fd = -1;
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}
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return rc;
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}
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