/* lockfile.c
 *
 *   Copyright (C) 2011       Henrik Hautakoski <henrik@fiktivkod.org>
 *   Copyright (C) 2005       Junio C Hamano
 *
 *   Based on lockfile.c from Git.
 *
 *   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 2 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, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 *   MA 02110-1301, USA.
 */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include "lockfile.h"

#define locked(x) ((x)->fd >= 0)

int hold_lock(struct lockfile *lock, const char *filename, int force) {

	int rc, mask = O_WRONLY | O_CREAT | O_TRUNC;

	if (locked(lock))
		return -1;

	if (!force)
		mask |= O_EXCL;

	rc = snprintf(lock->name, sizeof(lock->name), "%s.lock", filename);
	if (rc > sizeof(lock->name))
		return -1;

	lock->fd = open(lock->name, mask, 0600);
	if (lock->fd < 0) {
		if (errno == EEXIST) {
			fprintf(stderr, "'%s' is locked\n", lock->name);
		} else {
			fprintf(stderr, "unable to create lockfile '%s'",
				lock->name);
		}
		return -1;
	}
	return lock->fd;
}

int commit_lock(struct lockfile *lock) {

	char target[4096];
	int len;

	if (!locked(lock))
		return 0;

	len = strlen(lock->name) - 5; /* .lock */

	memcpy(target, lock->name, len);
	target[len] = '\0';

	if (rename(lock->name, target))
		return -1;
	lock->name[0] = '\0';
	close(lock->fd);
	lock->fd = -1;
	return 0;
}

int release_lock(struct lockfile *lock) {

	int rc;

	if (!locked(lock))
		return 0;
	rc = unlink(lock->name);
	if (rc == 0) {
		lock->name[0] = '\0';
		close(lock->fd);
		lock->fd = -1;
	}
	return rc;
}