lockfile.c

multi-line Adjunct Communication Server

/*
** Copyright (C) 1999-2000 Open System Telecom Corporation.
**  
** 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
**
** As a special exception to the GNU General Public License, permission is
** granted for additional uses of the text contained in its release
** of ACS as noted here.
**
** This exception is that permission is hereby granted to link ACS with
** the Pika MonteCarlo static libraries to produce a executable image
** without requiring MonteCarlo itself to be supplied in source form so
** long as each source file so linked contains this exclusion.
**
** This exception does not however invalidate any other reasons why
** the resulting executable file might be covered by the GNU General
** public license or invalidate the licensing requirements of any
** other component or library.
**
** This exception applies only to the code released by OST under the
** name ACS.  If you copy code from other releases into a copy of
** ACS, as the General Public License permits, the exception does not
** apply to the code that you add in this way.  To avoid misleading
** anyone as to the status of such modified files, you must delete
** this exception notice from them.
**
** If you write modifications of your own to ACS, it is your choice
** whether to permit this exception to apply to your modifications.
** If you do not wish that, delete this exception notice, at which
** point the terms of your modification would be covered under the GPL
** as explicitly stated in "COPYING".
*/

#include <config.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <lockfile.h>

#ifndef	_LOCK_FORMAT
#define	_LOCK_FORMAT	"%010d %s"
#endif

int	lockfile(const char *fpath, const char *option)
{
	int	fd;
	int	status;
	pid_t	pid;
	time_t	now;
	struct	stat	ino;
	int	len;
	int	mask;
	char	query[65];

	if(!option)
		option = "";

	for(;;)
	{
		fd = open(fpath, O_WRONLY | O_CREAT | O_EXCL, 0660);
		if(fd > 0)
		{
			pid = getpid();
			if(!strcmp(option, "disable"))
				pid = 1;
			sprintf(query, _LOCK_FORMAT, pid, option);
			write(fd, query, strlen(query));
			close(fd);
			return 0;
		}
		if(fd < 0 && errno != EEXIST)
			return -1;

		fd = open(fpath, O_RDONLY);
		if(fd < 0)
		{
			if(errno == ENOENT)
				continue;
			return -1;
		}
		sleep(2);
		status = read(fd, query, sizeof(query) - 1);
		if(status < 1)
		{
			close(fd);
			continue;
		}

		query[status] = 0;
		pid = atoi(query);
		if(pid)
		{
			if(pid == getpid())
			{
				status = -1;
				errno = 0;
			}
			else
				status = kill(pid, 0);
			if(!status || (errno == EPERM))
			{
				close(fd);
				return pid;
			}
		}	
		close(fd);			
		unlink(fpath);
	}
}