#!/bin/bash
###############################################################################
#                                                                             #
# IPFire.org - A linux based firewall                                         #
# Copyright (C) 2012  Michael Tremer & Christian Schmidt                      #
#                                                                             #
# 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 <http://www.gnu.org/licenses/>.       #
#                                                                             #
###############################################################################

function lock_acquire() {
	local lockfile="${1}"
	assert isset lockfile

	# timeout value in seconds
	local timeout=60
	timeout=$(( ${timeout} * 10 ))

	log DEBUG "Acquiring lock '${lockfile}'."

	local free="false"
	while [ ${timeout} -gt 0 ]; do
		if [ ! -e "${lockfile}" ]; then
			free="true"
			break
		fi

		timeout=$(( ${timeout} - 1 ))
		sleep 0.1
	done

	assert ${free} "Could not acquire lock '${lockfile}'."

	# Write out pid to the lockfile and make sure that
	# nobody else can access it.
	echo "$$" > ${lockfile}
	chmod 600 ${lockfile}
}

function lock_release() {
	local lockfile="${1}"

	log DEBUG "Releasing lock '${lockfile}'."

	# Remove the lockfile (okay if it does not exist).
	rm -f ${lockfile}
}