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# Functions for locking and unlocking mutex objects
#
# Copyright (C) 2014 Patrick "P. J." McDermott
#
# This file is part of the ProteanOS Development Kit.
#
# The ProteanOS Development Kit 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.
#
# The ProteanOS Development Kit 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 the ProteanOS Development Kit. If not, see
# <http://www.gnu.org/licenses/>.
mutex_trylock()
{
local mutex="${1}"
(set -C; printf '%d\n' "${$}" >"${mutex}") 2>/dev/null
}
mutex_timedlock()
{
local mutex="${1}"
local timeout="${2}"
while ! mutex_trylock "${mutex}"; do
[ ${timeout} -eq 0 ] && return 1
timeout=$(($timeout - 1))
sleep 1
done
return 0
}
mutex_unlock()
{
local mutex="${1}"
rm "${mutex}"
}
mutex_is_unlockable()
{
local mutex="${1}"
[ "x$(cat "${mutex}" 2>/dev/null)" = "x${$}" ]
}
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