#   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/>.
#

# setalrm - set a timer to fire in N seconds and send SIGALRM to the shell
#
# usage: setalrm [-c] N
#
# -c means to reset the trap on ALRM if the timer is canceled
#
# If N = 0, we cancel any pending alarm by killing the background timeout
# process. Any value greater than 0 sets a timeout for N seconds. Values
# of N less than zero are errors.

declare -i alrmpid=

setalrm()
{
	local untrap=
	local setalrm_usage="setalrm: usage: setalrm [-c] N"

	while getopts c opt; do
		case $opt in
		c)	untrap=1 ;;
		*)	echo "$setalrm_usage" >&2 ; return 2;;
		esac
	done

	shift $(( $OPTIND - 1 ))

	if [[ -z $1 ]]; then
		echo "$setalrm_usage" >&2
		return 2
	fi

	if (( $1 < 0 )); then
		echo "setalrm: timeout must be greater than zero" >& 2
		return 2
	fi

	if [[ $1 -eq 0 ]] && [[ -n "$alrmpid" ]]; then
		kill -TERM $alrmpid ; es=$?
		alrmpid=
		if [ -n "$untrap" ]; then
			trap - ALRM	# caller saves if desired
		fi
		return $es
	fi

	# setting alarm
	{ trap - ALRM ; sleep $1; kill -ALRM $$; } &
	alrmpid=$!
	return 0
}