From d7c3d35101b3b0a63f492166e9c7463c3891c35c Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Sat, 04 Oct 2014 19:58:06 -0400
Subject: mutex_*(): New functions

---
diff --git a/lib/local.mk b/lib/local.mk
index d593289..3de79f7 100644
--- a/lib/local.mk
+++ b/lib/local.mk
@@ -9,6 +9,7 @@ pkgdata_sources = \
 	lib/control.sh \
 	lib/feed.sh \
 	lib/pkg.sh \
+	lib/mutex.sh \
 	lib/chroot.sh \
 	lib/opkg.sh \
 	lib/rand.sh \
diff --git a/lib/mutex.sh b/lib/mutex.sh
new file mode 100644
index 0000000..5fd6b70
--- /dev/null
+++ b/lib/mutex.sh
@@ -0,0 +1,50 @@
+# 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/>.
+
+[ "x${_MUTEX_SM+set}" = 'xset' ] && return 0
+_MUTEX_SM=1
+
+mutex_trylock()
+{
+	local mutex="${1}"
+
+	(set -C; printf '%d\n' "${$}" >"${mutex}") 2>/dev/null
+}
+
+mutex_lock_timeout()
+{
+	local mutex="${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}"
+}
--
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