# Mutual exclusion synchronization tool
#
# Instances of this class can only be acquired by a single thread at any one
# point in time. Uses the recursive protocol so they can be locked many time by
# the same thread, must then be unlocked as many time.
class Mutex
	super Finalizable

	private var native: nullable NativePthreadMutex is noinit

	init
	do
		var attr = new NativePthreadMutexAttr
		attr.set_type_recursive
		native = new NativePthreadMutex(attr)
		attr.destroy
		attr.free
	end

	# Acquire this lock, wait until it is available
	fun lock do native.lock

	# Acquire this lock only if it is available
	#
	# Returns `true` if the lock has been acquired.
	fun try_lock: Bool do return native.try_lock

	# Release this lock, unblocking all callers of `lock`
	fun unlock do native.unlock

	redef fun finalize
	do
		var native = self.native
		if native != null then
			native.destroy
			native.free
		end
		self.native = null
	end
end