locking.js

/**
 * Runs the given function while locking (synchronising on) the specified object.
 *
 * This uses Rhino's sync() function, but is a lot more flexible, allowing
 * unbound functions and closures. May of course be nested, but beware of deadlocks.
 * @param {Object} obj JavaScript object to be locked.
 * @param {Function} fn The function to call from within a synchronised block.
 * @param [args...] Any number of additional arguments to pass to fn.
 * @returns The value returned from calling fn.
 *
 * @example
 * function test(x) {
 *   print("entry");
 *   java.lang.Thread.sleep(x * 1000);
 *   print("exit");
 * }
 * var o = {};
 * spawn(function(){ locking(o, test, 3); });
 * spawn(function(){ locking(o, test, 3); });
 */
function locking(obj, fn) {
	var args = Array.prototype.slice.call(arguments, 2);
	var locked = sync(function() {
		return fn.apply(null, args);
	});
	return locked.apply(obj);
}