locking in node.js

fun1.js

#!/usr/bin/env node
var Lock = require('./lock.js');

var lock1 = new Lock();

console.log('lock1.get() #1: ' + lock1.get(function () {
	console.log('this will never run');
}));

console.log('lock1.get() #2: ' + lock1.get(function () {
	console.log('this will run');
}));

lock1.free();

lock.js

// http://www.howardism.org/Technical/JavaScript/Locks.html

function Lock() {
	return((function() {
		var locked = false;
		var requesters = [];

		function get(cb) {
			if (locked) {
				requesters.push(cb);
				return false;
			} else {
				locked = true;
				return true;
			}
		}

		function free() {
			var cb;
			if (requesters.length == 0) {
				locked = false;
			}
			if (requesters.length >= 1) {
				cb = requesters.pop();
				cb();
			}
			return locked;
		}

		return {
			get: get,
			free: free
		}
	})());
}

module.exports = Lock;