Add asyncqueue class

lib/asyncqueue.js

@@ -0,0 +1,45 @@
+var AsyncQueue = function () {
+    this._q = [];
+    this._lock = false;
+    this._tm = 0;
+};
+
+AsyncQueue.prototype.next = function () {
+    if (this._q.length > 0) {
+        if (!this.lock())
+            return;
+        var fn = this._q.shift();
+        fn(this);
+    }
+};
+
+AsyncQueue.prototype.lock = function () {
+    if (this._lock)
+        return false;
+
+    this._lock = true;
+    return true;
+};
+
+AsyncQueue.prototype.release = function () {
+    var self = this;
+    if (!self._lock)
+        return false;
+
+    self._lock = false;
+    process.nextTick(function () {
+        self.next();
+    });
+    return true;
+};
+
+AsyncQueue.prototype.queue = function (fn) {
+    var self = this;
+    self._q.push(fn);
+    self.next();
+};
+
+AsyncQueue.prototype.reset = function () {
+    this._q = [];
+    this._lock = false;
+};