Add mbrekey.

lib/utils.js

@@ -1,4 +1,6 @@
-var utils = {};
+var util = require('util'),
+    EventEmitter = require('events').EventEmitter,
+    utils = {};
 
 utils.table = function(fields) {
     if (!fields[0]) return;
@@ -18,4 +20,43 @@ utils.table = function(fields) {
     });
 };
 
+function Queue(callback, concurrency) {
+    this.callback = callback;
+    this.concurrency = concurrency || 10;
+    this.next = this.next.bind(this);
+    this.invoke = this.invoke.bind(this);
+    this.queue = [];
+    this.running = 0;
+}
+util.inherits(Queue, EventEmitter);
+
+Queue.prototype.add = function(item) {
+    this.queue.push(item);
+    if (this.running < this.concurrency) {
+        this.running++;
+        this.next();
+    }
+};
+
+Queue.prototype.invoke = function() {
+    if (this.queue.length) {
+        this.callback(this.queue.shift(), this.next);
+    } else {
+        this.next();
+    }
+};
+
+Queue.prototype.next = function(err) {
+    if (this.queue.length) {
+        process.nextTick(this.invoke);
+    } else {
+        this.running--;
+        if (!this.running) {
+            this.emit('empty');
+        }
+    }
+};
+
+utils.Queue = Queue;
+
 module.exports = utils;