Added getRandomBytes to improve generateId performance

lib/manager.js

@@ -730,7 +730,60 @@ Manager.prototype.handleClient = function (data, req) {
 };
 
 /**
- * Generates a session id.
+ * Get random bytes
+ *
+ * @api private
+ */
+
+Manager.prototype.getRandomBytes = function(bytes) {
+
+  var BUFFER_SIZE = 4096
+  var self = this;  
+
+  bytes = bytes || 12;
+
+  if (bytes > BUFFER_SIZE) {
+    return crypto.randomBytes(bytes);
+  }
+
+  var bytesInBuffer = parseInt(BUFFER_SIZE/bytes);
+  var threshold = parseInt(bytesInBuffer*0.85);
+
+  if (!threshold) {
+    return crypto.randomBytes(bytes);
+  }
+
+  if (this.bytesBufferIndex == null) {
+     this.bytesBufferIndex = -1;
+  }
+
+  if (this.bytesBufferIndex == bytesInBuffer) {
+    this.bytesBuffer = null;
+    this.bytesBufferIndex = -1;
+  }
+
+  // No buffered bytes available
+  if (this.bytesBufferIndex == -1 || this.bytesBufferIndex > threshold) {
+
+    if (!this.isGeneratingBytes) {
+      this.isGeneratingBytes = true;
+      crypto.randomBytes(BUFFER_SIZE, function(err, bytes) {
+        self.bytesBuffer = bytes;
+        self.bytesBufferIndex = 0;
+        self.isGeneratingBytes = false;
+      }); 
+    }
+    return crypto.randomBytes(bytes);
+  }
+
+  var result = this.bytesBuffer.slice(bytes*this.bytesBufferIndex, bytes*(this.bytesBufferIndex+1)); 
+  this.bytesBufferIndex++; 
+
+  return result;
+}
+
+/**
+ * Generates a session id
  *
  * @api private
  */
@@ -744,7 +797,7 @@ Manager.prototype.generateId = function () {
   this.sequenceNumber = (this.sequenceNumber + 1) | 0;
   rand.writeInt32BE(this.sequenceNumber, 11);
   if (crypto.randomBytes) {
-    crypto.randomBytes(12).copy(rand);
+    this.getRandomBytes(12).copy(rand);
   } else {
     // not secure for node 0.4
     [0, 4, 8].forEach(function(i) {