[fix] Do not mutate the input upon packet encoding (#105)

Fixes #95

Author: darrachequesne

lib/browser.js

@@ -158,8 +158,7 @@ function encodeBlobAsArrayBuffer(packet, supportsBinary, callback) {
 
   var fr = new FileReader();
   fr.onload = function() {
-    packet.data = fr.result;
-    exports.encodePacket(packet, supportsBinary, true, callback);
+    exports.encodePacket({ type: packet.type, data: fr.result }, supportsBinary, true, callback);
   };
   return fr.readAsArrayBuffer(packet.data);
 }

lib/index.js

@@ -64,8 +64,7 @@ exports.encodePacket = function (packet, supportsBinary, utf8encode, callback) {
   if (Buffer.isBuffer(packet.data)) {
     return encodeBuffer(packet, supportsBinary, callback);
   } else if (packet.data && (packet.data.buffer || packet.data) instanceof ArrayBuffer) {
-    packet.data = arrayBufferToBuffer(packet.data);
-    return encodeBuffer(packet, supportsBinary, callback);
+    return encodeBuffer({ type: packet.type, data: arrayBufferToBuffer(packet.data) }, supportsBinary, callback);
   }
 
   // Sending data as a utf-8 string
@@ -102,12 +101,9 @@ function encodeBuffer(packet, supportsBinary, callback) {
  */
 
 exports.encodeBase64Packet = function(packet, callback){
-  if (!Buffer.isBuffer(packet.data)) {
-    packet.data = arrayBufferToBuffer(packet.data);
-  }
-
+  var data = Buffer.isBuffer(packet.data) ? packet.data : arrayBufferToBuffer(packet.data);
   var message = 'b' + packets[packet.type];
-  message += packet.data.toString('base64');
+  message += data.toString('base64');
   return callback(message);
 };