function encodeArrayBuffer(packet, supportsBinary, callback) {
	  if (!supportsBinary) {
	    return exports.encodeBase64Packet(packet, callback);
	  }
	
	  var data = packet.data;
	  var contentArray = new Uint8Array(data);
	  var resultBuffer = new Uint8Array(1 + data.byteLength);
	
	  resultBuffer[0] = packets[packet.type];
	  for (var i = 0; i < contentArray.length; i++) {
	    resultBuffer[i+1] = contentArray[i];
	  }
	
	  return callback(resultBuffer.buffer);
	}
Encode packet helpers for binary types