lib/converter.js
function length(buffer, n, special) {
  var len = this.getLengthEncoding(n, special);
  return Buffer.concat([len, buffer], len.length + buffer.length);
}
function length(buffer, n, special) {
  var len = this.getLengthEncoding(n, special);
  return Buffer.concat([len, buffer], len.length + buffer.length);
}
Concatenate a buffer with length encoding.