code: function amf0encLongString(str) {
      var buf = new Buffer(5);
      buf.writeUInt8(0x0C, 0);
      buf.writeUInt32BE(str.length, 1);
      return Buffer.concat([buf, new Buffer(str, 'utf8')]);
  }
docs: AMF0 Encode Long String
  @param str
  @returns {Buffer}