}
      result.writeDecimalLong(readVariableLengthLong())
    }
    return result.readUtf8()
  }

  /** Used for tags and subidentifiers. */
  private fun readVariableLengthLong(): Long {
    // TODO(jwilson): detect overflow.
    var result = 0L
    while (true) {
      val byteN = source.readByte().toLong() and 0xff
      if ((byteN and 0b1000_0000L) == 0b1000_0000L) {