}

    // Write the length. This takes 1 byte if length is less than 128.
    val length = content.size
    if (length < 128) {
      sink.writeByte(length.toInt())
    } else {
      // count how many bytes we'll need to express the length.
      val lengthBitCount = 64 - java.lang.Long.numberOfLeadingZeros(length)
      val lengthByteCount = (lengthBitCount + 7) / 8
      sink.writeByte(0b1000_0000 or lengthByteCount)