private fun readHeaderBlock(
    length: Int,
    padding: Int,
    flags: Int,
    streamId: Int,
  ): List<Header> {
    continuation.left = length
    continuation.length = continuation.left
    continuation.padding = padding
    continuation.flags = flags
    continuation.streamId = streamId

    // TODO: Concat multi-value headers with 0x0, except COOKIE, which uses 0x3B, 0x20.