### 4. Excluded Types

- Already compressed objects are not fit for compression since they do not have compressible patterns.
Such objects do not produce efficient [`LZ compression`](https://en.wikipedia.org/wiki/LZ77_and_LZ78)
which is a fitness factor for a lossless data compression.

Pre-compressed input typically compresses in excess of 2GiB/s per core,

    // TODO: checkState open or half-closed (local) or raise STREAM_CLOSED
    val inFinished = flags and FLAG_END_STREAM != 0
    val gzipped = flags and FLAG_COMPRESSED != 0
    if (gzipped) {
      throw IOException("PROTOCOL_ERROR: FLAG_COMPRESSED without SETTINGS_COMPRESS_DATA")
    }

    val padding = if (flags and FLAG_PADDED != 0) source.readByte() and 0xff else 0
    val dataLength = lengthWithoutPadding(length, flags, padding)

    callback.assertTextMessage("Hello")
  }

  @Test fun serverWithCompressionCompressedHelloTwoChunks() {
    data.write("418460b420bb92fced72".decodeHex()) // first 4 bytes of compressed 'Hello'
    data.write("80833851d9d4f156d9".decodeHex()) // last 3 bytes of compressed 'Hello'
    serverReaderWithCompression.processNextFrame()
    callback.assertTextMessage("Hello")
  }

  @Test fun clientTwoFrameHello() {

    server.webSocket!!.send(message)
    taskFaker.runTasks()
    assertThat(client.clientSourceBufferSize())
      .isGreaterThan(message.length.toLong()) // Not compressed.
    assertThat(client.processNextFrame()).isTrue()
    client.listener.assertTextMessage(message)
  }

  @Test
  fun messagesCompressedWhenConfigured() {

      contentType: MediaType?,
      file: File,
    ): RequestBody = file.asRequestBody(contentType)

    /**
     * Returns a gzip version of the RequestBody, with compressed payload.
     * This is not automatic as not all servers support gzip compressed requests.
     *
     * ```
     * val request = Request.Builder().url("...")
     *  .addHeader("Content-Encoding", "gzip")
     *  .post(uncompressedBody.gzip())

    val server = serverListener.assertOpen()

    // Server to client message big enough to be compressed.
    val message1 = repeat('a', RealWebSocket.DEFAULT_MINIMUM_DEFLATE_SIZE.toInt())
    server.send(message1)
    clientListener.assertTextMessage(message1)

    // Client to server message big enough to be compressed.
    val message2 = repeat('b', RealWebSocket.DEFAULT_MINIMUM_DEFLATE_SIZE.toInt())

    the web socket's connections back to the pool before their resources were cleaned up.

 *  Fix: Don't infinite loop when a received web socket message has self-terminating compressed
    data.

 *  Fix: Don't fail the call when the response code is ‘HTTP 102 Processing’ or ‘HTTP 103 Early
    Hints’.

 *  Fix: Honor interceptors' changes to connect and read timeouts.

   * servers it should be the agreed-upon extensions immediately.
   */
  private var extensions: WebSocketExtensions?,
  /** If compression is negotiated, outbound messages of this size and larger will be compressed. */
  private var minimumDeflateSize: Long,
  private val webSocketCloseTimeout: Long,
) : WebSocket, WebSocketReader.FrameCallback {
  private val key: String

    compressing outbound web socket messages. Configure this with 0L to always compress outbound
    messages and `Long.MAX_VALUE` to never compress outbound messages. The default is 1024L which
    compresses messages of size 1 KiB and larger. (Inbound messages are compressed or not based on
    the web socket server's configuration.)

    frame.writeByte(Http2.TYPE_DATA)
    frame.writeByte(FLAG_COMPRESSED)
    frame.writeInt(expectedStreamId and 0x7fffffff)
    zipped.readAll(frame)
    assertFailsWith<IOException> {
      reader.nextFrame(requireSettings = false, BaseTestHandler())
    }.also { expected ->
      assertThat(expected.message)
        .isEqualTo("PROTOCOL_ERROR: FLAG_COMPRESSED without SETTINGS_COMPRESS_DATA")
    }
  }