exchange.flushRequest()
            val bufferedRequestBody = exchange.createRequestBody(request, true).buffer()
            requestBody.writeTo(bufferedRequestBody)
          } else {
            // Write the request body if the "Expect: 100-continue" expectation was met.
            val bufferedRequestBody = exchange.createRequestBody(request, false).buffer()
            requestBody.writeTo(bufferedRequestBody)

      trackFailure(e)
      throw e
    }
  }

  @Throws(IOException::class)
  fun createRequestBody(
    request: Request,
    duplex: Boolean,
  ): Sink {
    this.isDuplex = duplex
    val contentLength = request.body!!.contentLength()
    eventListener.requestBodyStart(call)
    val rawRequestBody = codec.createRequestBody(request, contentLength)
    return RequestBodySink(rawRequestBody, contentLength)
  }

interface ExchangeCodec {
  /** The connection or CONNECT tunnel that owns this codec. */
  val carrier: Carrier

  /** Returns an output stream where the request body can be streamed. */
  @Throws(IOException::class)
  fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink

  /** This should update the HTTP engine's sentRequestMillis field. */
  @Throws(IOException::class)
  fun writeRequestHeaders(request: Request)

    if (Protocol.H2_PRIOR_KNOWLEDGE in client.protocols) {
      Protocol.H2_PRIOR_KNOWLEDGE
    } else {
      Protocol.HTTP_2
    }

  @Volatile
  private var canceled = false

  override fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink {
    return stream!!.getSink()
  }

  override fun writeRequestHeaders(request: Request) {
    if (stream != null) return

   */
  private var trailers: Headers? = null

  /** Returns true if this connection is closed. */
  val isClosed: Boolean
    get() = state == STATE_CLOSED

  override fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink {
    return when {
      request.body?.isDuplex() == true -> throw ProtocolException(
        "Duplex connections are not supported for HTTP/1",
      )