// This check is imperfect: it doesn't tell us whether a handshake will succeed, just
        // that it will almost certainly fail because the proxy has sent unexpected data.
        if (source?.buffer?.exhausted() == false || sink?.buffer?.exhausted() == false) {
          throw IOException("TLS tunnel buffered too many bytes!")
        }

        user.secureConnectStart()

   *
   * A push promise contains all the headers that pertain to a server-initiated request, and a
   * `promisedStreamId` to which response frames will be delivered. Push promise frames are sent as
   * a part of the response to `streamId`. The `promisedStreamId` has a priority of one greater than
   * `streamId`.
   *
   * @param streamId client-initiated stream ID.  Must be an odd number.

      isTlsFallback = false,
    )
  }

  /**
   * Returns a request that creates a TLS tunnel via an HTTP proxy. Everything in the tunnel request
   * is sent unencrypted to the proxy server, so tunnels include only the minimum set of headers.
   * This avoids sending potentially sensitive data like HTTP cookies to the proxy unencrypted.
   *

    Settings().apply {
      // Flow control was designed more for servers, or proxies than edge clients. If we are a client,
      // set the flow control window to 16MiB.  This avoids thrashing window updates every 64KiB, yet
      // small enough to avoid blowing up the heap.
      if (builder.client) {
        set(Settings.INITIAL_WINDOW_SIZE, OKHTTP_CLIENT_WINDOW_SIZE)
      }
    }

  /**

  var writeBytesTotal = 0L
    internal set

  /** The total number of bytes permitted to be produced by incoming `WINDOW_UPDATE` frame. */
  var writeBytesMaximum: Long = connection.peerSettings.initialWindowSize.toLong()
    internal set

  /** Received headers yet to be [taken][takeHeaders]. */
  private val headersQueue = ArrayDeque<Headers>()

  /** True if response headers have been sent or received. */

    assertThat(connection.writer.maxDataLength()).isEqualTo(newMaxFrameSize)
  }

  /**
   * Webservers may set the initial window size to zero, which is a special case because it means
   * that we have to flush headers immediately before any request body can be sent.
   * https://github.com/square/okhttp/issues/2543
   */
  @Test fun peerSetsZeroFlowControl() {
    peer.setClient(true)