assertThat(response.trailers()).isEmpty()
  }

  @Test
  fun worksIfTrailersSet() {
    val response =
      newResponse("".toResponseBody()) {
        trailers(
          object : TrailersSource {
            override fun get() = Headers.headersOf("a", "b")
          },
        )
      }

    assertThat(response.trailers()["a"]).isEqualTo("b")
  }

    if (flushHeaders) {
      connection.flush()
    }
  }

  fun enqueueTrailers(trailers: Headers) {
    withLock {
      check(!sink.finished) { "already finished" }
      require(trailers.size != 0) { "trailers.size() == 0" }
      this.sink.trailers = trailers
    }
  }

  fun readTimeout(): Timeout = readTimeout

  fun writeTimeout(): Timeout = writeTimeout

  /**

 */
package okhttp3

import okio.IOException

/**
 * Returns the trailers that follow an HTTP response, blocking if they aren't ready yet.
 * Implementations of this interface should respond to [Call.cancel] by immediately throwing an
 * [IOException].
 *
 * Most callers won't need this interface, and should use [Response.trailers] instead.
 *

      .build()

  @Test
  fun trailersHttp1() {
    trailers(Protocol.HTTP_1_1)
  }

  @Test
  fun trailersHttp2() {
    trailers(Protocol.HTTP_2)
  }

  private fun trailers(protocol: Protocol) {
    enableProtocol(protocol)

    server.enqueue(
      MockResponse
        .Builder()
        .addHeader("h1", "v1")
        .trailers(headersOf("t1", "v2"))
        .body(protocol, "Hello")

     */
    fun responseBodyComplete(trailers: Headers) {
      if (state == STATE_CLOSED) return
      if (state != STATE_READING_RESPONSE_BODY) throw IllegalStateException("state: $state")

      detachTimeout(timeout)

      this@Http1ExchangeCodec.trailers = trailers
      state = STATE_CLOSED
      if (trailers.size > 0) {
        client?.cookieJar?.receiveHeaders(url, trailers)
      }
    }
  }

  for (pushPromise in pushPromises) {
    result.addPush(pushPromise.wrap())
  }

  result.settings(settings)
  result.status(status)
  result.headers(headers)
  result.trailers(trailers)

  when (socketPolicy) {
    SocketPolicy.EXPECT_CONTINUE, SocketPolicy.CONTINUE_ALWAYS -> result.add100Continue()
    SocketPolicy.UPGRADE_TO_SSL_AT_END -> result.inTunnel()

   * @throws IOException if the trailers cannot be loaded, such as if the network connection is
   *     dropped.
   */
  @Throws(IOException::class)
  fun trailers(): Headers = trailersSource.get()

  /**
   * Returns the trailers after the HTTP response, if they are available to read immediately. Unlike
   * [trailers], this doesn't block if the trailers are not immediately available, and instead

      }

      socket.sleepWhileOpen(response.headersDelayNanos)
      stream.writeHeaders(response.toHttp2Headers(), outFinished, flushHeaders)

      if (trailers.size > 0) {
        stream.enqueueTrailers(trailers)
      }
      pushPromises(stream, request, response.pushPromises)
      if (body != null) {
        socket.sleepWhileOpen(bodyDelayNanos)
        val responseBodySink =

    throwing in 5.0.0, we inadvertently removed the ability for callers to peek the trailers
    (by catching the `IllegalStateException` if they weren't available). This new API restores that
    capability.

 *  Fix: Don't crash on `trailers()` if the response doesn't have a body. We broke [Retrofit] users

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

  /** Returns true if the response body and (possibly empty) trailers have been received. */
  val isResponseComplete: Boolean

  /** The socket that carries this exchange. */
  val socket: Socket

  /** Returns an output stream where the request body can be streamed. */