* and the implementation should respond with a new request that sets the "Authorization" header.
 *
 * ```java
 * if (response.request().header("Authorization") != null) {
 *   return null; // Give up, we've already failed to authenticate.
 * }
 *
 * String credential = Credentials.basic(...)
 * return response.request().newBuilder()
 *     .header("Authorization", credential)
 *     .build();
 * ```
 *

          override fun authenticate(
            route: Route?,
            response: Response,
          ): Request? {
            if (response.request.header("Authorization") != null) {
              return null // Give up, we've already attempted to authenticate.
            }

            println("Authenticating for response: $response")
            println("Challenges: ${response.challenges()}")

      value = (value shl 4) + hexDigit
      i++
    }
    val groupLength = i - groupOffset
    if (groupLength == 0 || groupLength > 4) return null // Group is the wrong size.

    // We've successfully read a group. Assign its value to our byte array.
    address[b++] = (value.ushr(8) and 0xff).toByte()
    address[b++] = (value and 0xff).toByte()
  }

   * very flexible regarding wildcard rules, but this flexibility is not something currently used
   * in practice. To simplify the implementation, we've avoided implementing the flexible rules in
   * favor of supporting what's actually used in practice. That means if these assertions ever fail,
   * the implementation will need to be revisited to support a more flexible rule.
   */

      // current call to Source.read() has requested.
      try {
        val upstreamBytesRead = upstream!!.read(upstreamBuffer, bufferMaxSize)

        // If we've exhausted upstream, we're done.
        if (upstreamBytesRead == -1L) {
          commit(upstreamPos)
          return -1L
        }

        // Update this source and prepare this call's result.

    bufferA.writeUtf8("Dodgson, we've got Dodgson here!\n")
    operatorA.write(36, bufferA, 33)
    operatorB.read(0, bufferB, 9)
    assertThat(bufferB.readUtf8()).isEqualTo("Dodgson!\n")
    operatorA.read(9, bufferA, 27)
    assertThat(bufferA.readUtf8()).isEqualTo("You shouldn't use my name.\n")
    operatorB.read(36, bufferB, 33)
    assertThat(bufferB.readUtf8()).isEqualTo("Dodgson, we've got Dodgson here!\n")
  }

  @Test

    while (hasNextProxy()) {
      // Postponed routes are always tried last. For example, if we have 2 proxies and all the
      // routes for proxy1 should be postponed, we'll move to proxy2. Only after we've exhausted
      // all the good routes will we attempt the postponed routes.
      val proxy = nextProxy()
      for (inetSocketAddress in inetSocketAddresses) {
        val route = Route(address, proxy, inetSocketAddress)

Note that OkHttp won't use compression when sending messages smaller than 1 KiB.

 *  Fix: Don't crash when the URL hostname contains an underscore on Android.
 *  Fix: Change HTTP/2 to use a daemon thread for its socket reader. If you've ever seen a command
    line application hang after all of the work is done, it may be due to a non-daemon thread like
    this one.
 *  New: Include suppressed exceptions when all routes to a target service fail.

## Version 3.4.0-RC1

_2016-07-02_

 *  **We’ve rewritten HttpURLConnection and HttpsURLConnection.** Previously we
    shared a single HTTP engine between two frontend APIs: `HttpURLConnection`
    and `Call`. With this release we’ve rearranged things so that the
    `HttpURLConnection` frontend now delegates to the `Call` APIs internally.

  private val messageAndCloseQueue = ArrayDeque<Any>()

  /** The total size in bytes of enqueued but not yet transmitted messages. */
  private var queueSize = 0L

  /** True if we've enqueued a close frame. No further message frames will be enqueued. */
  private var enqueuedClose = false

  /** The close code from the peer, or -1 if this web socket has not yet read a close frame. */