* the response, the client will issue a conditional `GET`. The server will then send either
 * the updated response if it has changed, or a short 'not modified' response if the client's copy
 * is still valid. Such responses increment both the network count and hit count.
 *
 * The best way to improve the cache hit rate is by configuring the web server to return cacheable
 * responses. Although this client honors all [HTTP/1.1 (RFC 7234)][rfc_7234] cache headers, it

  if (candidate.range.first != index) return null // Didn't match where it should have.
  return candidate
}

@JvmField
val EMPTY_BYTE_ARRAY: ByteArray = ByteArray(0)

/** Byte order marks. */
internal val UNICODE_BOMS =
  Options.of(
    // UTF-8.
    "efbbbf".decodeHex(),
    // UTF-16BE.
    "feff".decodeHex(),
    // UTF-16LE.
    "fffe".decodeHex(),
    // UTF-32BE.
    "0000ffff".decodeHex(),
    // UTF-32LE.

 * `::1` will reach the IPv6 server.
 *
 * By orchestrating two different servers with the same port but different IP addresses, we can
 * test what OkHttp does when both are reachable, or if only one is reachable.
 *
 * This test only runs on host machines that have both IPv4 and IPv6 addresses for localhost.
 */
@Timeout(30)
class FastFallbackTest {
  @RegisterExtension
  val clientTestRule = OkHttpClientTestRule()

import okio.ByteString

/**
 * A one-shot stream from the origin server to the client application with the raw bytes of the
 * response body. Each response body is supported by an active connection to the webserver. This
 * imposes both obligations and limits on the client application.
 *
 * ### The response body must be closed.
 *
 * Each response body is backed by a limited resource like a socket (live network responses) or

  }

  @Test
  @Throws(Exception::class)
  fun serverMaxWindowBitsTooLow() {
    extensionNegotiationFailure("permessage-deflate; server_max_window_bits=7")
  }

  @Test
  @Throws(Exception::class)
  fun serverMaxWindowBitsTooHigh() {
    extensionNegotiationFailure("permessage-deflate; server_max_window_bits=16")
  }

  @Test

    taskFaker.runTasks()
    client.listener.assertClosing(1000, "Goodbye!")
    client.webSocket!!.finishReader()
    assertThat(client.closed).isTrue()

    // Server and client both finished closing, connection is closed.
    server.listener.assertClosed(1000, "Hello!")
    client.listener.assertClosed(1000, "Goodbye!")
  }

  @Test
  fun clientCloseCancelsConnectionAfterTimeout() {

   * the already-requested ones are in service, otherwise we might create more threads than we need.
   *
   * We use [executeCallCount] and [runCallCount] to defend against starting more threads than we
   * need. Both fields are guarded by [lock].
   */
  private var executeCallCount = 0
  private var runCallCount = 0

  /** Queues with tasks that are currently executing their [TaskQueue.activeTask]. */

  vararg args: Any,
): String {
  return String.format(Locale.US, format, *args)
}

@Throws(IOException::class)
internal fun BufferedSource.readBomAsCharset(default: Charset): Charset {
  return when (select(UNICODE_BOMS)) {
    0 -> UTF_8
    1 -> UTF_16BE
    2 -> UTF_16LE
    3 -> UTF_32BE
    4 -> UTF_32LE
    -1 -> default
    else -> throw AssertionError()
  }
}

internal fun checkDuration(

     * will fail with a `504 Unsatisfiable Request`.
     */
    @JvmField
    val FORCE_CACHE = commonForceCache()

    /**
     * Returns the cache directives of [headers]. This honors both Cache-Control and Pragma headers
     * if they are present.
     */
    @JvmStatic
    fun parse(headers: Headers): CacheControl = commonParse(headers)
  }

        timeZone = utc
      }

    return dateFormat.format(date)
  }

  /**
   * Returns a composite adapter for a struct or data class. This may be used for both SEQUENCE and
   * SET types.
   *
   * The fields are specified as a list of member adapters. When decoding, a value for each
   * non-optional member but be included in sequence.
   *