* the event source has already been closed or canceled.
   */
  fun cancel()

  fun interface Factory {
    /**
     * Creates a new event source and immediately returns it. Creating an event source initiates an
     * asynchronous process to connect the socket. Once that succeeds or fails, `listener` will be

    @JvmField val PREFIX_CLEAN = "OkHttp cache v1\n".encodeUtf8()

    @JvmField val PREFIX_DIRTY = "OkHttp DIRTY :(\n".encodeUtf8()
    private const val FILE_HEADER_SIZE = 32L

    /**
     * Creates a new relay that reads a live stream from [upstream], using [file] to share that data
     * with other sources.
     *
     * **Warning:** callers to this method must immediately call [newSource] to create a source and

 *
 * To make HTTPS calls using an HTTP proxy server OkHttp must first negotiate a connection with
 * the proxy. This proxy connection is called a "TLS Tunnel" and is specified by
 * [RFC 2817][1]. The HTTP CONNECT request that creates this tunnel connection is special: it
 * does not participate in any [interceptors][Interceptor] or [event listeners][EventListener]. It
 * doesn't include the motivating request's HTTP headers or even its full URL; only the target

This [sample factory](https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/PrintEvents.java) creates a unique ID for each call and uses that ID to differentiate calls in log messages.

```java
class PrintingEventListener extends EventListener {
  public static final Factory FACTORY = new Factory() {

/** Returns true if this string is not a host name and might be an IP address. */
fun String.canParseAsIpAddress(): Boolean = VERIFY_AS_IP_ADDRESS.matches(this)

/**
 * Returns true if the length is not valid for DNS (empty or greater than 253 characters), or if any
 * label is longer than 63 characters. Trailing dots are okay.
 */
internal fun String.containsInvalidLabelLengths(): Boolean {
  if (length !in 1..253) return true

  var labelStart = 0

    inputStream.close()
    val elapsedNanos = System.nanoTime() - startNanos
    val elapsedMillis = TimeUnit.NANOSECONDS.toMillis(elapsedNanos)

    // If we're working correctly, this should be greater than 100ms, but less than double that.
    // Previously we had a bug where we would download the entire response body as long as no
    // individual read took longer than 100ms.
    assertThat(elapsedMillis).isLessThan(500L)

    operator.write(80, buffer, buffer.size)
    assertThat(snapshot()).isEqualTo(
      (
        "" +
          "god creates dinosaurs. " +
          "god destroys dinosaurs. " +
          "god creates man. " +
          "man destroys god. " +
          "man creates dinosaurs. "
      ).encodeUtf8(),
    )
  }

  @Test
  fun multipleOperatorsShareOneFile() {
    val operatorA =

   * `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.
   * @param promisedStreamId server-initiated stream ID.  Must be an even number.

 *
 * This implementation assumes we do not send an increased [frame][Settings.getMaxFrameSize] to the
 * peer. Hence, we expect all frames to have a max length of [Http2.INITIAL_MAX_FRAME_SIZE].
 */
class Http2Reader(
  /** Creates a frame reader with max header table size of 4096. */
  private val source: BufferedSource,
  private val client: Boolean,
) : Closeable {
  private val continuation: ContinuationSource = ContinuationSource(this.source)

    `new Challenge(scheme, realm)` you must provide non-null values. These were
    never null in challenges created by OkHttp, but could have been null in
    application code that creates challenges.

 *  New: The `TlsVersion` of a `Handshake` is now non-null. If you are calling
    `Handshake.get()` with a null TLS version, you must instead now provide a