*  * [onHeaders] (unless canceled)
 *  * [onData] (optional sequence of data frames)
 *
 * As a stream ID is scoped to a single HTTP/2 connection, implementations which target multiple
 * connections should expect repetition of stream IDs.
 *
 * Return true to request cancellation of a pushed stream.  Note that this does not guarantee
 * future frames won't arrive on the stream ID.
 */
interface PushObserver {
  /**

import okio.buffer
import okio.source

/** Replays prerecorded outgoing frames and records incoming frames.  */
class MockHttp2Peer : Closeable {
  private var frameCount = 0
  private var client = false
  private val bytesOut = Buffer()
  private var writer = Http2Writer(bytesOut, client)
  private val outFrames: MutableList<OutFrame> = ArrayList()
  private val inFrames: BlockingQueue<InFrame> = LinkedBlockingQueue()
  private var port = 0

  val showHeaders: Boolean by option("-i", "--include").help("Include protocol headers in the output").flag()

  val showHttp2Frames: Boolean by option("--frames").help("Log HTTP/2 frames to STDERR").flag()

  val referer: String? by option("-e", "--referer").help("Referer URL")

  val verbose: Boolean by option("-v", "--verbose").help("Makes $NAME verbose during the operation").flag()

So we have a dedicated thread for every socket that just reads frames and dispatches them.

The reader thread must never run application-layer code. Otherwise one slow stream can hold up the entire connection.

```
$ adb shell setprop log.tag.okhttp.Http2 DEBUG
$ adb shell setprop log.tag.okhttp.TaskRunner DEBUG
$ adb logcat '*:E' 'okhttp.Http2:D' 'okhttp.TaskRunner:D'
```

### HTTP/2 Frame Logging

This logs inbound (`<<`) and outbound (`>>`) frames for HTTP/2 connections.

```
[2020-01-01 00:00:00] >> CONNECTION 505249202a20485454502f322e300d0a0d0a534d0d0a0d0a
[2020-01-01 00:00:00] >> 0x00000000     6 SETTINGS

class WindowCounter(
  val streamId: Int,
) {
  /** The total number of bytes consumed. */
  var total: Long = 0L
    private set

  /** The total number of bytes acknowledged by outgoing `WINDOW_UPDATE` frames. */
  var acknowledged: Long = 0L
    private set

  val unacknowledged: Long
    @Synchronized get() = total - acknowledged

  @Synchronized
  fun update(
    total: Long = 0,
    acknowledged: Long = 0,

import okhttp3.internal.http2.Header.Companion.TARGET_SCHEME_UTF8
import okhttp3.internal.immutableListOf
import okio.Sink
import okio.Socket
import okio.Source

/** Encode requests and responses using HTTP/2 frames. */
class Http2ExchangeCodec(
  client: OkHttpClient,
  override val carrier: Carrier,
  private val chain: RealInterceptorChain,
  private val http2Connection: Http2Connection,
) : ExchangeCodec {

      .isEqualTo("<< 0x00000003   226 DATA          END_STREAM")
    assertThat(frameLog(false, 0, 8, TYPE_GOAWAY, FLAG_NONE))
      .isEqualTo(">> 0x00000000     8 GOAWAY        ")
  }

  /** Window update frames have special formatting.  */
  @Test
  fun windowUpdateFrames() {
    assertThat(frameLogWindowUpdate(false, 0, 4, Int.MAX_VALUE.toLong()))
      .isEqualTo(">> 0x00000000     4 WINDOW_UPDATE 2147483647")

  /** Byte 0 reserved flag 3. Must be 0 unless negotiated otherwise. */
  internal const val B0_FLAG_RSV3 = 16

  /** Byte 0 mask for the frame opcode. */
  internal const val B0_MASK_OPCODE = 15

  /** Flag in the opcode which indicates a control frame. */
  internal const val OPCODE_FLAG_CONTROL = 8

  /**
   * Byte 1 flag for whether the payload data is masked.
   *
   * If this flag is set, the next four

      direction,
      streamId,
      length,
      formattedType,
      formattedFlags,
    )
  }

  /**
   * Returns a human-readable representation of a `WINDOW_UPDATE` frame. This frame includes the
   * window size increment instead of flags.
   */
  fun frameLogWindowUpdate(
    inbound: Boolean,
    streamId: Int,
    length: Int,
    windowSizeIncrement: Long,
  ): String {