/** HTTP/2: The peer must not send a PUSH_PROMISE frame when this is 0. */
    const val ENABLE_PUSH = 2

    /** Sender's maximum number of concurrent streams. */
    const val MAX_CONCURRENT_STREAMS = 4

    /** HTTP/2: Size in bytes of the largest frame payload the sender will accept. */
    const val MAX_FRAME_SIZE = 5

import okio.ByteString
import okio.Source
import okio.Timeout

/**
 * Reads HTTP/2 transport frames.
 *
 * 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,

    writeMedium(frame, (headerBlock.size / 2).toInt() + paddingLength + 1)
    frame.writeByte(Http2.TYPE_HEADERS)
    frame.writeByte(FLAG_PADDED)
    frame.writeInt(expectedStreamId and 0x7fffffff)
    frame.writeByte(paddingLength)
    frame.write(headerBlock, headerBlock.size / 2)
    frame.write(padding)

    // Write the continuation frame, specifying no more frames are expected.

Blocking APIs may be inefficient because you hold a thread idle while waiting on the network. Threads are expensive because they have both a memory overhead and a context-switching overhead.

#### Framed protocols

  ): Boolean {
    // Don't send new frames after we've failed or enqueued a close frame.
    if (failed || enqueuedClose) return false

    // If this frame overflows the buffer, reject it and close the web socket.
    if (queueSize + data.size > MAX_QUEUE_SIZE) {
      close(CLOSE_CLIENT_GOING_AWAY, null)
      return false
    }

    // Enqueue the message frame.
    queueSize += data.size.toLong()

      reason: String,
    )
  }

  /**
   * Process the next protocol frame.
   *
   *  * If it is a control frame this will result in a single call to [FrameCallback].
   *  * If it is a message frame this will result in a single call to [FrameCallback.onReadMessage].
   *    If the message spans multiple frames, each interleaved control frame will result in a
   *    corresponding call to [FrameCallback].
   */

  /** 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

        }

        // Write a frame.
        val length = (end - start).toInt()
        outputStream.write(outBytes, start.toInt(), length)

        // If the last frame was truncated, immediately close the connection.
        if (truncated) {
          socket.close()
        }
      } else {
        // read a frame
        val inFrame = InFrame(i, reader)

import okio.Buffer
import okio.BufferedSink

/** Writes HTTP/2 transport frames. */
@Suppress("NAME_SHADOWING")
class Http2Writer(
  private val sink: BufferedSink,
  private val client: Boolean,
) : Closeable {
  internal val lock: ReentrantLock = ReentrantLock()

  private val hpackBuffer: Buffer = Buffer()
  private var maxFrameSize: Int = INITIAL_MAX_FRAME_SIZE
  private var closed: Boolean = false

    // Note: we don't process server frames so our client 'close' doesn't receive a server 'close'.
    assertThat(client.canceled).isFalse()

    taskFaker.advanceUntil(ns(4_999))
    assertThat(client.canceled).isFalse()

    taskFaker.advanceUntil(ns(5_000))
    assertThat(client.canceled).isTrue()

    client.processNextFrame() // This won't get a frame, but it will get a closed pipe.