writeBytesTotal += toWrite
        outFinished = outFinishedOnLastFrame && toWrite == sendBuffer.size
      }

      writeTimeout.enter()
      try {
        connection.writeData(id, outFinished, sendBuffer, toWrite)
      } finally {
        writeTimeout.exitAndThrowIfTimedOut()
      }
    }

    @Throws(IOException::class)
    override fun flush() {
      assertLockNotHeld()

   *
   * Zero [byteCount] writes are not subject to flow control and will not block. The only use case
   * for zero [byteCount] is closing a flushed output stream.
   */
  @Throws(IOException::class)
  fun writeData(
    streamId: Int,
    outFinished: Boolean,
    buffer: Buffer?,
    byteCount: Long,
  ) {
    // Empty data frames are not flow-controlled.
    if (byteCount == 0L) {