source: Buffer,
      byteCount: Long,
    ) {
      lock.assertNotHeld()

      sendBuffer.write(source, byteCount)
      while (sendBuffer.size >= EMIT_BUFFER_SIZE) {
        emitFrame(false)
      }
    }

    /**
     * Emit a single data frame to the connection. The frame's size be limited by this stream's
     * write window. This method will block until the write window is nonempty.
     */