StreamId overflow and reuse #892

StreamId RSocketStateMachine::getNextStreamId() {
  constexpr auto limit =
      static_cast<uint32_t>(std::numeric_limits<int32_t>::max() - 2);

  auto const streamId = nextStreamId_;
  if (streamId >= limit) {
    throw std::runtime_error{"Ran out of stream IDs"};
  }

  CHECK_EQ(0, streams_.count(streamId))
      << "Next stream ID already exists in the streams map";

  nextStreamId_ += 2;
  return streamId;
}