C++ SPSCQueue::Pop方法代码示例

static void DVDThread()
{
  Common::SetCurrentThreadName("DVD thread");

  while (true)
  {
    s_request_queue_expanded.Wait();

    if (s_dvd_thread_exiting.IsSet())
      return;

    ReadRequest request;
    while (s_request_queue.Pop(request))
    {
      FileMonitor::Log(*s_disc, request.partition, request.dvd_offset);

      std::vector<u8> buffer(request.length);
      if (!s_disc->Read(request.dvd_offset, request.length, buffer.data(), request.partition))
        buffer.resize(0);

      request.realtime_done_us = Common::Timer::GetTimeUs();

      s_result_queue.Push(ReadResult(std::move(request), std::move(buffer)));
      s_result_queue_expanded.Set();

      if (s_dvd_thread_exiting.IsSet())
        return;
    }
  }
}

static void FinishRead(u64 id, s64 cycles_late)
{
  // We can't simply pop s_result_queue and always get the ReadResult
  // we want, because the DVD thread may add ReadResults to the queue
  // in a different order than we want to get them. What we do instead
  // is to pop the queue until we find the ReadResult we want (the one
  // whose ID matches userdata), which means we may end up popping
  // ReadResults that we don't want. We can't add those unwanted results
  // back to the queue, because the queue can only have one writer.
  // Instead, we add them to a map that only is used by the CPU thread.
  // When this function is called again later, it will check the map for
  // the wanted ReadResult before it starts searching through the queue.
  ReadResult result;
  auto it = s_result_map.find(id);
  if (it != s_result_map.end())
  {
    result = std::move(it->second);
    s_result_map.erase(it);
  }
  else
  {
    while (true)
    {
      while (!s_result_queue.Pop(result))
        s_result_queue_expanded.Wait();

      if (result.first.id == id)
        break;
      else
        s_result_map.emplace(result.first.id, std::move(result));
    }
  }
  // We have now obtained the right ReadResult.

  const ReadRequest& request = result.first;
  const std::vector<u8>& buffer = result.second;

  DEBUG_LOG(DVDINTERFACE, "Disc has been read. Real time: %" PRIu64 " us. "
                          "Real time including delay: %" PRIu64 " us. "
                          "Emulated time including delay: %" PRIu64 " us.",
            request.realtime_done_us - request.realtime_started_us,
            Common::Timer::GetTimeUs() - request.realtime_started_us,
            (CoreTiming::GetTicks() - request.time_started_ticks) /
                (SystemTimers::GetTicksPerSecond() / 1000000));

  if (buffer.size() != request.length)
  {
    PanicAlertT("The disc could not be read (at 0x%" PRIx64 " - 0x%" PRIx64 ").",
                request.dvd_offset, request.dvd_offset + request.length);
  }
  else
  {
    if (request.copy_to_ram)
      Memory::CopyToEmu(request.output_address, buffer.data(), request.length);
  }

  // Notify the emulated software that the command has been executed
  DVDInterface::FinishExecutingCommand(request.reply_type, DVDInterface::INT_TCINT, cycles_late,
                                       buffer);
}

void MoveEvents()
{
  for (Event ev; s_ts_queue.Pop(ev);)
  {
    ev.fifo_order = s_event_fifo_id++;
    s_event_queue.emplace_back(std::move(ev));
    std::push_heap(s_event_queue.begin(), s_event_queue.end(), std::greater<Event>());
  }
}

void DoState(PointerWrap& p)
{
  // By waiting for the DVD thread to be done working, we ensure
  // that s_request_queue will be empty and that the DVD thread
  // won't be touching anything while this function runs.
  WaitUntilIdle();

  // Move all results from s_result_queue to s_result_map because
  // PointerWrap::Do supports std::map but not Common::SPSCQueue.
  // This won't affect the behavior of FinishRead.
  ReadResult result;
  while (s_result_queue.Pop(result))
    s_result_map.emplace(result.first.id, std::move(result));

  // Both queues are now empty, so we don't need to savestate them.
  p.Do(s_result_map);
  p.Do(s_next_id);

  // s_disc isn't savestated (because it points to files on the
  // local system). Instead, we check that the status of the disc
  // is the same as when the savestate was made. This won't catch
  // cases of having the wrong disc inserted, though.
  // TODO: Check the game ID, disc number, revision?
  bool had_disc = HasDisc();
  p.Do(had_disc);
  if (had_disc != HasDisc())
  {
    if (had_disc)
      PanicAlertT("An inserted disc was expected but not found.");
    else
      s_disc.reset();
  }

  // TODO: Savestates can be smaller if the buffers of results aren't saved,
  // but instead get re-read from the disc when loading the savestate.

  // TODO: It would be possible to create a savestate faster by stopping
  // the DVD thread regardless of whether there are pending requests.

  // After loading a savestate, the debug log in FinishRead will report
  // screwed up times for requests that were submitted before the savestate
  // was made. Handling that properly may be more effort than it's worth.
}