Method MainLoop

libs/search/engine.cpp:200–253

}

void Engine::MainLoop(Context & context)
{
  while (true)
  {
    bool hasBroadcast = false;
    queue<Message> messages;

    {
      unique_lock<mutex> lock(m_mu);
      m_cv.wait(lock, [&]() { return m_shutdown || !m_messages.empty() || !context.m_messages.empty(); });

      if (m_shutdown)
        break;

      // As SearchEngine is thread-safe, there is a global order on
      // public API requests, and this order is kept by the global
      // |m_messages| queue.  When a broadcast message arrives, it
      // must be executed in any case by all threads, therefore the
      // first free thread extracts as many as possible broadcast
      // messages from |m_messages| front and replicates them to all
      // thread-specific |m_messages| queues.
      while (!m_messages.empty() && m_messages.front().m_type == Message::TYPE_BROADCAST)
      {
        for (auto & b : m_contexts)
          b.m_messages.push(m_messages.front());
        m_messages.pop();
        hasBroadcast = true;
      }

      // Consumes first non-broadcast message, if any.  We process
      // only a single task message (in constrast with broadcast
      // messages) because task messages are actually search queries,
      // whose processing may take an arbitrary amount of time. So
      // it's better to process only one message and leave rest to the
      // next free search thread.
      if (!m_messages.empty())
      {
        context.m_messages.push(std::move(m_messages.front()));
        m_messages.pop();
      }

      messages.swap(context.m_messages);
    }

    if (hasBroadcast)
      m_cv.notify_all();

    while (!messages.empty())
    {
      messages.front()(*context.m_processor);
      messages.pop();
    }
  }
}

template <typename... Args>
void Engine::PostMessage(Args &&... args)