Class CCheckQueue

src/checkqueue.h:33–202

  */
template <typename T, typename R = std::remove_cvref_t<decltype(std::declval<T>()().value())>>
class CCheckQueue
{
private:
    //! Mutex to protect the inner state
    Mutex m_mutex;

    //! Worker threads block on this when out of work
    std::condition_variable m_worker_cv;

    //! Master thread blocks on this when out of work
    std::condition_variable m_master_cv;

    //! The queue of elements to be processed.
    //! As the order of booleans doesn't matter, it is used as a LIFO (stack)
    std::vector<T> queue GUARDED_BY(m_mutex);

    //! The number of workers (including the master) that are idle.
    int nIdle GUARDED_BY(m_mutex){0};

    //! The total number of workers (including the master).
    int nTotal GUARDED_BY(m_mutex){0};

    //! The temporary evaluation result.
    std::optional<R> m_result GUARDED_BY(m_mutex);

    /**
     * Number of verifications that haven't completed yet.
     * This includes elements that are no longer queued, but still in the
     * worker's own batches.
     */
    unsigned int nTodo GUARDED_BY(m_mutex){0};

    //! The maximum number of elements to be processed in one batch
    const unsigned int nBatchSize;

    std::vector<std::thread> m_worker_threads;
    bool m_request_stop GUARDED_BY(m_mutex){false};

    /// \anchor checkqueue
    /** Internal function that does bulk of the verification work. If fMaster, return the final result. */
    std::optional<R> Loop(bool fMaster) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
    {
        std::condition_variable& cond = fMaster ? m_master_cv : m_worker_cv;
        std::vector<T> vChecks;
        vChecks.reserve(nBatchSize);
        unsigned int nNow = 0;
        std::optional<R> local_result;
        bool do_work;
        do {
            {
                WAIT_LOCK(m_mutex, lock);
                // first do the clean-up of the previous loop run (allowing us to do it in the same critsect)
                if (nNow) {
                    if (local_result.has_value() && !m_result.has_value()) {
                        std::swap(local_result, m_result);
                    }
                    nTodo -= nNow;
                    if (nTodo == 0 && !fMaster) {