Method PromoteCandidateReady

src/txrequest.cpp:400–425

Convert a CANDIDATE_DELAYED announcement into a CANDIDATE_READY. If this makes it the new best CANDIDATE_READY (and no REQUESTED exists) and better than the CANDIDATE_BEST (if any), it becomes the new CANDIDATE_BEST.

    //! CANDIDATE_READY (and no REQUESTED exists) and better than the CANDIDATE_BEST (if any), it becomes the new
    //! CANDIDATE_BEST.
    void PromoteCandidateReady(Iter<ByTxHash> it)
    {
        assert(it != m_index.get<ByTxHash>().end());
        assert(it->GetState() == State::CANDIDATE_DELAYED);
        // Convert CANDIDATE_DELAYED to CANDIDATE_READY first.
        Modify<ByTxHash>(it, [](Announcement& ann){ ann.SetState(State::CANDIDATE_READY); });
        // The following code relies on the fact that the ByTxHash is sorted by txhash, and then by state (first
        // _DELAYED, then _READY, then _BEST/REQUESTED). Within the _READY announcements, the best one (highest
        // priority) comes last. Thus, if an existing _BEST exists for the same txhash that this announcement may
        // be preferred over, it must immediately follow the newly created _READY.
        auto it_next = std::next(it);
        if (it_next == m_index.get<ByTxHash>().end() || it_next->m_txhash != it->m_txhash ||
            it_next->GetState() == State::COMPLETED) {
            // This is the new best CANDIDATE_READY, and there is no IsSelected() announcement for this txhash
            // already.
            Modify<ByTxHash>(it, [](Announcement& ann){ ann.SetState(State::CANDIDATE_BEST); });
        } else if (it_next->GetState() == State::CANDIDATE_BEST) {
            Priority priority_old = m_computer(*it_next);
            Priority priority_new = m_computer(*it);
            if (priority_new > priority_old) {
                // There is a CANDIDATE_BEST announcement already, but this one is better.
                Modify<ByTxHash>(it_next, [](Announcement& ann){ ann.SetState(State::CANDIDATE_READY); });
                Modify<ByTxHash>(it, [](Announcement& ann){ ann.SetState(State::CANDIDATE_BEST); });
            }
        }
    }

    //! Change the state of an announcement to something non-IsSelected(). If it was IsSelected(), the next best
    //! announcement will be marked CANDIDATE_BEST.