Method RequestedTx

src/txrequest.cpp:625–668

    }

    void RequestedTx(NodeId peer, const uint256& txhash, std::chrono::microseconds expiry)
    {
        auto it = m_index.get<ByPeer>().find(ByPeerView{peer, true, txhash});
        if (it == m_index.get<ByPeer>().end()) {
            // There is no CANDIDATE_BEST announcement, look for a _READY or _DELAYED instead. If the caller only
            // ever invokes RequestedTx with the values returned by GetRequestable, and no other non-const functions
            // other than ForgetTxHash and GetRequestable in between, this branch will never execute (as txhashes
            // returned by GetRequestable always correspond to CANDIDATE_BEST announcements).

            it = m_index.get<ByPeer>().find(ByPeerView{peer, false, txhash});
            if (it == m_index.get<ByPeer>().end() || (it->GetState() != State::CANDIDATE_DELAYED &&
                                                      it->GetState() != State::CANDIDATE_READY)) {
                // There is no CANDIDATE announcement tracked for this peer, so we have nothing to do. Either this
                // txhash wasn't tracked at all (and the caller should have called ReceivedInv), or it was already
                // requested and/or completed for other reasons and this is just a superfluous RequestedTx call.
                return;
            }

            // Look for an existing CANDIDATE_BEST or REQUESTED with the same txhash. We only need to do this if the
            // found announcement had a different state than CANDIDATE_BEST. If it did, invariants guarantee that no
            // other CANDIDATE_BEST or REQUESTED can exist.
            auto it_old = m_index.get<ByTxHash>().lower_bound(ByTxHashView{txhash, State::CANDIDATE_BEST, 0});
            if (it_old != m_index.get<ByTxHash>().end() && it_old->m_txhash == txhash) {
                if (it_old->GetState() == State::CANDIDATE_BEST) {
                    // The data structure's invariants require that there can be at most one CANDIDATE_BEST or one
                    // REQUESTED announcement per txhash (but not both simultaneously), so we have to convert any
                    // existing CANDIDATE_BEST to another CANDIDATE_* when constructing another REQUESTED.
                    // It doesn't matter whether we pick CANDIDATE_READY or _DELAYED here, as SetTimePoint()
                    // will correct it at GetRequestable() time. If time only goes forward, it will always be
                    // _READY, so pick that to avoid extra work in SetTimePoint().
                    Modify<ByTxHash>(it_old, [](Announcement& ann) { ann.SetState(State::CANDIDATE_READY); });
                } else if (it_old->GetState() == State::REQUESTED) {
                    // As we're no longer waiting for a response to the previous REQUESTED announcement, convert it
                    // to COMPLETED. This also helps guaranteeing progress.
                    Modify<ByTxHash>(it_old, [](Announcement& ann) { ann.SetState(State::COMPLETED); });
                }
            }
        }

        Modify<ByPeer>(it, [expiry](Announcement& ann) {
            ann.SetState(State::REQUESTED);
            ann.m_time = expiry;
        });
    }

    void ReceivedResponse(NodeId peer, const uint256& txhash)
    {