Method onReadComplete

src/controller.cpp:2007–2070

}

void RcxController::onReadComplete() {
    m_readInFlight = false;

    if (m_readGen != m_refreshGen) return;

    PageMap newPages;
    try {
        newPages = m_refreshWatcher->result();
    } catch (const std::exception& e) {
        qWarning() << "[Refresh] async read threw:" << e.what();
        return;
    } catch (...) {
        qWarning() << "[Refresh] async read threw unknown exception";
        return;
    }

    // All-zero guard: if page 0 is all zeros and we already have data, discard
    if (!m_prevPages.isEmpty() && newPages.contains(0)) {
        const QByteArray& p0 = newPages.value(0);
        bool allZero = true;
        for (int i = 0; i < p0.size(); ++i) {
            if (p0[i] != 0) { allZero = false; break; }
        }
        if (allZero) {
            qDebug() << "[Refresh] discarding all-zero page-0, keeping stale snapshot";
            return;
        }
    }

    // Fast path: no changes at all
    if (newPages == m_prevPages)
        return;

    // Compute which byte offsets changed (for change highlighting).
    // Skip on first snapshot — nothing to compare against.
    m_changedOffsets.clear();
    if (!m_prevPages.isEmpty()) {
        for (auto it = newPages.constBegin(); it != newPages.constEnd(); ++it) {
            uint64_t pageAddr = it.key();
            const QByteArray& newPage = it.value();
            auto oldIt = m_prevPages.constFind(pageAddr);
            if (oldIt == m_prevPages.constEnd())
                continue;   // new page, no previous data to diff against
            const QByteArray& oldPage = oldIt.value();
            int cmpLen = qMin(oldPage.size(), newPage.size());
            for (int i = 0; i < cmpLen; ++i) {
                if (oldPage[i] != newPage[i])
                    m_changedOffsets.insert(static_cast<int64_t>(pageAddr) + i);
            }
        }
    }

    int mainExtent = computeDataExtent();
    m_prevPages = newPages;

    if (m_snapshotProv)
        m_snapshotProv->updatePages(std::move(newPages), mainExtent);
    else