Function CleanupBlockRevFiles

src/node/blockstorage.cpp:454–489

If we're using -prune with -reindex, then delete block files that will be ignored by the reindex. Since reindexing works by starting at block file 0 and looping until a blockfile is missing, do the same here to delete any later block files after a gap. Also delete all rev files since they'll be rewritten by the reindex anyway. This ensures that m_blockfile_info is in sync with what's actually o

// is in sync with what's actually on disk by the time we start downloading, so that pruning
// works correctly.
void CleanupBlockRevFiles()
{
    std::map<std::string, fs::path> mapBlockFiles;

    // Glob all blk?????.dat and rev?????.dat files from the blocks directory.
    // Remove the rev files immediately and insert the blk file paths into an
    // ordered map keyed by block file index.
    LogPrintf("Removing unusable blk?????.dat and rev?????.dat files for -reindex with -prune\n");
    fs::path blocksdir = gArgs.GetBlocksDirPath();
    for (fs::directory_iterator it(blocksdir); it != fs::directory_iterator(); it++) {
        const std::string path = fs::PathToString(it->path().filename());
        if (fs::is_regular_file(*it) &&
            path.length() == 12 &&
            path.substr(8,4) == ".dat")
        {
            if (path.substr(0, 3) == "blk") {
                mapBlockFiles[path.substr(3, 5)] = it->path();
            } else if (path.substr(0, 3) == "rev") {
                remove(it->path());
            }
        }
    }

    // Remove all block files that aren't part of a contiguous set starting at
    // zero by walking the ordered map (keys are block file indices) by
    // keeping a separate counter.  Once we hit a gap (or if 0 doesn't exist)
    // start removing block files.
    int nContigCounter = 0;
    for (const std::pair<const std::string, fs::path>& item : mapBlockFiles) {
        if (LocaleIndependentAtoi<int>(item.first) == nContigCounter) {
            nContigCounter++;
            continue;
        }
        remove(item.second);
    }
}

CBlockFileInfo* BlockManager::GetBlockFileInfo(size_t n)
{