kdelibs/kioslave/http/http_cache_cleaner.cpp

/*
This file is part of KDE

 Copyright (C) 1999-2000 Waldo Bastian (bastian@kde.org)
 Copyright (C) 2009 Andreas Hartmetz (ahartmetz@gmail.com)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
//----------------------------------------------------------------------------
//
// KDE HTTP Cache cleanup tool

#include <cstring>
#include <time.h>
#include <stdlib.h>
#include <zlib.h>

#include <QtCore/QDir>
#include <QtCore/QString>
#include <QtCore/qdatetime.h>
#include <QtDBus/QtDBus>
#include <QtNetwork/QLocalServer>
#include <QtNetwork/QLocalSocket>
#include <QtCore/qcoreapplication.h>
#include <QtCore/qcryptographichash.h>

#include <kcmdlineargs.h>
#include <kcomponentdata.h>
#include <kdatetime.h>
#include <kdebug.h>
#include <kglobal.h>
#include <klocale.h>
#include <kprotocolmanager.h>
#include <kstandarddirs.h>

#include <unistd.h>

time_t g_currentDate;
int g_maxCacheAge;
qint64 g_maxCacheSize;

static const char appFullName[] = "org.kde.kio_http_cache_cleaner";
static const char appName[] = "kio_http_cache_cleaner";

// !START OF SYNC!
// Keep the following in sync with the cache code in http.cpp

static const int s_hashedUrlBits = 160;   // this number should always be divisible by eight
static const int s_hashedUrlNibbles = s_hashedUrlBits / 4;
static const int s_hashedUrlBytes = s_hashedUrlBits / 8;

static const char version[] = "A\n";

// never instantiated, on-disk / wire format only
struct SerializedCacheFileInfo {
// from http.cpp
    quint8 version[2];
    quint8 compression; // for now fixed to 0
    quint8 reserved;    // for now; also alignment
    static const int useCountOffset = 4;
    qint32 useCount;
    qint64 servedDate;
    qint64 lastModifiedDate;
    qint64 expireDate;
    qint32 bytesCached;
    static const int size = 36;

    QString url;
    QString etag;
    QString mimeType;
    QStringList responseHeaders; // including status response like "HTTP 200 OK"
};

static QString dateString(qint64 date)
{
    KDateTime dt;
    dt.setTime_t(date);
    return dt.toString(KDateTime::ISODate);
}

struct MiniCacheFileInfo {
// data from cache entry file, or from scoreboard file
    qint32 useCount;
// from filesystem
    qint64 lastUsedDate;
    qint64 sizeOnDisk;
    // we want to delete the least "useful" files and we'll have to sort a list for that...
    bool operator<(const MiniCacheFileInfo &other) const;
    void debugPrint() const
    {
        kDebug(7113) << "useCount:" << useCount
                     << "\nlastUsedDate:" << lastUsedDate
                     << "\nsizeOnDisk:" << sizeOnDisk << '\n';
    }
};

struct CacheFileInfo : MiniCacheFileInfo {
    quint8 version[2];
    quint8 compression; // for now fixed to 0
    quint8 reserved;    // for now; also alignment


    qint64 servedDate;
    qint64 lastModifiedDate;
    qint64 expireDate;
    qint32 bytesCached;

    QString baseName;
    QString url;
    QString etag;
    QString mimeType;
    QStringList responseHeaders; // including status response like "HTTP 200 OK"

    void prettyPrint() const
    {
        QTextStream out(stdout, QIODevice::WriteOnly);
        out << "File " << baseName << " version " << version[0] << version[1];
        out << "\n cached bytes     " << bytesCached << " useCount " << useCount;
        out << "\n servedDate       " << dateString(servedDate);
        out << "\n lastModifiedDate " << dateString(lastModifiedDate);
        out << "\n expireDate       " << dateString(expireDate);
        out << "\n entity tag       " << etag;
        out << "\n encoded URL      " << url;
        out << "\n mimetype         " << mimeType;
        out << "\nResponse headers follow...\n";
        Q_FOREACH (const QString &h, responseHeaders) {
            out << h << '\n';
        }
    }
};


bool MiniCacheFileInfo::operator<(const MiniCacheFileInfo &other) const
{
    const int thisUseful = useCount / qMax(g_currentDate - lastUsedDate, qint64(1));
    const int otherUseful = other.useCount / qMax(g_currentDate - other.lastUsedDate, qint64(1));
    return thisUseful < otherUseful;
}

bool CacheFileInfoPtrLessThan(const CacheFileInfo *cf1, const CacheFileInfo *cf2)
{
    return *cf1 < *cf2;
}

enum OperationMode {
    CleanCache = 0,
    DeleteCache,
    FileInfo
};

static bool timeSizeFits(qint64 intTime)
{
    time_t tTime = static_cast<time_t>(intTime);
    qint64 check = static_cast<qint64>(tTime);
    return check == intTime;
}

static bool readBinaryHeader(const QByteArray &d, CacheFileInfo *fi)
{
    if (d.size() < SerializedCacheFileInfo::size) {
        kDebug(7113) << "readBinaryHeader(): file too small?";
        return false;
    }
    QDataStream stream(d);

    stream >> fi->version[0];
    stream >> fi->version[1];
    if (fi->version[0] != version[0] || fi->version[1] != version[1]) {
        kDebug(7113) << "readBinaryHeader(): wrong magic bytes";
        return false;
    }
    stream >> fi->compression;
    stream >> fi->reserved;

    stream >> fi->useCount;

    stream >> fi->servedDate;
    stream >> fi->lastModifiedDate;
    stream >> fi->expireDate;
    bool timeSizeOk = timeSizeFits(fi->servedDate) && timeSizeFits(fi->lastModifiedDate) &&
                      timeSizeFits(fi->expireDate);

    stream >> fi->bytesCached;
    return timeSizeOk;
}

static QString filenameFromUrl(const QByteArray &url)
{
    QCryptographicHash hash(QCryptographicHash::Sha1);
    hash.addData(url);
    return QString::fromLatin1(hash.result().toHex());
}

static QString filePath(const QString &baseName)
{
    QString cacheDirName = KGlobal::dirs()->saveLocation("cache", "http");
    if (!cacheDirName.endsWith('/')) {
        cacheDirName.append('/');
    }
    return cacheDirName + baseName;
}

static bool readLineChecked(QIODevice *dev, QByteArray *line)
{
    *line = dev->readLine(8192);
    // if nothing read or the line didn't fit into 8192 bytes(!)
    if (line->isEmpty() || !line->endsWith('\n')) {
        return false;
    }
    // we don't actually want the newline!
    line->chop(1);
    return true;
}

static bool readTextHeader(QFile *file, CacheFileInfo *fi, OperationMode mode)
{
    bool ok = true;
    QByteArray readBuf;

    ok = ok && readLineChecked(file, &readBuf);
    fi->url = QString::fromLatin1(readBuf);
    if (filenameFromUrl(readBuf) != QFileInfo(*file).baseName()) {
        kDebug(7103) << "You have witnessed a very improbable hash collision!";
        return false;
    }

    // only read the necessary info for cache cleaning. Saves time and (more importantly) memory.
    if (mode != FileInfo) {
        return true;
    }

    ok = ok && readLineChecked(file, &readBuf);
    fi->etag = QString::fromLatin1(readBuf);

    ok = ok && readLineChecked(file, &readBuf);
    fi->mimeType = QString::fromLatin1(readBuf);

    // read as long as no error and no empty line found
    while (true) {
        ok = ok && readLineChecked(file, &readBuf);
        if (ok && !readBuf.isEmpty()) {
            fi->responseHeaders.append(QString::fromLatin1(readBuf));
        } else {
            break;
        }
    }
    return ok; // it may still be false ;)
}

// TODO common include file with http.cpp?
enum CacheCleanerCommand {
    InvalidCommand = 0,
    CreateFileNotificationCommand,
    UpdateFileCommand
};

static bool readCacheFile(const QString &baseName, CacheFileInfo *fi, OperationMode mode)
{
    QFile file(filePath(baseName));
    if (!file.open(QIODevice::ReadOnly)) {
        return false;
    }
    fi->baseName = baseName;

    QByteArray header = file.read(SerializedCacheFileInfo::size);
    // do *not* modify/delete the file if we're in file info mode.
    if (!(readBinaryHeader(header, fi) && readTextHeader(&file, fi, mode)) && mode != FileInfo) {
        kDebug(7113) << "read(Text|Binary)Header() returned false, deleting file" << baseName;
        file.remove();
        return false;
    }
    // get meta-information from the filesystem
    QFileInfo fileInfo(file);
    fi->lastUsedDate = fileInfo.lastModified().toTime_t();
    fi->sizeOnDisk = fileInfo.size();
    return true;
}

class Scoreboard;

class CacheIndex
{
public:
    explicit CacheIndex(const QString &baseName)
    {
        QByteArray ba = baseName.toLatin1();
        const int sz = ba.size();
        const char *input = ba.constData();
        Q_ASSERT(sz == s_hashedUrlNibbles);

        int translated = 0;
        for (int i = 0; i < sz; i++) {
            int c = input[i];

            if (c >= '0' && c <= '9') {
                translated |= c - '0';
            } else if (c >= 'a' && c <= 'f') {
                translated |= c - 'a' + 10;
            } else {
                Q_ASSERT(false);
            }

            if (i & 1) {
                // odd index
                m_index[i >> 1] = translated;
                translated = 0;
            } else  {
                translated = translated << 4;
            }
        }

        computeHash();
    }

    bool operator==(const CacheIndex &other) const
    {
        const bool isEqual = memcmp(m_index, other.m_index, s_hashedUrlBytes) == 0;
        if (isEqual) {
            Q_ASSERT(m_hash == other.m_hash);
        }
        return isEqual;
    }

private:
    explicit CacheIndex(const QByteArray &index)
    {
        Q_ASSERT(index.length() >= s_hashedUrlBytes);
        memcpy(m_index, index.constData(), s_hashedUrlBytes);
        computeHash();
    }

    void computeHash()
    {
        uint hash = 0;
        const int ints = s_hashedUrlBytes / sizeof(uint);
        for (int i = 0; i < ints; i++) {
            hash ^= reinterpret_cast<uint *>(&m_index[0])[i];
        }
        if (const int bytesLeft = s_hashedUrlBytes % sizeof(uint)) {
            // dead code until a new url hash algorithm or architecture with sizeof(uint) != 4 appears.
            // we have the luxury of ignoring endianness because the hash is never written to disk.
            // just merge the bits into the the hash in some way.
            const int offset = ints * sizeof(uint);
            for (int i = 0; i < bytesLeft; i++) {
                hash ^= static_cast<uint>(m_index[offset + i]) << (i * 8);
            }
        }
        m_hash = hash;
    }

    friend uint qHash(const CacheIndex &);
    friend class Scoreboard;

    quint8 m_index[s_hashedUrlBytes]; // packed binary version of the hexadecimal name
    uint m_hash;
};

uint qHash(const CacheIndex &ci)
{
    return ci.m_hash;
}


static CacheCleanerCommand readCommand(const QByteArray &cmd, CacheFileInfo *fi)
{
    readBinaryHeader(cmd, fi);
    QDataStream stream(cmd);
    stream.skipRawData(SerializedCacheFileInfo::size);

    quint32 ret;
    stream >> ret;

    QByteArray baseName;
    baseName.resize(s_hashedUrlNibbles);
    stream.readRawData(baseName.data(), s_hashedUrlNibbles);
    Q_ASSERT(stream.atEnd());
    fi->baseName = QString::fromLatin1(baseName);

    Q_ASSERT(ret == CreateFileNotificationCommand || ret == UpdateFileCommand);
    return static_cast<CacheCleanerCommand>(ret);
}


// never istantiated, on-disk format only
struct ScoreboardEntry {
// from scoreboard file
    quint8 index[s_hashedUrlBytes];
    static const int indexSize = s_hashedUrlBytes;
    qint32 useCount;
// from scoreboard file, but compared with filesystem to see if scoreboard has current data
    qint64 lastUsedDate;
    qint32 sizeOnDisk;
    static const int size = 36;
    // we want to delete the least "useful" files and we'll have to sort a list for that...
    bool operator<(const MiniCacheFileInfo &other) const;
};


class Scoreboard
{
public:
    Scoreboard()
    {
        // read in the scoreboard...
        QFile sboard(filePath(QLatin1String("scoreboard")));
        sboard.open(QIODevice::ReadOnly);
        while (true) {
            QByteArray baIndex = sboard.read(ScoreboardEntry::indexSize);
            QByteArray baRest = sboard.read(ScoreboardEntry::size - ScoreboardEntry::indexSize);
            if (baIndex.size() + baRest.size() != ScoreboardEntry::size) {
                break;
            }

            const QString entryBasename = QString::fromLatin1(baIndex.toHex());
            MiniCacheFileInfo mcfi;
            if (readAndValidateMcfi(baRest, entryBasename, &mcfi)) {
                m_scoreboard.insert(CacheIndex(baIndex), mcfi);
            }
        }
    }

    void writeOut()
    {
        // write out the scoreboard
        QFile sboard(filePath(QLatin1String("scoreboard")));
        if (!sboard.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
            return;
        }
        QDataStream stream(&sboard);

        QHash<CacheIndex, MiniCacheFileInfo>::ConstIterator it = m_scoreboard.constBegin();
        for (; it != m_scoreboard.constEnd(); ++it) {
            const char *indexData = reinterpret_cast<const char *>(it.key().m_index);
            stream.writeRawData(indexData, s_hashedUrlBytes);

            stream << it.value().useCount;
            stream << it.value().lastUsedDate;
            stream << it.value().sizeOnDisk;
        }
    }

    bool fillInfo(const QString &baseName, MiniCacheFileInfo *mcfi)
    {
        QHash<CacheIndex, MiniCacheFileInfo>::ConstIterator it =
                                       m_scoreboard.constFind(CacheIndex(baseName));
        if (it == m_scoreboard.constEnd()) {
            return false;
        }
        *mcfi = it.value();
        return true;
    }

    qint64 runCommand(const QByteArray &cmd)
    {
        // execute the command; return number of bytes if a new file was created, zero otherwise.
        Q_ASSERT(cmd.size() == 80);
        CacheFileInfo fi;
        const CacheCleanerCommand ccc = readCommand(cmd, &fi);
        QString fileName = filePath(fi.baseName);

        switch (ccc) {
        case CreateFileNotificationCommand:
            kDebug(7113) << "CreateNotificationCommand for" << fi.baseName;
            if (!readBinaryHeader(cmd, &fi)) {
                return 0;
            }
            break;

        case UpdateFileCommand: {
            kDebug(7113) << "UpdateFileCommand for" << fi.baseName;
            QFile file(fileName);
            file.open(QIODevice::ReadWrite);

            CacheFileInfo fiFromDisk;
            QByteArray header = file.read(SerializedCacheFileInfo::size);
            if (!readBinaryHeader(header, &fiFromDisk) || fiFromDisk.bytesCached != fi.bytesCached) {
                return 0;
            }

            // adjust the use count, to make sure that we actually count up. (slaves read the file
            // asynchronously...)
            const quint32 newUseCount = fiFromDisk.useCount + 1;
            QByteArray newHeader = cmd.mid(0, SerializedCacheFileInfo::size);
            {
                QDataStream stream(&newHeader, QIODevice::WriteOnly);
                stream.skipRawData(SerializedCacheFileInfo::useCountOffset);
                stream << newUseCount;
            }

            file.seek(0);
            file.write(newHeader);
            file.close();

            if (!readBinaryHeader(newHeader, &fi)) {
                return 0;
            }
            break;
        }

        default:
            kDebug(7113) << "received invalid command";
            return 0;
        }

        QFileInfo fileInfo(fileName);
        fi.lastUsedDate = fileInfo.lastModified().toTime_t();
        fi.sizeOnDisk = fileInfo.size();
        fi.debugPrint();
        // a CacheFileInfo is-a MiniCacheFileInfo which enables the following assignment...
        add(fi);
        // finally, return cache dir growth (only relevant if a file was actually created!)
        return ccc == CreateFileNotificationCommand ? fi.sizeOnDisk : 0;
    }

    void add(const CacheFileInfo &fi)
    {
        m_scoreboard[CacheIndex(fi.baseName)] = fi;
    }

    void remove(const QString &basename)
    {
        m_scoreboard.remove(CacheIndex(basename));
    }

    // keep memory usage reasonably low - otherwise entries of nonexistent files don't hurt.
    void maybeRemoveStaleEntries(const QList<CacheFileInfo *> &fiList)
    {
        // don't bother when there are a few bogus entries
        if (m_scoreboard.count() < fiList.count() + 100) {
            return;
        }
        kDebug(7113) << "we have too many fake/stale entries, cleaning up...";
        QSet<CacheIndex> realFiles;
        Q_FOREACH (CacheFileInfo *fi, fiList) {
            realFiles.insert(CacheIndex(fi->baseName));
        }
        QHash<CacheIndex, MiniCacheFileInfo>::Iterator it = m_scoreboard.begin();
        while (it != m_scoreboard.end()) {
            if (realFiles.contains(it.key())) {
                ++it;
            } else {
                it = m_scoreboard.erase(it);
            }
        }
    }

private:
    bool readAndValidateMcfi(const QByteArray &rawData, const QString &basename, MiniCacheFileInfo *mcfi)
    {
        QDataStream stream(rawData);
        stream >> mcfi->useCount;
        // check those against filesystem
        stream >> mcfi->lastUsedDate;
        stream >> mcfi->sizeOnDisk;

        QFileInfo fileInfo(filePath(basename));
        if (!fileInfo.exists()) {
            return false;
        }
        bool ok = true;
        ok = ok && fileInfo.lastModified().toTime_t() == mcfi->lastUsedDate;
        ok = ok && fileInfo.size() == mcfi->sizeOnDisk;
        if (!ok) {
            // size or last-modified date not consistent with entry file; reload useCount
            // note that avoiding to open the file is the whole purpose of the scoreboard - we only
            // open the file if we really have to.
            QFile entryFile(fileInfo.absoluteFilePath());
            if (!entryFile.open(QIODevice::ReadOnly)) {
                return false;
            }
            if (entryFile.size() < SerializedCacheFileInfo::size) {
                return false;
            }
            QDataStream stream(&entryFile);
            stream.skipRawData(SerializedCacheFileInfo::useCountOffset);

            stream >> mcfi->useCount;
            mcfi->lastUsedDate = fileInfo.lastModified().toTime_t();
            mcfi->sizeOnDisk = fileInfo.size();
            ok = true;
        }
        return ok;
    }

    QHash<CacheIndex, MiniCacheFileInfo> m_scoreboard;
};


// Keep the above in sync with the cache code in http.cpp
// !END OF SYNC!

// remove files and directories used by earlier versions of the HTTP cache.
static void removeOldFiles()
{
    const char *oldDirs = "0abcdefghijklmnopqrstuvwxyz";
    const int n = strlen(oldDirs);
    QDir cacheRootDir(filePath(QString()));
    for (int i = 0; i < n; i++) {
        QString dirName = QString::fromLatin1(&oldDirs[i], 1);
        // delete files in directory...
        Q_FOREACH (const QString &baseName, QDir(filePath(dirName)).entryList()) {
            QFile::remove(filePath(dirName + '/' + baseName));
        }
        // delete the (now hopefully empty!) directory itself
        cacheRootDir.rmdir(dirName);
    }
    QFile::remove(filePath(QLatin1String("cleaned")));
}

class CacheCleaner
{
public:
    CacheCleaner(const QDir &cacheDir)
     : m_totalSizeOnDisk(0)
    {
        kDebug(7113);
        m_fileNameList = cacheDir.entryList();
    }

    // Delete some of the files that need to be deleted. Return true when done, false otherwise.
    // This makes interleaved cleaning / serving ioslaves possible.
    bool processSlice(Scoreboard *scoreboard = 0)
    {
        QTime t;
        t.start();
        // phase one: gather information about cache files
        if (!m_fileNameList.isEmpty()) {
            while (t.elapsed() < 100 && !m_fileNameList.isEmpty()) {
                QString baseName = m_fileNameList.takeFirst();
                // check if the filename is of the $s_hashedUrlNibbles letters, 0...f type
                if (baseName.length() < s_hashedUrlNibbles) {
                    continue;
                }
                bool nameOk = true;
                for (int i = 0; i < s_hashedUrlNibbles && nameOk; i++) {
                    QChar c = baseName[i];
                    nameOk = (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f');
                }
                if (!nameOk) {
                    continue;
                }
                if (baseName.length() > s_hashedUrlNibbles) {
                    if (g_currentDate - QFileInfo(filePath(baseName)).lastModified().toTime_t() > 15*60) {
                        // it looks like a temporary file that hasn't been touched in > 15 minutes...
                        QFile::remove(filePath(baseName));
                    }
                    // the temporary file might still be written to, leave it alone
                    continue;
                }

                CacheFileInfo *fi = new CacheFileInfo();
                fi->baseName = baseName;

                bool gotInfo = false;
                if (scoreboard) {
                    gotInfo = scoreboard->fillInfo(baseName, fi);
                }
                if (!gotInfo) {
                    gotInfo = readCacheFile(baseName, fi, CleanCache);
                    if (gotInfo && scoreboard) {
                        scoreboard->add(*fi);
                    }
                }
                if (gotInfo) {
                    m_fiList.append(fi);
                    m_totalSizeOnDisk += fi->sizeOnDisk;
                } else {
                    delete fi;
                }
            }
            kDebug(7113) << "total size of cache files is" << m_totalSizeOnDisk;

            if (m_fileNameList.isEmpty()) {
                // final step of phase one
                qSort(m_fiList.begin(), m_fiList.end(), CacheFileInfoPtrLessThan);
            }
            return false;
        }

        // phase two: delete files until cache is under maximum allowed size

        // TODO: delete files larger than allowed for a single file
        while (t.elapsed() < 100) {
            if (m_totalSizeOnDisk <= g_maxCacheSize || m_fiList.isEmpty()) {
                kDebug(7113) << "total size of cache files after cleaning is" << m_totalSizeOnDisk;
                if (scoreboard) {
                    scoreboard->maybeRemoveStaleEntries(m_fiList);
                    scoreboard->writeOut();
                }
                qDeleteAll(m_fiList);
                m_fiList.clear();
                return true;
            }
            CacheFileInfo *fi = m_fiList.takeFirst();
            QString filename = filePath(fi->baseName);
            if (QFile::remove(filename)) {
                m_totalSizeOnDisk -= fi->sizeOnDisk;
                if (scoreboard) {
                    scoreboard->remove(fi->baseName);
                }
            }
            delete fi;
        }
        return false;
    }

private:
    QStringList m_fileNameList;
    QList<CacheFileInfo *> m_fiList;
    qint64 m_totalSizeOnDisk;
};


int main(int argc, char **argv)
{
    KCmdLineArgs::init(argc, argv, appName, "kdelibs4",
                       ki18n("KDE HTTP cache maintenance tool"), version,
                       ki18n("KDE HTTP cache maintenance tool"), KCmdLineArgs::CmdLineArgNone);

    KCmdLineOptions options;
    options.add("clear-all", ki18n("Empty the cache"));
    options.add("file-info <filename>", ki18n("Display information about cache file"));

    KCmdLineArgs::addCmdLineOptions( options );
    KCmdLineArgs *args = KCmdLineArgs::parsedArgs();
    KComponentData componentData(appName);

    // we need a QCoreApplication so QCoreApplication::processEvents() works as intended
    QCoreApplication app(argc, argv);

    OperationMode mode = CleanCache;
    if (args->isSet("clear-all")) {
        mode = DeleteCache;
    } else if (args->isSet("file-info")) {
        mode = FileInfo;
    }

    // file info mode: no scanning of directories, just output info and exit.
    if (mode == FileInfo) {
        CacheFileInfo fi;
        if (!readCacheFile(args->getOption("file-info"), &fi, mode)) {
            return 1;
        }
        fi.prettyPrint();
        return 0;
    }

    // make sure we're the only running instance of the cleaner service
    if (mode == CleanCache) {
        if (!QDBusConnection::sessionBus().isConnected()) {
            QDBusError error(QDBusConnection::sessionBus().lastError());
            fprintf(stderr, "%s: Could not connect to D-Bus! (%s: %s)\n", appName,
                    qPrintable(error.name()), qPrintable(error.message()));
            return 1;
        }

        if (!QDBusConnection::sessionBus().registerService(appFullName)) {
            fprintf(stderr, "%s: Already running!\n", appName);
            return 0;
        }
    }


    g_currentDate = time(0);
    g_maxCacheAge = KProtocolManager::maxCacheAge();
    g_maxCacheSize = mode == DeleteCache ? -1 : KProtocolManager::maxCacheSize() * 1024;

    QString cacheDirName = KGlobal::dirs()->saveLocation("cache", "http");
    QDir cacheDir(cacheDirName);
    if (!cacheDir.exists()) {
        fprintf(stderr, "%s: '%s' does not exist.\n", appName, qPrintable(cacheDirName));
        return 0;
    }

    removeOldFiles();

    if (mode == DeleteCache) {
        QTime t;
        t.start();
        cacheDir.refresh();
        //qDebug() << "time to refresh the cacheDir QDir:" << t.elapsed();
        CacheCleaner cleaner(cacheDir);
        while (!cleaner.processSlice()) { }
        return 0;
    }

    QLocalServer lServer;
    QString socketFileName = KStandardDirs::locateLocal("socket", "kio_http_cache_cleaner");
    // we need to create the file by opening the socket, otherwise it won't work
    QFile::remove(socketFileName);
    lServer.listen(socketFileName);
    QList<QLocalSocket *> sockets;
    qint64 newBytesCounter = LLONG_MAX;  // force cleaner run on startup

    Scoreboard scoreboard;
    CacheCleaner *cleaner = 0;
    while (true) {
        g_currentDate = time(0);
        if (cleaner) {
            QCoreApplication::processEvents(QEventLoop::AllEvents, 100);
        } else {
            // We will not immediately know when a socket was disconnected. Causes:
            // - WaitForMoreEvents does not make processEvents() return when a socket disconnects
            // - WaitForMoreEvents *and* a timeout is not possible.
            QCoreApplication::processEvents(QEventLoop::WaitForMoreEvents);
        }
        if (!lServer.isListening()) {
            return 1;
        }
        lServer.waitForNewConnection(1);

        while (QLocalSocket *sock = lServer.nextPendingConnection()) {
            sock->waitForConnected();
            sockets.append(sock);
        }

        for (int i = 0; i < sockets.size(); i++) {
            QLocalSocket *sock = sockets[i];
            if (sock->state() != QLocalSocket::ConnectedState) {
                if (sock->state() != QLocalSocket::UnconnectedState) {
                    sock->waitForDisconnected();
                }
                delete sock;
                sockets.removeAll(sock);
                i--;
                continue;
            }
            sock->waitForReadyRead(0);
            while (true) {
                QByteArray recv = sock->read(80);
                if (recv.isEmpty()) {
                    break;
                }
                Q_ASSERT(recv.size() == 80);
                newBytesCounter += scoreboard.runCommand(recv);
            }
        }

        // interleave cleaning with serving ioslaves to reduce "garbage collection pauses"
        if (cleaner) {
            if (cleaner->processSlice(&scoreboard)) {
                // that was the last slice, done
                delete cleaner;
                cleaner = 0;
            }
        } else if (newBytesCounter > (g_maxCacheSize / 8)) {
            cacheDir.refresh();
            cleaner = new CacheCleaner(cacheDir);
            newBytesCounter = 0;
        }
    }
    return 0;
}