qnetworkdiskcache.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
//#define QNETWORKDISKCACHE_DEBUG
 
 
#include "qnetworkdiskcache.h"
#include "qnetworkdiskcache_p.h"
#include "QtCore/qscopedpointer.h"
 
#include <qfile.h>
#include <qdir.h>
#include <qdatastream.h>
#include <qdatetime.h>
#include <qdiriterator.h>
#include <qurl.h>
#include <qcryptographichash.h>
#include <qdebug.h>
 
#include <memory>
 
#define CACHE_POSTFIX ".d"_L1
#define CACHE_VERSION 8
#define DATA_DIR "data"_L1
 
#define MAX_COMPRESSION_SIZE (1024 * 1024 * 3)
 
QT_BEGIN_NAMESPACE
 
using namespace Qt::StringLiterals;
 
QNetworkDiskCache::QNetworkDiskCache(QObject *parent)
    : QAbstractNetworkCache(*new QNetworkDiskCachePrivate, parent)
{
}
 
QNetworkDiskCache::~QNetworkDiskCache()
{
    Q_D(QNetworkDiskCache);
    qDeleteAll(d->inserting);
}
 
QString QNetworkDiskCache::cacheDirectory() const
{
    Q_D(const QNetworkDiskCache);
    return d->cacheDirectory;
}
 
void QNetworkDiskCache::setCacheDirectory(const QString &cacheDir)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::setCacheDirectory()" << cacheDir;
#endif
    Q_D(QNetworkDiskCache);
    if (cacheDir.isEmpty())
        return;
    d->cacheDirectory = cacheDir;
    QDir dir(d->cacheDirectory);
    d->cacheDirectory = dir.absolutePath();
    if (!d->cacheDirectory.endsWith(u'/'))
        d->cacheDirectory += u'/';
 
    d->dataDirectory = d->cacheDirectory + DATA_DIR + QString::number(CACHE_VERSION) + u'/';
    d->prepareLayout();
}
 
qint64 QNetworkDiskCache::cacheSize() const
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug("QNetworkDiskCache::cacheSize()");
#endif
    Q_D(const QNetworkDiskCache);
    if (d->cacheDirectory.isEmpty())
        return 0;
    if (d->currentCacheSize < 0) {
        QNetworkDiskCache *that = const_cast<QNetworkDiskCache*>(this);
        that->d_func()->currentCacheSize = that->expire();
    }
    return d->currentCacheSize;
}
 
QIODevice *QNetworkDiskCache::prepare(const QNetworkCacheMetaData &metaData)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::prepare()" << metaData.url();
#endif
    Q_D(QNetworkDiskCache);
    if (!metaData.isValid() || !metaData.url().isValid() || !metaData.saveToDisk())
        return nullptr;
 
    if (d->cacheDirectory.isEmpty()) {
        qWarning("QNetworkDiskCache::prepare() The cache directory is not set");
        return nullptr;
    }
 
    const auto headers = metaData.rawHeaders();
    for (const auto &header : headers) {
        if (header.first.compare("content-length", Qt::CaseInsensitive) == 0) {
            const qint64 size = header.second.toLongLong();
            if (size > (maximumCacheSize() * 3)/4)
                return nullptr;
            break;
        }
    }
    std::unique_ptr<QCacheItem> cacheItem = std::make_unique<QCacheItem>();
    cacheItem->metaData = metaData;
 
    QIODevice *device = nullptr;
    if (cacheItem->canCompress()) {
        cacheItem->data.open(QBuffer::ReadWrite);
        device = &(cacheItem->data);
    } else {
        QString fileName = d->cacheFileName(cacheItem->metaData.url());
        QT_TRY {
            cacheItem->file = new QSaveFile(fileName, &cacheItem->data);
        } QT_CATCH(...) {
            cacheItem->file = nullptr;
        }
        if (!cacheItem->file || !cacheItem->file->open(QFileDevice::WriteOnly)) {
            qWarning("QNetworkDiskCache::prepare() unable to open temporary file");
            cacheItem.reset();
            return nullptr;
        }
        cacheItem->writeHeader(cacheItem->file);
        device = cacheItem->file;
    }
    d->inserting[device] = cacheItem.release();
    return device;
}
 
void QNetworkDiskCache::insert(QIODevice *device)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::insert()" << device;
#endif
    Q_D(QNetworkDiskCache);
    const auto it = d->inserting.constFind(device);
    if (Q_UNLIKELY(it == d->inserting.cend())) {
        qWarning() << "QNetworkDiskCache::insert() called on a device we don't know about" << device;
        return;
    }
 
    d->storeItem(it.value());
    delete it.value();
    d->inserting.erase(it);
}
 
 
void QNetworkDiskCachePrivate::prepareLayout()
{
    QDir helper;
 
    //Create directory and subdirectories 0-F
    helper.mkpath(dataDirectory);
    for (uint i = 0; i < 16 ; i++) {
        QString str = QString::number(i, 16);
        QString subdir = dataDirectory + str;
        helper.mkdir(subdir);
    }
}
 
 
void QNetworkDiskCachePrivate::storeItem(QCacheItem *cacheItem)
{
    Q_Q(QNetworkDiskCache);
    Q_ASSERT(cacheItem->metaData.saveToDisk());
 
    QString fileName = cacheFileName(cacheItem->metaData.url());
    Q_ASSERT(!fileName.isEmpty());
 
    if (QFile::exists(fileName)) {
        if (!removeFile(fileName)) {
            qWarning() << "QNetworkDiskCache: couldn't remove the cache file " << fileName;
            return;
        }
    }
 
    currentCacheSize = q->expire();
    if (!cacheItem->file) {
        cacheItem->file = new QSaveFile(fileName, &cacheItem->data);
        if (cacheItem->file->open(QFileDevice::WriteOnly)) {
            cacheItem->writeHeader(cacheItem->file);
            cacheItem->writeCompressedData(cacheItem->file);
        }
    }
 
    if (cacheItem->file
        && cacheItem->file->isOpen()
        && cacheItem->file->error() == QFileDevice::NoError) {
        // We have to call size() here instead of inside the if-body because
        // commit() invalidates the file-engine, and size() will create a new
        // one, pointing at an empty filename.
        qint64 size = cacheItem->file->size();
        if (cacheItem->file->commit())
            currentCacheSize += size;
        // Delete and unset the QSaveFile, it's invalid now.
        delete std::exchange(cacheItem->file, nullptr);
    }
    if (cacheItem->metaData.url() == lastItem.metaData.url())
        lastItem.reset();
}
 
bool QNetworkDiskCache::remove(const QUrl &url)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::remove()" << url;
#endif
    Q_D(QNetworkDiskCache);
 
    // remove is also used to cancel insertions, not a common operation
    for (auto it = d->inserting.cbegin(), end = d->inserting.cend(); it != end; ++it) {
        QCacheItem *item = it.value();
        if (item && item->metaData.url() == url) {
            delete item;
            d->inserting.erase(it);
            return true;
        }
    }
 
    if (d->lastItem.metaData.url() == url)
        d->lastItem.reset();
    return d->removeFile(d->cacheFileName(url));
}
 
bool QNetworkDiskCachePrivate::removeFile(const QString &file)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::removFile()" << file;
#endif
    if (file.isEmpty())
        return false;
    QFileInfo info(file);
    QString fileName = info.fileName();
    if (!fileName.endsWith(CACHE_POSTFIX))
        return false;
    qint64 size = info.size();
    if (QFile::remove(file)) {
        currentCacheSize -= size;
        return true;
    }
    return false;
}
 
QNetworkCacheMetaData QNetworkDiskCache::metaData(const QUrl &url)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::metaData()" << url;
#endif
    Q_D(QNetworkDiskCache);
    if (d->lastItem.metaData.url() == url)
        return d->lastItem.metaData;
    return fileMetaData(d->cacheFileName(url));
}
 
QNetworkCacheMetaData QNetworkDiskCache::fileMetaData(const QString &fileName) const
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::fileMetaData()" << fileName;
#endif
    Q_D(const QNetworkDiskCache);
    QFile file(fileName);
    if (!file.open(QFile::ReadOnly))
        return QNetworkCacheMetaData();
    if (!d->lastItem.read(&file, false)) {
        file.close();
        QNetworkDiskCachePrivate *that = const_cast<QNetworkDiskCachePrivate*>(d);
        that->removeFile(fileName);
    }
    return d->lastItem.metaData;
}
 
QIODevice *QNetworkDiskCache::data(const QUrl &url)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::data()" << url;
#endif
    Q_D(QNetworkDiskCache);
    std::unique_ptr<QBuffer> buffer;
    if (!url.isValid())
        return nullptr;
    if (d->lastItem.metaData.url() == url && d->lastItem.data.isOpen()) {
        buffer.reset(new QBuffer);
        buffer->setData(d->lastItem.data.data());
    } else {
        QScopedPointer<QFile> file(new QFile(d->cacheFileName(url)));
        if (!file->open(QFile::ReadOnly | QIODevice::Unbuffered))
            return nullptr;
 
        if (!d->lastItem.read(file.data(), true)) {
            file->close();
            remove(url);
            return nullptr;
        }
        if (d->lastItem.data.isOpen()) {
            // compressed
            buffer.reset(new QBuffer);
            buffer->setData(d->lastItem.data.data());
        } else {
            buffer.reset(new QBuffer);
            buffer->setData(file->readAll());
        }
    }
    buffer->open(QBuffer::ReadOnly);
    return buffer.release();
}
 
void QNetworkDiskCache::updateMetaData(const QNetworkCacheMetaData &metaData)
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug() << "QNetworkDiskCache::updateMetaData()" << metaData.url();
#endif
    QUrl url = metaData.url();
    QIODevice *oldDevice = data(url);
    if (!oldDevice) {
#if defined(QNETWORKDISKCACHE_DEBUG)
        qDebug("QNetworkDiskCache::updateMetaData(), no device!");
#endif
        return;
    }
 
    QIODevice *newDevice = prepare(metaData);
    if (!newDevice) {
#if defined(QNETWORKDISKCACHE_DEBUG)
        qDebug() << "QNetworkDiskCache::updateMetaData(), no new device!" << url;
#endif
        return;
    }
    char data[1024];
    while (!oldDevice->atEnd()) {
        qint64 s = oldDevice->read(data, 1024);
        newDevice->write(data, s);
    }
    delete oldDevice;
    insert(newDevice);
}
 
qint64 QNetworkDiskCache::maximumCacheSize() const
{
    Q_D(const QNetworkDiskCache);
    return d->maximumCacheSize;
}
 
void QNetworkDiskCache::setMaximumCacheSize(qint64 size)
{
    Q_D(QNetworkDiskCache);
    bool expireCache = (size < d->maximumCacheSize);
    d->maximumCacheSize = size;
    if (expireCache)
        d->currentCacheSize = expire();
}
 
qint64 QNetworkDiskCache::expire()
{
    Q_D(QNetworkDiskCache);
    if (d->currentCacheSize >= 0 && d->currentCacheSize < maximumCacheSize())
        return d->currentCacheSize;
 
    if (cacheDirectory().isEmpty()) {
        qWarning("QNetworkDiskCache::expire() The cache directory is not set");
        return 0;
    }
 
    // close file handle to prevent "in use" error when QFile::remove() is called
    d->lastItem.reset();
 
    const QDir::Filters filters = QDir::AllDirs | QDir:: Files | QDir::NoDotAndDotDot;
    QDirIterator it(cacheDirectory(), filters, QDirIterator::Subdirectories);
 
    struct CacheItem
    {
        std::chrono::milliseconds msecs;
        QString path;
        qint64 size = 0;
    };
    std::vector<CacheItem> cacheItems;
    qint64 totalSize = 0;
    while (it.hasNext()) {
        QFileInfo info = it.nextFileInfo();
        if (!info.fileName().endsWith(CACHE_POSTFIX))
            continue;
 
        QDateTime fileTime = info.birthTime(QTimeZone::UTC);
        if (!fileTime.isValid())
            fileTime = info.metadataChangeTime(QTimeZone::UTC);
        const std::chrono::milliseconds msecs{fileTime.toMSecsSinceEpoch()};
        const qint64 size = info.size();
        cacheItems.push_back(CacheItem{msecs, info.filePath(), size});
        totalSize += size;
    }
 
    const qint64 goal = (maximumCacheSize() * 9) / 10;
    if (totalSize < goal)
        return totalSize; // Nothing to do
 
    auto byFileTime = [&](const auto &a, const auto &b) { return a.msecs < b.msecs; };
    std::sort(cacheItems.begin(), cacheItems.end(), byFileTime);
 
    [[maybe_unused]] int removedFiles = 0; // used under QNETWORKDISKCACHE_DEBUG
    for (const CacheItem &cached : cacheItems) {
        QFile::remove(cached.path);
        ++removedFiles;
        totalSize -= cached.size;
        if (totalSize < goal)
            break;
    }
#if defined(QNETWORKDISKCACHE_DEBUG)
    if (removedFiles > 0) {
        qDebug() << "QNetworkDiskCache::expire()"
                << "Removed:" << removedFiles
                << "Kept:" << cacheItems.count() - removedFiles;
    }
#endif
    return totalSize;
}
 
void QNetworkDiskCache::clear()
{
#if defined(QNETWORKDISKCACHE_DEBUG)
    qDebug("QNetworkDiskCache::clear()");
#endif
    Q_D(QNetworkDiskCache);
    qint64 size = d->maximumCacheSize;
    d->maximumCacheSize = 0;
    d->currentCacheSize = expire();
    d->maximumCacheSize = size;
}
 
QString QNetworkDiskCachePrivate::uniqueFileName(const QUrl &url)
{
    QUrl cleanUrl = url;
    cleanUrl.setPassword(QString());
    cleanUrl.setFragment(QString());
 
    const QByteArray hash = QCryptographicHash::hash(cleanUrl.toEncoded(), QCryptographicHash::Sha1);
    // convert sha1 to base36 form and return first 8 bytes for use as string
    const QByteArray id = QByteArray::number(*(qlonglong*)hash.data(), 36).left(8);
    // generates <one-char subdir>/<8-char filename.d>
    uint code = (uint)id.at(id.size()-1) % 16;
    QString pathFragment = QString::number(code, 16) + u'/' + QLatin1StringView(id) + CACHE_POSTFIX;
 
    return pathFragment;
}
 
QString QNetworkDiskCachePrivate::cacheFileName(const QUrl &url) const
{
    if (!url.isValid())
        return QString();
 
    QString fullpath = dataDirectory + uniqueFileName(url);
    return  fullpath;
}
 
bool QCacheItem::canCompress() const
{
    bool sizeOk = false;
    bool typeOk = false;
    const auto headers = metaData.rawHeaders();
    for (const auto &header : headers) {
        if (header.first.compare("content-length", Qt::CaseInsensitive) == 0) {
            qint64 size = header.second.toLongLong();
            if (size > MAX_COMPRESSION_SIZE)
                return false;
            else
                sizeOk = true;
        }
 
        if (header.first.compare("content-type", Qt::CaseInsensitive) == 0) {
            QByteArray type = header.second;
            if (type.startsWith("text/")
                    || (type.startsWith("application/")
                        && (type.endsWith("javascript") || type.endsWith("ecmascript"))))
                typeOk = true;
            else
                return false;
        }
        if (sizeOk && typeOk)
            return true;
    }
    return false;
}
 
enum
{
    CacheMagic = 0xe8,
    CurrentCacheVersion = CACHE_VERSION
};
 
void QCacheItem::writeHeader(QFileDevice *device) const
{
    QDataStream out(device);
 
    out << qint32(CacheMagic);
    out << qint32(CurrentCacheVersion);
    out << static_cast<qint32>(out.version());
    out << metaData;
    bool compressed = canCompress();
    out << compressed;
}
 
void QCacheItem::writeCompressedData(QFileDevice *device) const
{
    QDataStream out(device);
 
    out << qCompress(data.data());
}
 
bool QCacheItem::read(QFileDevice *device, bool readData)
{
    reset();
 
    QDataStream in(device);
 
    qint32 marker;
    qint32 v;
    in >> marker;
    in >> v;
    if (marker != CacheMagic)
        return true;
 
    // If the cache magic is correct, but the version is not we should remove it
    if (v != CurrentCacheVersion)
        return false;
 
    qint32 streamVersion;
    in >> streamVersion;
    // Default stream version is also the highest we can handle
    if (streamVersion > in.version())
        return false;
    in.setVersion(streamVersion);
 
    bool compressed;
    QByteArray dataBA;
    in >> metaData;
    in >> compressed;
    if (readData && compressed) {
        in >> dataBA;
        data.setData(qUncompress(dataBA));
        data.open(QBuffer::ReadOnly);
    }
 
    // quick and dirty check if metadata's URL field and the file's name are in synch
    QString expectedFilename = QNetworkDiskCachePrivate::uniqueFileName(metaData.url());
    if (!device->fileName().endsWith(expectedFilename))
        return false;
 
    return metaData.isValid() && !metaData.rawHeaders().isEmpty();
}
 
QT_END_NAMESPACE
 
#include "moc_qnetworkdiskcache.cpp"