The QNetworkDiskCache class provides a very basic disk cache. More...

Inheritance diagram for QNetworkDiskCache:

Public Slots
void	clear ()

Public Slots inherited from QAbstractNetworkCache
virtual void	clear ()

Public Slots inherited from QObject
void	deleteLater ()

Public Methods
	QNetworkDiskCache (QObject *parent=nullptr)

	~QNetworkDiskCache ()

QString	cacheDirectory () const

qint64	cacheSize () const override

QIODevice *	data (const QUrl &url) override

QNetworkCacheMetaData	fileMetaData (const QString &fileName) const

void	insert (QIODevice *device) override

qint64	maximumCacheSize () const

QNetworkCacheMetaData	metaData (const QUrl &url) override

QIODevice *	prepare (const QNetworkCacheMetaData &metaData) override

bool	remove (const QUrl &url) override

void	setCacheDirectory (const QString &cacheDir)

void	setMaximumCacheSize (qint64 size)

void	updateMetaData (const QNetworkCacheMetaData &metaData) override

Public Methods inherited from QAbstractNetworkCache
virtual	~QAbstractNetworkCache ()

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Protected Methods
virtual qint64	expire ()

Protected Methods inherited from QAbstractNetworkCache
	QAbstractNetworkCache (QObject *parent=nullptr)

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Additional Inherited Members
Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Properties inherited from QObject
	objectName

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

The QNetworkDiskCache class provides a very basic disk cache. This class stores each url in its own file inside of the cacheDirectory using QDataStream. Files with a text MimeType are compressed using qCompress. Each cache file starts with "cache_" and ends in ".cache". Data is written to disk only in insert() and updateMetaData().

Currently you can not share the same cache files with more then one disk cache. By default this class limits the amount of space the cache will use on the system to 50MB. You have to set the cache directory before it will work.

A network disk cache can be enabled by doing the following.

QNetworkAccessManager *manager = new QNetworkAccessManager(this);
 
QNetworkDiskCache *diskCache   = new QNetworkDiskCache(this);
diskCache->setCacheDirectory("cacheDir");
 
manager->setCache(diskCache);

When sending requests to control the preference of when to use the cache and when to use the network, consider using the following code.

// do a normal request (preferred from network, as this is the default)
QNetworkRequest request(QUrl(QString("https://www.copperspice.com")));
manager->get(request);
 
// do a request preferred from cache
QNetworkRequest request2(QUrl(QString("https://www.copperspice.com")));
request2.setAttribute(QNetworkRequest::CacheLoadControlAttribute, QNetworkRequest::PreferCache);
manager->get(request2);

To check whether the response came from the cache or from the network, the following can be applied.

void replyFinished(QNetworkReply *reply) {
    QVariant fromCache = reply->attribute(QNetworkRequest::SourceIsFromCacheAttribute);
    qDebug() << "page from cache?" << fromCache.toBool();
}

See also: setCacheDirectory()

Constructor & Destructor Documentation

QNetworkDiskCache::QNetworkDiskCache ( QObject * parent = nullptr )

explicit

Creates a new disk cache. The parent argument is passed to QAbstractNetworkCache's constructor.

QNetworkDiskCache::~QNetworkDiskCache ( )

Destroys the cache object. This does not clear the disk cache.

Method Documentation

QString QNetworkDiskCache::cacheDirectory ( ) const

Returns the location where cached files will be stored.

See also: setCacheDirectory()

qint64 QNetworkDiskCache::cacheSize ( ) const

overridevirtual

Implements QAbstractNetworkCache::cacheSize()

void QNetworkDiskCache::clear ( )

slot

Reimplemented from QAbstractNetworkCache::clear()

QIODevice * QNetworkDiskCache::data ( const QUrl & url )

overridevirtual

Implements QAbstractNetworkCache::data()

qint64 QNetworkDiskCache::expire ( )

protectedvirtual

Cleans the cache so that its size is under the maximum cache size. Returns the current size of the cache.

When the current size of the cache is greater than the maximumCacheSize() older cache files are removed until the total size is less then 90% of maximumCacheSize() starting with the oldest ones first using the file creation date to determine how old a cache file is.

Subclasses can reimplement this function to change the order that cache files are removed taking into account information in the application knows about that QNetworkDiskCache does not, for example the number of times a cache is accessed.

Note: cacheSize() calls expire if the current cache size is unknown.

See also: maximumCacheSize(), fileMetaData()

QNetworkCacheMetaData QNetworkDiskCache::fileMetaData ( const QString & fileName ) const

Returns the QNetworkCacheMetaData for the cache file fileName.

If fileName is not a cache file QNetworkCacheMetaData will be invalid.

void QNetworkDiskCache::insert ( QIODevice * device )

overridevirtual

Implements QAbstractNetworkCache::insert()

qint64 QNetworkDiskCache::maximumCacheSize ( ) const

Returns the current maximum size in bytes for the disk cache.

See also: setMaximumCacheSize()

QNetworkCacheMetaData QNetworkDiskCache::metaData ( const QUrl & url )

overridevirtual

Implements QAbstractNetworkCache::metaData()

QIODevice * QNetworkDiskCache::prepare ( const QNetworkCacheMetaData & metaData )

overridevirtual

Implements QAbstractNetworkCache::prepare()

bool QNetworkDiskCache::remove ( const QUrl & url )

overridevirtual

Implements QAbstractNetworkCache::remove()

void QNetworkDiskCache::setCacheDirectory ( const QString & cacheDir )

Sets the directory where cached files will be stored to cacheDir. QNetworkDiskCache will create this directory if it does not exists. Prepared cache items will be stored in the new cache directory when they are inserted.

See also: cacheDirectory(), QStandardPaths::StandardLocation

void QNetworkDiskCache::setMaximumCacheSize ( qint64 size )

Sets the maximum size of the disk cache to be size in bytes. If the new size is smaller then the current cache size then the cache will call expire().

See also: maximumCacheSize()

void QNetworkDiskCache::updateMetaData ( const QNetworkCacheMetaData & metaData )

overridevirtual

Implements QAbstractNetworkCache::updateMetaData()

Public Slots

Public Methods

Protected Methods

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Method Documentation