The QBuffer class provides a QIODevice interface for a QByteArray. More...

Inheritance diagram for QBuffer:

Public Methods
	QBuffer (QByteArray buffer, QObject parent=nullptr)

	QBuffer (QObject *parent=nullptr)

	~QBuffer ()

bool	atEnd () const override

QByteArray &	buffer ()

const QByteArray &	buffer () const

bool	canReadLine () const override

void	close () override

const QByteArray &	data () const

bool	open (OpenMode openMode) override

qint64	pos () const override

bool	seek (qint64 pos) override

void	setBuffer (QByteArray *buffer)

void	setData (const char *data, int size)

void	setData (const QByteArray &buffer)

qint64	size () const override

Public Methods inherited from QIODevice
	QIODevice ()

	QIODevice (QObject *parent)

virtual	~QIODevice ()

virtual qint64	bytesAvailable () const

virtual qint64	bytesToWrite () const

QString	errorString () const

bool	getChar (char *c)

bool	isOpen () const

bool	isReadable () const

virtual bool	isSequential () const

bool	isTextModeEnabled () const

bool	isWritable () const

OpenMode	openMode () const

qint64	peek (char *data, qint64 maxSize)

QByteArray	peek (qint64 maxSize)

bool	putChar (char c)

qint64	read (char *data, qint64 maxSize)

QByteArray	read (qint64 maxSize)

QByteArray	readAll ()

qint64	readLine (char *data, qint64 maxSize)

QByteArray	readLine (qint64 maxSize=0)

virtual bool	reset ()

void	setTextModeEnabled (bool enabled)

void	ungetChar (char c)

virtual bool	waitForBytesWritten (int msecs)

virtual bool	waitForReadyRead (int msecs)

qint64	write (const char *data)

qint64	write (const char *data, qint64 maxSize)

qint64	write (const QByteArray &data)

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
void	connectNotify (const QMetaMethod &signalMethod) const override

void	disconnectNotify (const QMetaMethod &signalMethod) const override

qint64	readData (char *data, qint64 size) override

qint64	writeData (const char *data, qint64 size) override

Protected Methods inherited from QIODevice
virtual qint64	readLineData (char *data, qint64 maxSize)

void	setErrorString (const QString &errorString)

void	setOpenMode (OpenMode openMode)

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

virtual void	customEvent (QEvent *event)

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 Typedefs inherited from QIODevice
using	OpenMode = QFlags< OpenModeFlag >

Public Types inherited from QIODevice
enum	OpenModeFlag

Public Signals inherited from QIODevice
void	aboutToClose ()

void	bytesWritten (qint64 bytes)

void	readChannelFinished ()

void	readyRead ()

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

void	objectNameChanged (const QString &objectName)

Public Slots inherited from QObject
void	deleteLater ()

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 QBuffer class provides a QIODevice interface for a QByteArray. This class allows you to access a QByteArray using the QIODevice interface. The QByteArray is treated just as a standard random-accessed file.

QBuffer buffer;
char ch;
 
buffer.open(QBuffer::ReadWrite);
buffer.write("CopperSpice is cool");
buffer.seek(0);
buffer.getChar(&ch);  // ch == 'C'
buffer.getChar(&ch);  // ch == 'o'
buffer.getChar(&ch);  // ch == 'p'
buffer.getChar(&ch);  // ch == 'p'
buffer.getChar(&ch);  // ch == 'e'
buffer.getChar(&ch);  // ch == 'r'

By default, an internal QByteArray buffer is created for you when you create a QBuffer. You can access this buffer directly by calling buffer(). You can also use QBuffer with an existing QByteArray by calling setBuffer() or by passing your array to the QBuffer constructor.

Call open() to open the buffer. Then call write() or putChar() to write to the buffer, and read(), readLine(), readAll(), or getChar() to read from it. size() returns the current size of the buffer, and you can seek to arbitrary positions in the buffer by calling seek(). When you are done with accessing the buffer, call close().

The following code shows how to write data to a QByteArray using QDataStream and QBuffer.

QByteArray byteArray;
QBuffer buffer(&byteArray);
buffer.open(QIODevice::WriteOnly);
 
QDataStream out(&buffer);
out << QApplication::palette();

Effectively, we convert the application's QPalette into a byte array. This is an example of how to read the data from the QByteArray.

QPalette palette;
QBuffer buffer(&byteArray);
buffer.open(QIODevice::ReadOnly);
 
QDataStream in(&buffer);
in >> palette;

QTextStream and QDataStream also provide constructors which take a QByteArray and create a QBuffer.

QBuffer emits readyRead() when new data has arrived in the buffer. By connecting to this signal, you can use QBuffer to store temporary data before processing it. For example, you can pass the buffer to QFtp when downloading a file from an FTP server. Whenever a new payload of data has been downloaded, readyRead() is emitted, and you can process the data that just arrived. QBuffer also emits bytesWritten() every time new data has been written to the buffer.

See also: QFile, QDataStream, QTextStream, QByteArray

Constructor & Destructor Documentation

QBuffer::QBuffer ( QObject * parent = nullptr )

explicit

Constructs an empty buffer with the given parent. You can call setData() to fill the buffer with data, or you can open it in write mode and use write().

See also: open()

QBuffer::QBuffer	(	QByteArray *	buffer,
		QObject *	parent = `nullptr`
	)

Constructs a QBuffer that uses the QByteArray pointed to by buffer as its internal buffer, and with the given parent. The caller is responsible for ensuring that buffer remains valid until the QBuffer is destroyed, or until setBuffer() is called to change the buffer. QBuffer does not take ownership of the QByteArray.

If you open the buffer in write-only mode or read-write mode and write something into the QBuffer, buffer will be modified.

QByteArray data("abc");
 
QBuffer buffer(&data);
buffer.open(QIODevice::WriteOnly);
 
buffer.seek(3);
buffer.write("def", 3);
buffer.close();                             // data == "abcdef"

See also: open(), setBuffer(), setData()

QBuffer::~QBuffer ( )

Destroys the buffer.

Method Documentation

bool QBuffer::atEnd ( ) const

overridevirtual

Reimplemented from QIODevice::atEnd()

QByteArray & QBuffer::buffer ( )

Returns a reference to the QBuffer's internal buffer. You can use it to modify the QByteArray.

See also: setBuffer(), data()

const QByteArray & QBuffer::buffer ( ) const

Equivalent to calling data().

bool QBuffer::canReadLine ( ) const

overridevirtual

Reimplemented from QIODevice::canReadLine()

void QBuffer::close ( )

overridevirtual

Reimplemented from QIODevice::close()

void QBuffer::connectNotify ( const QMetaMethod & signalMethod ) const

overrideprotectedvirtual

This method is called when a connection has been made to signalMethod in this object.

See also: connect(), disconnectNotify()

Reimplemented from QObject::connectNotify()

const QByteArray & QBuffer::data ( ) const

Returns the data contained in the buffer. Equivalent to calling buffer().

See also: setData(), setBuffer()

void QBuffer::disconnectNotify ( const QMetaMethod & signalMethod ) const

overrideprotectedvirtual

This method is called when a slot is disconnected from signalMethod in this object.

See also: disconnect(), connectNotify()

Reimplemented from QObject::disconnectNotify()

bool QBuffer::open ( OpenMode openMode )

overridevirtual

Reimplemented from QIODevice::open()

qint64 QBuffer::pos ( ) const

overridevirtual

Reimplemented from QIODevice::pos()

qint64 QBuffer::readData	(	char *	data,
		qint64	size
	)

overrideprotectedvirtual

Implements QIODevice::readData()

bool QBuffer::seek ( qint64 pos )

overridevirtual

Reimplemented from QIODevice::seek()

void QBuffer::setBuffer ( QByteArray * buffer )

Makes QBuffer uses the QByteArray pointed to by buffer as its internal buffer. The caller is responsible for ensuring that byteArray remains valid until the QBuffer is destroyed, or until setBuffer() is called to change the buffer. QBuffer does not take ownership of the QByteArray.

Does nothing if isOpen() is true.

If you open the buffer in write-only mode or read-write mode and write something buffer will be modified.

QByteArray data("abc");
 
QBuffer buffer(&data);
buffer.open(QIODevice::WriteOnly);
 
buffer.seek(3);
buffer.write("def", 3);
buffer.close();                             // data == "abcdef"

If buffer is a nullptr the QBuffer creates its own internal QByteArray. This byte array is initially empty.

See also: buffer(), setData(), open()

void QBuffer::setData	(	const char *	data,
		int	size
	)

inline

Sets the contents of the internal buffer to be the first size bytes of data.

void QBuffer::setData ( const QByteArray & buffer )

Sets the contents of the internal buffer to be buffer. This is the same as assigning data to buffer(). This method does nothing if isOpen() is true.

See also: data(), setBuffer()

qint64 QBuffer::size ( ) const

overridevirtual

Reimplemented from QIODevice::size()

qint64 QBuffer::writeData	(	const char *	data,
		qint64	size
	)

overrideprotectedvirtual

Implements QIODevice::writeData()

Public Methods

Protected Methods

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Method Documentation