\inmodule QtCore \reentrant More...

#include <qbuffer.h>

Inheritance diagram for QBuffer:

Collaboration diagram for QBuffer:

Public Member Functions
	QBuffer (QObject *parent=nullptr)
	Constructs an empty buffer with the given parent.

	QBuffer (QByteArray buf, QObject parent=nullptr)
	Constructs a QBuffer that uses the QByteArray pointed to by byteArray as its internal buffer, and with the given parent.

	~QBuffer ()
	Destroys the buffer.

QByteArray &	buffer ()
	Returns a reference to the QBuffer's internal buffer.

const QByteArray &	buffer () const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.This is the same as data().

void	setBuffer (QByteArray *a)
	Makes QBuffer use the QByteArray pointed to by byteArray as its internal buffer.

void	setData (const QByteArray &data)
	Sets the contents of the internal buffer to be data.

void	setData (const char *data, qsizetype len)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets the contents of the internal buffer to be the first size bytes of data.

const QByteArray &	data () const
	Returns the data contained in the buffer.

bool	open (OpenMode openMode) override
	\reimp

void	close () override
	\reimp

qint64	size () const override
	\reimp

qint64	pos () const override
	\reimp

bool	seek (qint64 off) override
	\reimp

bool	atEnd () const override
	\reimp

bool	canReadLine () const override
	\reimp

Public Member Functions inherited from QIODevice
	QIODevice ()
	Constructs a QIODevice object.

	QIODevice (QObject *parent)
	Constructs a QIODevice object with the given parent.

virtual	~QIODevice ()
	The destructor is virtual, and QIODevice is an abstract base class.

QIODeviceBase::OpenMode	openMode () const
	Returns the mode in which the device has been opened; i.e.

void	setTextModeEnabled (bool enabled)
	If enabled is true, this function sets the \l Text flag on the device; otherwise the \l Text flag is removed.

bool	isTextModeEnabled () const
	Returns `true` if the \l Text flag is enabled; otherwise returns `false`.

bool	isOpen () const
	Returns `true` if the device is open; otherwise returns `false`.

bool	isReadable () const
	Returns `true` if data can be read from the device; otherwise returns false.

bool	isWritable () const
	Returns `true` if data can be written to the device; otherwise returns false.

virtual bool	isSequential () const
	Returns `true` if this device is sequential; otherwise returns false.

int	readChannelCount () const

int	writeChannelCount () const

int	currentReadChannel () const

void	setCurrentReadChannel (int channel)

int	currentWriteChannel () const

void	setCurrentWriteChannel (int channel)

virtual bool	open (QIODeviceBase::OpenMode mode)
	Opens the device and sets its OpenMode to mode.

virtual bool	reset ()
	Seeks to the start of input for random-access devices.

virtual qint64	bytesAvailable () const
	Returns the number of bytes that are available for reading.

virtual qint64	bytesToWrite () const
	For buffered devices, this function returns the number of bytes waiting to be written.

qint64	read (char *data, qint64 maxlen)
	Reads at most maxSize bytes from the device into data, and returns the number of bytes read.

QByteArray	read (qint64 maxlen)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads at most maxSize bytes from the device, and returns the data read as a QByteArray.

QByteArray	readAll ()
	Reads all remaining data from the device, and returns it as a byte array.

qint64	readLine (char *data, qint64 maxlen)
	This function reads a line of ASCII characters from the device, up to a maximum of maxSize - 1 bytes, stores the characters in data, and returns the number of bytes read.

QByteArray	readLine (qint64 maxlen=0)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a line from the device, but no more than maxSize characters, and returns the result as a byte array.

bool	readLineInto (QByteArray *result, qint64 maxlen=0)

void	startTransaction ()

void	commitTransaction ()

void	rollbackTransaction ()

bool	isTransactionStarted () const

qint64	write (const char *data, qint64 len)
	Writes at most maxSize bytes of data from data to the device.

qint64	write (const char *data)

qint64	write (const QByteArray &data)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes the content of data to the device.

qint64	peek (char *data, qint64 maxlen)

QByteArray	peek (qint64 maxlen)

qint64	skip (qint64 maxSize)

virtual bool	waitForReadyRead (int msecs)
	Blocks until new data is available for reading and the readyRead() signal has been emitted, or until msecs milliseconds have passed.

virtual bool	waitForBytesWritten (int msecs)
	For buffered devices, this function waits until a payload of buffered written data has been written to the device and the bytesWritten() signal has been emitted, or until msecs milliseconds have passed.

void	ungetChar (char c)
	Puts the character c back into the device, and decrements the current position unless the position is 0.

bool	putChar (char c)
	Writes the character c to the device.

bool	getChar (char *c)
	Reads one character from the device and stores it in c.

QString	errorString () const
	Returns a human-readable description of the last device error that occurred.

Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)
	Constructs an object with parent object parent.

virtual	~QObject ()
	Destroys the object, deleting all its child objects.

virtual bool	event (QEvent *event)
	This virtual function receives events to an object and should return true if the event e was recognized and processed.

virtual bool	eventFilter (QObject watched, QEvent event)
	Filters events if this object has been installed as an event filter for the watched object.

QString	objectName () const

Q_WEAK_OVERLOAD void	setObjectName (const QString &name)
	Sets the object's name to name.

void	setObjectName (QAnyStringView name)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QBindable< QString >	bindableObjectName ()

bool	isWidgetType () const
	Returns `true` if the object is a widget; otherwise returns `false`.

bool	isWindowType () const
	Returns `true` if the object is a window; otherwise returns `false`.

bool	isQuickItemType () const
	Returns `true` if the object is a QQuickItem; otherwise returns `false`.

bool	signalsBlocked () const noexcept
	Returns `true` if signals are blocked; otherwise returns `false`.

bool	blockSignals (bool b) noexcept
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it).

QThread *	thread () const
	Returns the thread in which the object lives.

bool	moveToThread (QThread *thread QT6_DECL_NEW_OVERLOAD_TAIL)
	Changes the thread affinity for this object and its children and returns `true` on success.

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
	This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.

int	startTimer (std::chrono::nanoseconds time, Qt::TimerType timerType=Qt::CoarseTimer)

void	killTimer (int id)
	Kills the timer with timer identifier, id.

void	killTimer (Qt::TimerId id)

template<typename T >
T	findChild (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.

template<typename T >
QList< T >	findChildren (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects.

template<typename T >
T	findChild (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

template<typename T >
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

const QObjectList &	children () const
	Returns a list of child objects.

void	setParent (QObject *parent)
	Makes the object a child of parent.

void	installEventFilter (QObject *filterObj)
	Installs an event filter filterObj on this object.

void	removeEventFilter (QObject *obj)
	Removes an event filter object obj from this object.

QMetaObject::Connection	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const

bool	disconnect (const char signal=nullptr, const QObject receiver=nullptr, const char *member=nullptr) const

bool	disconnect (const QObject receiver, const char member=nullptr) const

void	dumpObjectTree () const
	Dumps a tree of children to the debug output.

void	dumpObjectInfo () const
	Dumps information about signal connections, etc.

bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value.

bool	setProperty (const char *name, QVariant &&value)

QVariant	property (const char *name) const
	Returns the value of the object's name property.

QList< QByteArray >	dynamicPropertyNames () const

QBindingStorage *	bindingStorage ()

const QBindingStorage *	bindingStorage () const

QObject *	parent () const
	Returns a pointer to the parent object.

bool	inherits (const char *classname) const
	Returns `true` if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns `false`.

Protected Member Functions
void	connectNotify (const QMetaMethod &) override
	\reimp

void	disconnectNotify (const QMetaMethod &) override
	\reimp

qint64	readData (char *data, qint64 maxlen) override
	\reimp

qint64	writeData (const char *data, qint64 len) override
	\reimp

Protected Member Functions inherited from QIODevice
	QIODevice (QIODevicePrivate &dd, QObject *parent=nullptr)

virtual qint64	readLineData (char *data, qint64 maxlen)
	Reads up to maxSize characters into data and returns the number of characters read.

virtual qint64	skipData (qint64 maxSize)

void	setOpenMode (QIODeviceBase::OpenMode openMode)
	Sets the OpenMode of the device to openMode.

void	setErrorString (const QString &errorString)
	Sets the human readable description of the last device error that occurred to str.

Protected Member Functions inherited from QObject
QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns \nullptr.

int	senderSignalIndex () const

int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal.

bool	isSignalConnected (const QMetaMethod &signal) const

virtual void	timerEvent (QTimerEvent *event)
	This event handler can be reimplemented in a subclass to receive timer events for the object.

virtual void	childEvent (QChildEvent *event)
	This event handler can be reimplemented in a subclass to receive child events.

virtual void	customEvent (QEvent *event)
	This event handler can be reimplemented in a subclass to receive custom events.

	QObject (QObjectPrivate &dd, QObject *parent=nullptr)

Protected Member Functions inherited from QIODeviceBase
	~QIODeviceBase ()=default

Additional Inherited Members
Public Types inherited from QIODeviceBase
enum	OpenModeFlag { NotOpen = 0x0000 , ReadOnly = 0x0001 , WriteOnly = 0x0002 , ReadWrite = ReadOnly \| WriteOnly , Append = 0x0004 , Truncate = 0x0008 , Text = 0x0010 , Unbuffered = 0x0020 , NewOnly = 0x0040 , ExistingOnly = 0x0080 }
	This enum is used with QIODevice::open() to describe the mode in which a device is opened. More...

Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

Signals inherited from QIODevice
void	readyRead ()
	This signal is emitted once every time new data is available for reading from the device's current read channel.

void	channelReadyRead (int channel)

void	bytesWritten (qint64 bytes)
	This signal is emitted every time a payload of data has been written to the device's current write channel.

void	channelBytesWritten (int channel, qint64 bytes)

void	aboutToClose ()
	This signal is emitted when the device is about to close.

void	readChannelFinished ()

Signals inherited from QObject
void	destroyed (QObject *=nullptr)
	This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.

void	objectNameChanged (const QString &objectName, QPrivateSignal)
	This signal is emitted after the object's name has been changed.

Static Public Member Functions inherited from QObject
static QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	\threadsafe

static QMetaObject::Connection	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	\threadsafe

static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)

static bool	disconnect (const QMetaObject::Connection &)
	Disconnect a connection.

template<typename Func1 , typename Func2 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object receiver, Func2 slot)

template<typename Func1 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject receiver, void **zero)

Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Properties inherited from QObject
QString	objectName
	the name of this object

Related Symbols inherited from QObject
template< class T > T	qobject_cast (const QObject *object)
	Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.

template< typename T > T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

template< typename T > QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()

	QObjectList
	\macro Q_CLASSINFO(Name, Value)

Detailed Description

\inmodule QtCore \reentrant

The QBuffer class provides a QIODevice interface for a QByteArray.

QBuffer allows you to access a QByteArray using the QIODevice interface. The QByteArray is treated just as a standard random-accessed file. Example:

    QBuffer buffer;
    char ch;
 
    buffer.open(QBuffer::ReadWrite);
    buffer.write("Qt rocks!");
    buffer.seek(0);
    buffer.getChar(&ch);  // ch == 'Q'
    buffer.getChar(&ch);  // ch == 't'
    buffer.getChar(&ch);  // ch == ' '
    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 QBuffer's 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 snippet 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. Here's 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 convenience constructors that take a QByteArray and that create a QBuffer behind the scenes.

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. QBuffer also emits bytesWritten() every time new data has been written to the buffer.

See also: QFile, QDataStream, QTextStream, QByteArray

Definition at line 15 of file qbuffer.h.

Constructor & Destructor Documentation

◆ QBuffer() [1/2]

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()

Definition at line 133 of file qbuffer.cpp.

◆ QBuffer() [2/2]

QBuffer::QBuffer	(	QByteArray *	byteArray,
		QObject *	parent = nullptr )

Constructs a QBuffer that uses the QByteArray pointed to by byteArray as its internal buffer, and with the given parent.

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 doesn't take ownership of the QByteArray.

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

Example:

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

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

Definition at line 157 of file qbuffer.cpp.

◆ ~QBuffer()

QBuffer::~QBuffer ( )

Destroys the buffer.

Definition at line 170 of file qbuffer.cpp.

Member Function Documentation

◆ atEnd()

bool QBuffer::atEnd ( ) const

overridevirtual

\reimp

Reimplemented from QIODevice.

Definition at line 364 of file qbuffer.cpp.

◆ buffer() [1/2]

QByteArray & QBuffer::buffer ( )

Returns a reference to the QBuffer's internal buffer.

You can use it to modify the QByteArray behind the QBuffer's back.

See also: setBuffer(), data()

Definition at line 218 of file qbuffer.cpp.

Here is the caller graph for this function:

◆ buffer() [2/2]

Makes QBuffer use the QByteArray pointed to by byteArray 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 doesn't 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 into the QBuffer, byteArray will be modified.

Example:

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

If byteArray is \nullptr, the buffer creates its own internal QByteArray to work on. This byte array is initially empty.

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

Definition at line 196 of file qbuffer.cpp.

◆ setData() [1/2]

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

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets the contents of the internal buffer to be the first size bytes of data.

Note: In Qt versions prior to 6.5, this function took the length as an {int} parameter, potentially truncating sizes.

Definition at line 278 of file qbuffer.cpp.

◆ setData() [2/2]

void QBuffer::setData ( const QByteArray & data )

Sets the contents of the internal buffer to be data.

This is the same as assigning data to buffer().

Does nothing if isOpen() is true.

See also: setBuffer()

Definition at line 259 of file qbuffer.cpp.

◆ size()

qint64 QBuffer::size ( ) const

overridevirtual

\reimp

Reimplemented from QIODevice.

Definition at line 331 of file qbuffer.cpp.

◆ writeData()

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

overrideprotectedvirtual

\reimp

Implements QIODevice.

Definition at line 396 of file qbuffer.cpp.

The documentation for this class was generated from the following files:

qtbase/src/corelib/io/qbuffer.h (52c5f286950a56a8714a0be9b8ecb088f07d7eb8)
qtbase/src/corelib/io/qbuffer.cpp (439b20eb460618b6c6afa22836a9de6129db4db5)

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QBuffer() [1/2]

◆ QBuffer() [2/2]

◆ ~QBuffer()

Member Function Documentation

◆ atEnd()

◆ buffer() [1/2]

◆ buffer() [2/2]

◆ canReadLine()

◆ close()

◆ connectNotify()

◆ data()

◆ disconnectNotify()

◆ open()

◆ pos()

◆ readData()

◆ seek()

◆ setBuffer()

◆ setData() [1/2]

◆ setData() [2/2]

◆ size()

◆ writeData()