The QFileDevice class provides an interface for reading from and writing to open files. More...

#include <qfiledevice.h>

Inheritance diagram for QFileDevice:

Collaboration diagram for QFileDevice:

Public Types
enum	FileError { NoError = 0 , ReadError = 1 , WriteError = 2 , FatalError = 3 , ResourceError = 4 , OpenError = 5 , AbortError = 6 , TimeOutError = 7 , UnspecifiedError = 8 , RemoveError = 9 , RenameError = 10 , PositionError = 11 , ResizeError = 12 , PermissionsError = 13 , CopyError = 14 }

enum	FileTime { FileAccessTime , FileBirthTime , FileMetadataChangeTime , FileModificationTime }

enum	Permission { ReadOwner = 0x4000 , WriteOwner = 0x2000 , ExeOwner = 0x1000 , ReadUser = 0x0400 , WriteUser = 0x0200 , ExeUser = 0x0100 , ReadGroup = 0x0040 , WriteGroup = 0x0020 , ExeGroup = 0x0010 , ReadOther = 0x0004 , WriteOther = 0x0002 , ExeOther = 0x0001 }

enum	FileHandleFlag { AutoCloseHandle = 0x0001 , DontCloseHandle = 0 }

enum	MemoryMapFlag { NoOptions = 0 , MapPrivateOption = 0x0001 }

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 }

Public Member Functions
	~QFileDevice ()

FileError	error () const

void	unsetError ()

void	close () override

bool	isSequential () const override

int	handle () const

virtual QString	fileName () const

qint64	pos () const override

bool	seek (qint64 offset) override

bool	atEnd () const override

bool	flush ()

qint64	size () const override

virtual bool	resize (qint64 sz)

virtual Permissions	permissions () const

virtual bool	setPermissions (Permissions permissionSpec)

uchar *	map (qint64 offset, qint64 size, MemoryMapFlags flags=NoOptions)

bool	unmap (uchar *address)

QDateTime	fileTime (QFileDevice::FileTime time) const

bool	setFileTime (const QDateTime &newDate, QFileDevice::FileTime fileTime)

Public Member Functions inherited from QIODevice
	QIODevice ()

	QIODevice (QObject *parent)

virtual	~QIODevice ()

QIODeviceBase::OpenMode	openMode () const

void	setTextModeEnabled (bool enabled)

bool	isTextModeEnabled () const

bool	isOpen () const

bool	isReadable () const

bool	isWritable () const

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)

virtual bool	reset ()

virtual qint64	bytesAvailable () const

virtual qint64	bytesToWrite () const

qint64	read (char *data, qint64 maxlen)

QByteArray	read (qint64 maxlen)

QByteArray	readAll ()

qint64	readLine (char *data, qint64 maxlen)

QByteArray	readLine (qint64 maxlen=0)

virtual bool	canReadLine () const

void	startTransaction ()

void	commitTransaction ()

void	rollbackTransaction ()

bool	isTransactionStarted () const

qint64	write (const char *data, qint64 len)

qint64	write (const char *data)

qint64	write (const QByteArray &data)

qint64	peek (char *data, qint64 maxlen)

QByteArray	peek (qint64 maxlen)

qint64	skip (qint64 maxSize)

virtual bool	waitForReadyRead (int msecs)

virtual bool	waitForBytesWritten (int msecs)

void	ungetChar (char c)

bool	putChar (char c)

bool	getChar (char *c)

QString	errorString () const

Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)

virtual	~QObject ()

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

QString	objectName () const

void	setObjectName (const QString &name)

QBindable< QString >	bindableObjectName ()

bool	isWidgetType () const

bool	isWindowType () const

bool	signalsBlocked () const noexcept

bool	blockSignals (bool b) noexcept

QThread *	thread () const

void	moveToThread (QThread *thread)

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

void	killTimer (int id)

template<typename T >
T	findChild (const QString &aName=QString(), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

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

template<typename T >
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

const QObjectList &	children () const

void	setParent (QObject *parent)

void	installEventFilter (QObject *filterObj)

void	removeEventFilter (QObject *obj)

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

void	dumpObjectInfo () const

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

QVariant	property (const char *name) const

QList< QByteArray >	dynamicPropertyNames () const

QBindingStorage *	bindingStorage ()

const QBindingStorage *	bindingStorage () const

QObject *	parent () const

bool	inherits (const char *classname) const

Protected Member Functions
	QFileDevice ()

	QFileDevice (QObject *parent)

	QFileDevice (QFileDevicePrivate &dd, QObject *parent=nullptr)

qint64	readData (char *data, qint64 maxlen) override

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

qint64	readLineData (char *data, qint64 maxlen) override

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

virtual qint64	skipData (qint64 maxSize)

void	setOpenMode (QIODeviceBase::OpenMode openMode)

void	setErrorString (const QString &errorString)

Protected Member Functions inherited from QObject
QObject *	sender () const

int	senderSignalIndex () const

int	receivers (const char *signal) const

bool	isSignalConnected (const QMetaMethod &signal) const

virtual void	timerEvent (QTimerEvent *event)

virtual void	childEvent (QChildEvent *event)

virtual void	customEvent (QEvent *event)

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	disconnectNotify (const QMetaMethod &signal)

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

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

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()

Signals inherited from QIODevice
void	readyRead ()

void	channelReadyRead (int channel)

void	bytesWritten (qint64 bytes)

void	channelBytesWritten (int channel, qint64 bytes)

void	aboutToClose ()

void	readChannelFinished ()

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

void	objectNameChanged (const QString &objectName, QPrivateSignal)

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)

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::FunctionPointer< Func2 >::Object receiver, Func2 slot, Qt::ConnectionType type=Qt::AutoConnection)

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

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

template<typename Func1 , typename Func2 >
static std::enable_if< QtPrivate::FunctionPointer< Func2 >::ArgumentCount==-1 &&!std::is_convertible_v< Func2, const char * >, QMetaObject::Connection >::type	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 slot)

template<typename Func1 , typename Func2 >
static std::enable_if< QtPrivate::FunctionPointer< Func2 >::ArgumentCount==-1 &&!std::is_convertible_v< Func2, const char * >, QMetaObject::Connection >::type	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject context, Func2 slot, Qt::ConnectionType type=Qt::AutoConnection)

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

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

static bool	disconnect (const QMetaObject::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 More...

Related Functions inherited from QObject
template< class T > T	qobject_cast (const QObject *object)

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

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

	QObjectList

Detailed Description

The QFileDevice class provides an interface for reading from and writing to open files.

\inmodule QtCore

Since: 5.0

\reentrant

QFileDevice is the base class for I/O devices that can read and write text and binary files and \l{The Qt Resource System}{resources}. QFile offers the main functionality, QFileDevice serves as a base class for sharing functionality with other file devices such as QTemporaryFile, by providing all the operations that can be done on files that have been opened by QFile or QTemporaryFile.

See also: QFile, QTemporaryFile

Definition at line 51 of file qfiledevice.h.

Member Enumeration Documentation

◆ FileError

enum QFileDevice::FileError

This enum describes the errors that may be returned by the error() function.

\value NoError No error occurred. \value ReadError An error occurred when reading from the file. \value WriteError An error occurred when writing to the file. \value FatalError A fatal error occurred. \value ResourceError Out of resources (e.g., too many open files, out of memory, etc.) \value OpenError The file could not be opened. \value AbortError The operation was aborted. \value TimeOutError A timeout occurred. \value UnspecifiedError An unspecified error occurred. \value RemoveError The file could not be removed. \value RenameError The file could not be renamed. \value PositionError The position in the file could not be changed. \value ResizeError The file could not be resized. \value PermissionsError The file could not be accessed. \value CopyError The file could not be copied.

Enumerator
NoError
ReadError
WriteError
FatalError
ResourceError
OpenError
AbortError
TimeOutError
UnspecifiedError
RemoveError
RenameError
PositionError
ResizeError
PermissionsError
CopyError

Definition at line 59 of file qfiledevice.h.

◆ FileHandleFlag

enum QFileDevice::FileHandleFlag

This enum is used when opening a file to specify additional options which only apply to files and not to a generic QIODevice.

\value AutoCloseHandle The file handle passed into open() should be closed by close(), the default behavior is that close just flushes the file and the application is responsible for closing the file handle. When opening a file by name, this flag is ignored as Qt always owns the file handle and must close it. \value DontCloseHandle If not explicitly closed, the underlying file handle is left open when the QFile object is destroyed.

Enumerator
AutoCloseHandle
DontCloseHandle

Definition at line 92 of file qfiledevice.h.

◆ FileTime

enum QFileDevice::FileTime

Since: 5.10

This enum is used by the fileTime() and setFileTime() functions.

\value FileAccessTime When the file was most recently accessed (e.g. read or written to). \value FileBirthTime When the file was created (may not be not supported on UNIX). \value FileMetadataChangeTime When the file's metadata was last changed. \value FileModificationTime When the file was most recently modified.

See also: setFileTime(), fileTime(), QFileInfo::fileTime()

Enumerator
FileAccessTime
FileBirthTime
FileMetadataChangeTime
FileModificationTime

Definition at line 77 of file qfiledevice.h.

◆ MemoryMapFlag

enum QFileDevice::MemoryMapFlag

Since: 4.4

This enum describes special options that may be used by the map() function.

\value NoOptions No options. \value MapPrivateOption The mapped memory will be private, so any modifications will not be visible to other processes and will not be written to disk. Any such modifications will be lost when the memory is unmapped. It is unspecified whether modifications made to the file made after the mapping is created will be visible through the mapped memory. This enum value was introduced in Qt 5.4.

Enumerator
NoOptions
MapPrivateOption

Definition at line 121 of file qfiledevice.h.

◆ Permission

enum QFileDevice::Permission

This enum is used by the permission() function to report the permissions and ownership of a file. The values may be OR-ed together to test multiple permissions and ownership values.

\value ReadOwner The file is readable by the owner of the file. \value WriteOwner The file is writable by the owner of the file. \value ExeOwner The file is executable by the owner of the file. \value ReadUser The file is readable by the user. \value WriteUser The file is writable by the user. \value ExeUser The file is executable by the user. \value ReadGroup The file is readable by the group. \value WriteGroup The file is writable by the group. \value ExeGroup The file is executable by the group. \value ReadOther The file is readable by anyone. \value WriteOther The file is writable by anyone. \value ExeOther The file is executable by anyone.

Warning: Because of differences in the platforms supported by Qt, the semantics of ReadUser, WriteUser and ExeUser are platform-dependent: On Unix, the rights of the owner of the file are returned and on Windows the rights of the current user are returned. This behavior might change in a future Qt version.

Note: On NTFS file systems, ownership and permissions checking is disabled by default for performance reasons. To enable it, include the following line:

Permission checking is then turned on and off by incrementing and decrementing qt_ntfs_permission_lookup by 1.

Enumerator
ReadOwner
WriteOwner
ExeOwner
ReadUser
WriteUser
ExeUser
ReadGroup
WriteGroup
ExeGroup
ReadOther
WriteOther
ExeOther

Definition at line 84 of file qfiledevice.h.

Constructor & Destructor Documentation

◆ ~QFileDevice()

QFileDevice::~QFileDevice ( )

Destroys the file device, closing it if necessary.

Definition at line 224 of file qfiledevice.cpp.

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◆ QFileDevice() [1/3]

QFileDevice::QFileDevice ( )

protected

Definition at line 201 of file qfiledevice.cpp.

◆ QFileDevice() [2/3]

QFileDevice::QFileDevice ( QObject * parent )

explicitprotected

Definition at line 208 of file qfiledevice.cpp.

◆ QFileDevice() [3/3]

QFileDevice::QFileDevice	(	QFileDevicePrivate &	dd,
		QObject *	parent = `nullptr`
	)

protected

Definition at line 215 of file qfiledevice.cpp.

Member Function Documentation

◆ atEnd()

bool QFileDevice::atEnd ( ) const

overridevirtual

Returns true if the end of the file has been reached; otherwise returns false.

For regular empty files on Unix (e.g. those in /proc), this function returns true, since the file system reports that the size of such a file is 0. Therefore, you should not depend on atEnd() when reading data from such a file, but rather call read() until no more data can be read.

Reimplemented from QIODevice.

Definition at line 353 of file qfiledevice.cpp.

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◆ close()

void QFileDevice::close ( )

overridevirtual

Calls QFileDevice::flush() and closes the file. Errors from flush are ignored.

See also: QIODevice::close()

Reimplemented from QIODevice.

Definition at line 314 of file qfiledevice.cpp.

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◆ error()

QFileDevice::FileError QFileDevice::error ( ) const

Returns the file error status.

The I/O device status returns an error code. For example, if open() returns false, or a read/write operation returns -1, this function can be called to find out the reason why the operation failed.

See also: unsetError()

Definition at line 574 of file qfiledevice.cpp.

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◆ fileName()

QString QFileDevice::fileName ( ) const

virtual

Returns the name of the file. The default implementation in QFileDevice returns a null string.

Reimplemented in QTemporaryFile, QSaveFile, and QFile.

Definition at line 268 of file qfiledevice.cpp.

◆ fileTime()

QDateTime QFileDevice::fileTime ( QFileDevice::FileTime time ) const

Since: 5.10 Returns the file time specified by time. If the time cannot be determined return QDateTime() (an invalid date time).

See also: setFileTime(), FileTime, QDateTime::isValid()

Definition at line 771 of file qfiledevice.cpp.

◆ flush()

bool QFileDevice::flush ( )

Flushes any buffered data to the file. Returns true if successful; otherwise returns false.

Definition at line 277 of file qfiledevice.cpp.

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◆ handle()

int QFileDevice::handle ( ) const

Returns the file handle of the file.

This is a small positive integer, suitable for use with C library functions such as fdopen() and fcntl(). On systems that use file descriptors for sockets (i.e. Unix systems, but not Windows) the handle can be used with QSocketNotifier as well.

If the file is not open, or there is an error, handle() returns -1.

See also: QSocketNotifier

Definition at line 255 of file qfiledevice.cpp.

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◆ isSequential()

bool QFileDevice::isSequential ( ) const

overridevirtual

Returns true if the file can only be manipulated sequentially; otherwise returns false.

Most files support random-access, but some special files may not.

See also: QIODevice::isSequential()

Reimplemented from QIODevice.

Reimplemented in QSequentialFile.

Definition at line 237 of file qfiledevice.cpp.

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◆ map()

uchar * QFileDevice::map	(	qint64	offset,
		qint64	size,
		MemoryMapFlags	flags = `NoOptions`
	)

Maps size bytes of the file into memory starting at offset. A file should be open for a map to succeed but the file does not need to stay open after the memory has been mapped. When the QFile is destroyed or a new file is opened with this object, any maps that have not been unmapped will automatically be unmapped.

The mapping will have the same open mode as the file (read and/or write), except when using MapPrivateOption, in which case it is always possible to write to the mapped memory.

Any mapping options can be passed through flags.

Returns a pointer to the memory or \nullptr if there is an error.

See also: unmap()

Definition at line 702 of file qfiledevice.cpp.

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◆ permissions()

QFile::Permissions QFileDevice::permissions ( ) const

virtual

Returns the complete OR-ed together combination of QFile::Permission for the file.

See also: setPermissions()

Reimplemented in QFile.

Definition at line 641 of file qfiledevice.cpp.

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◆ pos()

qint64 QFileDevice::pos ( ) const

overridevirtual

\reimp

Reimplemented from QIODevice.

Definition at line 339 of file qfiledevice.cpp.

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◆ readData()

qint64 QFileDevice::readData	(	char *	data,
		qint64	len
	)

overrideprotectedvirtual

\reimp

Implements QIODevice.

Definition at line 449 of file qfiledevice.cpp.

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◆ readLineData()

qint64 QFileDevice::readLineData	(	char *	data,
		qint64	maxlen
	)

overrideprotectedvirtual

\reimp

Reimplemented from QIODevice.

Definition at line 423 of file qfiledevice.cpp.

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◆ resize()

bool QFileDevice::resize ( qint64 sz )

virtual

Sets the file size (in bytes) sz. Returns true if the resize succeeds; false otherwise. If sz is larger than the file currently is, the new bytes will be set to 0; if sz is smaller, the file is simply truncated.

Warning: This function can fail if the file doesn't exist.

See also: size()

Reimplemented in QFile.

Definition at line 617 of file qfiledevice.cpp.

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◆ seek()

bool QFileDevice::seek ( qint64 pos )

overridevirtual

For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred. For sequential devices, the default behavior is to do nothing and return false.

Seeking beyond the end of a file: If the position is beyond the end of a file, then seek() will not immediately extend the file. If a write is performed at this position, then the file will be extended. The content of the file between the previous end of file and the newly written data is UNDEFINED and varies between platforms and file systems.

Reimplemented from QIODevice.

Definition at line 398 of file qfiledevice.cpp.

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◆ setFileTime()

bool QFileDevice::setFileTime	(	const QDateTime &	newDate,
		QFileDevice::FileTime	fileTime
	)

Since: 5.10 Sets the file time specified by fileTime to newDate, returning true if successful; otherwise returns false.

Note: The file must be open to use this function.

See also: fileTime(), FileTime

Definition at line 790 of file qfiledevice.cpp.

◆ setPermissions()

bool QFileDevice::setPermissions ( Permissions permissions )

virtual

Sets the permissions for the file to the permissions specified. Returns true if successful, or false if the permissions cannot be modified.

Warning: This function does not manipulate ACLs, which may limit its effectiveness.

See also: permissions()

Reimplemented in QFile.

Definition at line 658 of file qfiledevice.cpp.

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◆ size()

qint64 QFileDevice::size ( ) const

overridevirtual

Returns the size of the file.

For regular empty files on Unix (e.g. those in /proc), this function returns 0; the contents of such a file are generated on demand in response to you calling read().

Reimplemented from QIODevice.

Definition at line 598 of file qfiledevice.cpp.

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◆ unmap()

bool QFileDevice::unmap ( uchar * address )

Unmaps the memory address.

Returns true if the unmap succeeds; false otherwise.

See also: map()

Definition at line 723 of file qfiledevice.cpp.

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◆ unsetError()

void QFileDevice::unsetError ( )

Sets the file's error to QFileDevice::NoError.

See also: error()

Definition at line 585 of file qfiledevice.cpp.

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◆ writeData()

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

overrideprotectedvirtual

\reimp

Implements QIODevice.

Reimplemented in QSaveFile.

Definition at line 534 of file qfiledevice.cpp.

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

src/corelib/io/qfiledevice.h
src/corelib/io/qfiledevice.cpp

Public Types

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ FileError

◆ FileHandleFlag

◆ FileTime

◆ MemoryMapFlag

◆ Permission

Constructor & Destructor Documentation

◆ ~QFileDevice()

◆ QFileDevice() [1/3]

◆ QFileDevice() [2/3]

◆ QFileDevice() [3/3]

Member Function Documentation

◆ atEnd()

◆ close()

◆ error()

◆ fileName()

◆ fileTime()

◆ flush()

◆ handle()

◆ isSequential()

◆ map()

◆ permissions()

◆ pos()

◆ readData()

◆ readLineData()

◆ resize()

◆ seek()

◆ setFileTime()

◆ setPermissions()

◆ size()

◆ unmap()

◆ unsetError()

◆ writeData()