KSaveFile

#include <KSaveFile>

Inheritance diagram for KSaveFile:

[legend]

Public Member Functions
	KSaveFile ()

	KSaveFile (const QString &filename)

	~KSaveFile () override

void	abort ()

bool	directWriteFallback () const

QFile::FileError	error () const

QString	errorString () const

QString	fileName () const override

bool	finalize ()

bool	open (OpenMode flags=QIODevice::ReadWrite) override

void	setDirectWriteFallback (bool enabled)

void	setFileName (const QString &filename)

Public Member Functions inherited from QFile
	QFile (const QString &name)

	QFile (const QString &name, QObject *parent)

	QFile (QObject *parent)

bool	copy (const QString &newName)

bool	exists () const const

bool	link (const QString &linkName)

bool	moveToTrash ()

bool	open (FILE *fh, QIODevice::OpenMode mode, QFileDevice::FileHandleFlags handleFlags)

bool	open (int fd, QIODevice::OpenMode mode, QFileDevice::FileHandleFlags handleFlags)

virtual bool	open (QIODevice::OpenMode mode) override

virtual QFileDevice::Permissions	permissions () const const override

QString	readLink () const const

bool	remove ()

bool	rename (const QString &newName)

virtual bool	resize (qint64 sz) override

void	setFileName (const QString &name)

virtual bool	setPermissions (QFileDevice::Permissions permissions) override

virtual qint64	size () const const override

QString	symLinkTarget () const const

Public Member Functions inherited from QFileDevice
virtual bool	atEnd () const const override

virtual void	close () override

QFileDevice::FileError	error () const const

QDateTime	fileTime (QFileDevice::FileTime time) const const

bool	flush ()

int	handle () const const

virtual bool	isSequential () const const override

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

virtual qint64	pos () const const override

virtual bool	seek (qint64 pos) override

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

bool	unmap (uchar *address)

void	unsetError ()

Public Member Functions inherited from QIODevice
	QIODevice (QObject *parent)

void	aboutToClose ()

virtual qint64	bytesAvailable () const const

virtual qint64	bytesToWrite () const const

void	bytesWritten (qint64 bytes)

virtual bool	canReadLine () const const

void	channelBytesWritten (int channel, qint64 bytes)

void	channelReadyRead (int channel)

void	commitTransaction ()

int	currentReadChannel () const const

int	currentWriteChannel () const const

QString	errorString () const const

bool	getChar (char *c)

bool	isOpen () const const

bool	isReadable () const const

bool	isTextModeEnabled () const const

bool	isTransactionStarted () const const

bool	isWritable () const const

QIODevice::OpenMode	openMode () const 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 ()

int	readChannelCount () const const

void	readChannelFinished ()

qint64	readLine (char *data, qint64 maxSize)

QByteArray	readLine (qint64 maxSize)

void	readyRead ()

virtual bool	reset ()

void	rollbackTransaction ()

void	setCurrentReadChannel (int channel)

void	setCurrentWriteChannel (int channel)

void	setTextModeEnabled (bool enabled)

qint64	skip (qint64 maxSize)

void	startTransaction ()

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 &byteArray)

int	writeChannelCount () const const

Public Member Functions inherited from QObject
	QObject (QObject *parent)

bool	blockSignals (bool block)

const QObjectList &	children () const const

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

void	deleteLater ()

void	destroyed (QObject *obj)

bool	disconnect (const char signal, const QObject receiver, const char *method) const const

bool	disconnect (const QObject receiver, const char method) const const

void	dumpObjectInfo ()

void	dumpObjectInfo () const const

void	dumpObjectTree ()

void	dumpObjectTree () const const

QList< QByteArray >	dynamicPropertyNames () const const

virtual bool	event (QEvent *e)

virtual bool	eventFilter (QObject watched, QEvent event)

T	findChild (const QString &name, Qt::FindChildOptions options) const const

QList< T >	findChildren (const QRegExp &regExp, Qt::FindChildOptions options) const const

QList< T >	findChildren (const QRegularExpression &re, Qt::FindChildOptions options) const const

QList< T >	findChildren (const QString &name, Qt::FindChildOptions options) const const

bool	inherits (const char *className) const const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const const

bool	isWindowType () const const

void	killTimer (int id)

virtual const QMetaObject *	metaObject () const const

void	moveToThread (QThread *targetThread)

QString	objectName () const const

void	objectNameChanged (const QString &objectName)

QObject *	parent () const const

QVariant	property (const char *name) const const

	Q_CLASSINFO (Name, Value)

	Q_DISABLE_COPY (Class)

	Q_DISABLE_COPY_MOVE (Class)

	Q_DISABLE_MOVE (Class)

	Q_EMIT Q_EMIT

	Q_ENUM (...)

	Q_ENUM_NS (...)

	Q_ENUMS (...)

	Q_FLAG (...)

	Q_FLAG_NS (...)

	Q_FLAGS (...)

	Q_GADGET Q_GADGET

	Q_INTERFACES (...)

	Q_INVOKABLE Q_INVOKABLE

	Q_NAMESPACE Q_NAMESPACE

	Q_NAMESPACE_EXPORT (EXPORT_MACRO)

	Q_OBJECT Q_OBJECT

	Q_PROPERTY (...)

	Q_REVISION Q_REVISION

	Q_SET_OBJECT_NAME (Object)

	Q_SIGNAL Q_SIGNAL

	Q_SIGNALS Q_SIGNALS

	Q_SLOT Q_SLOT

	Q_SLOTS Q_SLOTS

T	qFindChild (const QObject *obj, const QString &name)

QList< T >	qFindChildren (const QObject *obj, const QRegExp &regExp)

QList< T >	qFindChildren (const QObject *obj, const QString &name)

T	qobject_cast (const QObject *object)

T	qobject_cast (QObject *object)

	QT_NO_NARROWING_CONVERSIONS_IN_CONNECT QT_NO_NARROWING_CONVERSIONS_IN_CONNECT

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

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

bool	signalsBlocked () const const

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

int	startTimer (std::chrono::milliseconds time, Qt::TimerType timerType)

QThread *	thread () const const

Additional Inherited Members
Public Types inherited from QFileDevice
enum	FileError

enum	FileHandleFlag

enum	FileTime

enum	MemoryMapFlags

enum	Permission

Public Types inherited from QIODevice
enum	OpenModeFlag

Properties inherited from QObject
	objectName

Static Public Member Functions inherited from QFile
bool	copy (const QString &fileName, const QString &newName)

QString	decodeName (const char *localFileName)

QString	decodeName (const QByteArray &localFileName)

QByteArray	encodeName (const QString &fileName)

bool	exists (const QString &fileName)

bool	link (const QString &fileName, const QString &linkName)

bool	moveToTrash (const QString &fileName, QString *pathInTrash)

QFileDevice::Permissions	permissions (const QString &fileName)

QString	readLink (const QString &fileName)

bool	remove (const QString &fileName)

bool	rename (const QString &oldName, const QString &newName)

bool	resize (const QString &fileName, qint64 sz)

void	setDecodingFunction (QFile::DecoderFn function)

void	setEncodingFunction (QFile::EncoderFn function)

bool	setPermissions (const QString &fileName, QFileDevice::Permissions permissions)

QString	symLinkTarget (const QString &fileName)

Static Public Member Functions inherited from QObject
QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char method, Qt::ConnectionType type)

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

QMetaObject::Connection	connect (const QObject sender, PointerToMemberFunction signal, const QObject context, Functor functor, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject sender, PointerToMemberFunction signal, const QObject receiver, PointerToMemberFunction method, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject *sender, PointerToMemberFunction signal, Functor functor)

bool	disconnect (const QMetaObject::Connection &connection)

bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char method)

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

bool	disconnect (const QObject sender, PointerToMemberFunction signal, const QObject receiver, PointerToMemberFunction method)

QString	tr (const char sourceText, const char disambiguation, int n)

QString	trUtf8 (const char sourceText, const char disambiguation, int n)

Public Attributes inherited from QFile
typedef	DecoderFn

typedef	EncoderFn

Public Attributes inherited from QFileDevice
	AbortError

	AutoCloseHandle

	CopyError

	DontCloseHandle

	ExeGroup

	ExeOther

	ExeOwner

	ExeUser

	FatalError

	FileAccessTime

	FileBirthTime

typedef	FileHandleFlags

	FileMetadataChangeTime

	FileModificationTime

	MapPrivateOption

	NoError

	NoOptions

	OpenError

typedef	Permissions

	PermissionsError

	PositionError

	ReadError

	ReadGroup

	ReadOther

	ReadOwner

	ReadUser

	RemoveError

	RenameError

	ResizeError

	ResourceError

	TimeOutError

	UnspecifiedError

	WriteError

	WriteGroup

	WriteOther

	WriteOwner

	WriteUser

Public Attributes inherited from QIODevice
	Append

	ExistingOnly

	NewOnly

	NotOpen

typedef	OpenMode

	ReadOnly

	ReadWrite

	Text

	Truncate

	Unbuffered

	WriteOnly

Public Attributes inherited from QObject
typedef	QObjectList

Protected Member Functions inherited from QFileDevice
virtual qint64	readData (char *data, qint64 len) override

virtual qint64	readLineData (char *data, qint64 maxlen) override

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

Protected Member Functions inherited from QIODevice
void	setErrorString (const QString &str)

void	setOpenMode (QIODevice::OpenMode openMode)

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

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signal)

bool	isSignalConnected (const QMetaMethod &signal) const const

int	receivers (const char *signal) const const

QObject *	sender () const const

int	senderSignalIndex () const const

virtual void	timerEvent (QTimerEvent *event)

Detailed Description

Class to allow for atomic file I/O, as well as utility functions.

The KSaveFile class has been made to write out changes to an existing file atomically. This means that either ALL changes will be written to the file, or NO changes have been written, and the original file (if any) has been unchanged. This is useful if you have lots of time-consuming processing to perform during which an interruption could occur, or if any error in the file structure will cause the entire file to be corrupt.

When you create a KSaveFile for a given file, a temporary file is instead created and all your I/O occurs in the save file. Once you call finalize() the temporary file is renamed to the target file, so that all your changes happen at once. If abort() is called then the temporary file is removed and the target file is untouched. KSaveFile derives from QFile so you can use it just as you would a normal QFile.

This class also includes several static utility functions available that can help ensure data integrity. See the individual functions for details.

Here is a quick example of how to use KSaveFile:

First we create the KSaveFile and open it.

KSaveFile saveFile;
saveFile.setFileName("/lib/foo/bar.dat");
if ( !saveFile.open() ) {
    //Handle error
}

At this point the file "/lib/foo/bar.dat" has not been altered in any way. Now, let's write out some data to the file.

QTextStream stream ( &saveFile );
stream << "Add some data.";
// Perform long processing
stream << "Add some more data.";
stream.flush();

Even after writing this data, the target file "/lib/foo/bar.dat" still has not been altered in any way. Now that we are done writing our data, we can write out all the changes that we have made by calling finalize().

if ( !saveFile.finalize() ) {
    //Handle error
}

If a user interruption or error occurred while we were writing out our changes, we would instead call abort() to cancel all the I/O without affecting the target file.

See also: QFile

Author: Jaison Lee lee.j[email protected]aiso[email protected][email protected][email protected]il.c[email protected]om; Waldo Bastian basti[email protected][email protected][email protected]de.or[email protected]g

Deprecated:: since 5.0, port to QSaveFile.

Definition at line 98 of file ksavefile.h.

Constructor & Destructor Documentation

◆ KSaveFile() [1/2]

KSaveFile::KSaveFile ( )

Default constructor.

Definition at line 72 of file ksavefile.cpp.

◆ KSaveFile() [2/2]

KSaveFile::KSaveFile ( const QString & filename )

explicit

Creates a new KSaveFile and sets the target file to filename.

Parameters

filename the path of the file

Definition at line 77 of file ksavefile.cpp.

◆ ~KSaveFile()

KSaveFile::~KSaveFile ( )

override

Destructor.

Note: If the file has been opened but not yet finalized, the destructor will call finalize(). If you do not want the target file to be affected you need to call abort() before destroying the object.

Definition at line 83 of file ksavefile.cpp.

Member Function Documentation

◆ abort()

void KSaveFile::abort ( )

Discard changes without affecting the target file.

This will discard all changes that have been made to this file. The target file will not be altered in any way.

Definition at line 213 of file ksavefile.cpp.

◆ directWriteFallback()

bool KSaveFile::directWriteFallback ( ) const

Returns true if the fallback solution for saving files in read-only directories is enabled.

Since: 4.10.3

Definition at line 298 of file ksavefile.cpp.

◆ error()

QFile::FileError KSaveFile::error ( ) const

Returns the last error that occurred.

Use this function to check for errors.

Returns: The last error that occurred, or QFile::NoError.

Definition at line 190 of file ksavefile.cpp.

◆ errorString()

QString KSaveFile::errorString ( ) const

Returns a human-readable description of the last error.

Use this function to get a human-readable description of the last error that occurred.

Returns: A string describing the last error that occurred.

Definition at line 199 of file ksavefile.cpp.

◆ fileName()

QString KSaveFile::fileName ( ) const

overridevirtual

Returns the name of the target file.

This function returns the name of the target file, or an empty QString if it has not yet been set.

Returns: The name of the target file.

Reimplemented from QFile.

Definition at line 208 of file ksavefile.cpp.

◆ finalize()

bool KSaveFile::finalize ( )

Finalize changes to the file.

This will commit all the changes that have been made to the file.

Returns: true if successful, or false if an error has occurred.

Definition at line 228 of file ksavefile.cpp.

◆ open()

bool KSaveFile::open ( OpenMode flags = QIODevice::ReadWrite )

override

Open the save file.

This function will open the save file by creating a temporary file to write to. It will also check to ensure that there are sufficient permissions to write to the target file.

Parameters

flags Sets the QIODevice::OpenMode. It should contain the write flag, otherwise you have a save file you cannot save to.

Returns: true if successful, or false if an error has occurred.

Definition at line 90 of file ksavefile.cpp.

◆ setDirectWriteFallback()

void KSaveFile::setDirectWriteFallback ( bool enabled )

Allows writing over the existing file if necessary.

QSaveFile creates a temporary file in the same directory as the final file and atomically renames it. However this is not possible if the directory permissions do not allow creating new files. In order to preserve atomicity guarantees, open() fails when it cannot create the temporary file.

In order to allow users to edit files with write permissions in a directory with restricted permissions, call setDirectWriteFallback() with enabled set to true, and the following calls to open() will fallback to opening the existing file directly and writing into it, without the use of a temporary file. This does not have atomicity guarantees, i.e. an application crash or for instance a power failure could lead to a partially-written file on disk. It also means cancelWriting() has no effect, in such a case.

Typically, to save documents edited by the user, call setDirectWriteFallback(true), and to save application internal files (configuration files, data files, ...), keep the default setting which ensures atomicity.