#include <KSaveFile>

Inherits QFile.

Public Member Functions
	KSaveFile ()

	KSaveFile (const QString &filename, const KComponentData &componentData=KGlobal::mainComponent())

virtual	~KSaveFile ()

void	abort ()

bool	directWriteFallback () const

QFile::FileError	error () const

QString	errorString () const

QString	fileName () const

bool	finalize ()

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

void	setDirectWriteFallback (bool enabled)

void	setFileName (const QString &filename)

Static Public Member Functions
static bool	backupFile (const QString &filename, const QString &backupDir=QString())

static bool	numberedBackupFile (const QString &filename, const QString &backupDir=QString(), const QString &backupExtension=QString::fromLatin1("~"), const uint maxBackups=10)

static bool	rcsBackupFile (const QString &filename, const QString &backupDir=QString(), const QString &backupMessage=QString())

static bool	simpleBackupFile (const QString &filename, const QString &backupDir=QString(), const QString &backupExtension=QLatin1String("~"))

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.nosp@m.aiso.nosp@m.n@gma.nosp@m.il.c.nosp@m.om; Waldo Bastian basti.nosp@m.an@k.nosp@m.de.or.nosp@m.g

Definition at line 96 of file ksavefile.h.

Constructor & Destructor Documentation

KSaveFile::KSaveFile ( )

Default constructor.

Definition at line 62 of file ksavefile.cpp.

KSaveFile::KSaveFile	(	const QString &	filename,
		const KComponentData &	componentData = `KGlobal::mainComponent()`
	)

explicit

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

Parameters

filename	the path of the file
componentData	unused

Definition at line 68 of file ksavefile.cpp.

KSaveFile::~KSaveFile ( )

virtual

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 74 of file ksavefile.cpp.

Member Function Documentation

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 204 of file ksavefile.cpp.

bool KSaveFile::backupFile	(	const QString &	filename,
		const QString &	backupDir = `QString()`
	)

static

Static method to create a backup file before saving.

If empty (the default), the backup will be in the same directory as filename. The backup type (simple, rcs, or numbered), extension string, and maximum number of backup files are read from the user's global configuration. Use simpleBackupFile() or numberedBackupFile() to force one of these specific backup styles. You can use this method even if you don't use KSaveFile.

Parameters

filename	the file to backup
backupDir	optional directory where to save the backup file in.

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

Definition at line 285 of file ksavefile.cpp.

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 280 of file ksavefile.cpp.

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 181 of file ksavefile.cpp.

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 190 of file ksavefile.cpp.

QString KSaveFile::fileName ( ) const

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.

Definition at line 199 of file ksavefile.cpp.

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 219 of file ksavefile.cpp.

bool KSaveFile::numberedBackupFile	(	const QString &	filename,
		const QString &	backupDir = `QString()`,
		const QString &	backupExtension = `QString::fromLatin1( "~" )`,
		const uint	maxBackups = `10`
	)

static

Static method to create a backup file for a given filename.

This function creates a series of numbered backup files from the given filename.

The backup file names will be of the form: <name>.<number><extension> for instance

chat.3.log

The new backup file will be have the backup number 1. Each existing backup file will have its number incremented by 1. Any backup files with numbers greater than the maximum number permitted (maxBackups) will be removed. You can use this method even if you don't use KSaveFile.

Parameters

filename	the file to backup
backupDir	optional directory where to save the backup file in. If empty (the default), the backup will be in the same directory as `filename`.
backupExtension	the extension to append to `filename`, which is "~" by default. Do not use an extension containing digits.
maxBackups	the maximum number of backup files permitted. For best performance a small number (10) is recommended.

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

Definition at line 388 of file ksavefile.cpp.

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

virtual

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 81 of file ksavefile.cpp.

bool KSaveFile::rcsBackupFile	(	const QString &	filename,
		const QString &	backupDir = `QString()`,
		const QString &	backupMessage = `QString()`
	)

static

Static method to create an rcs backup file for a given filename.

This function creates a rcs-formatted backup file from the given filename.

The backup file names will be of the form: <name>,v for instance

photo.jpg,v

The new backup file will be in RCS format. Each existing backup file will be committed as a new revision. You can use this method even if you don't use KSaveFile.

Parameters

filename	the file to backup
backupDir	optional directory where to save the backup file in. If empty (the default), the backup will be in the same directory as `filename`.
backupMessage	is the RCS commit message for this revision.

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

Definition at line 321 of file ksavefile.cpp.

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.

Since: 4.10.3

Definition at line 275 of file ksavefile.cpp.

void KSaveFile::setFileName ( const QString & filename )

Set the target filename for the save file.

You must use this to set the filename of the target file if you do not use the contructor that does so.

Parameters

filename Name of the target file.

Definition at line 166 of file ksavefile.cpp.

bool KSaveFile::simpleBackupFile	(	const QString &	filename,
		const QString &	backupDir = `QString()`,
		const QString &	backupExtension = `QLatin1String( "~" )`
	)

static

Static method to create a backup file for a given filename.

This function creates a backup file from the given filename. You can use this method even if you don't use KSaveFile.

Parameters

filename	the file to backup
backupDir	optional directory where to save the backup file in. If empty (the default), the backup will be in the same directory as `filename`.
backupExtension	the extension to append to `filename`, "~" by default.

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

Definition at line 305 of file ksavefile.cpp.

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

KDECore

Public Member Functions

Static Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

KDECore

kdelibs API Reference

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