KAutoSaveFile Class Reference

#include <KAutoSaveFile>

Inheritance diagram for KAutoSaveFile:

Public Member Functions
	KAutoSaveFile (const QUrl &filename, QObject *parent=nullptr)
	KAutoSaveFile (QObject *parent=nullptr)
	~KAutoSaveFile () override
QUrl	managedFile () const
bool	open (OpenMode openmode) override
virtual void	releaseLock ()
void	setManagedFile (const QUrl &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
virtual QString	fileName () const const override
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

Static Public Member Functions
static QList< KAutoSaveFile * >	allStaleFiles (const QString &applicationName=QString())
static QList< KAutoSaveFile * >	staleFiles (const QUrl &url, const QString &applicationName=QString())
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)

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
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

Creates and manages a temporary "auto-save" file. Autosave files are temporary files that applications use to store the unsaved data in a file they have open for editing. KAutoSaveFile allows you to easily create and manage such files, as well as to recover the unsaved data left over by a crashed or otherwise gone process.

Each KAutoSaveFile object is associated with one specific file that the application holds open. KAutoSaveFile is also a QObject, so it can be reparented to the actual opened file object, so as to manage the lifetime of the temporary file.

Typical use consists of:

• verifying whether stale autosave files exist for the opened file
• deciding whether to recover the old, autosaved data
• if not recovering, creating a KAutoSaveFile object for the opened file
• during normal execution of the program, periodically save unsaved data into the KAutoSaveFile file.

KAutoSaveFile holds a lock on the autosave file, so it's safe to delete the file and recreate it later. Because of that, disposing of stale autosave files should be done with releaseLock(). No lock is held on the managed file.

Examples: Opening a new file:

void Document::open(const QUrl &url)
{
    // check whether autosave files exist:
    const QList<KAutoSaveFile *> staleFiles = KAutoSaveFile::staleFiles(url);
    if (!staleFiles.isEmpty()) {
        if (KMessageBox::questionTwoActions(parent,
                                            "Auto-saved files exist. Do you want to recover them now?",
                                            "File Recovery",
                                            KGuiItem("Recover"), KGuiItem("Do Not recover")) == KMessageBox::PrimaryAction) {
            recoverFiles(staleFiles);
            return;
        } else {
            // remove the stale files
            for (KAutoSaveFile *stale : staleFiles) {
                stale->open(QIODevice::ReadWrite);
                delete stale;
            }
        }
    }
 
    // create new autosave object
    m_autosave = new KAutoSaveFile(url, this);
 
    // continue the process of opening file 'url'
    ...
}

The function recoverFiles could loop over the list of files and do this:

for (KAutoSaveFile *stale : staleFiles) {
    if (!stale->open(QIODevice::ReadWrite)) {
        // show an error message; we could not steal the lockfile
        // maybe another application got to the file before us?
        delete stale;
        continue;
    }
    Document *doc = new Document;
    doc->m_autosave = stale;
    stale->setParent(doc); // reparent
 
    doc->setUrl(stale->managedFile());
    doc->setContents(stale->readAll());
    doc->setState(Document::Modified); // mark it as modified and unsaved
 
    documentManager->addDocument(doc);
}

If the file is unsaved, periodically write the contents to the save file:

if (!m_autosave->isOpen() && !m_autosave->open(QIODevice::ReadWrite)) {
    // show error: could not open the autosave file
}
m_autosave->write(contents());

When the user saves the file, the autosaved file is no longer necessary and can be removed or emptied.

m_autosave->resize(0);    // leaves the file open

m_autosave->remove();     // closes the file

Author

Jacob R Rideout [email protected][email protected]acob[email protected]rideo[email protected]ut.n[email protected]et

Definition at line 120 of file kautosavefile.h.

Constructor & Destructor Documentation

KAutoSaveFile() [1/2]

KAutoSaveFile::KAutoSaveFile ( const QUrl &  filename, QObject *  parent = nullptr  )

explicit

Constructs a KAutoSaveFile for file filename.

The temporary file is not opened or created until actually needed. The file filename does not have to exist for KAutoSaveFile to be constructed (if it exists, it will not be touched).

Parameters

filename	the filename that this KAutoSaveFile refers to
parent	the parent object

Definition at line 85 of file kautosavefile.cpp.

KAutoSaveFile() [2/2]

KAutoSaveFile::KAutoSaveFile ( QObject *  parent = nullptr )

explicit

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Constructs a KAutoSaveFile object.

Note that you need to call setManagedFile() before calling open().

Parameters

parent

the parent object

Definition at line 92 of file kautosavefile.cpp.

~KAutoSaveFile()

KAutoSaveFile::~KAutoSaveFile ( )

override

Destroys the KAutoSaveFile object, removes the autosave file and drops the lock being held (if any).

Definition at line 98 of file kautosavefile.cpp.

Member Function Documentation

allStaleFiles()

QList< KAutoSaveFile * > KAutoSaveFile::allStaleFiles ( const QString &  applicationName = QString() )

static

Returns all stale autosave files left behind by crashed or otherwise gone instances of this application.

If not given, the application name is obtained from QCoreApplication, so be sure to have set it correctly before calling this function.

See staleFiles() for information on the returned objects.

The application owns all returned KAutoSaveFile objects and is responsible for deleting them when no longer needed. Remember that deleting the KAutoSaveFile will release the file lock and remove the stale autosave file.

Definition at line 227 of file kautosavefile.cpp.

managedFile()

QUrl KAutoSaveFile::managedFile

(

)

const

Retrieves the URL of the file managed by KAutoSaveFile.

This is the same URL that was given to setManagedFile() or the KAutoSaveFile constructor.

This is the name of the real file being edited by the application. To get the name of the temporary file where data can be saved, use fileName() (after you have called open()).

Definition at line 104 of file kautosavefile.cpp.

open()

bool KAutoSaveFile::open ( OpenMode  openmode )

override

Opens the autosave file and locks it if it wasn't already locked.

The name of the temporary file where data can be saved to will be set by this function and can be retrieved with fileName(). It will not change unless releaseLock() is called. No other application will attempt to edit such a file either while the lock is held.

Parameters

openmode

the mode that should be used to open the file, probably QIODevice::ReadWrite

Returns

true if the file could be opened (= locked and created), false if the operation failed

Definition at line 128 of file kautosavefile.cpp.

releaseLock()

void KAutoSaveFile::releaseLock ( )

virtual

Closes the autosave file resource and removes the lock file.

The file name returned by fileName() will no longer be protected and can be overwritten by another application at any time. To obtain a new lock, call open() again.

This function calls remove(), so the autosave temporary file will be removed too.

Definition at line 117 of file kautosavefile.cpp.

setManagedFile()

void KAutoSaveFile::setManagedFile

(

const QUrl &

filename

)

Sets the URL of the file managed by KAutoSaveFile.

This should be the name of the real file being edited by the application. If the file was previously set, this function calls releaseLock().

Parameters

filename

the filename that this KAutoSaveFile refers to

Definition at line 109 of file kautosavefile.cpp.

staleFiles()

QList< KAutoSaveFile * > KAutoSaveFile::staleFiles ( const QUrl &  url, const QString &  applicationName = QString()  )

static

Checks for stale autosave files for the file url.

Returns a list of autosave files that contain autosaved data left behind by other instances of the application, due to crashing or otherwise uncleanly exiting.

It is the application's job to determine what to do with such unsaved data. Generally, this is done by asking the user if he wants to see the recovered data, and then allowing the user to save if he wants to.

If not given, the application name is obtained from QCoreApplication, so be sure to have set it correctly before calling this function.

This function returns a list of unopened KAutoSaveFile objects. By calling open() on them, the application will steal the lock. Subsequent releaseLock() or deleting of the object will then erase the stale autosave file.

The application owns all returned KAutoSaveFile objects and is responsible for deleting them when no longer needed. Remember that deleting the KAutoSaveFile will release the file lock and remove the stale autosave file.

Definition at line 199 of file kautosavefile.cpp.

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

• kautosavefile.h
• kautosavefile.cpp