KAutoSaveFile

#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 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
 
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 ()
 
QByteArray readLine (qint64 maxSize)
 
qint64 readLine (char *data, 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 QByteArray &byteArray)
 
qint64 write (const char *data, qint64 maxSize)
 
int writeChannelCount () const const
 
- Public Member Functions inherited from QObject
 QObject (QObject *parent)
 
bool blockSignals (bool block)
 
const QObjectListchildren () 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< QByteArraydynamicPropertyNames () const const
 
virtual bool event (QEvent *e)
 
virtual bool eventFilter (QObject *watched, QEvent *event)
 
findChild (const QString &name, Qt::FindChildOptions options) const const
 
QList< T > findChildren (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
 
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 QMetaObjectmetaObject () const const
 
void moveToThread (QThread *targetThread)
 
QString objectName () const const
 
void objectNameChanged (const QString &objectName)
 
QObjectparent () 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
 
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)
 
qobject_cast (QObject *object)
 
qobject_cast (const 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)
 
QThreadthread () 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 QByteArray &localFileName)
 
QString decodeName (const char *localFileName)
 
QByteArray encodeName (const QString &fileName)
 
bool exists (const QString &fileName)
 
QFileDevice::Permissions permissions (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 *receiver, PointerToMemberFunction method, Qt::ConnectionType type)
 
QMetaObject::Connection connect (const QObject *sender, PointerToMemberFunction signal, Functor functor)
 
QMetaObject::Connection connect (const QObject *sender, PointerToMemberFunction signal, const QObject *context, Functor functor, Qt::ConnectionType type)
 
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, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method)
 
bool disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method)
 
QString tr (const char *sourceText, const char *disambiguation, int n)
 
QString trUtf8 (const char *sourceText, const char *disambiguation, int n)
 

Additional Inherited Members

- Properties inherited from QObject
 objectName
 
- Public Attributes inherited from QFile
typedef DecoderFn
 
typedef EncoderFn
 
- Public Attributes inherited from QFileDevice
typedef FileHandleFlags
 
typedef Permissions
 
- Public Attributes inherited from QIODevice
typedef OpenMode
 
- 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
 
QObjectsender () 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:
if (!staleFiles.isEmpty()) {
"Auto-saved files exist. Do you want to recover them now?",
"File Recovery",
"Recover", "Don't recover") == KMessage::Yes) {
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 118 of file kautosavefile.h.

Constructor & Destructor Documentation

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
filenamethe filename that this KAutoSaveFile refers to
parentthe parent object

Definition at line 86 of file kautosavefile.cpp.

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
parentthe parent object

Definition at line 93 of file kautosavefile.cpp.

KAutoSaveFile::~KAutoSaveFile ( )
override

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

Definition at line 100 of file kautosavefile.cpp.

Member Function Documentation

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.

Definition at line 230 of file kautosavefile.cpp.

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 107 of file kautosavefile.cpp.

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
openmodethe 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 131 of file kautosavefile.cpp.

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 120 of file kautosavefile.cpp.

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
filenamethe filename that this KAutoSaveFile refers to

Definition at line 112 of file kautosavefile.cpp.

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.

Definition at line 202 of file kautosavefile.cpp.


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