Creates and manages an "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 KUrl &url)
{
// check whether autosave files exist:
QList staleFiles = KAutoSaveFile.staleFiles(url);
if (!staleFiles.isEmpty()) {
if (KMessageBox.questionYesNo(parent,
"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
foreach (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:
foreach (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