QTemporaryFile Class Reference

#include <qtemporaryfile.h>

Inheritance diagram for QTemporaryFile:

[legend]Collaboration diagram for QTemporaryFile:

[legend]List of all members.

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Detailed Description

The QTemporaryFile class is an I/O device that operates on temporary files.

QTemporaryFile is used to create unique temporary files safely. The file itself is created by calling open(). The name of the temporary file is guaranteed to be unique (i.e., you are guaranteed to not overwrite an existing file), and the file will subsequently be removed upon destruction of the QTemporaryFile object. This is an important technique that avoids data corruption for applications that store data in temporary files. The file name is either auto-generated, or created based on a template, which is passed to QTemporaryFile's constructor.

Example:

        {
            QTemporaryFile file;
            if (file.open()) {
                // file.fileName() returns the unique file name
            }

            // the QTemporaryFile destructor removes the temporary file
        }

Reopening a QTemporaryFile after calling close() is safe. For as long as the QTemporaryFile object itself is not destroyed, the unique temporary file will exist and be kept open internally by QTemporaryFile.

A temporary file will have some static part of the name and some part that is calculated to be unique. The default filename qt_temp will be placed into the temporary path as returned by QDir::tempPath().

See also:

QDir::tempPath(), QFile

Definition at line 40 of file qtemporaryfile.h.

Public Member Functions
	QTemporaryFile ()
	QTemporaryFile (const QString &templateName)
	QTemporaryFile (QObject *parent)
	QTemporaryFile (const QString &templateName, QObject *parent)
	~QTemporaryFile ()
bool	autoRemove () const
void	setAutoRemove (bool b)
bool	open ()
QString	fileName () const
QString	fileTemplate () const
void	setFileTemplate (const QString &name)
virtual QAbstractFileEngine *	fileEngine () const
Static Public Member Functions
static QTemporaryFile *	createLocalFile (const QString &fileName)
static QTemporaryFile *	createLocalFile (QFile &file)
Protected Member Functions
bool	open (OpenMode flags)

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Constructor & Destructor Documentation

QTemporaryFile::QTemporaryFile

(

)

Constructs a QTemporaryFile in QDir::tempPath(), using the file template "qt_temp.XXXXXX". The file is stored in the system's temporary directory.

See also:

setFileTemplate(), QDir::tempPath()

Definition at line 364 of file qtemporaryfile.cpp.

References d, and QDir::tempPath().

    : QFile(*new QTemporaryFilePrivate, 0)
{
    Q_D(QTemporaryFile);
    d->templateName = QDir::tempPath() + QLatin1String("/qt_temp.XXXXXX");
}

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QTemporaryFile::QTemporaryFile

(

const QString &

templateName

)

[explicit]

Constructs a QTemporaryFile with a template filename of templateName. Upon opening the temporary file this will be used to create a unique filename. If the templateName does not contain XXXXXX it will automatically be appended and used as the dynamic portion of the filename.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory.

See also:

open(), fileTemplate()

Definition at line 383 of file qtemporaryfile.cpp.

References setFileTemplate().

    : QFile(*new QTemporaryFilePrivate, 0)
{
    setFileTemplate(templateName);
}

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QTemporaryFile::QTemporaryFile

(

QObject *

parent

)

[explicit]

Constructs a QTemporaryFile (with the given parent) in QDir::tempPath(), using the file template "qt_temp.XXXXXX".

See also:

setFileTemplate()

Definition at line 395 of file qtemporaryfile.cpp.

References d, and QDir::tempPath().

    : QFile(*new QTemporaryFilePrivate, parent)
{
    Q_D(QTemporaryFile);
    d->templateName = QDir::tempPath() + QLatin1String("/qt_temp.XXXXXX");
}

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QTemporaryFile::QTemporaryFile	(	const QString &	templateName,
		QObject *	parent
	)

Constructs a QTemporaryFile with a template filename of templateName and the specified parent. Upon opening the temporary file this will be used to create a unique filename. If the templateName does end in XXXXXX it will automatically be appended and used as the dynamic portion of the filename.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory.

See also:

open(), fileTemplate()

Definition at line 416 of file qtemporaryfile.cpp.

References setFileTemplate().

    : QFile(*new QTemporaryFilePrivate, parent)
{
    setFileTemplate(templateName);
}

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QTemporaryFile::~QTemporaryFile

(

)

Destroys the temporary file object, the file is automatically closed if necessary and if in auto remove mode it will automatically delete the file.

See also:

autoRemove()

Definition at line 430 of file qtemporaryfile.cpp.

References QFile::close(), d, and QFile::remove().

{
    Q_D(QTemporaryFile);
    close();
    if (!d->fileName.isEmpty() && d->autoRemove)
        remove();
}

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Member Function Documentation

bool QTemporaryFile::autoRemove

(

)

const

Returns true if the QTemporaryFile is in auto remove mode. Auto-remove mode will automatically delete the filename from disk upon destruction. This makes it very easy to create your QTemporaryFile object on the stack, fill it with data, read from it, and finally on function return it will automatically clean up after itself.

Auto-remove is on by default.

See also:

setAutoRemove(), remove()

Definition at line 461 of file qtemporaryfile.cpp.

References d.

{
    Q_D(const QTemporaryFile);
    return d->autoRemove;
}

void QTemporaryFile::setAutoRemove

(

bool

b

)

Sets the QTemporaryFile into auto-remove mode if b is true.

Auto-remove is on by default.

See also:

autoRemove(), remove()

Definition at line 474 of file qtemporaryfile.cpp.

References d.

{
    Q_D(QTemporaryFile);
    d->autoRemove = b;
}

bool QTemporaryFile::open

(

)

[inline]

A QTemporaryFile will always be opened in QIODevice::ReadWrite mode, this allows easy access to the data in the file. This function will return true upon success and will set the fileName() to the unique filename used.

See also:

fileName()

Definition at line 60 of file qtemporaryfile.h.

References QIODevice::ReadWrite.

Referenced by QFile::copy(), createLocalFile(), defaultMacros(), QConfFileSettingsPrivate::isWritable(), and registerFont().

{ return open(QIODevice::ReadWrite); }

QString QTemporaryFile::fileName

(

)

const

Returns the complete unique filename backing the QTemporaryFile object. This string is null before the QTemporaryFile is opened, afterwards it will contain the fileTemplate() plus additional characters to make it unique.

See also:

fileTemplate()

Reimplemented from QFile.

Definition at line 489 of file qtemporaryfile.cpp.

References QAbstractFileEngine::DefaultName, fileEngine(), QAbstractFileEngine::fileName(), and QIODevice::isOpen().

Referenced by defaultMacros(), and registerFont().

{
    if(!isOpen())
        return QString();
    return fileEngine()->fileName(QAbstractFileEngine::DefaultName);
}

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QString QTemporaryFile::fileTemplate

(

)

const

Returns the set file template. The default file template will be called qt_temp and be placed in QDir::tempPath().

See also:

setFileTemplate()

Definition at line 502 of file qtemporaryfile.cpp.

References d.

{
    Q_D(const QTemporaryFile);
    return d->templateName;
}

void QTemporaryFile::setFileTemplate

(

const QString &

name

)

Sets the static portion of the file name to name. If the file template ends in XXXXXX that will automatically be replaced with the unique part of the filename, otherwise a filename will be determined automatically based on the static portion specified.

If name contains a relative file path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct name if you want use the system's temporary directory.

See also:

fileTemplate()

Definition at line 520 of file qtemporaryfile.cpp.

References d, fileEngine(), QIODevice::isOpen(), name, and QAbstractFileEngine::setFileName().

Referenced by QTemporaryFile().

{
    Q_ASSERT(!isOpen());
    Q_D(QTemporaryFile);
    fileEngine()->setFileName(name);
    d->templateName = name;
}

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QTemporaryFile * QTemporaryFile::createLocalFile

(

const QString &

fileName

)

[inline, static]

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Works on the given fileName rather than an existing QFile object.

Definition at line 66 of file qtemporaryfile.h.

        { QFile file(fileName); return createLocalFile(file); }

QTemporaryFile * QTemporaryFile::createLocalFile

(

QFile &

file

)

[static]

Creates and returns a local temporary file whose contents are a copy of the contents of the given file.

Definition at line 541 of file qtemporaryfile.cpp.

References buffer, QFile::close(), QFile::fileEngine(), QAbstractFileEngine::FlagsMask, QIODevice::isOpen(), len, QAbstractFileEngine::LocalDiskFlag, open(), QFile::open(), QFile::pos(), QIODevice::read(), QIODevice::ReadOnly, QFile::seek(), and QIODevice::write().

{
    if (QAbstractFileEngine *engine = file.fileEngine()) {
        if(engine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::LocalDiskFlag)
            return 0; //local already
        //cache
        bool wasOpen = file.isOpen();
        qint64 old_off = 0;
        if(wasOpen)
            old_off = file.pos();
        else
            file.open(QIODevice::ReadOnly);
        //dump data
        QTemporaryFile *ret = new QTemporaryFile;
        ret->open();
        file.seek(0);
        char buffer[1024];
        while(true) {
            qint64 len = file.read(buffer, 1024);
            if(len < 1)
                break;
            ret->write(buffer, len);
        }
        ret->seek(0);
        //restore
        if(wasOpen)
            file.seek(old_off);
        else
            file.close();
        //done
        return ret;
    }
    return 0;
}

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QAbstractFileEngine * QTemporaryFile::fileEngine

(

)

const [virtual]

Reimplemented from QFile.

Definition at line 580 of file qtemporaryfile.cpp.

References d.

Referenced by fileName(), and setFileTemplate().

{
    Q_D(const QTemporaryFile);
    if(!d->fileEngine)
        d->fileEngine = new QTemporaryFileEngine(d->templateName);
    return d->fileEngine;
}

bool QTemporaryFile::open

(

OpenMode

flags

)

[protected, virtual]

Creates a unique file name for the temporary file, and opens it. You can get the unique name later by calling fileName(). The file is guaranteed to have been created by this function (i.e., it has never existed before).

Reimplemented from QFile.

Definition at line 595 of file qtemporaryfile.cpp.

References d, QAbstractFileEngine::DefaultName, QFile::open(), and QIODevice::setOpenMode().

{
    Q_D(QTemporaryFile);
    if (!d->fileName.isEmpty()) {
        setOpenMode(flags);
        return true;
    }

    if (QFile::open(flags)) {
        d->fileName = d->fileEngine->fileName(QAbstractFileEngine::DefaultName);
        return true;
    }
    return false;
}

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

• src/corelib/io/qtemporaryfile.h
• src/corelib/io/qtemporaryfile.cpp

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