The QFile class is an I/O device that operates on files. More...

#include <qfile.h>

Inheritance diagram for QFile:

Public Types
typedef QCString(*	EncoderFn) (const QString &fileName)

typedef QString(*	DecoderFn) (const QCString &localfileName)

Public Member Functions
	QFile ()

	QFile (const QString &name)

virtual	~QFile ()

QString	name () const

void	setName (const QString &name)

bool	exists () const

bool	remove ()

bool	open (int)

bool	open (int, FILE *)

bool	open (int, int)

void	close ()

void	flush ()

uint	size () const

int	at () const

bool	at (int)

bool	atEnd () const

int	readBlock (char *data, uint len)

int	writeBlock (const char *data, uint len)

int	writeBlock (const QByteArray &data)

int	readLine (char *data, uint maxlen)

int	readLine (QString &, uint maxlen)

int	getch ()

int	putch (int)

int	ungetch (int)

int	handle () const

int64	pos () const

int64	toEnd ()

bool	seek (int64 pos)

Public Member Functions inherited from QIODevice
	QIODevice ()

virtual	~QIODevice ()

int	flags () const

int	mode () const

int	state () const

bool	isDirectAccess () const

bool	isSequentialAccess () const

bool	isCombinedAccess () const

bool	isBuffered () const

bool	isRaw () const

bool	isSynchronous () const

bool	isAsynchronous () const

bool	isTranslated () const

bool	isReadable () const

bool	isWritable () const

bool	isReadWrite () const

bool	isInactive () const

bool	isOpen () const

int	status () const

void	resetStatus ()

bool	reset ()

int	writeBlock (const QByteArray &data)

QByteArray	readAll ()

Static Public Member Functions
static QCString	encodeName (const QString &fileName)

static QString	decodeName (const QCString &localFileName)

static void	setEncodingFunction (EncoderFn)

static void	setDecodingFunction (DecoderFn)

static bool	exists (const QString &fileName)

static bool	remove (const QString &fileName)

Protected Attributes
QString	fn

FILE *	fh

int	fd

int	length

bool	ext_f

void *	d

Protected Attributes inherited from QIODevice
int	ioIndex

Additional Inherited Members
Protected Member Functions inherited from QIODevice
void	setFlags (int f)

void	setType (int)

void	setMode (int)

void	setState (int)

void	setStatus (int)

Detailed Description

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

QFile is an I/O device for reading and writing binary and text files. A QFile may be used by itself (readBlock and writeBlock) or by more conveniently using QDataStream or QTextStream.

Here is a code fragment that uses QTextStream to read a text file line by line. It prints each line with a line number.

QFile f("file.txt");
if ( f.open(IO_ReadOnly) ) {    // file opened successfully
QTextStream t( &f );      // use a text stream
QString s;
int n = 1;
while ( !t.eof() ) {      // until end of file...
    s = t.readLine();     // line of text excluding '\n'
    printf( "%3d: %s\n", n++, (const char *)s );
}
f.close();
}

The QFileInfo class holds detailed information about a file, such as access permissions, file dates and file types.

The QDir class manages directories and lists of file names.

See also: QDataStream, QTextStream

Constructor & Destructor Documentation

§ QFile() [1/2]

QFile::QFile ( )

Constructs a QFile with no name.

§ QFile() [2/2]

QFile::QFile ( const QString & name )

Constructs a QFile with a file name name.

See also: setName()

§ ~QFile()

QFile::~QFile ( )

virtual

Destructs a QFile. Calls close().

Member Function Documentation

§ at() [1/2]

int QFile::at ( ) const

inlinevirtual

Returns the file index.

See also: size()

Reimplemented from QIODevice.

§ at() [2/2]

bool QFile::at ( int pos )

virtual

Sets the file index to pos. Returns TRUE if successful, otherwise FALSE.

Example:

QFile f( "data.bin" );
f.open( IO_ReadOnly );            // index set to 0
f.at( 100 );              // set index to 100
f.at( f.at()+50 );                // set index to 150
f.at( f.size()-80 );          // set index to 80 before EOF
f.close();

Warning: The result is undefined if the file was opened using the IO_Append specifier.

See also: size(), open()

Reimplemented from QIODevice.

§ atEnd()

bool QFile::atEnd ( ) const

virtual

Returns TRUE if the end of file has been reached, otherwise FALSE.

See also: size()

Reimplemented from QIODevice.

§ close()

void QFile::close ( )

virtual

Closes an open file.

The file is not closed if it was opened with an existing file handle. If the existing file handle is a FILE*, the file is flushed. If the existing file handle is an int file descriptor, nothing is done to the file.

Some "write-behind" filesystems may report an unspecified error on closing the file. These errors only indicate that something may have gone wrong since the previous open(). In such a case status() reports IO_UnspecifiedError after close(), otherwise IO_Ok.

See also: open(), flush()

Implements QIODevice.

§ decodeName()

QString QFile::decodeName ( const QCString & localFileName )

static

This does the reverse of QFile::encodeName().

See also: setDecodingFunction()

§ encodeName()

QCString QFile::encodeName ( const QString & fileName )

static

When you use QFile, QFileInfo, and QDir to access the filesystem with Qt, you can use Unicode filenames. On Unix, these filenames are converted to an 8-bit encoding. If you want to do your own file I/O on Unix, you should convert the filename using this function. On Windows NT, Unicode filenames are supported directly in the filesystem and this function should be avoided. On Windows 95, non-Latin1 locales are not supported at this time.

By default, this function converts to the local 8-bit encoding determined by the user's locale. This is sufficient for filenames that the user chooses. Filenames hard-coded into the application should only use 7-bit ASCII filename characters.

The conversion scheme can be changed using setEncodingFunction(). This might be useful if you wish to give the user an option to store in filenames in UTF-8, etc., but beware that such filenames would probably then be unrecognizable when seen by other programs.

See also: decodeName()

§ exists() [1/2]

bool QFile::exists ( ) const

Returns TRUE if this file exists, otherwise FALSE.

See also: name()

§ exists() [2/2]

bool QFile::exists ( const QString & fileName )

static

Returns TRUE if the file given by fileName exists, otherwise FALSE.

§ flush()

void QFile::flush ( )

virtual

Flushes the file buffer to the disk.

close() also flushes the file buffer.

Implements QIODevice.

§ getch()

int QFile::getch ( )

virtual

Reads a single byte/character from the file.

Returns the byte/character read, or -1 if the end of the file has been reached.

See also: putch(), ungetch()

Implements QIODevice.

§ handle()

int QFile::handle ( ) const

Returns the file handle of the file.

This is a small positive integer, suitable for use with C library functions such as fdopen() and fcntl(), as well as with QSocketNotifier.

If the file is not open or there is an error, handle() returns -1.

See also: QSocketNotifier

§ name()

QString QFile::name ( ) const

inline

Returns the name set by setName().

See also: setName(), QFileInfo::fileName()

§ open() [1/3]

bool QFile::open ( int m )

virtual

Opens the file specified by the file name currently set, using the mode m. Returns TRUE if successful, otherwise FALSE.

The mode parameter m must be a combination of the following flags:

IO_Raw specified raw (non-buffered) file access.
IO_ReadOnly opens the file in read-only mode.
IO_WriteOnly opens the file in write-only mode (and truncates).
IO_ReadWrite opens the file in read/write mode, equivalent to (IO_ReadOnly|IO_WriteOnly).
IO_Append opens the file in append mode. This mode is very useful when you want to write something to a log file. The file index is set to the end of the file. Note that the result is undefined if you position the file index manually using at() in append mode.
IO_Truncate truncates the file.
IO_Translate enables carriage returns and linefeed translation for text files under MS-DOS, Windows and OS/2.

The raw access mode is best when I/O is block-operated using 4kB block size or greater. Buffered access works better when reading small portions of data at a time.

Important: When working with buffered files, data may not be written to the file at once. Call flush to make sure the data is really written.

Warning: We have experienced problems with some C libraries when a buffered file is opened for both reading and writing. If a read operation takes place immediately after a write operation, the read buffer contains garbage data. Worse, the same garbage is written to the file. Calling flush() before readBlock() solved this problem.

If the file does not exist and IO_WriteOnly or IO_ReadWrite is specified, it is created.

Example:

QFile f1( "/tmp/data.bin" );
QFile f2( "readme.txt" );
f1.open( IO_Raw | IO_ReadWrite | IO_Append );
f2.open( IO_ReadOnly | IO_Translate );

See also: name(), close(), isOpen(), flush()

Implements QIODevice.

§ open() [2/3]

bool QFile::open	(	int	m,
		FILE *	f
	)

Opens a file in the mode m using an existing file handle f. Returns TRUE if successful, otherwise FALSE.

Example:

#include <stdio.h>
void printError( const char* msg )
{
QFile f;
f.open( IO_WriteOnly, stderr );
f.writeBlock( msg, qstrlen(msg) );    // write to stderr
f.close();
}

When a QFile is opened using this function, close() does not actually close the file, only flushes it.

Warning: If f is stdin, stdout, stderr, you may not be able to seek. See QIODevice::isSequentialAccess() for more information.

See also: close()

§ open() [3/3]

bool QFile::open	(	int	m,
		int	f
	)

Opens a file in the mode m using an existing file descriptor f. Returns TRUE if successful, otherwise FALSE.

When a QFile is opened using this function, close() does not actually close the file.

Warning: If f is one of 0 (stdin), 1 (stdout) or 2 (stderr), you may not be able to seek. size() is set to INT_MAX (in limits.h).

See also: close()

§ putch()

int QFile::putch ( int ch )

virtual

Writes the character ch to the file.

Returns ch, or -1 if some error occurred.

See also: getch(), ungetch()

Implements QIODevice.

§ readBlock()

int QFile::readBlock	(	char *	p,
		uint	len
	)

virtual

Reads at most len bytes from the file into p and returns the number of bytes actually read.

Returns -1 if a serious error occurred.

Warning: We have experienced problems with some C libraries when a buffered file is opened for both reading and writing. If a read operation takes place immediately after a write operation, the read buffer contains garbage data. Worse, the same garbage is written to the file. Calling flush() before readBlock() solved this problem.

See also: writeBlock()

Implements QIODevice.

§ readLine() [1/2]

int QFile::readLine	(	char *	p,
		uint	maxlen
	)

virtual

Reads a line of text.

Reads bytes from the file until end-of-line is reached, or up to maxlen bytes, and returns the number of bytes read, or -1 in case of error. The terminating newline is not stripped.

This function is efficient only for buffered files. Avoid readLine() for files that have been opened with the IO_Raw flag.

See also: readBlock(), QTextStream::readLine()

Reimplemented from QIODevice.

§ readLine() [2/2]

int QFile::readLine	(	QString &	s,
		uint	maxlen
	)

Reads a line of text.

Reads bytes from the file until end-of-line is reached, or up to maxlen bytes, and returns the number of bytes read, or -1 in case of error. The terminating newline is not stripped.

This function is efficient only for buffered files. Avoid readLine() for files that have been opened with the IO_Raw flag.

Note that the string is read as plain Latin1 bytes, not Unicode.

See also: readBlock(), QTextStream::readLine()

§ remove() [1/2]

bool QFile::remove ( )

Removes the file specified by the file name currently set. Returns TRUE if successful, otherwise FALSE.

The file is closed before it is removed.

§ remove() [2/2]

bool QFile::remove ( const QString & fileName )

static

Removes the file fileName. Returns TRUE if successful, otherwise FALSE.

§ setDecodingFunction()

void QFile::setDecodingFunction ( DecoderFn f )

static

Sets the function for decoding 8-bit filenames. The default uses the locale-specific 8-bit encoding.

See also: encodeName(), decodeName()

§ setEncodingFunction()

void QFile::setEncodingFunction ( EncoderFn f )

static

Sets the function for encoding Unicode filenames. The default encodes in the locale-specific 8-bit encoding.

See also: encodeName()

§ setName()

void QFile::setName ( const QString & name )

Sets the name of the file. The name can include an absolute directory path or it can be a name or a path relative to the current directory.

Do not call this function if the file has already been opened.

Note that if the name is relative QFile does not associate it with the current directory. If you change directory before calling open(), open uses the new current directory.

Example:

QFile f;
QDir::setCurrent( "/tmp" );
f.setName( "readme.txt" );
QDir::setCurrent( "/home" );
f.open( IO_ReadOnly );      // opens "/home/readme.txt" under UNIX

Also note that the directory separator '/' works for all operating systems supported by Qt.

See also: name(), QFileInfo, QDir

§ size()

uint QFile::size ( ) const

virtual

Returns the file size.

See also: at()

Implements QIODevice.

§ ungetch()

int QFile::ungetch ( int ch )

virtual

Puts the character ch back into the file and decrements the index if it is not zero.

This function is normally called to "undo" a getch() operation.

Returns ch, or -1 if some error occurred.

See also: getch(), putch()

Implements QIODevice.

§ writeBlock() [1/2]

int QFile::writeBlock	(	const char *	p,
		uint	len
	)

virtual

Writes len bytes from p to the file and returns the number of bytes actually written.

Returns -1 if a serious error occurred.

Warning: When working with buffered files, data may not be written to the file at once. Call flush() to make sure the data is really written.

See also: readBlock()

Implements QIODevice.

§ writeBlock() [2/2]

int QFile::writeBlock ( const QByteArray & data )

inline

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

qtools/qfile.h
qtools/qfile.cpp
qtools/qfile_unix.cpp
qtools/qfile_win32.cpp

Public Types

Public Member Functions

Static Public Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

§ QFile() [1/2]

§ QFile() [2/2]

§ ~QFile()

Member Function Documentation

§ at() [1/2]

§ at() [2/2]

§ atEnd()

§ close()

§ decodeName()

§ encodeName()

§ exists() [1/2]

§ exists() [2/2]

§ flush()

§ getch()

§ handle()

§ name()

§ open() [1/3]

§ open() [2/3]

§ open() [3/3]

§ putch()

§ readBlock()

§ readLine() [1/2]

§ readLine() [2/2]

§ remove() [1/2]

§ remove() [2/2]

§ setDecodingFunction()

§ setEncodingFunction()

§ setName()

§ size()

§ ungetch()

§ writeBlock() [1/2]

§ writeBlock() [2/2]