HomeHome

Classes - Annotated - Tree - Functions - Home - Structure Qte

QIODevice Class Reference


The QIODevice class is the base class of I/O devices. More...

#include <qiodevice.h>

Inherited by QBuffer, QFile, QSocket and QSocketDevice.

List of all member functions.

Public Members

Protected Members


Detailed Description

The QIODevice class is the base class of I/O devices.

An I/O device represents a medium that one can read bytes from and/or write bytes to. The QIODevice class is the abstract superclass of all such devices; classes like QFile, QBuffer and QSocket inherit QIODevice and implement virtual functions like write() appropriately.

While applications sometimes use QIODevice directly, mostly it is better to go through QTextStream and QDataStream, which provide stream operations on any QIODevice subclass. QTextStream provides text-oriented stream functionality (for human-readable ASCII files, for example), while QDataStream deals with binary data in a totally platform-independent manner.

The public member functions in QIODevice roughly fall into two groups: The action functions and the state access functions. The most important action functions are:

There are also some other, less used, action functions: The state access are all "get" functions. The QIODevice subclass calls setState() to update the state, and simple access functions tell the user of the device what the device's state is. Here are the settings, and their associated access functions:

QIODevice provides numerous pure virtual functions you need to implement when subclassing it. Here is a skeleton subclass with all the members you are certain to need, and some it's likely that you will need:

    class YourDevice : public QIODevice
    {
    public:
        YourDevice();
       ~YourDevice();

        bool open( int mode );
        void close();
        void flush();

        uint size() const;
        int  at() const;        // not a pure virtual function
        bool at( int );         // not a pure virtual function
        bool atEnd() const;     // not a pure virtual function

        int readBlock( char *data, uint maxlen );
        int writeBlock( const char *data, uint len );
        int readLine( char *data, uint maxlen );

        int getch();
        int putch( int );
        int ungetch( int );
    };

The three non-pure virtual functions can be ignored if your device is sequential (e.g. an RS-232 port).

See also QDataStream and QTextStream.


Member Function Documentation

QIODevice::QIODevice ()

Constructs an I/O device.

QIODevice::~QIODevice () [virtual]

Destructs the I/O device.

bool QIODevice::at ( int pos ) [virtual]

Virtual function that sets the I/O device index to pos.

See also size().

Reimplemented in QSocket, QSocketDevice, QBuffer and QFile.

int QIODevice::at () const [virtual]

Virtual function that returns the current I/O device index.

This index is the data read/write head of the I/O device.

See also size().

Reimplemented in QSocket, QSocketDevice, QBuffer and QFile.

bool QIODevice::atEnd () const [virtual]

Virtual function that returns TRUE if the I/O device index is at the end of the input.

Reimplemented in QFile, QSocket and QSocketDevice.

void QIODevice::close () [virtual]

Closes the I/O device.

This virtual function must be reimplemented by all subclasses.

See also open().

Reimplemented in QFile, QBuffer, QSocketDevice and QSocket.

int QIODevice::flags () const

Returns the current I/O device flags setting.

Flags consists of mode flags and state flags.

See also mode() and state().

void QIODevice::flush () [virtual]

Flushes an open I/O device.

This virtual function must be reimplemented by all subclasses.

Reimplemented in QSocketDevice, QBuffer, QFile and QSocket.

int QIODevice::getch () [virtual]

Reads a single byte/character from the I/O device.

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

This virtual function must be reimplemented by all subclasses.

See also putch() and ungetch().

Reimplemented in QBuffer, QSocketDevice, QSocket and QFile.

bool QIODevice::isAsynchronous () const

Returns TRUE if the I/O device is a asynchronous device, otherwise FALSE.

This mode is currently not in use.

See also isSynchronous().

bool QIODevice::isBuffered () const

Returns TRUE if the I/O device is a buffered (not raw) device, otherwise FALSE.

See also isRaw().

bool QIODevice::isCombinedAccess () const

Returns TRUE if the I/O device is a combined access (both direct and sequential) device, otherwise FALSE.

This access method is currently not in use.

bool QIODevice::isDirectAccess () const

Returns TRUE if the I/O device is a direct access (not sequential) device, otherwise FALSE.

See also isSequentialAccess().

bool QIODevice::isInactive () const

Returns TRUE if the I/O device state is 0, i.e. the device is not open.

See also isOpen().

bool QIODevice::isOpen () const

Returns TRUE if the I/O device state has been opened, otherwise FALSE.

See also isInactive().

bool QIODevice::isRaw () const

Returns TRUE if the I/O device is a raw (not buffered) device, otherwise FALSE.

See also isBuffered().

bool QIODevice::isReadWrite () const

Returns TRUE if the I/O device was opened using IO_ReadWrite mode.

See also isReadable() and isWritable().

bool QIODevice::isReadable () const

Returns TRUE if the I/O device was opened using IO_ReadOnly or IO_ReadWrite mode.

See also isWritable() and isReadWrite().

bool QIODevice::isSequentialAccess () const

Returns TRUE if the I/O device is a sequential access (not direct) device, otherwise FALSE. Operations involving size() and at(int) are not valid on sequential devices.

See also isDirectAccess().

bool QIODevice::isSynchronous () const

Returns TRUE if the I/O device is a synchronous device, otherwise FALSE.

See also isAsynchronous().

bool QIODevice::isTranslated () const

Returns TRUE if the I/O device translates carriage-return and linefeed characters.

A QFile is translated if it is opened with the IO_Translate mode flag.

bool QIODevice::isWritable () const

Returns TRUE if the I/O device was opened using IO_WriteOnly or IO_ReadWrite mode.

See also isReadable() and isReadWrite().

int QIODevice::mode () const

Returns bits OR'ed together that specify the current operation mode.

These are the flags that were given to the open() function.

The flags are: IO_ReadOnly, IO_WriteOnly, IO_ReadWrite, IO_Append, IO_Truncate and IO_Translate.

bool QIODevice::open ( int mode ) [virtual]

Opens the I/O device using the specified mode. Returns TRUE if successful, or FALSE if the device could not be opened.

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

This virtual function must be reimplemented by all subclasses.

See also close().

Reimplemented in QBuffer, QSocket, QSocketDevice and QFile.

int QIODevice::putch ( int ch ) [virtual]

Writes the character ch to the I/O device.

Returns ch, or -1 if some error occurred.

This virtual function must be reimplemented by all subclasses.

See also getch() and ungetch().

Reimplemented in QSocketDevice, QFile, QSocket and QBuffer.

QByteArray QIODevice::readAll ()

This convenience function returns all of the remaining data in the device. Note that this only works for direct access devices, such as QFile.

See also isDirectAccess().

int QIODevice::readBlock ( char * data, uint maxlen ) [virtual]

Reads at most maxlen bytes from the I/O device into data and returns the number of bytes actually read.

This virtual function must be reimplemented by all subclasses.

See also writeBlock().

Reimplemented in QSocketDevice, QSocket, QBuffer and QFile.

int QIODevice::readLine ( char * data, uint maxlen ) [virtual]

Reads a line of text, up to maxlen bytes including a terminating \0. If there is a newline at the end if the line, it is not stripped.

Returns the number of bytes read including the terminating \0, or -1 in case of error.

This virtual function can be reimplemented much more efficiently by the most subclasses.

See also readBlock() and QTextStream::readLine().

Reimplemented in QFile, QBuffer and QSocket.

bool QIODevice::reset ()

Sets the device index to 0.

See also at().

void QIODevice::resetStatus ()

Sets the I/O device status to IO_Ok.

See also status().

uint QIODevice::size () const [virtual]

Virtual function that returns the size of the I/O device.

See also at().

Reimplemented in QSocket, QSocketDevice, QBuffer and QFile.

int QIODevice::state () const

Returns bits OR'ed together that specify the current state.

The flags are: IO_Open.

Subclasses may define more flags.

int QIODevice::status () const

Returns the I/O device status.

The I/O device status returns an error code. If open() returns FALSE or readBlock() or writeBlock() return -1, this function can be called to get the reason why the operation did not succeed.

The status codes are:

See also resetStatus().

int QIODevice::ungetch ( int ch ) [virtual]

Puts the character ch back into the I/O device 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.

This virtual function must be reimplemented by all subclasses.

See also getch() and putch().

Reimplemented in QBuffer, QSocketDevice, QFile and QSocket.

int QIODevice::writeBlock ( const QByteArray & data )

This convenience function is the same as calling writeBlock( data.data(), data.size() ).

int QIODevice::writeBlock ( const char * data, uint len ) [virtual]

Writes len bytes from p to the I/O device and returns the number of bytes actually written.

This virtual function must be reimplemented by all subclasses.

See also readBlock().

Reimplemented in QBuffer, QFile, QSocket and QSocketDevice.

void QIODevice::setFlags ( int f ) [protected]

For internal use only.

void QIODevice::setMode ( int m ) [protected]

For internal use only.

void QIODevice::setState ( int s ) [protected]

For internal use only.

void QIODevice::setStatus ( int s ) [protected]

For internal use only.

void QIODevice::setType ( int t ) [protected]

For internal use only.


Search the documentation, FAQ, qt-interest archive and more (uses www.trolltech.com):


This file is part of the Qt toolkit, copyright © 1995-2005 Trolltech, all rights reserved.


Copyright © 2005 TrolltechTrademarks
Qt version 2.3.10