QIODevice - The base class of I/O devices

       #include <qiodevice.h>

       Inherited by QBuffer, QFile, QSocket and QSocketDevice.

   Public Members
       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 ()
       virtual bool open ( int mode )
       virtual void close ()
       virtual void flush ()
       virtual uint size () const
       virtual int at () const
       virtual bool at ( int )
       virtual bool atEnd () const
       bool reset ()
       virtual int readBlock ( char * data, uint maxlen )
       virtual int writeBlock ( const char * data, uint len )
       virtual int readLine ( char * data, uint maxlen )
       int writeBlock ( const QByteArray & data )
       QByteArray readAll ()
       virtual int getch ()
       virtual int putch ( int )
       virtual int ungetch ( int )

   Protected Members
       void setFlags ( int f ) (internal)
       void setType ( int ) (internal)
       void setMode ( int ) (internal)
       void setState ( int ) (internal)
       void setStatus ( int ) (internal)

       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:

       open() opens a device for reading and/or writing,
              depending on the argument to open().

       close() closes the device and tidies up.

       readBlock() reads a block of data from the device.

       writeBlock() writes a block of data to the device.

       readLine() reads a line (of text, usually) from the
              device.

       flush() ensures that all buffered data are written to the
              real device.

              There are also some other, less used, action
              functions:

       getch() reads a single character.

       ungetch() forgets the last call to getch(), if possible.

       putch() writes a single character.

       size() returns the size of the device, if there is one.

       at() returns the current read/write pointer, if there is
              one for this device, or it moves the pointer.

       atEnd() says whether there is more to read, if that is a
              meaningful question for this device.

              device, if that is possible for this device.

              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:

       Access type. Some devices are direct access (it is
              possible to read/write anywhere) while others are
              sequential. QIODevice provides the access functions
              isDirectAccess(), isSequentialAccess() and
              isCombinedAccess() to tell users what a given I/O
              device supports.

       Buffering. Some devices are accessed in raw mode while
              others are buffered. Buffering usually provides
              greater efficiency, particularly for small
              read/write operations. isBuffered() tells the user
              whether a given device is buffered. (This can often
              be set by the application in the call to open().)

       Synchronicity. Synchronous devices work there and then,
              for example files. When you read from a file, the
              file delivers its data right away. Others, such as
              a socket connected to a HTTP server, may not
              deliver the data until seconds after you ask to
              read it. isSynchronous() and isAsynchronous() tells
              the user how this device operates.

       CR/LF translation. For simplicity, applications often like
              to see just a single CR/LF style, and QIODevice
              subclasses can provide that. isTranslated() returns
              TRUE if this object translates CR/LF to just LF.
              (This can often be set by the application in the
              call to open().)

       Accessibility. Some files cannot be written, for example.
              isReadable(), isWritable and isReadWrite() tells
              the application whether it can read from and write
              to a given device. (This can often be set by the
              application in the call to open().)

       Finally, isOpen() returns TRUE if the device is open. This
              can quite obviously be set using open() :)

       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 QBuffer, QSocketDevice, QSocket 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 QBuffer, QFile, QSocket and
       QSocketDevice.


bool QIODevice::atEnd () const [virtual]

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



void QIODevice::close () [virtual]

       Closes the I/O device.

       This virtual function must be reimplemented by all
       subclasses.

       See also open().

       Reimplemented in QBuffer, QSocketDevice, QFile 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 QFile, QSocket, QBuffer and
       QSocketDevice.


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 QSocketDevice, QFile, QBuffer and
       QSocket.


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.



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.



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.

       IO_Raw specified raw (unbuffered) file access.

       IO_ReadOnly opens a file in read-only mode.

       IO_WriteOnly opens a file in write-only mode.

       IO_ReadWrite opens a file in read/write mode.

       IO_Append sets the file index to the end of the file.

       IO_Truncate truncates the file.

       IO_Translate enables carriage returns and linefeed
              translation for text files under MS-DOS, Window,
              OS/2 and Macintosh. On Unix systems this flag has
              no effect. Use with caution as it will also
              transform every linefeed written to the file into a
              CRLF pair. This is likely to corrupt your file when
              writing binary data to it. Cannot be combined with
              IO_Raw.

       subclasses.

       See also close().

       Reimplemented in QBuffer, QFile, QSocketDevice and
       QSocket.


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 QSocket, QBuffer, QSocketDevice and
       QFile.


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 QBuffer, QSocket, QSocketDevice 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, 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 QSocket, QBuffer and QFile.

       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, QFile, QBuffer and
       QSocketDevice.


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:

       IO_Ok The operation was successful.

       IO_ReadError Could not read from the device.

       IO_WriteError Could not write to the device.

       IO_FatalError A fatal unrecoverable error occurred.

       IO_OpenError Could not open the device.

       IO_ConnectError Could not connect to the device.

       IO_AbortError The operation was unexpectedly aborted.

       IO_TimeOutError The operation timed out.

       IO_OnCloseError An unspecified error happened on close.



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, QFile, QSocketDevice 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, QSocketDevice, QFile and
       QSocket.


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.


SEE ALSO

       http://doc.trolltech.com/qiodevice.html
       http://www.trolltech.com/faq/tech.html

       Copyright 1992-2001 Trolltech AS,
       http://www.trolltech.com.  See the license file included
       in the distribution for a complete license statement.


AUTHOR

       Generated automatically from the source code.


BUGS

       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.  Good bug reports
       make our job much simpler. Thank you.

       In case of content or formattting problems with this
       manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qiodevice.3qt)
       and the Qt version (2.3.1).


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