/****************************************************************************

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** Implementation of QIODevice class

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#include "qiodevice.h"

// NOT REVISED

/*!

  \class QIODevice qiodevice.h

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

  \ingroup io

  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: <ul>

  <li> open() opens a device for reading and/or writing, depending on

  the argument to open().

  <li> close() closes the device and tidies up.

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

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

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

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

  </ul>There are also some other, less used, action functions: <ul>

  <li> getch() reads a single character.

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

  <li> putch() writes a single character.

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

  <li> at() returns the current read/write pointer, if there is one

  for this device, or it moves the pointer.

  <li> atEnd() says whether there is more to read, if that is a

  meaningful question for this device.

  <li> reset() moves the read/write pointer to the start of the

  device, if that is possible for this device.

  </ul>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: <ul>

  <li> 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.

  <li> 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().)

  <li> 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.

  <li> 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().)

  <li> 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().)

  <li> Finally, isOpen() returns TRUE if the device is open.  This can

  quite obviously be set using open() :)

  </ul>

  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:

  \code

    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 );

    };

  \endcode

  The three non-pure virtual functions can be ignored if your device

  is sequential (e.g. an RS-232 port).

  \sa QDataStream, QTextStream

*/

/*!

  Constructs an I/O device.

*/

QIODevice::QIODevice()

{

    ioMode = 0;					// initial mode

    ioSt = IO_Ok;

    ioIndex = 0;

}

/*!

  Destructs the I/O device.

*/

QIODevice::~QIODevice()

{

}

/*!

  \fn int QIODevice::flags() const

  Returns the current I/O device flags setting.

  Flags consists of mode flags and state flags.

  \sa mode(), state()

*/

/*!

  \fn 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: \c IO_ReadOnly, \c IO_WriteOnly, \c IO_ReadWrite,

  \c IO_Append, \c IO_Truncate and \c IO_Translate.

*/

/*!

  \fn int QIODevice::state() const

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

  The flags are: \c IO_Open.

  Subclasses may define more flags.

*/

/*!

  \fn bool QIODevice::isDirectAccess() const

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

  otherwise FALSE.

  \sa isSequentialAccess()

*/

/*!

  \fn 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.

  \sa isDirectAccess()

*/

/*!

  \fn 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.

*/

/*!

  \fn bool QIODevice::isBuffered() const

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

  FALSE.

  \sa isRaw()

*/

/*!

  \fn bool QIODevice::isRaw() const

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

  FALSE.

  \sa isBuffered()

*/

/*!

  \fn bool QIODevice::isSynchronous() const

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

  FALSE.

  \sa isAsynchronous()

*/

/*!

  \fn bool QIODevice::isAsynchronous() const

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

  FALSE.

  This mode is currently not in use.

  \sa isSynchronous()

*/

/*!

  \fn 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 \c IO_Translate mode

  flag.

*/

/*!

  \fn bool QIODevice::isReadable() const

  Returns TRUE if the I/O device was opened using \c IO_ReadOnly or

  \c IO_ReadWrite mode.

  \sa isWritable(), isReadWrite()

*/

/*!

  \fn bool QIODevice::isWritable() const

  Returns TRUE if the I/O device was opened using \c IO_WriteOnly or

  \c IO_ReadWrite mode.

  \sa isReadable(), isReadWrite()

*/

/*!

  \fn bool QIODevice::isReadWrite() const

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

  \sa isReadable(), isWritable()

*/

/*!

  \fn bool QIODevice::isInactive() const

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

  \sa isOpen()

*/

/*!

  \fn bool QIODevice::isOpen() const

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

  \sa isInactive()

*/

/*!

  \fn 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:

  <ul>

  <li>\c IO_Ok The operation was successful.

  <li>\c IO_ReadError Could not read from the device.

  <li>\c IO_WriteError Could not write to the device.

  <li>\c IO_FatalError A fatal unrecoverable error occurred.

  <li>\c IO_OpenError Could not open the device.

  <li>\c IO_ConnectError Could not connect to the device.

  <li>\c IO_AbortError The operation was unexpectedly aborted.

  <li>\c IO_TimeOutError The operation timed out.

  <li>\c IO_OnCloseError An unspecified error happened on close.

  </ul>

  \sa resetStatus()

*/

/*!

  \fn void QIODevice::resetStatus()

  Sets the I/O device status to \c IO_Ok.

  \sa status()

*/

/*!

  \fn void QIODevice::setFlags( int f )

  \internal

  Used by subclasses to set the device flags.

*/

/*!

  \internal

  Used by subclasses to set the device type.

*/

void QIODevice::setType( int t )

{

#if defined(CHECK_RANGE)

    if ( (t & IO_TypeMask) != t )

	qWarning( "QIODevice::setType: Specified type out of range" );

#endif

    ioMode &= ~IO_TypeMask;			// reset type bits

    ioMode |= t;

}

/*!

  \internal

  Used by subclasses to set the device mode.

*/

void QIODevice::setMode( int m )

{

#if defined(CHECK_RANGE)

    if ( (m & IO_ModeMask) != m )

	qWarning( "QIODevice::setMode: Specified mode out of range" );

#endif

    ioMode &= ~IO_ModeMask;			// reset mode bits

    ioMode |= m;

}

/*!

  \internal

  Used by subclasses to set the device state.

*/

void QIODevice::setState( int s )

{

#if defined(CHECK_RANGE)

    if ( ((uint)s & IO_StateMask) != (uint)s )

	qWarning( "QIODevice::setState: Specified state out of range" );

#endif

    ioMode &= ~IO_StateMask;			// reset state bits

    ioMode |= (uint)s;

}

/*!

  \internal

  Used by subclasses to set the device status (not state).

*/

void QIODevice::setStatus( int s )

{

    ioSt = s;

}

/*!

  \fn bool QIODevice::open( int mode )

  Opens the I/O device using the specified \e mode.

  Returns TRUE if successful, or FALSE if the device could not be opened.

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

  <ul>

  <li>\c IO_Raw specified raw (unbuffered) file access.

  <li>\c IO_ReadOnly opens a file in read-only mode.

  <li>\c IO_WriteOnly opens a file in write-only mode.

  <li>\c IO_ReadWrite opens a file in read/write mode.

  <li>\c IO_Append sets the file index to the end of the file.

  <li>\c IO_Truncate truncates the file.

  <li>\c 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 \c IO_Raw.

  </ul>

  This virtual function must be reimplemented by all subclasses.

  \sa close()

*/

/*!

  \fn void QIODevice::close()

  Closes the I/O device.

  This virtual function must be reimplemented by all subclasses.

  \sa open()

*/

/*!

  \fn void QIODevice::flush()

  Flushes an open I/O device.

  This virtual function must be reimplemented by all subclasses.

*/

/*!

  \fn uint QIODevice::size() const

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

  \sa at()

*/

/*!

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

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

  \sa size()

*/

int QIODevice::at() const

{

    return ioIndex;

}

/*!

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

  \sa size()

*/

bool QIODevice::at( int pos )

{

#if defined(CHECK_RANGE)

    if ( (uint)pos > size() ) {

	qWarning( "QIODevice::at: Index %d out of range", pos );

	return FALSE;

    }

#endif

    ioIndex = pos;

    return TRUE;

}

/*!

  Virtual function that returns TRUE if the I/O device index is at the

  end of the input.

*/

bool QIODevice::atEnd() const

{

    if ( isSequentialAccess() || isTranslated() ) {

	QIODevice* that = (QIODevice*)this;

	int c = that->getch();

	bool result = c < 0;

	that->ungetch(c);

	return result;

    } else {

	return at() == (int)size();

    }

}

/*!

  \fn bool QIODevice::reset()

  Sets the device index to 0.

  \sa at()

*/

/*!

  \fn int QIODevice::readBlock( char *data, uint maxlen )

  Reads at most \e maxlen bytes from the I/O device into \e data and

  returns the number of bytes actually read.

  This virtual function must be reimplemented by all subclasses.

  \sa writeBlock()

*/

/*!