qiodevice.cpp

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/****************************************************************************
** $Id: qt/src/tools/qiodevice.cpp   2.2.3   edited 2000-09-05 $
**
** Implementation of QIODevice class
**
** Created : 940913
**
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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