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|
/****************************************************************************
**
** Implementation of QIODevice class
**
** Created : 940913
**
** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
**
** This file is part of the tools module of the Qt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
** Software Foundation and appearing in the files LICENSE.GPL2
** and LICENSE.GPL3 included in the packaging of this file.
** Alternatively you may (at your option) use any later version
** of the GNU General Public License if such license has been
** publicly approved by Trolltech ASA (or its successors, if any)
** and the KDE Free Qt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** This file may be used under the terms of the Q Public License as
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
** included in the packaging of this file. Licensees holding valid Qt
** Commercial licenses may use this file in accordance with the Qt
** Commercial License Agreement provided with the Software.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
** herein.
**
**********************************************************************/
#include "qiodevice.h"
/*!
\class QIODevice qiodevice.h
\reentrant
\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 such as QFile, QBuffer and
QSocket inherit QIODevice and implement virtual functions such as
write() appropriately.
Although applications sometimes use QIODevice directly, it is
usually better to use QTextStream and QDataStream, which provide
stream operations on any QIODevice subclass. QTextStream provides
text-oriented stream functionality (for human-readable ASCII
files, for example), whereas 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:
\list
\i open() opens a device for reading and/or writing, depending on
the mode argument.
\i close() closes the device and tidies up (e.g. flushes buffered
data)
\i readBlock() reads a block of data from the device.
\i writeBlock() writes a block of data to the device.
\i readLine() reads a line (of text, usually) from the device.
\i flush() ensures that all buffered data are written to the real device.
\endlist
There are also some other, less used, action functions:
\list
\i getch() reads a single character.
\i ungetch() forgets the last call to getch(), if possible.
\i putch() writes a single character.
\i size() returns the size of the device, if there is one.
\i at() returns the current read/write pointer's position, if there
is one for this device, or it moves the pointer if given an offset.
\i atEnd() indicates whether there is more to read, if this is
meaningful for this device.
\i reset() moves the read/write pointer to the start of the
device, if that is possible for this device.
\endlist
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:
\list
\i Access type. Some devices are direct access (it is possible
to read/write anywhere), whereas others are sequential. QIODevice
provides the access functions (isDirectAccess(),
isSequentialAccess(), and isCombinedAccess()) to tell users what a
given I/O device supports.
\i Buffering. Some devices are accessed in raw mode, whereas
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().)
\i Synchronicity. Synchronous devices work immediately (for
example, files). When you read from a file, the file delivers its
data straight away. Other kinds of device, 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()
tell the user how this device operates.
\i CR/LF translation. For simplicity, applications often like to
see just a single CR/LF style, and QIODevice subclasses can
provide this. 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().)
\i Permissions. Some files cannot be written. For example,
isReadable(), isWritable() and isReadWrite() tell 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().)
\i Finally, isOpen() returns TRUE if the device is open, i.e.
after an open() call.
\endlist
QIODevice provides numerous pure virtual functions that you need
to implement when subclassing it. Here is a skeleton subclass with
all the members you are sure to need and some that you will
probably need:
\code
class MyDevice : public QIODevice
{
public:
MyDevice();
~MyDevice();
bool open( int mode );
void close();
void flush();
uint size() const;
int at() const; // non-pure virtual
bool at( int ); // non-pure virtual
bool atEnd() const; // non-pure virtual
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 need not be reimplemented for
sequential devices.
\sa QDataStream, QTextStream
*/
/*!
\enum QIODevice::Offset
The offset within the device.
*/
/*!
Constructs an I/O device.
*/
QIODevice::QIODevice()
{
ioMode = 0; // initial mode
ioSt = IO_Ok;
ioIndex = 0;
}
/*!
Destroys 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 additional flags.
*/
/*!
\fn bool QIODevice::isDirectAccess() const
Returns TRUE if the I/O device is a direct access device;
otherwise returns FALSE, i.e. if the device is a sequential access
device.
\sa isSequentialAccess()
*/
/*!
\fn bool QIODevice::isSequentialAccess() const
Returns TRUE if the device is a sequential access device;
otherwise returns FALSE, i.e. if the device is a direct access
device.
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 returns FALSE.
This access method is currently not in use.
*/
/*!
\fn bool QIODevice::isBuffered() const
Returns TRUE if the I/O device is a buffered device; otherwise
returns FALSE, i.e. the device is a raw device.
\sa isRaw()
*/
/*!
\fn bool QIODevice::isRaw() const
Returns TRUE if the device is a raw device; otherwise returns
FALSE, i.e. if the device is a buffered device.
\sa isBuffered()
*/
/*!
\fn bool QIODevice::isSynchronous() const
Returns TRUE if the I/O device is a synchronous device; otherwise
returns FALSE, i.e. the device is an asynchronous device.
\sa isAsynchronous()
*/
/*!
\fn bool QIODevice::isAsynchronous() const
Returns TRUE if the device is an asynchronous device; otherwise
returns FALSE, i.e. if the device is a synchronous device.
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; otherwise returns FALSE.
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; otherwise returns FALSE.
\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; otherwise returns FALSE.
\sa isReadable(), isReadWrite()
*/
/*!
\fn bool QIODevice::isReadWrite() const
Returns TRUE if the I/O device was opened using \c IO_ReadWrite
mode; otherwise returns FALSE.
\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; otherwise returns FALSE.
\sa isOpen()
*/
/*!
\fn bool QIODevice::isOpen() const
Returns TRUE if the I/O device has been opened; otherwise returns
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 find out the reason why the operation failed.
\keyword IO_Ok
\keyword IO_ReadError
\keyword IO_WriteError
\keyword IO_FatalError
\keyword IO_OpenError
\keyword IO_ConnectError
\keyword IO_AbortError
\keyword IO_TimeOutError
\keyword IO_UnspecifiedError
The status codes are:
\table
\header \i Status code \i Meaning
\row \i \c IO_Ok \i The operation was successful.
\row \i \c IO_ReadError \i Could not read from the device.
\row \i \c IO_WriteError \i Could not write to the device.
\row \i \c IO_FatalError \i A fatal unrecoverable error occurred.
\row \i \c IO_OpenError \i Could not open the device.
\row \i \c IO_ConnectError \i Could not connect to the device.
\row \i \c IO_AbortError \i The operation was unexpectedly aborted.
\row \i \c IO_TimeOutError \i The operation timed out.
\row \i \c IO_UnspecifiedError \i An unspecified error happened on close.
\endtable
\sa resetStatus()
*/
/*!
\fn void QIODevice::resetStatus()
Sets the I/O device status to \c IO_Ok.
\sa status()
*/
/*!
\fn void QIODevice::setFlags( int flags )
Used by subclasses to set the device flags to the \a flags specified.
*/
/*!
\fn void QIODevice::setType( int type )
Used by subclasses to set the device type to the \a type specified.
*/
void QIODevice::setType( int t )
{
#if defined(QT_CHECK_RANGE)
if ( (t & IO_TypeMask) != t )
qWarning( "QIODevice::setType: Specified type out of range" );
#endif
ioMode &= ~IO_TypeMask; // reset type bits
ioMode |= t;
}
/*!
\fn void QIODevice::setMode( int mode )
Used by subclasses to set the device mode to the \a mode specified.
*/
void QIODevice::setMode( int m )
{
#if defined(QT_CHECK_RANGE)
if ( (m & IO_ModeMask) != m )
qWarning( "QIODevice::setMode: Specified mode out of range" );
#endif
ioMode &= ~IO_ModeMask; // reset mode bits
ioMode |= m;
}
/*!
\fn void QIODevice::setState( int state )
Used by subclasses to set the device state to the \a state specified.
*/
void QIODevice::setState( int s )
{
#if defined(QT_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;
}
/*!
Used by subclasses to set the device status (not state) to \a s.
*/
void QIODevice::setStatus( int s )
{
ioSt = s;
}
/*!
\fn bool QIODevice::open( int mode )
Opens the I/O device using the specified \a mode. Returns TRUE if
the device was successfully opened; otherwise returns FALSE.
The mode parameter \a mode must be an OR'ed combination of the
following flags.
\table
\header \i Mode flags \i Meaning
\row \i \c IO_Raw \i specifies raw (unbuffered) file access.
\row \i \c IO_ReadOnly \i opens a file in read-only mode.
\row \i \c IO_WriteOnly \i opens a file in write-only mode.
\row \i \c IO_ReadWrite \i opens a file in read/write mode.
\row \i \c IO_Append \i sets the file index to the end of the file.
\row \i \c IO_Truncate \i truncates the file.
\row \i \c IO_Translate \i enables carriage returns and linefeed
translation for text files under MS-DOS, Windows 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 if you write write
binary data. Cannot be combined with \c IO_Raw.
\endtable
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 QIODevice::Offset 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 position.
This is the position of the data read/write head of the I/O
device.
\sa size()
*/
QIODevice::Offset QIODevice::at() const
{
return ioIndex;
}
/*
The following is a "bad" overload, since it does "not behave essentially
the same" like the above. So don't use \overload in the documentation of
this function and we have to live with the qdoc warning which is generated
for this.
*/
/*!
Virtual function that sets the I/O device position to \a pos.
Returns TRUE if the position was successfully set, i.e. \a pos is
within range and the seek was successful; otherwise returns FALSE.
\sa size()
*/
bool QIODevice::at( Offset pos )
{
#if defined(QT_CHECK_RANGE)
if ( pos > size() ) {
#if defined(QT_ABI_QT4)
qWarning( "QIODevice::at: Index %lld out of range", pos );
#else
qWarning( "QIODevice::at: Index %lu out of range", pos );
#endif
return FALSE;
}
#endif
ioIndex = pos;
return TRUE;
}
/*!
Virtual function that returns TRUE if the I/O device position is
at the end of the input; otherwise returns FALSE.
*/
bool QIODevice::atEnd() const
{
if ( isSequentialAccess() || isTranslated() ) {
QIODevice* that = (QIODevice*)this;
const int oldStatus = ioSt;
int c = that->getch();
bool result = c < 0;
that->ungetch(c);
if (ioSt != oldStatus)
that->ioSt = oldStatus;
return result;
} else {
return at() == size();
}
}
/*!
\fn bool QIODevice::reset()
Sets the device index position to 0.
\sa at()
*/
/*!
\fn int QIODevice::readBlock( char *data, Q_ULONG maxlen )
Reads at most \a maxlen bytes from the I/O device into \a data and
returns the number of bytes actually read.
This function should return -1 if a fatal error occurs and should
return 0 if there are no bytes to read.
The device must be opened for reading, and \a data must not be 0.
This virtual function must be reimplemented by all subclasses.
\sa writeBlock() isOpen() isReadable()
*/
/*!
This convenience function returns all of the remaining data in the
device.
*/
QByteArray QIODevice::readAll()
{
if ( isDirectAccess() ) {
// we know the size
int n = size()-at(); // ### fix for 64-bit or large files?
int totalRead = 0;
QByteArray ba( n );
char* c = ba.data();
while ( n ) {
int r = readBlock( c, n );
if ( r < 0 )
return QByteArray();
n -= r;
c += r;
totalRead += r;
// If we have a translated file, then it is possible that
// we read less bytes than size() reports
if ( atEnd() ) {
ba.resize( totalRead );
break;
}
}
return ba;
} else {
// read until we reach the end
const int blocksize = 512;
int nread = 0;
QByteArray ba;
while ( !atEnd() ) {
ba.resize( nread + blocksize );
int r = readBlock( ba.data()+nread, blocksize );
if ( r < 0 )
return QByteArray();
nread += r;
}
ba.resize( nread );
return ba;
}
}
/*!
\fn int QIODevice::writeBlock( const char *data, Q_ULONG len )
Writes \a len bytes from \a data to the I/O device and returns the
number of bytes actually written.
This function should return -1 if a fatal error occurs.
This virtual function must be reimplemented by all subclasses.
\sa readBlock()
*/
/*!
\overload
This convenience function is the same as calling writeBlock(
data.data(), data.size() ).
*/
Q_LONG QIODevice::writeBlock( const QByteArray& data )
{
return writeBlock( data.data(), data.size() );
}
/*!
Reads a line of text, (or up to \a maxlen bytes if a newline isn't
encountered) plus a terminating '\0' into \a data. 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 if an error occurred.
This virtual function can be reimplemented much more efficiently
by the most subclasses.
\sa readBlock(), QTextStream::readLine()
*/
Q_LONG QIODevice::readLine( char *data, Q_ULONG maxlen )
{
if ( maxlen == 0 ) // application bug?
return 0;
char *p = data;
while ( --maxlen && (readBlock(p,1)>0) ) { // read one byte at a time
if ( *p++ == '\n' ) // end of line
break;
}
*p++ = '\0';
return p - data;
}
/*!
\fn int QIODevice::getch()
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.
\sa putch(), ungetch()
*/
/*!
\fn int QIODevice::putch( int ch )
Writes the character \a ch to the I/O device.
Returns \a ch, or -1 if an error occurred.
This virtual function must be reimplemented by all subclasses.
\sa getch(), ungetch()
*/
/*!
\fn int QIODevice::ungetch( int ch )
Puts the character \a ch back into the I/O device and decrements
the index position if it is not zero.
This function is normally called to "undo" a getch() operation.
Returns \a ch, or -1 if an error occurred.
This virtual function must be reimplemented by all subclasses.
\sa getch(), putch()
*/
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