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/* This file is part of the KDE libraries
Copyright (C) 2001, 2002 David Faure <[email protected]>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License version 2 as published by the Free Software Foundation.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with this library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/
#ifndef klimitediodevice_h
#define klimitediodevice_h
#include <kdebug.h>
#include <qiodevice.h>
/**
* A readonly device that reads from an underlying device
* from a given point to another (e.g. to give access to a single
* file inside an archive).
* @author David Faure <[email protected]>
* @since 3.1
*/
class KIO_EXPORT KLimitedIODevice : public QIODevice
{
public:
/**
* Creates a new KLimitedIODevice.
* @param dev the underlying device, opened or not
* This device itself auto-opens (in readonly mode), no need to open it.
* @param start where to start reading (position in bytes)
* @param length the length of the data to read (in bytes)
*/
KLimitedIODevice( QIODevice *dev, int start, int length )
: m_dev( dev ), m_start( start ), m_length( length )
{
//kdDebug(7005) << "KLimitedIODevice::KLimitedIODevice start=" << start << " length=" << length << endl;
setType( IO_Direct ); // we support sequential too, but then atEnd() tries getch/ungetch !
open( IO_ReadOnly );
}
virtual ~KLimitedIODevice() {}
virtual bool open( int m ) {
//kdDebug(7005) << "KLimitedIODevice::open m=" << m << endl;
if ( m & IO_ReadOnly ) {
/*bool ok = false;
if ( m_dev->isOpen() )
ok = ( m_dev->mode() == IO_ReadOnly );
else
ok = m_dev->open( m );
if ( ok )*/
m_dev->at( m_start ); // No concurrent access !
}
else
kdWarning(7005) << "KLimitedIODevice::open only supports IO_ReadOnly!" << endl;
setState( IO_Open );
setMode( m );
return true;
}
virtual void close() {}
virtual void flush() {}
virtual Offset size() const { return m_length; }
virtual Q_LONG readBlock ( char * data, Q_ULONG maxlen )
{
maxlen = QMIN( maxlen, m_length - at() ); // Apply upper limit
return m_dev->readBlock( data, maxlen );
}
virtual Q_LONG writeBlock ( const char *, Q_ULONG ) { return -1; } // unsupported
virtual int putch( int ) { return -1; } // unsupported
virtual int getch() {
char c[2];
if ( readBlock(c, 1) == -1)
return -1;
else
return c[0];
}
virtual int ungetch( int c ) { return m_dev->ungetch(c); } // ## apply lower limit ?
virtual Offset at() const { return m_dev->at() - m_start; }
virtual bool at( Offset pos ) {
Q_ASSERT( pos <= m_length );
pos = QMIN( pos, m_length ); // Apply upper limit
return m_dev->at( m_start + pos );
}
virtual bool atEnd() const { return m_dev->atEnd() || m_dev->at() >= m_start + m_length; }
private:
QIODevice* m_dev;
Q_ULONG m_start;
Q_ULONG m_length;
};
#endif
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