Source: klimitediodevice.h

# Source: klimitediodevice.h |
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    /* This file is part of the KDE libraries
       Copyright (C) 2001, 2002 David Faure

       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., 59 Temple Place - Suite 330,
       Boston, MA 02111-1307, USA.
    */

    #ifndef klimitediodevice_h
    #define klimitediodevice_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
     * @since 3.1
     */
    class KLimitedIODevice : public QIODevice
    {
    public:
        /**
         * @param dev the underlying device, opened or not
         * This device itself auto-opens (in readonly mode), no need to open it.
         */
        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->at() >= m_start + m_length; }
    private:
        QIODevice* m_dev;
        Q_ULONG m_start;
        Q_ULONG m_length;
    };

    #endif

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