BlockArray.h

/*
    This file is part of Konsole, an X terminal.
    SPDX-FileCopyrightText: 2000 Stephan Kulow <coolo@kde.org>
 
    Rewritten for QT4 by e_k <e_k at users.sourceforge.net>, Copyright (C)2008
 
    SPDX-License-Identifier: GPL-2.0-or-later
 
    This program 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 General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA.
*/
 
#ifndef BLOCKARRAY_H
#define BLOCKARRAY_H
 
#include <cstdio>
#include <unistd.h>
 
constexpr auto QTERMWIDGET_BLOCKSIZE = 1 << 12;
constexpr auto ENTRIES = ((QTERMWIDGET_BLOCKSIZE - sizeof(size_t)) / sizeof(unsigned char));
 
namespace Konsole
{
 
struct Block {
    constexpr Block()
    {
        size = 0;
    }
    unsigned char data[ENTRIES];
    size_t size;
};
 
// ///////////////////////////////////////////////////////
 
class BlockArray
{
public:
    /**
     * Creates a history file for holding
     * maximal size blocks. If more blocks
     * are requested, then it drops earlier
     * added ones.
     */
    BlockArray();
 
    /// destructor
    ~BlockArray();
 
    /**
     * adds the Block at the end of history.
     * This may drop other blocks.
     *
     * The ownership on the block is transfered.
     * An unique index number is returned for accessing
     * it later (if not yet dropped then)
     *
     * Note, that the block may be dropped completely
     * if history is turned off.
     */
    size_t append(Block *block);
 
    /**
     * gets the block at the index. Function may return
     * 0 if the block isn't available any more.
     *
     * The returned block is strictly readonly as only
     * maped in memory - and will be invalid on the next
     * operation on this class.
     */
    const Block *at(size_t index);
 
    /**
     * reorders blocks as needed. If newsize is null,
     * the history is emptied completely. The indices
     * returned on append won't change their semantic,
     * but they may not be valid after this call.
     */
    bool setHistorySize(size_t newsize);
 
    size_t newBlock();
 
    Block *lastBlock() const;
 
    /**
     * Convenient function to set the size in KBytes
     * instead of blocks
     */
    bool setSize(size_t newsize);
 
    size_t len() const
    {
        return length;
    }
 
    bool has(size_t index) const;
 
    size_t getCurrent() const
    {
        return current;
    }
 
private:
    void unmap();
    void increaseBuffer();
    void decreaseBuffer(size_t newsize);
    void moveBlock(FILE *fion, int cursor, int newpos, char *buffer2);
 
    size_t size;
    // current always shows to the last inserted block
    size_t current;
    size_t index;
 
    Block *lastmap;
    size_t lastmap_index;
    Block *lastblock;
 
    int ion;
    size_t length;
 
    int blocksize = 0;
};
 
}
 
#endif