sprites.h

/*
 * This file is part of libsidplayfp, a SID player engine.
 *
 * Copyright 2011-2014 Leandro Nini <drfiemost@users.sourceforge.net>
 * Copyright 2009-2014 VICE Project
 * Copyright 2007-2010 Antti Lankila
 * Copyright 2001 Simon White
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 SPRITES_H
#define SPRITES_H
 
#include <stdint.h>
 
#include <cstring>
 
#define SPRITES 8
 
namespace libsidplayfp
{
 
class Sprites
{
private:
    const uint8_t &enable, &y_expansion;
 
    uint8_t exp_flop;
    uint8_t dma;
    uint8_t mc_base[SPRITES];
    uint8_t mc[SPRITES];
 
public:
    Sprites(uint8_t regs[0x40]) :
        enable(regs[0x15]),
        y_expansion(regs[0x17]) {}
 
    void reset()
    {
        exp_flop = 0xff;
        dma = 0;
 
        memset(mc_base, 0, sizeof(mc_base));
        memset(mc, 0, sizeof(mc));
    }
 
    void updateMc()
    {
        uint8_t mask = 1;
        for (unsigned int i = 0; i < SPRITES; i++, mask <<= 1)
        {
            if (dma & mask)
                mc[i] = (mc[i] + 3) & 0x3f;
        }
    }
 
    void updateMcBase()
    {
        uint8_t mask = 1;
        for (unsigned int i = 0; i < SPRITES; i++, mask <<= 1)
        {
            if (exp_flop & mask)
            {
                mc_base[i] = mc[i];
                if (mc_base[i] == 0x3f)
                    dma &= ~mask;
            }
        }
    }
 
    void checkExp()
    {
        exp_flop ^= dma & y_expansion;
    }
 
    void checkDisplay()
    {
        for (unsigned int i = 0; i < SPRITES; i++)
        {
            mc[i] = mc_base[i];
        }
    }
 
    void checkDma(unsigned int rasterY, uint8_t regs[0x40])
    {
        const uint8_t y = rasterY & 0xff;
        uint8_t mask = 1;
        for (unsigned int i = 0; i < SPRITES; i++, mask <<= 1)
        {
            if ((enable & mask) && (y == regs[(i << 1) + 1]) && !(dma & mask))
            {
                dma |= mask;
                mc_base[i] = 0;
                exp_flop |= mask;
            }
        }
    }
 
    void lineCrunch(uint8_t data, unsigned int lineCycle)
    {
        uint8_t mask = 1;
        for (unsigned int i = 0; i < SPRITES; i++, mask <<= 1)
        {
            if (!(data & mask) && !(exp_flop & mask))
            {
                // sprite crunch
                if (lineCycle == 14)
                {
                    const uint8_t mc_i = mc[i];
                    const uint8_t mcBase_i = mc_base[i];
 
                    mc[i] = (0x2a & (mcBase_i & mc_i)) | (0x15 & (mcBase_i | mc_i));
 
                    // mcbase will be set from mc on the following clock call
                }
 
                exp_flop |= mask;
            }
        }
    }
 
    inline bool isDma(unsigned int val) const
    {
        return dma & val;
    }
};
 
}
 
#endif