PagedMemory.java

/*
 * Copyright (C) 2012 Brendan Robert (BLuRry) brendan.robert@gmail.com.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301  USA
 */
package jace.core;

import jace.state.StateManager;
import jace.state.Stateful;
import java.util.Arrays;

/**
 * This represents bank-switchable ram which can reside at fixed portions of the
 * computer's memory. This makes it possible to switch out memory pages in a
 * very efficient manner so that the MMU abstraction doesn't bury the rest of
 * the emulator in messy conditionals.
 *
 * @author Brendan Robert (BLuRry) brendan.robert@gmail.com 
 */
@Stateful
public class PagedMemory {

    public enum Type {

        CARD_FIRMWARE(0x0c800),
        LANGUAGE_CARD(0x0d000),
        FIRMWARE_MAIN(0x0d000),
        FIRMWARE_80COL(0x0c300),
        SLOW_ROM(0x0c100),
        RAM(0x0000);
        protected int baseAddress;

        private Type(int newBase) {
            baseAddress = newBase;
        }

        public int getBaseAddress() {
            return baseAddress;
        }
    }
    // This is a fixed array, used for internal-only!!
    @Stateful
    public byte[][] internalMemory = new byte[0][];
    @Stateful
    public Type type;

    /**
     * Creates a new instance of PagedMemory
     */
    Computer computer;
    public PagedMemory(int size, Type memType, Computer computer) {
        this.computer = computer;
        type = memType;
        internalMemory = new byte[size >> 8][256];
        for (int i = 0; i < size; i += 256) {
            byte[] b = new byte[256];
            Arrays.fill(b, (byte) 0x00);
            internalMemory[i >> 8] = b;
        }
    }

    public PagedMemory(byte[] romData, Type memType) {
        type = memType;
        loadData(romData);
    }

    public void loadData(byte[] romData) {
        for (int i = 0; i < romData.length; i += 256) {
            byte[] b = new byte[256];
            for (int j = 0; j < 256; j++) {
                b[j] = romData[i + j];
            }
            internalMemory[i >> 8] = b;
        }
    }

    public void loadData(byte[] romData, int offset, int length) {
        for (int i = 0; i < length; i += 256) {
            byte[] b = new byte[256];
            for (int j = 0; j < 256; j++) {
                b[j] = romData[offset + i + j];
            }
            internalMemory[i >> 8] = b;
        }
    }

    public byte[][] getMemory() {
        return internalMemory;
    }

    public byte[] get(int pageNumber) {
        return internalMemory[pageNumber];
    }

    public void set(int pageNumber, byte[] bank) {
        internalMemory[pageNumber] = bank;
    }

    public byte[] getMemoryPage(int memoryBase) {
        int offset = memoryBase - type.baseAddress;
//        int page = offset >> 8;
        int page = (offset >> 8) & 0x0ff;
//        return get(page);
        return internalMemory[page];
    }

    public void setBanks(int sourceStart, int sourceLength, int targetStart, PagedMemory source) {
        for (int i = 0; i < sourceLength; i++) {
            set(targetStart + i, source.get(sourceStart + i));
        }
    }

    public byte readByte(int address) {
        return getMemoryPage(address)[address & 0x0ff];
    }

    public void writeByte(int address, byte value) {
        byte[] page = getMemoryPage(address);
        StateManager.markDirtyValue(page, computer);
        getMemoryPage(address)[address & 0x0ff] = value;
    }

    public void fillBanks(PagedMemory source) {
        byte[][] sourceMemory = source.getMemory();
        int sourceBase = source.type.getBaseAddress() >> 8;
        int thisBase = type.getBaseAddress() >> 8;
        int start = sourceBase > thisBase ? sourceBase : thisBase;
        int sourceEnd = sourceBase + source.getMemory().length;
        int thisEnd = thisBase + getMemory().length;
        int end = sourceEnd < thisEnd ? sourceEnd : thisEnd;
        for (int i = start; i < end; i++) {
            set(i - thisBase, sourceMemory[i - sourceBase]);
        }
    }
}