GameDataImpl.java

/*
 * $Id: GameDataImpl.java 536 2008-02-19 06:03:27Z weiju $
 * 
 * Created on 2005/10/10
 * Copyright 2005-2008 by Wei-ju Wu
 * This file is part of The Z-machine Preservation Project (ZMPP).
 *
 * ZMPP 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 3 of the License, or
 * (at your option) any later version.
 *
 * ZMPP 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 ZMPP.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.zmpp.vm;

import org.zmpp.base.DefaultMemory;
import org.zmpp.base.Memory;
import org.zmpp.encoding.AccentTable;
import org.zmpp.encoding.AlphabetTable;
import org.zmpp.encoding.AlphabetTableV1;
import org.zmpp.encoding.AlphabetTableV2;
import org.zmpp.encoding.CustomAccentTable;
import org.zmpp.encoding.CustomAlphabetTable;
import org.zmpp.encoding.DefaultAccentTable;
import org.zmpp.encoding.DefaultAlphabetTable;
import org.zmpp.encoding.DefaultZCharDecoder;
import org.zmpp.encoding.DefaultZCharTranslator;
import org.zmpp.encoding.ZCharDecoder;
import org.zmpp.encoding.ZCharEncoder;
import org.zmpp.encoding.ZCharTranslator;
import org.zmpp.encoding.ZsciiEncoding;
import org.zmpp.encoding.ZsciiString;
import org.zmpp.media.Resources;

/**
 * This class implements the GameData interface.
 *
 * @author Wei-ju Wu
 * @version 1.0
 */
public class GameDataImpl implements GameData {

    private StoryFileHeader fileheader;
    private Memory memory;
    private Dictionary dictionary;
    private ObjectTree objectTree;
    private ZsciiEncoding encoding;
    private ZCharDecoder decoder;
    private ZCharEncoder encoder;
    private AlphabetTable alphabetTable;
    private Resources resources;
    private byte[] storyfileData;
    private int checksum;

    /**
     * Constructor.
     *
     * @param storyfile the story file as a byte array
     * @param resources the media resources
     */
    public GameDataImpl(byte[] storyfile, Resources resources) {
        storyfileData = storyfile;
        this.resources = resources;
        reset();
    }

    /**
     * {@inheritDoc}
     */
    public final void reset() {
        // Make a copy and initialize from the copy
        final byte[] data = new byte[storyfileData.length];
        System.arraycopy(storyfileData, 0, data, 0, storyfileData.length);

        memory = new DefaultMemory(data);
        fileheader = new DefaultStoryFileHeader(memory);
        checksum = calculateChecksum();

        // Install the whole character code system here
        initEncodingSystem();

        // The object tree and dictionaries depend on the code system
        if (fileheader.getVersion() <= 3) {
            objectTree = new ClassicObjectTree(memory,
                    fileheader.getObjectTableAddress());
        } else {
            objectTree = new ModernObjectTree(memory,
                    fileheader.getObjectTableAddress());
        }
        final DictionarySizes sizes = (fileheader.getVersion() <= 3)
                ? new DictionarySizesV1ToV3() : new DictionarySizesV4ToV8();
        dictionary = new DefaultDictionary(memory,
                fileheader.getDictionaryAddress(), decoder, sizes);
    }

    private void initEncodingSystem() {
        final AccentTable accentTable = (fileheader.getCustomAccentTable() == 0)
                ? new DefaultAccentTable()
                : new CustomAccentTable(memory, fileheader.getCustomAccentTable());
        encoding = new ZsciiEncoding(accentTable);

        // Configure the alphabet table
        if (fileheader.getCustomAlphabetTable() == 0) {
            if (fileheader.getVersion() == 1) {
                alphabetTable = new AlphabetTableV1();
            } else if (fileheader.getVersion() == 2) {
                alphabetTable = new AlphabetTableV2();
            } else {
                alphabetTable = new DefaultAlphabetTable();
            }
        } else {
            alphabetTable = new CustomAlphabetTable(memory,
                    fileheader.getCustomAlphabetTable());
        }

        final ZCharTranslator translator
                = new DefaultZCharTranslator(alphabetTable);

        final Abbreviations abbreviations = new Abbreviations(memory,
                fileheader.getAbbreviationsAddress());
        decoder = new DefaultZCharDecoder(encoding, translator, abbreviations);
        encoder = new ZCharEncoder(translator);
        ZsciiString.initialize(encoding);
    }

    /**
     * {@inheritDoc}
     */
    public Memory getMemory() {
        return memory;
    }

    /**
     * {@inheritDoc}
     */
    public StoryFileHeader getStoryFileHeader() {
        return fileheader;
    }

    /**
     * {@inheritDoc}
     */
    public Dictionary getDictionary() {
        return dictionary;
    }

    /**
     * {@inheritDoc}
     */
    public ObjectTree getObjectTree() {
        return objectTree;
    }

    /**
     * {@inheritDoc}
     */
    public AlphabetTable getAlphabetTable() {
        return alphabetTable;
    }

    /**
     * {@inheritDoc}
     */
    public ZCharDecoder getZCharDecoder() {
        return decoder;
    }

    /**
     * {@inheritDoc}
     */
    public ZCharEncoder getZCharEncoder() {
        return encoder;
    }

    /**
     * {@inheritDoc}
     */
    public ZsciiEncoding getZsciiEncoding() {
        return encoding;
    }

    /**
     * {@inheritDoc}
     */
    public Resources getResources() {
        return resources;
    }

    /**
     * Calculates the checksum of the file.
     *
     * @param fileheader the file header
     * @return the check sum
     */
    private int calculateChecksum() {
        final int filelen = fileheader.getFileLength();
        int sum = 0;
        for (int i = 0x40; i < filelen; i++) {
            sum += getMemory().readUnsignedByte(i);
        }
        return (sum & 0xffff);
    }

    public int getCalculatedChecksum() {
        return checksum;
    }

    /**
     * {@inheritDoc}
     */
    public boolean hasValidChecksum() {
        return getStoryFileHeader().getChecksum() == checksum;
    }
}