CustomAlphabetTable.java

/*
 * $Id: CustomAlphabetTable.java 536 2008-02-19 06:03:27Z weiju $
 * 
 * Created on 2006/01/16
 * 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.encoding;

import org.zmpp.base.Memory;

/**
 * If the story file header defines a custom alphabet table, instances of this
 * class are used to retrieve the alphabet characters.
 *
 * @author Wei-ju Wu
 * @version 1.0
 */
public class CustomAlphabetTable implements AlphabetTable {

    private static final int ALPHABET_SIZE = 26;
    private Memory memory;
    private int tableAddress;

    /**
     * Constructor.
     *
     * @param memory the Memory object
     * @param address the table address
     */
    public CustomAlphabetTable(final Memory memory, final int address) {
        this.memory = memory;
        tableAddress = address;
    }

    /**
     * {@inheritDoc}
     */
    public char getA0Char(final byte zchar) {
        if (zchar == 0) {
            return ' ';
        }
        return (char) memory.readUnsignedByte(tableAddress
                + (zchar - ALPHABET_START));
    }

    /**
     * {@inheritDoc}
     */
    public char getA1Char(final byte zchar) {
        if (zchar == 0) {
            return ' ';
        }
        return (char) memory.readUnsignedByte(tableAddress
                + ALPHABET_SIZE
                + (zchar - ALPHABET_START));
    }

    /**
     * {@inheritDoc}
     */
    public char getA2Char(final byte zchar) {

        if (zchar == 0) {
            return ' ';
        }
        if (zchar == 7) {
            return (short) '\n';
        }
        return (char) memory.readUnsignedByte(tableAddress + 2 * ALPHABET_SIZE
                + (zchar - ALPHABET_START));
    }

    /**
     * {@inheritDoc}
     */
    public final byte getA0CharCode(final char zsciiChar) {
        for (int i = ALPHABET_START; i < ALPHABET_START + ALPHABET_SIZE; i++) {

            if (getA0Char((byte) i) == zsciiChar) {
                return (byte) i;
            }
        }
        return -1;
    }

    /**
     * {@inheritDoc}
     */
    public final byte getA1CharCode(final char zsciiChar) {
        for (int i = ALPHABET_START; i < ALPHABET_START + ALPHABET_SIZE; i++) {

            if (getA1Char((byte) i) == zsciiChar) {
                return (byte) i;
            }
        }
        return -1;
    }

    /**
     * {@inheritDoc}
     */
    public byte getA2CharCode(final char zsciiChar) {
        for (int i = ALPHABET_START; i < ALPHABET_START + ALPHABET_SIZE; i++) {

            if (getA2Char((byte) i) == zsciiChar) {
                return (byte) i;
            }
        }
        return -1;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isAbbreviation(final char zchar) {
        return 1 <= zchar && zchar <= 3;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isShift1(final char zchar) {
        return zchar == AlphabetTable.SHIFT_4;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isShift2(final char zchar) {
        return zchar == AlphabetTable.SHIFT_5;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isShiftLock(final char zchar) {
        return false;
    }

    /**
     * {@inheritDoc}
     */
    public boolean isShift(final char zchar) {
        return isShift1(zchar) || isShift2(zchar);
    }
}