AlphabetTable.java

/*
 * $Id: AlphabetTable.java 536 2008-02-19 06:03:27Z weiju $
 * 
 * Created on 2006/01/12
 * 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;

/**
 * The alphabet table is a central part of the Z encoding system. It stores the
 * characters that are mapped to each alphabet and provides information about
 * shift and escape situations.
 *
 * @author Wei-ju Wu
 * @version 1.0
 */
public interface AlphabetTable {

    /**
     * Defines the possible alphabets here.
     */
    public enum Alphabet {

        A0, A1, A2
    }

    public static final int ALPHABET_START = 6;
    public static final int ALPHABET_END = 31;

    public static final byte SHIFT_2 = 0x02; // Shift 1
    public static final byte SHIFT_3 = 0x03; // Shift 2
    public static final byte SHIFT_4 = 0x04; // Shift lock 1
    public static final byte SHIFT_5 = 0x05; // Shift lock 2

    /**
     * This character code, used from A2, denotes that a 10 bit value follows.
     */
    public static final byte A2_ESCAPE = 0x06; // escape character

    /**
     * Returns the ZSCII character from alphabet 0 at the specified index.
     *
     * @param zchar a Z encoded character
     * @return the specified character from alphabet 0
     */
    char getA0Char(byte zchar);

    /**
     * Returns the ZSCII character from alphabet 1 at the specified index.
     *
     * @param zchar a Z encoded character
     * @return the specified character from alphabet 1
     */
    char getA1Char(byte zchar);

    /**
     * Returns the ZSCII character from alphabet 2 at the specified index.
     *
     * @param zchar a Z encoded character
     * @return the specified character from alphabet 2
     */
    char getA2Char(byte zchar);

    /**
     * Returns the index of the specified ZSCII character in alphabet 0.
     *
     * @param zsciiChar a ZSCII chararacter
     * @return the index of the character in this alphabet or -1
     */
    byte getA0CharCode(char zsciiChar);

    /**
     * Returns the index of the specified ZSCII character in alphabet 2.
     *
     * @param zsciiChar a ZSCII chararacter
     * @return the index of the character in this alphabet or -1
     */
    byte getA1CharCode(char zsciiChar);

    /**
     * Returns the index of the specified ZSCII character in alphabet 2.
     *
     * @param zsciiChar a ZSCII chararacter
     * @return the index of the character in this alphabet or -1
     */
    byte getA2CharCode(char zsciiChar);

    /**
     * Determines if the specified character marks a abbreviation.
     *
     * @param zchar the zchar
     * @return true if abbreviation, false, otherwise
     */
    boolean isAbbreviation(char zchar);

    /**
     * Returns true if the specified character is a shift level 1 character.
     *
     * @param zchar a Z encoded character
     * @return true if shift, false, otherwise
     */
    boolean isShift1(char zchar);

    /**
     * Returns true if the specified character is a shift level 2 character.
     *
     * @param zchar a Z encoded character
     * @return true if shift, false, otherwise
     */
    boolean isShift2(char zchar);

    /**
     * Returns true if the specified character is a shift lock character.
     *
     * @param zchar a Z encoded character
     * @return true if shift lock, false otherwise
     */
    boolean isShiftLock(char zchar);

    /**
     * Returns true if the specified character is a shift character. Includes
     * shift lock.
     *
     * @param zchar a Z encoded character
     * @return true if either shift or shift lock
     */
    boolean isShift(char zchar);
}