UserDictionary.java

/*
 * $Id: UserDictionary.java 536 2008-02-19 06:03:27Z weiju $
 * 
 * Created on 2006/01/09
 * 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.Memory;
import org.zmpp.encoding.ZCharDecoder;
import org.zmpp.encoding.ZsciiString;

/**
 * This class implements a user dictionary. The specification suggests that
 * lookup is implemented using linear search in case the user dictionary is
 * specified as unordered (negative number of entries) and in case of ordered a
 * binary search will be performed.
 *
 * @author Wei-ju Wu
 * @version 1.0
 */
public class UserDictionary extends AbstractDictionary {

    /**
     * Constructor.
     *
     * @param memory the Memary object
     * @param address the start address of the dictionary
     * @param converter a Z char decoder object
     * @param sizes a sizes object
     */
    public UserDictionary(Memory memory, int address,
            ZCharDecoder decoder) {
        super(memory, address, decoder, new DictionarySizesV4ToV8());
    }

    /**
     * {@inheritDoc}
     */
    public int lookup(final ZsciiString token) {
        // We only implement linear search for the moment
        final int n = Math.abs(getNumberOfEntries());
        final ZsciiString lookupToken = truncateToken(token);

        for (int i = 0; i < n; i++) {

            final int entryAddress = getEntryAddress(i);
            final ZsciiString entry = getDecoder().decode2Zscii(getMemory(),
                    entryAddress,
                    getEntryLength());
            if (lookupToken.equals(entry)) {

                return entryAddress;
            }
        }
        return 0;
    }
}