/*
 * RS.java - Reed-Solomon Decoder Main.
 *
 * ------------------------------------------------------------------
 *
 * @begin[license]
 * Copyright (C) 2003  Kai Chen, Caltech
 *
 * This program 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 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * @author: Kai Chen
 * @email{kchen@cs.caltech.edu}
 * @end[license]
 *
 */


public class RS
{
    /* ASCII values for certain chars */
    private static final byte ASCII_1 = 0x31;
    private static final byte ASCII_A = 0x41;
    private static final byte ASCII_6 = 0x36;
    private static final byte ASCII_Z = 0x5A;
    private static final byte NUM_LETTERS = 26;
    
    public static void main(String[] args)
    {
        // build the GF we are working with
        int gfPoly[] = {1, 0, 1, 0, 0, 1};
        GF gf = new GF(2, 5, gfPoly);
        
        // build the RS decoder
        RSDecoder decoder = new RSDecoder(gf, 16);
        
        RSJFrame frame = new RSJFrame(decoder); 
    }
    
    /*
     * pre: s is the input string, 0 ... 31 are encoded as A, ..., Z, 1 ... 6
     * post: parses the values 0 ... 31 into the array values[]
     *       returns the number of chars parsed.
     */
    public static int parse(String s, int values[])
    {	
        int i;
        char c[] = s.toUpperCase().toCharArray();

        // incomplete input
        if(c.length < values.length)
            return -1;

        for(i=0; i<values.length; i++){
            char ch = c[i];
            if(ASCII_A <= ch && ch <= ASCII_Z)
                values[i] = ch - ASCII_A;
            else if(ASCII_1 <= ch && ch <= ASCII_6)
                values[i] = ch - ASCII_1 + NUM_LETTERS;
            else if(ch == '*')
                values[i] = -1;
            else break;
        }

        return i;
    }


    /*
     * pre: input is an array of integers with values 0, ..., 31
     * post: output a string encoded as A ... Z, 1 ... 6
     *       returns the null on error
     */
    public static String parseBack(int values[])
    {
        byte b[] = new byte[values.length];
        
        for(int i=0; i<values.length; i++){
            if(values[i]>=0 && values[i]<26)
                b[i] = new Integer(values[i]+ASCII_A).byteValue();
            else if(values[i]>=26 && values[i]<32)
                b[i] = new Integer(values[i]+ASCII_1-NUM_LETTERS).byteValue();
            else return null;
        }

        return new String(b);
    }
}