MoparScape/MoparScape/src/main/java/org/moparscape/res/Base32.java

/*
 * Copyright (C) 2009-2013 moparisthebest
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Official forums are http://www.moparscape.org/smf/
 * Email me at admin@moparisthebest.com.
 */

/* (PD) 2006 The Bitzi Corporation
 * Please see http://bitzi.com/publicdomain for more info.
 *
 * $Id: Base32.java,v 1.2 2006/07/14 04:58:39 gojomo Exp $
 */

package org.moparscape.res;

/**
 * Base32 - encodes and decodes RFC3548 Base32
 * (see http://www.faqs.org/rfcs/rfc3548.html )
 *
 * @author Robert Kaye
 * @author Gordon Mohr
 */
public class Base32 {
    private final String base32Chars =
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
    private final int[] base32Lookup =
            {0xFF, 0xFF, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, // '0', '1', '2', '3', '4', '5', '6', '7'
                    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // '8', '9', ':', ';', '<', '=', '>', '?'
                    0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G'
                    0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O'
                    0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W'
                    0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 'X', 'Y', 'Z', '[', '\', ']', '^', '_'
                    0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g'
                    0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o'
                    0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w'
                    0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF  // 'x', 'y', 'z', '{', '|', '}', '~', 'DEL'
            };

    /**
     * Encodes byte array to Base32 String.
     *
     * @param bytes Bytes to encode.
     * @return Encoded byte array <code>bytes</code> as a String.
     */
    public String encode(final byte[] bytes) {
        int i = 0, index = 0, digit = 0;
        int currByte, nextByte;
        StringBuffer base32 = new StringBuffer((bytes.length + 7) * 8 / 5);

        while (i < bytes.length) {
            currByte = (bytes[i] >= 0) ? bytes[i] : (bytes[i] + 256); // unsign

            /* Is the current digit going to span a byte boundary? */
            if (index > 3) {
                if ((i + 1) < bytes.length) {
                    nextByte =
                            (bytes[i + 1] >= 0) ? bytes[i + 1] : (bytes[i + 1] + 256);
                } else {
                    nextByte = 0;
                }

                digit = currByte & (0xFF >> index);
                index = (index + 5) % 8;
                digit <<= index;
                digit |= nextByte >> (8 - index);
                i++;
            } else {
                digit = (currByte >> (8 - (index + 5))) & 0x1F;
                index = (index + 5) % 8;
                if (index == 0)
                    i++;
            }
            base32.append(base32Chars.charAt(digit));
        }

        return base32.toString();
    }

    /**
     * Decodes the given Base32 String to a raw byte array.
     *
     * @param base32
     * @return Decoded <code>base32</code> String as a raw byte array.
     */
    public byte[] decode(final String base32) {
        int i, index, lookup, offset, digit;
        byte[] bytes = new byte[base32.length() * 5 / 8];

        for (i = 0, index = 0, offset = 0; i < base32.length(); i++) {
            lookup = base32.charAt(i) - '0';

            /* Skip chars outside the lookup table */
            if (lookup < 0 || lookup >= base32Lookup.length) {
                continue;
            }

            digit = base32Lookup[lookup];

            /* If this digit is not in the table, ignore it */
            if (digit == 0xFF) {
                continue;
            }

            if (index <= 3) {
                index = (index + 5) % 8;
                if (index == 0) {
                    bytes[offset] |= digit;
                    offset++;
                    if (offset >= bytes.length)
                        break;
                } else {
                    bytes[offset] |= digit << (8 - index);
                }
            } else {
                index = (index + 5) % 8;
                bytes[offset] |= (digit >>> index);
                offset++;

                if (offset >= bytes.length) {
                    break;
                }
                bytes[offset] |= digit << (8 - index);
            }
        }
        return bytes;
    }

    public String toSha1(String base32){
        return new java.math.BigInteger(1, decode(base32)).toString(16);
    }

    /**
     * For testing, take a command-line argument in Base32, decode, print in hex,
     * encode, print
     *
     * @param args
     */
    public static void main(String[] args) {
        if (args.length == 0) {
            System.out.println("Supply a Base32-encoded argument.");
            return;
        }
        System.out.println(" Original: " + args[0]);
        Base32 b32 = new Base32();
        byte[] decoded = b32.decode(args[0]);
        System.out.print("      Hex: ");
        for (int i = 0; i < decoded.length; i++) {
            int b = decoded[i];
            if (b < 0) {
                b += 256;
            }
            System.out.print((Integer.toHexString(b + 256)).substring(1));
        }
        System.out.println();
        System.out.println("Reencoded: " + b32.encode(decoded));
    }
}