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    1   /* Base32
    2   *
    3   * $Id: Base32.java 1828 2004-04-15 19:04:01Z stack-sf $
    4   *
    5   * Created on Jan 21, 2004
    6   *
    7   * Copyright (C) 2004 Internet Archive.
    8   *
    9   * This file is part of the Heritrix web crawler (crawler.archive.org).
    10  *
    11  * Heritrix is free software; you can redistribute it and/or modify
    12  * it under the terms of the GNU Lesser Public License as published by
    13  * the Free Software Foundation; either version 2.1 of the License, or
    14  * any later version.
    15  *
    16  * Heritrix is distributed in the hope that it will be useful,
    17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    19  * GNU Lesser Public License for more details.
    20  *
    21  * You should have received a copy of the GNU Lesser Public License
    22  * along with Heritrix; if not, write to the Free Software
    23  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    24  */
    25  package org.archive.util;
    26
    27  /***
    28   * Base32 - encodes and decodes RFC3548 Base32
    29   * (see http://www.faqs.org/rfcs/rfc3548.html )
    30   *
    31   * Imported public-domain code of Bitzi.
    32   *
    33   * @author Robert Kaye
    34   * @author Gordon Mohr
    35   */
    36  public class Base32 {
    37      private static final String base32Chars =
    38          "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
    39      private static final int[] base32Lookup =
    40      { 0xFF,0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F, // '0', '1', '2', '3', '4', '5', '6', '7'
    41        0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, // '8', '9', ':', ';', '<', '=', '>', '?'
    42        0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G'
    43        0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O'
    44        0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W'
    45        0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF, // 'X', 'Y', 'Z', '[', '\', ']', '^', '_'
    46        0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g'
    47        0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o'
    48        0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w'
    49        0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF  // 'x', 'y', 'z', '{', '|', '}', '~', 'DEL'
    50      };
    51
    52      /***
    53       * Encodes byte array to Base32 String.
    54       *
    55       * @param bytes Bytes to encode.
    56       * @return Encoded byte array <code>bytes</code> as a String.
    57       *
    58       */
    59      static public String encode(final byte[] bytes) {
    60          int i = 0, index = 0, digit = 0;
    61          int currByte, nextByte;
    62          StringBuffer base32 = new StringBuffer((bytes.length + 7) * 8 / 5);
    63
    64          while (i < bytes.length) {
    65              currByte = (bytes[i] >= 0) ? bytes[i] : (bytes[i] + 256); // unsign
    66
    67              /* Is the current digit going to span a byte boundary? */
    68              if (index > 3) {
    69                  if ((i + 1) < bytes.length) {
    70                      nextByte =
    71                          (bytes[i + 1] >= 0) ? bytes[i + 1] : (bytes[i + 1] + 256);
    72                  } else {
    73                      nextByte = 0;
    74                  }
    75
    76                  digit = currByte & (0xFF >> index);
    77                  index = (index + 5) % 8;
    78                  digit <<= index;
    79                  digit |= nextByte >> (8 - index);
    80                  i++;
    81              } else {
    82                  digit = (currByte >> (8 - (index + 5))) & 0x1F;
    83                  index = (index + 5) % 8;
    84                  if (index == 0)
    85                      i++;
    86              }
    87              base32.append(base32Chars.charAt(digit));
    88          }
    89
    90          return base32.toString();
    91      }
    92
    93      /***
    94       * Decodes the given Base32 String to a raw byte array.
    95       *
    96       * @param base32
    97       * @return Decoded <code>base32</code> String as a raw byte array.
    98       */
    99      static public byte[] decode(final String base32) {
    100         int i, index, lookup, offset, digit;
    101         byte[] bytes = new byte[base32.length() * 5 / 8];
    102
    103         for (i = 0, index = 0, offset = 0; i < base32.length(); i++) {
    104             lookup = base32.charAt(i) - '0';
    105
    106             /* Skip chars outside the lookup table */
    107             if (lookup < 0 || lookup >= base32Lookup.length) {
    108                 continue;
    109             }
    110
    111             digit = base32Lookup[lookup];
    112
    113             /* If this digit is not in the table, ignore it */
    114             if (digit == 0xFF) {
    115                 continue;
    116             }
    117
    118             if (index <= 3) {
    119                 index = (index + 5) % 8;
    120                 if (index == 0) {
    121                     bytes[offset] |= digit;
    122                     offset++;
    123                     if (offset >= bytes.length)
    124                         break;
    125                 } else {
    126                     bytes[offset] |= digit << (8 - index);
    127                 }
    128             } else {
    129                 index = (index + 5) % 8;
    130                 bytes[offset] |= (digit >>> index);
    131                 offset++;
    132
    133                 if (offset >= bytes.length) {
    134                     break;
    135                 }
    136                 bytes[offset] |= digit << (8 - index);
    137             }
    138         }
    139         return bytes;
    140     }
    141
    142     /*** For testing, take a command-line argument in Base32, decode, print in hex,
    143      * encode, print
    144      *
    145      * @param args
    146      */
    147     static public void main(String[] args) {
    148         if (args.length == 0) {
    149             System.out.println("Supply a Base32-encoded argument.");
    150             return;
    151         }
    152         System.out.println(" Original: " + args[0]);
    153         byte[] decoded = Base32.decode(args[0]);
    154         System.out.print("      Hex: ");
    155         for (int i = 0; i < decoded.length; i++) {
    156             int b = decoded[i];
    157             if (b < 0) {
    158                 b += 256;
    159             }
    160             System.out.print((Integer.toHexString(b + 256)).substring(1));
    161         }
    162         System.out.println();
    163         System.out.println("Reencoded: " + Base32.encode(decoded));
    164     }
    165 }