src/main/java/net/pterodactylus/fcp/FreenetBase64.java

   1 /*
   2  * jFCPlib - FreenetBase64.java - Copyright © 2015–2016 David Roden
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 package net.pterodactylus.fcp;
  19
  20 import java.io.ByteArrayOutputStream;
  21 import java.io.IOException;
  22
  23 /**
  24  * Freenet-specific Base64 implementation.
  25  *
  26  * @author <a href="mailto:bombe@freenetproject.org">David ‘Bombe’ Roden</a>
  27  */
  28 public class FreenetBase64 {
  29
  30         private static final char[] FREENET_BASE64_ALPHABET =
  31                 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789~-".toCharArray();
  32         private static final int[] REVERSE_FREENET_BASE64_ALPHABET = reverse(FREENET_BASE64_ALPHABET);
  33
  34         private static int[] reverse(char[] alphabet) {
  35                 String alphabetString = new String(alphabet);
  36                 int[] reversedAlphabet = new int[128];
  37                 for (int i = 0; i < 128; i++) {
  38                         if (alphabetString.indexOf(i) > -1) {
  39                                 reversedAlphabet[i] = alphabetString.indexOf(i);
  40                         } else {
  41                                 reversedAlphabet[i] = -1;
  42                         }
  43                 }
  44                 return reversedAlphabet;
  45         }
  46
  47         public String encode(byte[] data) {
  48                 StringBuilder result = new StringBuilder();
  49                 int currentValue = 0;
  50                 int index = 0;
  51                 while (index < data.length) {
  52                         currentValue = (currentValue << 8) | data[index];
  53                         if (index % 3 == 2) {
  54                                 result.append(FREENET_BASE64_ALPHABET[(currentValue >> 18) & 0x3f]);
  55                                 result.append(FREENET_BASE64_ALPHABET[(currentValue >> 12) & 0x3f]);
  56                                 result.append(FREENET_BASE64_ALPHABET[(currentValue >> 6) & 0x3f]);
  57                                 result.append(FREENET_BASE64_ALPHABET[currentValue & 0x3f]);
  58                         }
  59                         index++;
  60                 }
  61                 if (index % 3 == 1) {
  62                         result.append(FREENET_BASE64_ALPHABET[(currentValue >> 2) & 0x3f]);
  63                         result.append(FREENET_BASE64_ALPHABET[(currentValue << 4) & 0x3f]);
  64                         result.append("==");
  65                 } else if (index % 3 == 2) {
  66                         result.append(FREENET_BASE64_ALPHABET[(currentValue >> 10) & 0x3f]);
  67                         result.append(FREENET_BASE64_ALPHABET[(currentValue >> 4) & 0x3f]);
  68                         result.append(FREENET_BASE64_ALPHABET[(currentValue << 2) & 0x3f]);
  69                         result.append("=");
  70                 }
  71                 return result.toString();
  72         }
  73
  74         public byte[] decode(String data) {
  75                 ByteArrayOutputStream dataOutput = new ByteArrayOutputStream(data.length() * 3 / 4);
  76                 try {
  77                         int currentValue = 0;
  78                         int index = 0;
  79                         for (char c : data.toCharArray()) {
  80                                 if (c == '=') {
  81                                         break;
  82                                 }
  83                                 currentValue = (currentValue << 6) | REVERSE_FREENET_BASE64_ALPHABET[c];
  84                                 if (index % 4 == 3) {
  85                                         dataOutput.write((currentValue >> 16) & 0xff);
  86                                         dataOutput.write((currentValue >> 8) & 0xff);
  87                                         dataOutput.write(currentValue & 0xff);
  88                                 }
  89                                 index++;
  90                         }
  91                         if (index % 4 == 2) {
  92                                 dataOutput.write((currentValue >> 4) & 0xff);
  93                         } else if (index % 4 == 3) {
  94                                 dataOutput.write((currentValue >> 10) & 0xff);
  95                                 dataOutput.write((currentValue >> 2) & 0xff);
  96                         }
  97                         return dataOutput.toByteArray();
  98                 } finally {
  99                         try {
 100                                 dataOutput.close();
 101                         } catch (IOException e) {
 102                                 throw new RuntimeException(e);
 103                         }
 104                 }
 105         }
 106
 107 }