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1   package com.sun.syndication.io.impl;
2   
3   /*
4    * Copyright 2004 Sun Microsystems, Inc.
5    *
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   *
18   */
19  
20  /**
21   * Encodes/decodes byte arrays and Strings into/from a base 64 String.
22   * <p>
23   * @author Alejandro Abdelnur
24   *
25   */
26  public class Base64 {
27  
28      /**
29       * Encodes a String into a base 64 String. The resulting encoding is chunked at 76 bytes.
30       * <p>
31       * @param s String to encode.
32       * @return encoded string.
33       *
34       */
35      public static String encode(String s) {
36          byte[] sBytes =  s.getBytes();
37          sBytes = encode(sBytes);
38          s = new String(sBytes);
39          return s;
40      }
41  
42      /**
43       * Decodes a base 64 String into a String.
44       * <p>
45       * @param s String to decode.
46       * @return encoded string.
47       * @throws java.lang.IllegalArgumentException thrown if the given byte array was not valid com.sun.syndication.io.impl.Base64 encoding.
48       *
49       */
50      public static String decode(String s) throws IllegalArgumentException {
51          byte[] sBytes = s.getBytes();
52          sBytes = decode(sBytes);
53          s = new String(sBytes);
54          return s;
55      }
56  
57  
58      private static final byte[] ALPHASET =
59          "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".getBytes();
60  
61      private static final int I6O2 = 255 - 3;
62      private static final int O6I2 = 3;
63      private static final int I4O4 = 255 - 15;
64      private static final int O4I4 = 15;
65      private static final int I2O6 = 255 - 63;
66      private static final int O2I6 = 63;
67  
68      /**
69       * Encodes a byte array into a base 64 byte array.
70       * <p>
71       * @param dData byte array to encode.
72       * @return encoded byte array.
73       *
74       */
75      public static byte[] encode(byte[] dData) {
76          if (dData==null) {
77              throw new IllegalArgumentException("Cannot encode null");
78          }
79          byte[] eData = new byte[((dData.length+2)/3)*4];
80  
81          int eIndex = 0;
82          for (int i = 0; i<dData.length; i += 3) {
83              int d1;
84              int d2=0;
85              int d3=0;
86              int e1;
87              int e2;
88              int e3;
89              int e4;
90              int pad=0;
91  
92              d1 = dData[i];
93              if ((i+1)<dData.length) {
94                  d2 = dData[i+1];
95                  if ((i+2)<dData.length) {
96                      d3 = dData[i+2];
97                  }
98                  else {
99                      pad =1;
100                 }
101             }
102             else {
103                 pad =2;
104             }
105 
106             e1 = ALPHASET[(d1&I6O2)>>2];
107             e2 = ALPHASET[(d1&O6I2)<<4 | (d2&I4O4)>>4];
108             e3 = ALPHASET[(d2&O4I4)<<2 | (d3&I2O6)>>6];
109             e4 = ALPHASET[(d3&O2I6)];
110 
111             eData[eIndex++] = (byte)e1;
112             eData[eIndex++] = (byte)e2;
113             eData[eIndex++] = (pad<2) ?(byte)e3 : (byte)'=';
114             eData[eIndex++] = (pad<1) ?(byte)e4 : (byte)'=';
115 
116         }
117         return eData;
118     }
119 
120     private final static int[] CODES = new int[256];
121 
122     static {
123         for (int i=0;i<CODES.length;i++) {
124             CODES[i] = 64;
125         }
126         for (int i=0;i<ALPHASET.length;i++) {
127             CODES[ALPHASET[i]] = i;
128         }
129     }
130 
131     /**
132      * Dencodes a com.sun.syndication.io.impl.Base64 byte array.
133      * <p>
134      * @param eData byte array to decode.
135      * @return decoded byte array.
136      * @throws java.lang.IllegalArgumentException thrown if the given byte array was not valid com.sun.syndication.io.impl.Base64 encoding.
137      *
138      */
139     public static byte[] decode(byte[] eData) {
140         if (eData==null) {
141             throw new IllegalArgumentException("Cannot decode null");
142         }
143         byte[] cleanEData = (byte[]) eData.clone();
144         int cleanELength = 0;
145         for (int i=0;i<eData.length;i++) {
146             if (eData[i]<256 && CODES[eData[i]]<64) {
147                 cleanEData[cleanELength++] = eData[i];
148             }
149         }
150 
151         int dLength = (cleanELength/4)*3;
152         switch (cleanELength%4) {
153             case 3:
154                 dLength += 2;
155                 break;
156             case 2:
157                 dLength++;
158                 break;
159         }
160 
161         byte[] dData = new byte[dLength];
162         int dIndex = 0;
163         for (int i=0;i<cleanELength;i+=4) {
164             if ((i+3)>cleanELength) {
165                 throw new IllegalArgumentException("byte array is not a valid com.sun.syndication.io.impl.Base64 encoding");
166             }
167             int e1 = CODES[cleanEData[i]];
168             int e2 = CODES[cleanEData[i+1]];
169             int e3 = CODES[cleanEData[i+2]];
170             int e4 = CODES[cleanEData[i+3]];
171             dData[dIndex++] = (byte) ((e1<<2)|(e2>>4));
172             if (dIndex<dData.length) {
173                 dData[dIndex++] = (byte) ((e2<<4) | (e3>>2));
174             }
175             if (dIndex<dData.length) {
176                 dData[dIndex++] = (byte) ((e3<<6) | (e4));
177             }
178         }
179         return dData;
180     }
181 
182     public static void main(String[] args) throws Exception {
183         String s =
184                 "\nPGRpdiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMTk5OS94aHRtbCI+V2UncmUgcHJvcG9zaW5nIDxhIGhy\n"+
185 "ZWY9Imh0dHA6Ly93d3cuZ29vZ2xlLmNvbS9jb3Jwb3JhdGUvc29mdHdhcmVfcHJpbmNpcGxlcy5odG1sIj5z\n"+
186 "b21lIGd1aWRlbGluZXMgPC9hPnRvIGhlbHAgY3VyYiB0aGUgcHJvYmxlbSBvZiBJbnRlcm5ldCBzb2Z0d2Fy\n"+
187 "ZSB0aGF0IGluc3RhbGxzIGl0c2VsZiB3aXRob3V0IHRlbGxpbmcgeW91LCBvciBiZWhhdmVzIGJhZGx5IG9u\n"+
188 "Y2UgaXQgZ2V0cyBvbiB5b3VyIGNvbXB1dGVyLiBXZSd2ZSBiZWVuIGhlYXJpbmcgYSBsb3Qgb2YgY29tcGxh\n"+
189 "aW50cyBhYm91dCB0aGlzIGxhdGVseSBhbmQgaXQgc2VlbXMgdG8gYmUgZ2V0dGluZyB3b3JzZS4gV2UgdGhp\n"+
190 "bmsgaXQncyBpbXBvcnRhbnQgdGhhdCB5b3UgcmV0YWluIGNvbnRyb2wgb2YgeW91ciBjb21wdXRlciBhbmQg\n"+
191 "dGhhdCB0aGVyZSBiZSBzb21lIGNsZWFyIHN0YW5kYXJkcyBpbiBvdXIgaW5kdXN0cnkuIExldCB1cyBrbm93\n"+
192 "IGlmIHlvdSB0aGluayB0aGVzZSBndWlkZWxpbmVzIGFyZSB1c2VmdWwgb3IgaWYgeW91IGhhdmUgc3VnZ2Vz\n"+
193 "dGlvbnMgdG8gaW1wcm92ZSB0aGVtLgo8YnIgLz4KPGJyIC8+Sm9uYXRoYW4gUm9zZW5iZXJnCjxiciAvPgo8\n"+
194 "L2Rpdj4K\n";
195 
196         System.out.println(decode(s));
197     }
198 }
199