Save This Page
Home » openjdk-7 » sun » misc » [javadoc | source]
    1   /*
    2    * Copyright (c) 1995, 2000, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   package sun.misc;
   26   
   27   import java.io.OutputStream;
   28   import java.io.PushbackInputStream;
   29   import java.io.PrintStream;
   30   
   31   /**
   32    * This class implements a BASE64 Character decoder as specified in RFC1521.
   33    *
   34    * This RFC is part of the MIME specification which is published by the
   35    * Internet Engineering Task Force (IETF). Unlike some other encoding
   36    * schemes there is nothing in this encoding that tells the decoder
   37    * where a buffer starts or stops, so to use it you will need to isolate
   38    * your encoded data into a single chunk and then feed them this decoder.
   39    * The simplest way to do that is to read all of the encoded data into a
   40    * string and then use:
   41    * <pre>
   42    *      byte    mydata[];
   43    *      BASE64Decoder base64 = new BASE64Decoder();
   44    *
   45    *      mydata = base64.decodeBuffer(bufferString);
   46    * </pre>
   47    * This will decode the String in <i>bufferString</i> and give you an array
   48    * of bytes in the array <i>myData</i>.
   49    *
   50    * On errors, this class throws a CEFormatException with the following detail
   51    * strings:
   52    * <pre>
   53    *    "BASE64Decoder: Not enough bytes for an atom."
   54    * </pre>
   55    *
   56    * @author      Chuck McManis
   57    * @see         CharacterEncoder
   58    * @see         BASE64Decoder
   59    */
   60   
   61   public class BASE64Decoder extends CharacterDecoder {
   62   
   63       /** This class has 4 bytes per atom */
   64       protected int bytesPerAtom() {
   65           return (4);
   66       }
   67   
   68       /** Any multiple of 4 will do, 72 might be common */
   69       protected int bytesPerLine() {
   70           return (72);
   71       }
   72   
   73       /**
   74        * This character array provides the character to value map
   75        * based on RFC1521.
   76        */
   77       private final static char pem_array[] = {
   78           //       0   1   2   3   4   5   6   7
   79                   'A','B','C','D','E','F','G','H', // 0
   80                   'I','J','K','L','M','N','O','P', // 1
   81                   'Q','R','S','T','U','V','W','X', // 2
   82                   'Y','Z','a','b','c','d','e','f', // 3
   83                   'g','h','i','j','k','l','m','n', // 4
   84                   'o','p','q','r','s','t','u','v', // 5
   85                   'w','x','y','z','0','1','2','3', // 6
   86                   '4','5','6','7','8','9','+','/'  // 7
   87           };
   88   
   89       private final static byte pem_convert_array[] = new byte[256];
   90   
   91       static {
   92           for (int i = 0; i < 255; i++) {
   93               pem_convert_array[i] = -1;
   94           }
   95           for (int i = 0; i < pem_array.length; i++) {
   96               pem_convert_array[pem_array[i]] = (byte) i;
   97           }
   98       }
   99   
  100       byte decode_buffer[] = new byte[4];
  101   
  102       /**
  103        * Decode one BASE64 atom into 1, 2, or 3 bytes of data.
  104        */
  105       protected void decodeAtom(PushbackInputStream inStream, OutputStream outStream, int rem)
  106           throws java.io.IOException
  107       {
  108           int     i;
  109           byte    a = -1, b = -1, c = -1, d = -1;
  110   
  111           if (rem < 2) {
  112               throw new CEFormatException("BASE64Decoder: Not enough bytes for an atom.");
  113           }
  114           do {
  115               i = inStream.read();
  116               if (i == -1) {
  117                   throw new CEStreamExhausted();
  118               }
  119           } while (i == '\n' || i == '\r');
  120           decode_buffer[0] = (byte) i;
  121   
  122           i = readFully(inStream, decode_buffer, 1, rem-1);
  123           if (i == -1) {
  124               throw new CEStreamExhausted();
  125           }
  126   
  127           if (rem > 3 && decode_buffer[3] == '=') {
  128               rem = 3;
  129           }
  130           if (rem > 2 && decode_buffer[2] == '=') {
  131               rem = 2;
  132           }
  133           switch (rem) {
  134           case 4:
  135               d = pem_convert_array[decode_buffer[3] & 0xff];
  136               // NOBREAK
  137           case 3:
  138               c = pem_convert_array[decode_buffer[2] & 0xff];
  139               // NOBREAK
  140           case 2:
  141               b = pem_convert_array[decode_buffer[1] & 0xff];
  142               a = pem_convert_array[decode_buffer[0] & 0xff];
  143               break;
  144           }
  145   
  146           switch (rem) {
  147           case 2:
  148               outStream.write( (byte)(((a << 2) & 0xfc) | ((b >>> 4) & 3)) );
  149               break;
  150           case 3:
  151               outStream.write( (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3)) );
  152               outStream.write( (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf)) );
  153               break;
  154           case 4:
  155               outStream.write( (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3)) );
  156               outStream.write( (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf)) );
  157               outStream.write( (byte) (((c << 6) & 0xc0) | (d  & 0x3f)) );
  158               break;
  159           }
  160           return;
  161       }
  162   }

Save This Page
Home » openjdk-7 » sun » misc » [javadoc | source]