1 /*

     2  * Copyright 1995-1997 Sun Microsystems, Inc.  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.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 package sun.misc;

    26 

    27 import java.io.OutputStream;

    28 import java.io.InputStream;

    29 import java.io.PrintStream;

    30 import java.io.IOException;

    31 

    32 /**

    33  * This class implements a BASE64 Character encoder as specified in RFC1521.

    34  * This RFC is part of the MIME specification as published by the Internet

    35  * Engineering Task Force (IETF). Unlike some other encoding schemes there

    36  * is nothing in this encoding that indicates

    37  * where a buffer starts or ends.

    38  *

    39  * This means that the encoded text will simply start with the first line

    40  * of encoded text and end with the last line of encoded text.

    41  *

    42  * @author      Chuck McManis

    43  * @see         CharacterEncoder

    44  * @see         BASE64Decoder

    45  */

    46 

    47 public class BASE64Encoder extends CharacterEncoder {

    48 

    49     /** this class encodes three bytes per atom. */

    50     protected int bytesPerAtom() {

    51         return (3);

    52     }

    53 

    54     /**

    55      * this class encodes 57 bytes per line. This results in a maximum

    56      * of 57/3 * 4 or 76 characters per output line. Not counting the

    57      * line termination.

    58      */

    59     protected int bytesPerLine() {

    60         return (57);

    61     }

    62 

    63     /** This array maps the characters to their 6 bit values */

    64     private final static char pem_array[] = {

    65         //       0   1   2   3   4   5   6   7

    66                 'A','B','C','D','E','F','G','H', // 0

    67                 'I','J','K','L','M','N','O','P', // 1

    68                 'Q','R','S','T','U','V','W','X', // 2

    69                 'Y','Z','a','b','c','d','e','f', // 3

    70                 'g','h','i','j','k','l','m','n', // 4

    71                 'o','p','q','r','s','t','u','v', // 5

    72                 'w','x','y','z','0','1','2','3', // 6

    73                 '4','5','6','7','8','9','+','/'  // 7

    74         };

    75 

    76     /**

    77      * encodeAtom - Take three bytes of input and encode it as 4

    78      * printable characters. Note that if the length in len is less

    79      * than three is encodes either one or two '=' signs to indicate

    80      * padding characters.

    81      */

    82     protected void encodeAtom(OutputStream outStream, byte data[], int offset, int len)

    83         throws IOException {

    84         byte a, b, c;

    85 

    86         if (len == 1) {

    87             a = data[offset];

    88             b = 0;

    89             c = 0;

    90             outStream.write(pem_array[(a >>> 2) & 0x3F]);

    91             outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);

    92             outStream.write('=');

    93             outStream.write('=');

    94         } else if (len == 2) {

    95             a = data[offset];

    96             b = data[offset+1];

    97             c = 0;

    98             outStream.write(pem_array[(a >>> 2) & 0x3F]);

    99             outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);

   100             outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);

   101             outStream.write('=');

   102         } else {

   103             a = data[offset];

   104             b = data[offset+1];

   105             c = data[offset+2];

   106             outStream.write(pem_array[(a >>> 2) & 0x3F]);

   107             outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);

   108             outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);

   109             outStream.write(pem_array[c & 0x3F]);

   110         }

   111     }

   112 }