/* * Copyright (c) 1995, 2000, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package sun.misc; import java.io.OutputStream; import java.io.PushbackInputStream; import java.io.PrintStream; /** * This class implements a BASE64 Character decoder as specified in RFC1521. * * This RFC is part of the MIME specification which is published by the * Internet Engineering Task Force (IETF). Unlike some other encoding * schemes there is nothing in this encoding that tells the decoder * where a buffer starts or stops, so to use it you will need to isolate * your encoded data into a single chunk and then feed them this decoder. * The simplest way to do that is to read all of the encoded data into a * string and then use: *
 *      byte    mydata[];
 *      BASE64Decoder base64 = new BASE64Decoder();
 *
 *      mydata = base64.decodeBuffer(bufferString);
 * 
* This will decode the String in bufferString and give you an array * of bytes in the array myData. * * On errors, this class throws a CEFormatException with the following detail * strings: *
 *    "BASE64Decoder: Not enough bytes for an atom."
 * 
* * @author Chuck McManis * @see CharacterEncoder * @see BASE64Decoder */ public class BASE64Decoder extends CharacterDecoder { /** This class has 4 bytes per atom */ protected int bytesPerAtom() { return (4); } /** Any multiple of 4 will do, 72 might be common */ protected int bytesPerLine() { return (72); } /** * This character array provides the character to value map * based on RFC1521. */ private final static char pem_array[] = { // 0 1 2 3 4 5 6 7 'A','B','C','D','E','F','G','H', // 0 'I','J','K','L','M','N','O','P', // 1 'Q','R','S','T','U','V','W','X', // 2 'Y','Z','a','b','c','d','e','f', // 3 'g','h','i','j','k','l','m','n', // 4 'o','p','q','r','s','t','u','v', // 5 'w','x','y','z','0','1','2','3', // 6 '4','5','6','7','8','9','+','/' // 7 }; private final static byte pem_convert_array[] = new byte[256]; static { for (int i = 0; i < 255; i++) { pem_convert_array[i] = -1; } for (int i = 0; i < pem_array.length; i++) { pem_convert_array[pem_array[i]] = (byte) i; } } byte decode_buffer[] = new byte[4]; /** * Decode one BASE64 atom into 1, 2, or 3 bytes of data. */ protected void decodeAtom(PushbackInputStream inStream, OutputStream outStream, int rem) throws java.io.IOException { int i; byte a = -1, b = -1, c = -1, d = -1; if (rem < 2) { throw new CEFormatException("BASE64Decoder: Not enough bytes for an atom."); } do { i = inStream.read(); if (i == -1) { throw new CEStreamExhausted(); } } while (i == '\n' || i == '\r'); decode_buffer[0] = (byte) i; i = readFully(inStream, decode_buffer, 1, rem-1); if (i == -1) { throw new CEStreamExhausted(); } if (rem > 3 && decode_buffer[3] == '=') { rem = 3; } if (rem > 2 && decode_buffer[2] == '=') { rem = 2; } switch (rem) { case 4: d = pem_convert_array[decode_buffer[3] & 0xff]; // NOBREAK case 3: c = pem_convert_array[decode_buffer[2] & 0xff]; // NOBREAK case 2: b = pem_convert_array[decode_buffer[1] & 0xff]; a = pem_convert_array[decode_buffer[0] & 0xff]; break; } switch (rem) { case 2: outStream.write( (byte)(((a << 2) & 0xfc) | ((b >>> 4) & 3)) ); break; case 3: outStream.write( (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3)) ); outStream.write( (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf)) ); break; case 4: outStream.write( (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3)) ); outStream.write( (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf)) ); outStream.write( (byte) (((c << 6) & 0xc0) | (d & 0x3f)) ); break; } return; } }