BASE64Decoder.java revision 0
4632N/A/*
4632N/A * Copyright 1995-2000 Sun Microsystems, Inc. All Rights Reserved.
4632N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4632N/A *
4632N/A * This code is free software; you can redistribute it and/or modify it
4632N/A * under the terms of the GNU General Public License version 2 only, as
4632N/A * published by the Free Software Foundation. Sun designates this
4632N/A * particular file as subject to the "Classpath" exception as provided
4632N/A * by Sun in the LICENSE file that accompanied this code.
4632N/A *
4632N/A * This code is distributed in the hope that it will be useful, but WITHOUT
4632N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
4632N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
4632N/A * version 2 for more details (a copy is included in the LICENSE file that
4632N/A * accompanied this code).
4632N/A *
4632N/A * You should have received a copy of the GNU General Public License version
4632N/A * 2 along with this work; if not, write to the Free Software Foundation,
4632N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
4632N/A *
4632N/A * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
4632N/A * CA 95054 USA or visit www.sun.com if you need additional information or
4632N/A * have any questions.
4632N/A */
4632N/Apackage sun.misc;
4632N/A
4632N/Aimport java.io.OutputStream;
4632N/Aimport java.io.PushbackInputStream;
4632N/Aimport java.io.PrintStream;
4632N/A
4632N/A/**
4632N/A * This class implements a BASE64 Character decoder as specified in RFC1521.
4632N/A *
4632N/A * This RFC is part of the MIME specification which is published by the
4632N/A * Internet Engineering Task Force (IETF). Unlike some other encoding
4632N/A * schemes there is nothing in this encoding that tells the decoder
4632N/A * where a buffer starts or stops, so to use it you will need to isolate
4632N/A * your encoded data into a single chunk and then feed them this decoder.
4632N/A * The simplest way to do that is to read all of the encoded data into a
4632N/A * string and then use:
4632N/A * <pre>
4632N/A * byte mydata[];
4632N/A * BASE64Decoder base64 = new BASE64Decoder();
4632N/A *
4632N/A * mydata = base64.decodeBuffer(bufferString);
4632N/A * </pre>
4632N/A * This will decode the String in <i>bufferString</i> and give you an array
4632N/A * of bytes in the array <i>myData</i>.
4632N/A *
4632N/A * On errors, this class throws a CEFormatException with the following detail
4632N/A * strings:
4632N/A * <pre>
4632N/A * "BASE64Decoder: Not enough bytes for an atom."
4632N/A * </pre>
4632N/A *
4632N/A * @author Chuck McManis
4632N/A * @see CharacterEncoder
4632N/A * @see BASE64Decoder
4632N/A */
4632N/A
4632N/Apublic class BASE64Decoder extends CharacterDecoder {
4632N/A
4632N/A /** This class has 4 bytes per atom */
4632N/A protected int bytesPerAtom() {
4632N/A return (4);
4632N/A }
4632N/A
4632N/A /** Any multiple of 4 will do, 72 might be common */
4632N/A protected int bytesPerLine() {
4632N/A return (72);
4632N/A }
4632N/A
4632N/A /**
4632N/A * This character array provides the character to value map
4632N/A * based on RFC1521.
4632N/A */
4632N/A private final static char pem_array[] = {
4632N/A // 0 1 2 3 4 5 6 7
4632N/A 'A','B','C','D','E','F','G','H', // 0
4632N/A 'I','J','K','L','M','N','O','P', // 1
4632N/A 'Q','R','S','T','U','V','W','X', // 2
4632N/A 'Y','Z','a','b','c','d','e','f', // 3
4632N/A 'g','h','i','j','k','l','m','n', // 4
4632N/A 'o','p','q','r','s','t','u','v', // 5
4632N/A 'w','x','y','z','0','1','2','3', // 6
4632N/A '4','5','6','7','8','9','+','/' // 7
4632N/A };
4632N/A
4632N/A private final static byte pem_convert_array[] = new byte[256];
4632N/A
4632N/A static {
4632N/A for (int i = 0; i < 255; i++) {
4632N/A pem_convert_array[i] = -1;
4632N/A }
4632N/A for (int i = 0; i < pem_array.length; i++) {
4632N/A pem_convert_array[pem_array[i]] = (byte) i;
4632N/A }
4632N/A }
4632N/A
4632N/A byte decode_buffer[] = new byte[4];
4632N/A
4632N/A /**
4632N/A * Decode one BASE64 atom into 1, 2, or 3 bytes of data.
4632N/A */
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;
}
}