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