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/*
* Copyright (c) 1995, 2011, 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:
* <pre>
* byte mydata[];
* BASE64Decoder base64 = new BASE64Decoder();
*
* mydata = base64.decodeBuffer(bufferString);
* </pre>
* This will decode the String in <i>bufferString</i> and give you an array
* of bytes in the array <i>myData</i>.
*
* On errors, this class throws a CEFormatException with the following detail
* strings:
* <pre>
* "BASE64Decoder: Not enough bytes for an atom."
* </pre>
*
* @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.
*/
@SuppressWarnings("fallthrough")
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;
}
}
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