Mega Code Archive
A class to decode Base64 streams and strings
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/*
This file is part of Socks via HTTP.
This package is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
Socks via HTTP 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 for more details.
You should have received a copy of the GNU General Public License
along with Socks via HTTP; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
// Title : Base64Decoder.java
// Version : 1.2
// Copyright : Copyright (c) 2001-2002
// Author : Florent CUETO & Sebastien LEBRETON <socksviahttp@cqs.dyndns.org>
// Description : Base 64 Decoder
//package socksviahttp.core.util;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
/**
* A class to decode Base64 streams and strings. See RFC 1521 section 5.2 for
* details of the Base64 algorithm.
* <p>
* This class can be used for decoding strings: <blockquote>
*
* <pre>
* String encoded = "d2VibWFzdGVyOnRyeTJndWVTUw";
* String decoded = Base64Decoder.decode(encoded);
* </pre>
*
* </blockquote> or for decoding streams: <blockquote>
*
* <pre>
* InputStream in = new Base64Decoder(System.in);
* </pre>
*
* </blockquote>
*/
public class Base64Decoder extends FilterInputStream {
private static final char[] chars = { 'A', 'B', 'C', 'D', 'E', 'F', 'G',
'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6',
'7', '8', '9', '+', '/' };
// A mapping between char values and six-bit integers
private static final int[] ints = new int[128];
static {
for (int i = 0; i < 64; i++) {
ints[chars[i]] = i;
}
}
private int charCount;
private int carryOver;
/**
* Constructs a new Base64 decoder that reads input from the given
* InputStream.
*
* @param in
* the input stream
*/
public Base64Decoder(InputStream in) {
super(in);
}
/**
* Returns the next decoded character from the stream, or -1 if end of
* stream was reached.
*
* @return the decoded character, or -1 if the end of the input stream is
* reached
* @exception IOException
* if an I/O error occurs
*/
public int read() throws IOException {
// Read the next non-whitespace character
int x;
do {
x = in.read();
if (x == -1) {
return -1;
}
} while (Character.isWhitespace((char) x));
charCount++;
// The '=' sign is just padding
if (x == '=') {
return -1; // effective end of stream
}
// Convert from raw form to 6-bit form
x = ints[x];
// Calculate which character we're decoding now
int mode = (charCount - 1) % 4;
// First char save all six bits, go for another
if (mode == 0) {
carryOver = x & 63;
return read();
}
// Second char use previous six bits and first two new bits,
// save last four bits
else if (mode == 1) {
int decoded = ((carryOver << 2) + (x >> 4)) & 255;
carryOver = x & 15;
return decoded;
}
// Third char use previous four bits and first four new bits,
// save last two bits
else if (mode == 2) {
int decoded = ((carryOver << 4) + (x >> 2)) & 255;
carryOver = x & 3;
return decoded;
}
// Fourth char use previous two bits and all six new bits
else if (mode == 3) {
int decoded = ((carryOver << 6) + x) & 255;
return decoded;
}
return -1; // can't actually reach this line
}
/**
* Reads decoded data into an array of bytes and returns the actual number
* of bytes read, or -1 if end of stream was reached.
*
* @param buf
* the buffer into which the data is read
* @param off
* the start offset of the data
* @param len
* the maximum number of bytes to read
* @return the actual number of bytes read, or -1 if the end of the input
* stream is reached
* @exception IOException
* if an I/O error occurs
*/
public int read(byte[] b, int off, int len) throws IOException {
// This could of course be optimized
int i;
for (i = 0; i < len; i++) {
int x = read();
if (x == -1 && i == 0) { // an immediate -1 returns -1
return -1;
} else if (x == -1) { // a later -1 returns the chars read so far
break;
}
b[off + i] = (byte) x;
}
return i;
}
/**
* Returns the decoded form of the given encoded string.
*
* @param encoded
* the string to decode
* @return the decoded form of the encoded string
*/
public static String decode(String encoded) {
byte[] bytes = null;
try {
bytes = encoded.getBytes("8859_1");
} catch (UnsupportedEncodingException ignored) {
}
Base64Decoder in = new Base64Decoder(new ByteArrayInputStream(bytes));
ByteArrayOutputStream out = new ByteArrayOutputStream(
(int) (bytes.length * 0.67));
try {
byte[] buf = new byte[4 * 1024]; // 4K buffer
int bytesRead;
while ((bytesRead = in.read(buf)) != -1) {
out.write(buf, 0, bytesRead);
}
out.close();
return out.toString("8859_1");
} catch (IOException ignored) {
return null;
}
}
}
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