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Ian Darwin's assorted Java stuff, assembled as an API.
There is a newer version: 1.8.0
// Copyright 2003-2010 Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland
// www.source-code.biz, www.inventec.ch/chdh
//
// This module is multi-licensed and may be used under the terms
// of any of the following licenses:
//
//  EPL, Eclipse Public License, V1.0 or later, http://www.eclipse.org/legal
//  LGPL, GNU Lesser General Public License, V2.1 or later, http://www.gnu.org/licenses/lgpl.html
//  GPL, GNU General Public License, V2 or later, http://www.gnu.org/licenses/gpl.html
//  AL, Apache License, V2.0 or later, http://www.apache.org/licenses
//  BSD, BSD License, http://www.opensource.org/licenses/bsd-license.php
//  MIT, MIT License, http://www.opensource.org/licenses/MIT
//
// Please contact the author if you need another license.
// This module is provided "as is", without warranties of any kind.

package com.darwinsys.security;

/**
* A Base64 encoder/decoder.
*
* 
* This class is used to encode and decode data in Base64 format as described in RFC 1521.
*
* 
* Project home page: www.source-code.biz/base64coder/java

* Author: Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland

* Multi-licensed: EPL / LGPL / GPL / AL / BSD / MIT.
*/
public class Base64Coder {

	// The line separator string of the operating system.
	private static final String systemLineSeparator = System.getProperty("line.separator");

	// Mapping table from 6-bit nibbles to Base64 characters.
	private static final char[] map1 = new char[64];
	static {
		int i=0;
		for (char c='A'; c<='Z'; c++) map1[i++] = c;
		for (char c='a'; c<='z'; c++) map1[i++] = c;
		for (char c='0'; c<='9'; c++) map1[i++] = c;
		map1[i++] = '+'; map1[i++] = '/'; }

	// Mapping table from Base64 characters to 6-bit nibbles.
	private static final byte[] map2 = new byte[128];
	static {
		for (int i=0; isun.misc.BASE64Encoder.encodeBuffer(byte[]).
	 * @param in  An array containing the data bytes to be encoded.
	 * @return    A String containing the Base64 encoded data, broken into lines.
	 */
	public static String encodeLines (byte[] in) {
		return encodeLines(in, 0, in.length, 76, systemLineSeparator); }

	/**
	 * Encodes a byte array into Base 64 format and breaks the output into lines.
	 * @param in            An array containing the data bytes to be encoded.
	 * @param iOff          Offset of the first byte in in to be processed.
	 * @param iLen          Number of bytes to be processed in in, starting at iOff.
	 * @param lineLen       Line length for the output data. Should be a multiple of 4.
	 * @param lineSeparator The line separator to be used to separate the output lines.
	 * @return              A String containing the Base64 encoded data, broken into lines.
	 */
	public static String encodeLines (byte[] in, int iOff, int iLen, int lineLen, String lineSeparator) {
		int blockLen = (lineLen*3) / 4;
		if (blockLen <= 0) throw new IllegalArgumentException();
		int lines = (iLen+blockLen-1) / blockLen;
		int bufLen = ((iLen+2)/3)*4 + lines*lineSeparator.length();
		StringBuilder buf = new StringBuilder(bufLen);
		int ip = 0;
		while (ip < iLen) {
			int l = Math.min(iLen-ip, blockLen);
			buf.append (encode(in, iOff+ip, l));
			buf.append (lineSeparator);
			ip += l; }
		return buf.toString(); }

	/**
	 * Encodes a byte array into Base64 format.
	 * No blanks or line breaks are inserted in the output.
	 * @param in  An array containing the data bytes to be encoded.
	 * @return    A character array containing the Base64 encoded data.
	 */
	public static char[] encode (byte[] in) {
		return encode(in, 0, in.length); }

	/**
	 * Encodes a byte array into Base64 format.
	 * No blanks or line breaks are inserted in the output.
	 * @param in    An array containing the data bytes to be encoded.
	 * @param iLen  Number of bytes to process in in.
	 * @return      A character array containing the Base64 encoded data.
	 */
	public static char[] encode (byte[] in, int iLen) {
		return encode(in, 0, iLen); }

	/**
	 * Encodes a byte array into Base64 format.
	 * No blanks or line breaks are inserted in the output.
	 * @param in    An array containing the data bytes to be encoded.
	 * @param iOff  Offset of the first byte in in to be processed.
	 * @param iLen  Number of bytes to process in in, starting at iOff.
	 * @return      A character array containing the Base64 encoded data.
	 */
	public static char[] encode (byte[] in, int iOff, int iLen) {
		int oDataLen = (iLen*4+2)/3;       // output length without padding
		int oLen = ((iLen+2)/3)*4;         // output length including padding
		char[] out = new char[oLen];
		int ip = iOff;
		int iEnd = iOff + iLen;
		int op = 0;
		while (ip < iEnd) {
			int i0 = in[ip++] & 0xff;
			int i1 = ip < iEnd ? in[ip++] & 0xff : 0;
			int i2 = ip < iEnd ? in[ip++] & 0xff : 0;
			int o0 = i0 >>> 2;
			int o1 = ((i0 &   3) << 4) | (i1 >>> 4);
			int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
			int o3 = i2 & 0x3F;
			out[op++] = map1[o0];
			out[op++] = map1[o1];
			out[op] = op < oDataLen ? map1[o2] : '='; op++;
			out[op] = op < oDataLen ? map1[o3] : '='; op++; }
		return out; }

	/**
	 * Decodes a string from Base64 format.
	 * No blanks or line breaks are allowed within the Base64 encoded input data.
	 * @param s  A Base64 String to be decoded.
	 * @return   A String containing the decoded data.
	 * @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
	 */
	public static String decodeString (String s) {
		return new String(decode(s)); }

	/**
	 * Decodes a byte array from Base64 format and ignores line separators, tabs and blanks.
	 * CR, LF, Tab and Space characters are ignored in the input data.
	 * This method is compatible with sun.misc.BASE64Decoder.decodeBuffer(String).
	 * @param s  A Base64 String to be decoded.
	 * @return   An array containing the decoded data bytes.
	 * @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
	 */
	public static byte[] decodeLines (String s) {
		char[] buf = new char[s.length()];
		int p = 0;
		for (int ip = 0; ip < s.length(); ip++) {
			char c = s.charAt(ip);
			if (c != ' ' && c != '\r' && c != '\n' && c != '\t')
				buf[p++] = c; }
		return decode(buf, 0, p); }

	/**
	 * Decodes a byte array from Base64 format.
	 * No blanks or line breaks are allowed within the Base64 encoded input data.
	 * @param s  A Base64 String to be decoded.
	 * @return   An array containing the decoded data bytes.
	 * @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
	 */
	public static byte[] decode (String s) {
		return decode(s.toCharArray()); }

	/**
	 * Decodes a byte array from Base64 format.
	 * No blanks or line breaks are allowed within the Base64 encoded input data.
	 * @param in  A character array containing the Base64 encoded data.
	 * @return    An array containing the decoded data bytes.
	 * @throws    IllegalArgumentException If the input is not valid Base64 encoded data.
	 */
	public static byte[] decode (char[] in) {
		return decode(in, 0, in.length); }

	/**
	 * Decodes a byte array from Base64 format.
	 * No blanks or line breaks are allowed within the Base64 encoded input data.
	 * @param in    A character array containing the Base64 encoded data.
	 * @param iOff  Offset of the first character in in to be processed.
	 * @param iLen  Number of characters to process in in, starting at iOff.
	 * @return      An array containing the decoded data bytes.
	 * @throws      IllegalArgumentException If the input is not valid Base64 encoded data.
	 */
	public static byte[] decode (char[] in, int iOff, int iLen) {
		if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4.");
		while (iLen > 0 && in[iOff+iLen-1] == '=') iLen--;
		int oLen = (iLen*3) / 4;
		byte[] out = new byte[oLen];
		int ip = iOff;
		int iEnd = iOff + iLen;
		int op = 0;
		while (ip < iEnd) {
			int i0 = in[ip++];
			int i1 = in[ip++];
			int i2 = ip < iEnd ? in[ip++] : 'A';
			int i3 = ip < iEnd ? in[ip++] : 'A';
			if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
				throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
			int b0 = map2[i0];
			int b1 = map2[i1];
			int b2 = map2[i2];
			int b3 = map2[i3];
			if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
				throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
			int o0 = ( b0       <<2) | (b1>>>4);
			int o1 = ((b1 & 0xf)<<4) | (b2>>>2);
			int o2 = ((b2 &   3)<<6) |  b3;
			out[op++] = (byte)o0;
			if (op