package de.ugoe.cs.swe.memos.misc;

//Copyright 2003-2009 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, http://www.eclipse.org/legal
//LGPL, GNU Lesser General Public License, http://www.gnu.org/licenses/lgpl.html
//AL, Apache License, http://www.apache.org/licenses
//BSD, BSD License, http://www.opensource.org/licenses/bsd-license.php
//
//Please contact the author if you need another license.
//This module is provided "as is", without warranties of any kind.

/**
 * A Base64 Encoder/Decoder.
 * 
 * <p>
 * This class is used to encode and decode data in Base64 format as described in
 * RFC 1521.
 * 
 * <p>
 * Home page: <a href="http://www.source-code.biz">www.source-code.biz</a><br>
 * Author: Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland<br>
 * Multi-licensed: EPL/LGPL/AL/BSD.
 * 
 * <p>
 * Version history:<br>
 * 2003-07-22 Christian d'Heureuse (chdh): Module created.<br>
 * 2005-08-11 chdh: Lincense changed from GPL to LGPL.<br>
 * 2006-11-21 chdh:<br>
 * &nbsp; Method encode(String) renamed to encodeString(String).<br>
 * &nbsp; Method decode(String) renamed to decodeString(String).<br>
 * &nbsp; New method encode(byte[],int) added.<br>
 * &nbsp; New method decode(String) added.<br>
 * 2009-07-16: Additional licenses (EPL/AL) added.<br>
 * 2009-09-16: Additional license (BSD) added.<br>
 */

public class Base64Coder {

	// Mapping table from 6-bit nibbles to Base64 characters.
	private static 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 byte[] map2 = new byte[128];
	static {
		for (int i = 0; i < map2.length; i++)
			map2[i] = -1;
		for (int i = 0; i < 64; i++)
			map2[map1[i]] = (byte) i;
	}

	/**
	 * Encodes a string into Base64 format. No blanks or line breaks are
	 * inserted.
	 * 
	 * @param s
	 *            a String to be encoded.
	 * @return A String with the Base64 encoded data.
	 */
	public static String encodeString(String s) {
		return new String(encode(s.getBytes()));
	}

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

	/**
	 * Encodes a byte array into Base64 format. No blanks or line breaks are
	 * inserted.
	 * 
	 * @param in
	 *            an array containing the data bytes to be encoded.
	 * @param iLen
	 *            number of bytes to process in <code>in</code>.
	 * @return A character array with the Base64 encoded data.
	 */
	public static char[] encode(byte[] in, 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 = 0;
		int op = 0;
		while (ip < iLen) {
			int i0 = in[ip++] & 0xff;
			int i1 = ip < iLen ? in[ip++] & 0xff : 0;
			int i2 = ip < iLen ? 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.
	 * 
	 * @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.
	 * 
	 * @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 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) {
		int iLen = in.length;
		if (iLen % 4 != 0)
			throw new IllegalArgumentException(
					"Length of Base64 encoded input string is not a multiple of 4.");
		while (iLen > 0 && in[iLen - 1] == '=')
			iLen--;
		int oLen = (iLen * 3) / 4;
		byte[] out = new byte[oLen];
		int ip = 0;
		int op = 0;
		while (ip < iLen) {
			int i0 = in[ip++];
			int i1 = in[ip++];
			int i2 = ip < iLen ? in[ip++] : 'A';
			int i3 = ip < iLen ? 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 < oLen)
				out[op++] = (byte) o1;
			if (op < oLen)
				out[op++] = (byte) o2;
		}
		return out;
	}

	// Dummy constructor.
	private Base64Coder() {
	}

} // end class Base64Coder
