/*
 * Copyright (C) 2005 Luca Veltri - University of Parma - Italy
 * 
 * This file is part of MjSip (http://www.mjsip.org)
 * 
 * MjSip 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.
 * 
 * MjSip 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 MjSip; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 * Author(s):
 * Luca Veltri (luca.veltri@unipr.it)
 */

package org.zoolu.tools;

/**
 * Class Base64 can be used for base64-encoding a byte array and/or for
 * base64-decoding a base64-string.
 * 
 * @author Camilla Ferramola, Univeristy of Parma, Italy - 2004
 */
public class Base64 {
	private static final String base64codes = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	private static int[] aux = new int[4];

	/** Base64 encoder */
	public static String encode(byte[] input) {

		String stringacod = "";
		byte[] bin = new byte[3];

		int iter = (input.length) / 3;
		int nzero = (input.length) % 3;
		int i = 0;

		for (i = 0; i < iter; i++) {
			bin[0] = input[i * 3];
			bin[1] = input[i * 3 + 1];
			bin[2] = input[i * 3 + 2];

			aux[0] = ((bin[0] >>> 2) & 63);
			aux[1] = ((bin[0] & 3) << 4) + ((bin[1] >>> 4) & 15);
			aux[2] = ((bin[1] & 15) << 2) + ((bin[2] >>> 6) & 3);
			aux[3] = (bin[2] & 63);

			// uso gli interi memorizzati in aux[] come indice della stringa
			// base64codes
			// System.out.println("aux[0]="+aux[0]+" aux[1]="+aux[1]);
			stringacod = stringacod + base64codes.charAt(aux[0])
					+ base64codes.charAt(aux[1]) + base64codes.charAt(aux[2])
					+ base64codes.charAt(aux[3]);
		}

		if (i == iter) {
			if (nzero == 0) {
			} else if (nzero == 1) { // l'ultimo pacchetto da analizzare ha 8
				// bit
				// quindi ottengo due caratteri in base64 e due caratteri
				// padding "="
				aux[0] = ((input[iter * 3] >>> 2) & 63);
				aux[1] = (input[iter * 3] & 3) << 4;

				stringacod = stringacod + base64codes.charAt(aux[0])
						+ base64codes.charAt(aux[1]) + "==";
			} else if (nzero == 2) { // l'ultimo pacchetto da analizzare ha
				// 16 bit quindi ottengo
				// tre caratteri in base 64 e uno di padding "="
				aux[0] = ((input[iter * 3] >>> 2) & 63);
				aux[1] = ((input[iter * 3] & 3) << 4)
						+ ((input[iter * 3 + 1] >>> 4) & 15);
				aux[2] = (input[iter * 3 + 1] & 15) << 2;

				stringacod = stringacod + base64codes.charAt(aux[0])
						+ base64codes.charAt(aux[1])
						+ base64codes.charAt(aux[2]) + "=";
			}
		}

		return stringacod;

	}

	/** Base64 decoder */
	public static byte[] decode(String stringacod) {
		// tolgo gli eventuali "=" alla fine della stringa
		int uguale = stringacod.indexOf("=");
		if (uguale != -1)
			stringacod = stringacod.substring(0, uguale);

		int[] bin = new int[3];
		int iter = (stringacod.length()) / 4;
		int resto = (stringacod.length()) % 4;

		int nzero = 0;
		if (resto != 0)
			nzero = 1;
		byte[] output = new byte[iter * 3 + nzero * (resto - 1)];

		int i = 0;
		for (i = 0; i < iter; i++) {
			aux[0] = base64codes.indexOf(stringacod.charAt(i * 4));
			aux[1] = base64codes.indexOf(stringacod.charAt(i * 4 + 1));
			aux[2] = base64codes.indexOf(stringacod.charAt(i * 4 + 2));
			aux[3] = base64codes.indexOf(stringacod.charAt(i * 4 + 3));

			bin[0] = (aux[0] << 2) + (aux[1] >>> 4);
			bin[1] = (aux[1] % 16 << 4) + (aux[2] >>> 2);
			bin[2] = (aux[2] % 4 << 6) + aux[3];

			output[i * 3] = (byte) bin[0];
			output[i * 3 + 1] = (byte) bin[1];
			output[i * 3 + 2] = (byte) bin[2];
		}

		if (i == iter) {
			// per come e costruita la codifica a base64
			// togliendo gli eventuali caratteri "=" di padding
			// il resto puo essere 0, 2 o 3
			if (resto == 0) {
			}
			if (resto == 2) {
				aux[0] = base64codes.indexOf(stringacod.charAt(i * 4));
				aux[1] = base64codes.indexOf(stringacod.charAt(i * 4 + 1));

				bin[0] = (aux[0] << 2) + (aux[1] >>> 4);

				output[i * 3] = (byte) bin[0];
			}

			if (resto == 3) {
				aux[0] = base64codes.indexOf(stringacod.charAt(i * 4));
				aux[1] = base64codes.indexOf(stringacod.charAt(i * 4 + 1));
				aux[2] = base64codes.indexOf(stringacod.charAt(i * 4 + 2));

				bin[0] = (aux[0] << 2) + (aux[1] >>> 4);
				bin[1] = (aux[1] % 16 << 4) + (aux[2] >>> 2);

				output[i * 3] = (byte) bin[0];
				output[i * 3 + 1] = (byte) bin[1];
			}
		}
		return output;
	}

	// ******************************* MAIN *******************************

	public static void main(String[] args) {
		String messaggio = args[0];
		byte[] bmess = messaggio.getBytes();
		String mess64 = encode(bmess);
		System.out.println("messaggio codificato: " + mess64);
		byte[] decodificato = decode(mess64);
		String strdecodificato = "";
		try {
			strdecodificato = new String(decodificato, "ISO-8859-1");
		} catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println("messaggio decodificato e: " + strdecodificato);
	}
}
