Base64.java

package ch.unifr.pai.twice.authentication.client.security;

/*
 Copyright (c) 2009, Mark Renouf
 All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright
 notice, this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright
 notice, this list of conditions and the following disclaimer in the
 documentation and/or other materials provided with the distribution.
 * Neither the name of the <organization> nor the
 names of its contributors may be used to endorse or promote products
 derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY Mark Renouf ''AS IS'' AND ANY
 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED. IN NO EVENT SHALL <copyright holder> BE LIABLE FOR ANY
 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * Custom Base64 encode/decode implementation suitable for use in GWT applications (uses only translatable classes).
 */
public class Base64 {

	private static final String etab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

	private static byte[] dtab = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, 64, -1, -1, -1, 0, 1, 2, 3,
			4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
			36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 };

	public static String decode(String data) {
		StringBuffer out = new StringBuffer();

		// length must be multiple of 4 (with padding)
		if (data.length() % 4 != 0)
			return "";

		for (int i = 0; i < data.length();) {
			byte e0 = dtab[data.charAt(i++) & 0x7f];
			byte e1 = dtab[data.charAt(i++) & 0x7f];
			byte e2 = dtab[data.charAt(i++) & 0x7f];
			byte e3 = dtab[data.charAt(i++) & 0x7f];

			// Invalid characters in input
			if (e0 == -1 || e1 == -1 || e2 == -1 || e3 == -1)
				return "";

			byte d0 = (byte) ((e0 << 2) + ((e1 >>> 4) & 0x03));
			byte d1 = (byte) ((e1 << 4) + ((e2 >>> 2) & 0x0f));
			byte d2 = (byte) ((e2 << 6) + (e3 & 0x3f));

			out.append(Character.toString((char) d0));
			if (e2 != 64)
				out.append(Character.toString((char) d1));
			if (e3 != 64)
				out.append(Character.toString((char) d2));
		}
		return out.toString();
	}

	public static String encode(String data) {
		StringBuffer out = new StringBuffer();

		int i = 0;
		int r = data.length();
		while (r > 0) {
			byte d0, d1, d2;
			byte e0, e1, e2, e3;

			d0 = (byte) data.charAt(i++);
			--r;
			e0 = (byte) (d0 >>> 2);
			e1 = (byte) ((d0 & 0x03) << 4);

			if (r > 0) {
				d1 = (byte) data.charAt(i++);
				--r;
				e1 += (byte) (d1 >>> 4);
				e2 = (byte) ((d1 & 0x0f) << 2);
			}
			else {
				e2 = 64;
			}

			if (r > 0) {
				d2 = (byte) data.charAt(i++);
				--r;
				e2 += (byte) (d2 >>> 6);
				e3 = (byte) (d2 & 0x3f);
			}
			else {
				e3 = 64;
			}
			out.append(etab.charAt(e0));
			out.append(etab.charAt(e1));
			out.append(etab.charAt(e2));
			out.append(etab.charAt(e3));
		}

		return out.toString();
	}
}