VincenzoBase64.java

package gridpp.portal.voms;

// Gidon Moont
// Imperial College London
// Copyright (C) 2006

// Vincenzo Ciaschini's VOMS uses a non-standard Base-64 algorithm...

// This code is lifted from a standard Base64 decoder, replacing the standard matrix with that found in Vincenzo's C code

// It works...

//--------------------------------------------------------------------------------

public class VincenzoBase64 {

	// ------------------------------------------------------------------------------

	private static int[] decodemapint = new int[] { 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 52, 53, 54, 55,
			56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 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, 62, 0, 63, 0, 0, 0, 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, 0,
			0, 0, 0, 0 };

	private static byte[] decodemapbyte = new byte[128];
	static {
		for (int i = 0; i < 128; i++) {
			decodemapbyte[i] = (byte) decodemapint[i];
		}
	}

	// ------------------------------------------------------------------------------

	public static byte[] decode(String s) {

		char[] in = s.toCharArray();

		int iLen = in.length;

		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 = decodemapbyte[i0];
			int b1 = decodemapbyte[i1];
			int b2 = decodemapbyte[i2];
			int b3 = decodemapbyte[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;

	}

	// ------------------------------------------------------------------------------

}