/*
 * Copyright (C) 1995, 1996 Systemics Ltd (http://www.systemics.com/)
 * All rights reserved.
 */

package cryptix.pgp;
 
/**
 * This class performs the CRC check as required by pgp base64 Encoded packets.
 *
 * <hr>
 * <P>
 * <bold>Copyright</bold> &#169 1995, 1996, 1997
 * <a href="http://www.systemics.com/">Systemics Ltd</a>
 * on behalf of the
 * <a href="http://www.systemics.com/docs/cryptix/">
 * Cryptix Development Team</a>.
 * All rights reserved.
 */
public final class CRC 
{ 
	private static final int crctable[] =
	{
		0x00000000, 0x00864cfb, 0x018ad50d, 0x010c99f6, 0x0393e6e1, 0x0315aa1a, 0x021933ec, 0x029f7f17,
		0x07a18139, 0x0727cdc2, 0x062b5434, 0x06ad18cf, 0x043267d8, 0x04b42b23, 0x05b8b2d5, 0x053efe2e,
		0x0fc54e89, 0x0f430272, 0x0e4f9b84, 0x0ec9d77f, 0x0c56a868, 0x0cd0e493, 0x0ddc7d65, 0x0d5a319e,
		0x0864cfb0, 0x08e2834b, 0x09ee1abd, 0x09685646, 0x0bf72951, 0x0b7165aa, 0x0a7dfc5c, 0x0afbb0a7,
		0x1f0cd1e9, 0x1f8a9d12, 0x1e8604e4, 0x1e00481f, 0x1c9f3708, 0x1c197bf3, 0x1d15e205, 0x1d93aefe,
		0x18ad50d0, 0x182b1c2b, 0x192785dd, 0x19a1c926, 0x1b3eb631, 0x1bb8faca, 0x1ab4633c, 0x1a322fc7,
		0x10c99f60, 0x104fd39b, 0x11434a6d, 0x11c50696, 0x135a7981, 0x13dc357a, 0x12d0ac8c, 0x1256e077,
		0x17681e59, 0x17ee52a2, 0x16e2cb54, 0x166487af, 0x14fbf8b8, 0x147db443, 0x15712db5, 0x15f7614e,
		0x3e19a3d2, 0x3e9fef29, 0x3f9376df, 0x3f153a24, 0x3d8a4533, 0x3d0c09c8, 0x3c00903e, 0x3c86dcc5,
		0x39b822eb, 0x393e6e10, 0x3832f7e6, 0x38b4bb1d, 0x3a2bc40a, 0x3aad88f1, 0x3ba11107, 0x3b275dfc,
		0x31dced5b, 0x315aa1a0, 0x30563856, 0x30d074ad, 0x324f0bba, 0x32c94741, 0x33c5deb7, 0x3343924c,
		0x367d6c62, 0x36fb2099, 0x37f7b96f, 0x3771f594, 0x35ee8a83, 0x3568c678, 0x34645f8e, 0x34e21375,
		0x2115723b, 0x21933ec0, 0x209fa736, 0x2019ebcd, 0x228694da, 0x2200d821, 0x230c41d7, 0x238a0d2c,
		0x26b4f302, 0x2632bff9, 0x273e260f, 0x27b86af4, 0x252715e3, 0x25a15918, 0x24adc0ee, 0x242b8c15,
		0x2ed03cb2, 0x2e567049, 0x2f5ae9bf, 0x2fdca544, 0x2d43da53, 0x2dc596a8, 0x2cc90f5e, 0x2c4f43a5,
		0x2971bd8b, 0x29f7f170, 0x28fb6886, 0x287d247d, 0x2ae25b6a, 0x2a641791, 0x2b688e67, 0x2beec29c,
		0x7c3347a4, 0x7cb50b5f, 0x7db992a9, 0x7d3fde52, 0x7fa0a145, 0x7f26edbe, 0x7e2a7448, 0x7eac38b3,
		0x7b92c69d, 0x7b148a66, 0x7a181390, 0x7a9e5f6b, 0x7801207c, 0x78876c87, 0x798bf571, 0x790db98a,
		0x73f6092d, 0x737045d6, 0x727cdc20, 0x72fa90db, 0x7065efcc, 0x70e3a337, 0x71ef3ac1, 0x7169763a,
		0x74578814, 0x74d1c4ef, 0x75dd5d19, 0x755b11e2, 0x77c46ef5, 0x7742220e, 0x764ebbf8, 0x76c8f703,
		0x633f964d, 0x63b9dab6, 0x62b54340, 0x62330fbb, 0x60ac70ac, 0x602a3c57, 0x6126a5a1, 0x61a0e95a,
		0x649e1774, 0x64185b8f, 0x6514c279, 0x65928e82, 0x670df195, 0x678bbd6e, 0x66872498, 0x66016863,
		0x6cfad8c4, 0x6c7c943f, 0x6d700dc9, 0x6df64132, 0x6f693e25, 0x6fef72de, 0x6ee3eb28, 0x6e65a7d3,
		0x6b5b59fd, 0x6bdd1506, 0x6ad18cf0, 0x6a57c00b, 0x68c8bf1c, 0x684ef3e7, 0x69426a11, 0x69c426ea,
		0x422ae476, 0x42aca88d, 0x43a0317b, 0x43267d80, 0x41b90297, 0x413f4e6c, 0x4033d79a, 0x40b59b61,
		0x458b654f, 0x450d29b4, 0x4401b042, 0x4487fcb9, 0x461883ae, 0x469ecf55, 0x479256a3, 0x47141a58,
		0x4defaaff, 0x4d69e604, 0x4c657ff2, 0x4ce33309, 0x4e7c4c1e, 0x4efa00e5, 0x4ff69913, 0x4f70d5e8,
		0x4a4e2bc6, 0x4ac8673d, 0x4bc4fecb, 0x4b42b230, 0x49ddcd27, 0x495b81dc, 0x4857182a, 0x48d154d1,
		0x5d26359f, 0x5da07964, 0x5cace092, 0x5c2aac69, 0x5eb5d37e, 0x5e339f85, 0x5f3f0673, 0x5fb94a88,
		0x5a87b4a6, 0x5a01f85d, 0x5b0d61ab, 0x5b8b2d50, 0x59145247, 0x59921ebc, 0x589e874a, 0x5818cbb1,
		0x52e37b16, 0x526537ed, 0x5369ae1b, 0x53efe2e0, 0x51709df7, 0x51f6d10c, 0x50fa48fa, 0x507c0401,
		0x5542fa2f, 0x55c4b6d4, 0x54c82f22, 0x544e63d9, 0x56d11cce, 0x56575035, 0x575bc9c3, 0x57dd8538
	};

	public final static int ACCUM_INIT = 0xB704CE; 

	public static int
	checksum(byte buf[])
	{
		return checksum(ACCUM_INIT, buf);
	}

	public static int
	checksum(int accum, byte buf[])
	{
		int pos = 0, len = buf.length; 
		while ( len-- > 0 ) 
			accum = ( accum << 8 ) ^ crctable[( ( accum >>> 16 ) ^ buf[pos++] ) & 0xFF]; 
		return (accum & 0xFFFFFF); 
	}



	//
	//	Following only for CRC objects
	//

	private int accum = ACCUM_INIT; 
 
	/**
	 * This adds the contents of the buffer to the CRC.
	 * @param buf the buffer to add.
	 */
	public final void 
	add( byte buf[] ) 
	{ 
		accum = checksum(accum, buf);
	}  
 
	/**
	 * This adds the contents of the buffer to the CRC.
	 * @return the CRC value so far.
	 */
	public final int crc() { return accum; } 
}