/hdt-java-core/src/main/java/org/rdfhdt/hdt/util/crc/CRC8.java

package org.rdfhdt.hdt.util.crc;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * CRC8-CCIT Algorithm
 * 
 *    Width        = 8
 *    Poly         = 0x07
 *    XorIn        = 0x00
 *    ReflectIn    = False
 *    XorOut       = 0x00
 *    ReflectOut   = False
 * 
 * @author mario.arias
 *
 */
public class CRC8 implements CRC {
	byte crc8;
	
	private static final byte[] crc8_table = {
	    (byte)0x00, (byte)0x07, (byte)0x0e, (byte)0x09, (byte)0x1c, (byte)0x1b, (byte)0x12, (byte)0x15,
	    (byte)0x38, (byte)0x3f, (byte)0x36, (byte)0x31, (byte)0x24, (byte)0x23, (byte)0x2a, (byte)0x2d,
	    (byte)0x70, (byte)0x77, (byte)0x7e, (byte)0x79, (byte)0x6c, (byte)0x6b, (byte)0x62, (byte)0x65,
	    (byte)0x48, (byte)0x4f, (byte)0x46, (byte)0x41, (byte)0x54, (byte)0x53, (byte)0x5a, (byte)0x5d,
	    (byte)0xe0, (byte)0xe7, (byte)0xee, (byte)0xe9, (byte)0xfc, (byte)0xfb, (byte)0xf2, (byte)0xf5,
	    (byte)0xd8, (byte)0xdf, (byte)0xd6, (byte)0xd1, (byte)0xc4, (byte)0xc3, (byte)0xca, (byte)0xcd,
	    (byte)0x90, (byte)0x97, (byte)0x9e, (byte)0x99, (byte)0x8c, (byte)0x8b, (byte)0x82, (byte)0x85,
	    (byte)0xa8, (byte)0xaf, (byte)0xa6, (byte)0xa1, (byte)0xb4, (byte)0xb3, (byte)0xba, (byte)0xbd,
	    (byte)0xc7, (byte)0xc0, (byte)0xc9, (byte)0xce, (byte)0xdb, (byte)0xdc, (byte)0xd5, (byte)0xd2,
	    (byte)0xff, (byte)0xf8, (byte)0xf1, (byte)0xf6, (byte)0xe3, (byte)0xe4, (byte)0xed, (byte)0xea,
	    (byte)0xb7, (byte)0xb0, (byte)0xb9, (byte)0xbe, (byte)0xab, (byte)0xac, (byte)0xa5, (byte)0xa2,
	    (byte)0x8f, (byte)0x88, (byte)0x81, (byte)0x86, (byte)0x93, (byte)0x94, (byte)0x9d, (byte)0x9a,
	    (byte)0x27, (byte)0x20, (byte)0x29, (byte)0x2e, (byte)0x3b, (byte)0x3c, (byte)0x35, (byte)0x32,
	    (byte)0x1f, (byte)0x18, (byte)0x11, (byte)0x16, (byte)0x03, (byte)0x04, (byte)0x0d, (byte)0x0a,
	    (byte)0x57, (byte)0x50, (byte)0x59, (byte)0x5e, (byte)0x4b, (byte)0x4c, (byte)0x45, (byte)0x42,
	    (byte)0x6f, (byte)0x68, (byte)0x61, (byte)0x66, (byte)0x73, (byte)0x74, (byte)0x7d, (byte)0x7a,
	    (byte)0x89, (byte)0x8e, (byte)0x87, (byte)0x80, (byte)0x95, (byte)0x92, (byte)0x9b, (byte)0x9c,
	    (byte)0xb1, (byte)0xb6, (byte)0xbf, (byte)0xb8, (byte)0xad, (byte)0xaa, (byte)0xa3, (byte)0xa4,
	    (byte)0xf9, (byte)0xfe, (byte)0xf7, (byte)0xf0, (byte)0xe5, (byte)0xe2, (byte)0xeb, (byte)0xec,
	    (byte)0xc1, (byte)0xc6, (byte)0xcf, (byte)0xc8, (byte)0xdd, (byte)0xda, (byte)0xd3, (byte)0xd4,
	    (byte)0x69, (byte)0x6e, (byte)0x67, (byte)0x60, (byte)0x75, (byte)0x72, (byte)0x7b, (byte)0x7c,
	    (byte)0x51, (byte)0x56, (byte)0x5f, (byte)0x58, (byte)0x4d, (byte)0x4a, (byte)0x43, (byte)0x44,
	    (byte)0x19, (byte)0x1e, (byte)0x17, (byte)0x10, (byte)0x05, (byte)0x02, (byte)0x0b, (byte)0x0c,
	    (byte)0x21, (byte)0x26, (byte)0x2f, (byte)0x28, (byte)0x3d, (byte)0x3a, (byte)0x33, (byte)0x34,
	    (byte)0x4e, (byte)0x49, (byte)0x40, (byte)0x47, (byte)0x52, (byte)0x55, (byte)0x5c, (byte)0x5b,
	    (byte)0x76, (byte)0x71, (byte)0x78, (byte)0x7f, (byte)0x6a, (byte)0x6d, (byte)0x64, (byte)0x63,
	    (byte)0x3e, (byte)0x39, (byte)0x30, (byte)0x37, (byte)0x22, (byte)0x25, (byte)0x2c, (byte)0x2b,
	    (byte)0x06, (byte)0x01, (byte)0x08, (byte)0x0f, (byte)0x1a, (byte)0x1d, (byte)0x14, (byte)0x13,
	    (byte)0xae, (byte)0xa9, (byte)0xa0, (byte)0xa7, (byte)0xb2, (byte)0xb5, (byte)0xbc, (byte)0xbb,
	    (byte)0x96, (byte)0x91, (byte)0x98, (byte)0x9f, (byte)0x8a, (byte)0x8d, (byte)0x84, (byte)0x83,
	    (byte)0xde, (byte)0xd9, (byte)0xd0, (byte)0xd7, (byte)0xc2, (byte)0xc5, (byte)0xcc, (byte)0xcb,
	    (byte)0xe6, (byte)0xe1, (byte)0xe8, (byte)0xef, (byte)0xfa, (byte)0xfd, (byte)0xf4, (byte)0xf3
	};
	

	@Override
	public void update(byte[] buffer, int offset, int length) {
		int i=offset;
		int len=length;
		while(len-- != 0) {
	    	crc8 = crc8_table[(crc8 ^ buffer[i]) & 0xFF ];
	        i++;
	    }
	}

	
	   /**
     * Update the CRC value with a byte data.
     *
     * @param data  The byte data
     * @param crc   The starting CRC value
     * @return      The updated CRC value
     */
    public void update(byte data) {
        crc8 = crc8_table[(crc8 ^ data) & 0xFF ];
    }

	@Override
	public void writeCRC(OutputStream out) throws IOException {
		out.write(crc8);
	}

	@Override
	public boolean readAndCheck(InputStream in) throws IOException {
		int val = in.read();
		
		if(val==-1) {
			throw new IOException("Could not read from input.");
		}
		byte othercrc = (byte)(val & 0xFF);
		
		return othercrc==crc8;
	}

	@Override
	public long getValue() {
		return crc8;
	}

	@Override
	public void reset() {
		crc8=0;
	}

	@Override
	public int compareTo(CRC o) {
		if(o instanceof CRC8) {
			return ((CRC8)o).crc8-this.crc8;
		}
		throw new RuntimeException("Cannot compare CRC's of different types");
	}
	
	@Override
	public String toString() {
		return Long.toHexString(getValue()&0xFFL);
	}
}