package com.freud.modbus.algorithm;

import java.util.Arrays;

/**
 * LRC(Longitudinal redundancy check)
 * 
 * @author Freud
 *
 */
public class LRCUtil {

	public static byte[] LRC(byte[] src) {
		return LRC(new String(src));
	}

	public static byte[] LRC(String src) {

		int[] request = new int[src.length() / 2];
		for (int i = 0; i < src.length() - 1; i += 2) {
			request[i / 2] = Integer.valueOf(src.substring(i, i + 2), 16);
		}

		byte ret = 0;
		for (int b : request) {
			ret += (b & 0xFF);
		}

		return new byte[] { (byte) (~ret + 1) };
	}

	public static String bytesToHexString(byte[] src) {
		if (src == null || src.length <= 0) {
			return null;
		}
		StringBuilder stringBuilder = new StringBuilder("");
		for (int i = 0; i < src.length; i++) {
			int v = src[i] & 0xFF;
			String hv = Integer.toHexString(v);
			if (hv.length() < 2) {
				stringBuilder.append(0);
			}
			stringBuilder.append(hv);
		}

		return stringBuilder.toString().toUpperCase();
	}

	public static void main(String[] args) {
		// MODBUS ASCII REQUEST
		// 3A 30 31 30 33 30 30 30 30 30 30 30 41 46 32 0D 0A
		byte[] request = new byte[] { 0x30, 0x31, 0x30, 0x33, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
				0x30, 0x41 };
		String result = bytesToHexString(LRC(request));
		System.out.println("Calculated by LRC result : [" + result + "]");
		System.out.println("Calculated by LRC result to 10 radix: ["
				+ Arrays.toString(result.getBytes()) + "]");
		System.out.println("Calculated by LRC result to 16 radix: ["
				+ bytesToHexString(result.getBytes()) + "]");
	}

}
/**
 * Calculated by LRC result : [F2]
 * Calculated by LRC result to 10 radix: [[70, 50]]
 * Calculated by LRC result to 16 radix: [4632]
 */

package com.freud.pmb.algorithm;

/**
 * Checksum
 * 
 * @author Freud
 *
 */
public class CheckSumUtil {

	public static void main(String[] args) {
		String source = "1203400456ABCDFE";
		System.out.println(checksum(source));
	}

	public static String checksum(String chkstr) {
		int sum = 0;
		for (byte sbyte : chkstr.getBytes()) {
			sum += sbyte;
		}
		Integer intvalue = ~(sum % 65535) + 1;
		return Integer.toHexString(intvalue).substring(4).toUpperCase();
	}
}