和校驗、異或校驗、crc循環余校驗

不多逼逼，直接上代碼~~~

 

和校驗

/**
 * 和校驗
 * @param data 十六進制字符串
 * @return
 */

public static String makeChecksum(String data) {
    if (data == null || data.equals("")) {
        return "";
    }
    int total = 0;
    int len = data.length();
    int num = 0;
    while (num < len) {
        String s = data.substring(num, num + 2);
        total += Integer.parseInt(s, 16);
        num = num + 2;
    }
    /**
     * 用256求余最大是255，即16進制的FF
     */
    int mod = total % 256;
    String hex = Integer.toHexString(mod);
    len = hex.length();
    // 如果不夠校驗位的長度，補0,這里用的是兩位校驗
    if (len < 2) {
        hex = "0" + hex;
    }
    return hex.toUpperCase();
}

異或校驗

/***
 * 異或校驗
 * String para 十六進制字符串
 * @return
 */

public static String checkcode_0007(String para){
    String[] dateArr = new String[para.length()/2];
    for(int i = 0,k = 0;k<para.length()/2;i+=2,k++){
        dateArr[k] = para.substring(i,i+2);
    }
    String code = "";
    for (int i = 0; i < dateArr.length-1; i++) {
        if(i == 0){
            code = xorHex(dateArr[i], dateArr[i+1]);
        }else{
            code = xorHex(code, dateArr[i+1]);
        }
    }
    return code;
}

/**
 *
 * @param a 十六進制字節
 * @param b 十六進制字節
 * @return
 */
public static String xorHex(String a, String b) {
    char[] chars = new char[a.length()];
    for (int i = 0; i < chars.length; i++) {
        chars[i] = toHex(fromHex(a.charAt(i)) ^ fromHex(b.charAt(i)));
    }
    return new String(chars);
}

private static int fromHex(char c) {
    if (c >= '0' && c <= '9') {
        return c - '0';
    }
    if (c >= 'A' && c <= 'F') {
        return c - 'A' + 10;
    }
    if (c >= 'a' && c <= 'f') {
        return c - 'a' + 10;
    }
    throw new IllegalArgumentException();
}

private static char toHex(int nybble) {
    if (nybble < 0 || nybble > 15) {
        throw new IllegalArgumentException();
    }
    return "0123456789ABCDEF".charAt(nybble);
}

crc循環

使用方法： String crc = getBufHexStr(getSendBuf(""));

public static final String HEXES = "0123456789ABCDEF";

public static String getBufHexStr(byte [] raw){
    if(raw == null){
        return  null;
    }
    final StringBuffer hex = new StringBuffer(2*raw.length);
    for (final byte b : raw) {
        hex.append(HEXES.charAt((b&0xf0)>>4)).append(HEXES.charAt((b&0x0f)));
    }
    return hex.toString();
}

public static byte[] getSendBuf(String toSend) {
    byte[] bb = HexString2Buf(toSend);
    crcCheck crc16 = new crcCheck();
    crc16.update(bb, bb.length - 2);
    int ri = crc16.getValue();
    bb[bb.length - 1] = (byte) (0xff & ri);
    bb[bb.length - 2] = (byte) ((0xff00 & ri) >> 8);
    return bb;
}

private static byte uniteBytes(byte src0, byte src1) {
    byte _b0 = Byte.decode("0x" + new String(new byte[]{src0})).byteValue();
    _b0 = (byte) (_b0 << 4);
    byte _b1 = Byte.decode("0x" + new String(new byte[]{src1})).byteValue();
    byte ret = (byte) (_b0 ^ _b1);
    return ret;
}

private static byte[] HexString2Buf(String src) {
    int len = src.length();
    byte[] ret = new byte[len / 2 + 2];
    byte[] tmp = src.getBytes();
    for (int i = 0; i < len; i += 2) {
        ret[i / 2] = uniteBytes(tmp[i], tmp[i + 1]);
    }
    return ret;
}

均測試有效 ~~~