MySQL函数计算CRC16

如何解决MySQL函数计算CRC16

我正在使用一个大型MysqL数据库的系统上工作，我需要根据表中的某些列计算crc16。但是我找不到任何对我有帮助的功能。 MysqL只有crc32，但我需要CRC16 / ARC。

我试图创建一个sql代码来计算我在Java和C＃中的CRC16状况，但是没有成功。

有人可以帮助我吗？ 谢谢！

---编辑--------------------

MysqL的sql代码尝试...

CREATE FUNCTION `fn_crc16`(pValue varchar(255)) RETURNS varchar(50) CHARSET utf8mb4
BEGIN
    declare retval,b binary;
    declare c char(1) default '';
    declare i,len integer default 0;
    set retval = 0x0000;
    set len = length(pValue);
    set i = 1;
    repeat
        set c = substring(pValue,i,1);
        set b = (retval ^ cast(c as binary)) & 0xff;
        select value into b from tbl_crc16 where idx = b;
        set retval = b ^ (retval >> 8);
        set i = i + 1;
    until i > len end repeat;
    set retval = retval & 0xffff;
    return hex(retval);
END

tbl_crc16是十六进制代码的列表。

我的Java和C＃代码生成相同的CRC16十六进制值。

这是我在Android版Java中对CRC16的实现。

public class Crc16 {
    static int[] table = {
            0x0000,0xC0C1,0xC181,0x0140,0xC301,0x03C0,0x0280,0xC241,0xC601,0x06C0,0x0780,0xC741,0x0500,0xC5C1,0xC481,0x0440,0xCC01,0x0CC0,0x0D80,0xCD41,0x0F00,0xCFC1,0xCE81,0x0E40,0x0A00,0xCAC1,0xCB81,0x0B40,0xC901,0x09C0,0x0880,0xC841,0xD801,0x18C0,0x1980,0xD941,0x1B00,0xDBC1,0xDA81,0x1A40,0x1E00,0xDEC1,0xDF81,0x1F40,0xDD01,0x1DC0,0x1C80,0xDC41,0x1400,0xD4C1,0xD581,0x1540,0xD701,0x17C0,0x1680,0xD641,0xD201,0x12C0,0x1380,0xD341,0x1100,0xD1C1,0xD081,0x1040,0xF001,0x30C0,0x3180,0xF141,0x3300,0xF3C1,0xF281,0x3240,0x3600,0xF6C1,0xF781,0x3740,0xF501,0x35C0,0x3480,0xF441,0x3C00,0xFCC1,0xFD81,0x3D40,0xFF01,0x3FC0,0x3E80,0xFE41,0xFA01,0x3AC0,0x3B80,0xFB41,0x3900,0xF9C1,0xF881,0x3840,0x2800,0xE8C1,0xE981,0x2940,0xEB01,0x2BC0,0x2A80,0xEA41,0xEE01,0x2EC0,0x2F80,0xEF41,0x2D00,0xEDC1,0xEC81,0x2C40,0xE401,0x24C0,0x2580,0xE541,0x2700,0xE7C1,0xE681,0x2640,0x2200,0xE2C1,0xE381,0x2340,0xE101,0x21C0,0x2080,0xE041,0xA001,0x60C0,0x6180,0xA141,0x6300,0xA3C1,0xA281,0x6240,0x6600,0xA6C1,0xA781,0x6740,0xA501,0x65C0,0x6480,0xA441,0x6C00,0xACC1,0xAD81,0x6D40,0xAF01,0x6FC0,0x6E80,0xAE41,0xAA01,0x6AC0,0x6B80,0xAB41,0x6900,0xA9C1,0xA881,0x6840,0x7800,0xB8C1,0xB981,0x7940,0xBB01,0x7BC0,0x7A80,0xBA41,0xBE01,0x7EC0,0x7F80,0xBF41,0x7D00,0xBDC1,0xBC81,0x7C40,0xB401,0x74C0,0x7580,0xB541,0x7700,0xB7C1,0xB681,0x7640,0x7200,0xB2C1,0xB381,0x7340,0xB101,0x71C0,0x7080,0xB041,0x5000,0x90C1,0x9181,0x5140,0x9301,0x53C0,0x5280,0x9241,0x9601,0x56C0,0x5780,0x9741,0x5500,0x95C1,0x9481,0x5440,0x9C01,0x5CC0,0x5D80,0x9D41,0x5F00,0x9FC1,0x9E81,0x5E40,0x5A00,0x9AC1,0x9B81,0x5B40,0x9901,0x59C0,0x5880,0x9841,0x8801,0x48C0,0x4980,0x8941,0x4B00,0x8BC1,0x8A81,0x4A40,0x4E00,0x8EC1,0x8F81,0x4F40,0x8D01,0x4DC0,0x4C80,0x8C41,0x4400,0x84C1,0x8581,0x4540,0x8701,0x47C0,0x4680,0x8641,0x8201,0x42C0,0x4380,0x8341,0x4100,0x81C1,0x8081,0x4040,};

    public static String hash(String s) {
        byte[] bytes = s.getBytes();
        int crc16 = 0x0000;
        for (byte b : bytes)
            crc16 = table[(crc16 ^ b) & 0xff] ^ (crc16 >> 8);
        crc16 = crc16 & 0xFFFF;
        return Integer.toHexString(crc16);
    }
}

解决方法

如果您根据函数在varchars上进行操作，那么它将起作用：

declare retval,b,c integer;
declare i,len integer default 0;
set retval = 0x0000;
set len = length(pValue);
set i = 1;
repeat
    set c = ascii(substring(pValue,i,1));
    set b = (retval ^ c) & 0xff;
    select value into b from tbl_crc16 where idx = b + 1; -- my idx starts at 1
    set retval = b ^ (retval >> 8);
    set i = i + 1;
until i > len end repeat;
set retval = retval & 0xffff;
return hex(retval);

注意：

• 我的tbl_crc16的idx从1开始；如果您的条件从0开始，请将where条件更改为idx = b
您用于retval的
• binary数据类型，b是单字节类型，这就是为什么它不起作用的原因；我正在使用整数

Live example via dbfiddle.uk，用https://crccalc.com签出

,

这实现了CRC16 / modbus，而无需使用表

DELIMITER //
CREATE DEFINER=`root`@`%` FUNCTION `CRC16`( _STRING VARCHAR(25)) RETURNS varchar(50) CHARSET utf8mb4
    DETERMINISTIC
BEGIN
    DECLARE _myCRC integer;
    DECLARE _ord INTEGER;
    DECLARE _n Integer;
    DECLARE _m Integer;
    DECLARE _strlend Integer;
    SET _myCRC := x'FFFF';

      SET _n  := 1;  
      SET _strlend := LENGTH(_STRING) ;
      
        loop_crc:  LOOP
     
            IF  _n > _strlend THEN 
                LEAVE  loop_crc;
            END  IF;
              
            SET _ord := ORD(SUBSTRING(_STRING,_n,1) );
            SET _myCRC :=  _myCRC ^ _ord;
            SET _m := 0;     
            loop_bit:  LOOP
                IF  _m = 8 THEN 
                    LEAVE  loop_bit;
                END  IF;
                IF (_myCRC & x'0001') = x'0001' THEN
                    SET _myCRC := (_myCRC >> 1) ^ x'A001';
                ELSE
                    SET _myCRC := _myCRC >> 1;        
                END IF;
                SET  _m := _m + 1;
            END LOOP;
            SET  _n := _n + 1;

        END LOOP;

      return HEX(_myCRC); 
 END//
DELIMITER ;

查询SELECT CRC16("A");

返回

CRC16("A")
707F

您可以在https://crccalc.com/查看结果，也可以使用Java或C＃中的结果