CRC校验方法用C语言实现源代码(2)

{

unsigned int crc = 0; unsigned char crc_H8; unsigned char *ptr = test; while( len-- ) {

crc_H8 = (unsigned char)(crc >> 8); crc = crc << 8; crc = crc ^ crc_table[

crc_H8 ^ *ptr]; ptr++; }

printf("0x%x ",crc); }

4、按半字节计算CRC

是不是感觉上面的表太大了，不是很爽，我们再来改进一下，按半字节计算，原理我就不赘述了，程序如下： 复制代码 代码如下: unsigned

unsigned char len = 16; unsigned int crc_table[16] =

{0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef };

void main(void) {

unsigned int crc = 0; unsigned char crc_H4; unsigned char *ptr = test; while( len-- ) {

crc_H4 = (unsigned char)(crc >> 12); crc = crc << 4;

crc = crc ^ crc_table[ crc_H4 ^ (*ptr >> 4)]; crc_H4 = (unsigned char)(crc >> 12); crc = crc << 4;

crc = crc ^ crc_table[ crc_H4 ^ (*ptr & 0x0f)]; ptr++; }

char

test[16]

={0x00,0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88,0x99,0xaa,0xbb,0xcc,0xdd,0xee,0xff};

printf("0x%x ",crc); }