crc8校验查表法实现方法

/*

CRC-8 for Dallas iButton products

From Maxim/Dallas AP Note 27

\ Dallas Semiconductor iButton Products\

The Ap note describes the CRC-8 algorithm used in the iButton products. Their implementation involves a 256 byte CRC table. This algorithm is implemented here. In addition two other algorithms are shown. One uses nibble arrays and the other uses boolean arithmetic.

18JAN03 - T. Scott Dattalo */

/*

crc array from the Maxim ApNote */

unsigned char crc_array[256] = {

0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83, 0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41, 0x9d, 0xc3, 0x21, 0x7f, 0xfc, 0xa2, 0x40, 0x1e, 0x5f, 0x01, 0xe3, 0xbd, 0x3e, 0x60, 0x82, 0xdc, 0x23, 0x7d, 0x9f, 0xc1, 0x42, 0x1c, 0xfe, 0xa0, 0xe1, 0xbf, 0x5d, 0x03, 0x80, 0xde, 0x3c, 0x62, 0xbe, 0xe0, 0x02, 0x5c, 0xdf, 0x81, 0x63, 0x3d, 0x7c, 0x22, 0xc0, 0x9e, 0x1d, 0x43, 0xa1, 0xff, 0x46, 0x18, 0xfa, 0xa4, 0x27, 0x79, 0x9b, 0xc5, 0x84, 0xda, 0x38, 0x66, 0xe5, 0xbb, 0x59, 0x07, 0xdb, 0x85, 0x67, 0x39, 0xba, 0xe4, 0x06, 0x58, 0x19, 0x47, 0xa5, 0xfb, 0x78, 0x26, 0xc4, 0x9a, 0x65, 0x3b, 0xd9, 0x87, 0x04, 0x5a, 0xb8, 0xe6, 0xa7, 0xf9, 0x1b, 0x45, 0xc6, 0x98, 0x7a, 0x24, 0xf8, 0xa6, 0x44, 0x1a, 0x99, 0xc7, 0x25, 0x7b, 0x3a, 0x64, 0x86, 0xd8, 0x5b, 0x05, 0xe7, 0xb9, 0x8c, 0xd2, 0x30, 0x6e, 0xed, 0xb3, 0x51, 0x0f, 0x4e, 0x10, 0xf2, 0xac, 0x2f, 0x71, 0x93, 0xcd,

0x11, 0x4f, 0xad, 0xf3, 0x70, 0x2e, 0xcc, 0x92, 0xd3, 0x8d, 0x6f, 0x31, 0xb2, 0xec, 0x0e, 0x50, 0xaf, 0xf1, 0x13, 0x4d, 0xce, 0x90, 0x72, 0x2c, 0x6d, 0x33, 0xd1, 0x8f, 0x0c, 0x52, 0xb0, 0xee, 0x32, 0x6c, 0x8e, 0xd0, 0x53, 0x0d, 0xef, 0xb1, 0xf0, 0xae, 0x4c, 0x12, 0x91, 0xcf, 0x2d, 0x73, 0xca, 0x94, 0x76, 0x28, 0xab, 0xf5, 0x17, 0x49, 0x08, 0x56, 0xb4, 0xea, 0x69, 0x37, 0xd5, 0x8b, 0x57, 0x09, 0xeb, 0xb5, 0x36, 0x68, 0x8a, 0xd4, 0x95, 0xcb, 0x29, 0x77, 0xf4, 0xaa, 0x48, 0x16, 0xe9, 0xb7, 0x55, 0x0b, 0x88, 0xd6, 0x34, 0x6a, 0x2b, 0x75, 0x97, 0xc9, 0x4a, 0x14, 0xf6, 0xa8, 0x74, 0x2a, 0xc8, 0x96, 0x15, 0x4b, 0xa9, 0xf7, 0xb6, 0xe8, 0x0a, 0x54, 0xd7, 0x89, 0x6b, 0x35, };

unsigned char r1[16] = {

0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83, 0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41, };

unsigned char r2[16] = {

0x00, 0x9d, 0x23, 0xbe, 0x46, 0xdb, 0x65, 0xf8, 0x8c, 0x11, 0xaf, 0x32, 0xca, 0x57, 0xe9, 0x74 };

/*

crc - global crc stored here */

unsigned char crc;

/*===========================================================*/

unsigned char crc_bits(int data) {

int i = (data ^ crc) & 0xff;

crc = 0;

if(i & 1)

crc ^= 0x5e;

if(i & 2) crc ^= 0xbc; if(i & 4)

crc ^= 0x61; if(i & 8) crc ^= 0xc2; if(i & 0x10) crc ^= 0x9d; if(i & 0x20) crc ^= 0x23; if(i & 0x40) crc ^= 0x46; if(i & 0x80) crc ^= 0x8c;

return crc;

}

/*===========================================================*/

unsigned char crc_table(int data) {

int i = (data ^ crc) & 0xff;

crc = crc_array[(data ^ crc)&0xff];

return crc;

}

/*===========================================================*/ unsigned char crc_nibbles(int data) {

int i = (data ^ crc) & 0xff;

crc = r1[i&0xf] ^ r2[i>>4];

return crc; }

/*===========================================================*/ /* crc8 - test all three crc algorithms */

unsigned char crc8(int data) {

unsigned char c;

c = crc;

crc_table(data);

printf(\

crc = c;

crc_bits(data);

printf(\ crc = c;

crc_nibbles(data); printf(\

return crc; }

/*===========================================================*/

int main(int argc, char **argv) {

int i;

crc = 0xff; /*

Standard check for the string \ */

for(i='1'; i<='9'; i++) { crc8(i);

printf(\ }

printf(\

/*

Orthogonal check

Set the crc =0 and data = 2^n and compute new crc */

crc = 0x00; crc8(1); crc = 0x00; crc8(2);

crc = 0x00; crc8(4); crc = 0x00; crc8(8); crc = 0x00; crc8(16); crc = 0x00; crc8(32); crc = 0x00; crc8(64); crc = 0x00; crc8(128); /*

CRC example in the Dallas APNote */

crc=0; i = 0x02;

printf(\

i = 0x1c;

printf(\

i = 0xb8;

printf(\

i = 0x01;

printf(\

i = 0x00;

printf(\

i = 0x00;

printf(\

i = 0x00;

printf(\

i = 0xa2;

printf(\

return 0; }

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