16비트 CRC 알고리즘 코드

개요..

 

16비트(Bit) CRC 알고리즘을 구현한 코드입니다. 위 출처에서 구한 코드인데 코드가 참 좋네요.

Kyuseo가 약간 수정하였습니다.

 

코드 출처 : han.comp.lang.c++, http://blog.naver.com/programsite/140006734084

 

 

코드

 

#define POLYNOMIAL 0x8005 #define CRC_TABLE_SIZE 256 #define RCV_BUF_SIZE 4   #define USE_CRC_TABLE   #ifndef USE_CRC_TABLE            static unsigned short crc_table[CRC_TABLE_SIZE];   #else            static unsigned short crc_table[CRC_TABLE_SIZE] = {              0x0000, 0x8005, 0x800f, 0x000a, 0x801b, 0x001e, 0x0014, 0x8011,              0x8033, 0x0036, 0x003c, 0x8039, 0x0028, 0x802d, 0x8027, 0x0022,              0x8063, 0x0066, 0x006c, 0x8069, 0x0078, 0x807d, 0x8077, 0x0072,              0x0050, 0x8055, 0x805f, 0x005a, 0x804b, 0x004e, 0x0044, 0x8041,              0x80c3, 0x00c6, 0x00cc, 0x80c9, 0x00d8, 0x80dd, 0x80d7, 0x00d2,              0x00f0, 0x80f5, 0x80ff, 0x00fa, 0x80eb, 0x00ee, 0x00e4, 0x80e1,              0x00a0, 0x80a5, 0x80af, 0x00aa, 0x80bb, 0x00be, 0x00b4, 0x80b1,              0x8093, 0x0096, 0x009c, 0x8099, 0x0088, 0x808d, 0x8087, 0x0082,              0x8183, 0x0186, 0x018c, 0x8189, 0x0198, 0x819d, 0x8197, 0x0192,              0x01b0, 0x81b5, 0x81bf, 0x01ba, 0x81ab, 0x01ae, 0x01a4, 0x81a1,              0x01e0, 0x81e5, 0x81ef, 0x01ea, 0x81fb, 0x01fe, 0x01f4, 0x81f1,              0x81d3, 0x01d6, 0x01dc, 0x81d9, 0x01c8, 0x81cd, 0x81c7, 0x01c2,              0x0140, 0x8145, 0x814f, 0x014a, 0x815b, 0x015e, 0x0154, 0x8151,              0x8173, 0x0176, 0x017c, 0x8179, 0x0168, 0x816d, 0x8167, 0x0162,              0x8123, 0x0126, 0x012c, 0x8129, 0x0138, 0x813d, 0x8137, 0x0132,              0x0110, 0x8115, 0x811f, 0x011a, 0x810b, 0x010e, 0x0104, 0x8101,              0x8303, 0x0306, 0x030c, 0x8309, 0x0318, 0x831d, 0x8317, 0x0312,              0x0330, 0x8335, 0x833f, 0x033a, 0x832b, 0x032e, 0x0324, 0x8321,              0x0360, 0x8365, 0x836f, 0x036a, 0x837b, 0x037e, 0x0374, 0x8371,              0x8353, 0x0356, 0x035c, 0x8359, 0x0348, 0x834d, 0x8347, 0x0342,              0x03c0, 0x83c5, 0x83cf, 0x03ca, 0x83db, 0x03de, 0x03d4, 0x83d1,              0x83f3, 0x03f6, 0x03fc, 0x83f9, 0x03e8, 0x83ed, 0x83e7, 0x03e2,              0x83a3, 0x03a6, 0x03ac, 0x83a9, 0x03b8, 0x83bd, 0x83b7, 0x03b2,              0x0390, 0x8395, 0x839f, 0x039a, 0x838b, 0x038e, 0x0384, 0x8381,              0x0280, 0x8285, 0x828f, 0x028a, 0x829b, 0x029e, 0x0294, 0x8291,              0x82b3, 0x02b6, 0x02bc, 0x82b9, 0x02a8, 0x82ad, 0x82a7, 0x02a2,              0x82e3, 0x02e6, 0x02ec, 0x82e9, 0x02f8, 0x82fd, 0x82f7, 0x02f2,              0x02d0, 0x82d5, 0x82df, 0x02da, 0x82cb, 0x02ce, 0x02c4, 0x82c1,              0x8243, 0x0246, 0x024c, 0x8249, 0x0258, 0x825d, 0x8257, 0x0252,              0x0270, 0x8275, 0x827f, 0x027a, 0x826b, 0x026e, 0x0264, 0x8261,              0x0220, 0x8225, 0x822f, 0x022a, 0x823b, 0x023e, 0x0234, 0x8231,              0x8213, 0x0216, 0x021c, 0x8219, 0x0208, 0x820d, 0x8207, 0x0202      }; #endif        void gen_crc_table();      unsigned short update_crc(unsigned short crc_accum, unsigned char          *data_blk_ptr,          unsigned short data_blk_size);          void gen_crc_table()      { #ifndef USE_CRC_TABLE          register unsigned short i, j;          register unsigned short crc_accum;            /* 0 ~ CRC_TABLE_SIZE-1 까지의CRC를미리계산*/          /* ex) i=2 이면0x020000 을polynomial로CRC 나눗셈하는것임*/          for(i=0; iif(crc_accum & 0x8000L)              crc_accum = (crc_accum << 1) ^ POLYNOMIAL;              /* 참이면1-bit shift하고polynomial을빼줌(==XOR) */ else crc_accum = (crc_accum << 1); /* 거짓이면1-bit shift만함*/      }      /* 결과적으로총16-bit가shift 되었고*/      /* 나머지만남게됨*/      crc_table[i] = crc_accum;        printf("0x%04x, ", crc_accum);      if((i+1)%8 == 0)          printf("\n");   } #endif return; }     /* 이전에계산한CRC 값을추가된데이터에맞춰갱신함 이전: ___________ 8005 | XX 00 00 yy yy ---> CRC   갱신: ______________ 8005 | XX ZZ 00 00 yy yy 00 ww ww ---> CRC' */ unsigned short update_crc(unsigned short crc_accum, unsigned char                          *data_blk_ptr,unsigned short data_blk_size) {     register unsigned short i, j;       for(j=0; j> 8) ^ *data_blk_ptr++) & 0xff;     crc_accum = (crc_accum << 8) ^ crc_table[i];     /* 나머지항의하위바이트는뒤에0x00 이 */     /* 추가되어자리수가올라가고앞자리의 */     /* 나머지와더해짐*/ } return crc_accum; }     /********************************************************** CRC-16 test sample **********************************************************/   void main() {       unsigned char i;     unsigned short crc, check;     unsigned char in_frame[RCV_BUF_SIZE+2];     unsigned char out_frame[RCV_BUF_SIZE+2];       gen_crc_table();       /* 임의데이터생성*/     in_frame[0] = 0x55;     in_frame[1] = 0xA1;     in_frame[2] = 0x12;     in_frame[3] = 0x34;       /* 송신측의CRC 생성*/     crc = update_crc(0, in_frame, RCV_BUF_SIZE);     printf("\n====== CRC-16 Demo ========\n");     printf("\nTransmitter CRC result = 0x%04X", crc);       /* 수신측의검증*/     for(i=0;i>8) ;     out_frame[RCV_BUF_SIZE+1] = (crc & 0x00FF);       check = update_crc(0, out_frame,RCV_BUF_SIZE+2);     printf("\nReceiver CRC check = 0x%04X\n", check); }