#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>

unsigned int CRC16R(char data, unsigned int crc16);

void main(int argc, char *argv[])
{
        FILE *in;        
        //unsigned char data[250];
        unsigned char *data;
        long len,fl,i;
        int tc;
        unsigned char temp;
        
        unsigned int crc1,crc2,crc16;
        
        crc1=0;
        crc2=0;
        crc16=0xffff;

        if(argc<2){
                printf("usage : crc <filename>\n");
                return;
        }

        if((in = fopen(argv[1],"rb")) == NULL){
                printf("can't open %s\n",argv[1]);
                return;
        }

        // read from file
        fseek(in,0L,SEEK_END);
        fl = ftell(in);
        fseek(in,0L,SEEK_SET);

        data = (unsigned char *)malloc(fl);
        memset(data, '\0', sizeof(data));

        for(len=0;len<fl;len++) {
                tc = fgetc(in);
                if (EOF==tc) {
                        fclose(in);
                }
                data[len]= (unsigned char)tc;
        }
        
        data[len]='\0';

        // calc. crc
        for     (i=0;i<len;i++){
                temp = data[i];
                crc16=CRC16R(temp, crc16);
                printf("0x%2x, 0x%4x\n", temp, crc16);
        }

        crc1 = crc16 & 0xff;
        if (crc1 <0x80) crc1 ^= 0xff;
        crc2 = ((crc16>>8)&0xff);
        if (crc2 <0x80) crc2 ^= 0xff;

        printf("crc16 is 0x%4x\n",crc16);
        printf("crc1 is 0x%2x\n",crc1);
        printf("crc2 is 0x%2x\n",crc2);

        free(data);
        getch();
}

unsigned int CRC16R(unsigned char data, unsigned int crc16)
{
        int i;
        unsigned int temp_crc16;
        unsigned char temp_data;

        temp_crc16 = crc16;
        temp_data = (unsigned char) data;

        temp_data <<=1;
        for ( i = 8; i > 0; i--){

                temp_data >>= 1;
                if ((temp_data ^ temp_crc16) & 0x0001)
                        temp_crc16 = (temp_crc16 >> 1) ^ 0x8408;
                else
                        temp_crc16 >>= 1;
        }
        return(temp_crc16);
}

사용 방법은 crc값을 만들고자 하는 데이타를 파일로 저장하고 아래 함수의 인자로 파일명을 전달해 주면 된다.

이렇게 나와있는데, 파일을 만들어서 코드의 어디를 어떻게 고쳐야할지 모르겠네요..

아시는분은 한번 예를 들어서 설명해주시면 감사하겠습니다.