server/tools/gethash.c

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

int main(int argc, char **argv)
{
    char key[4];
    char code[4];
    char result[4];
    int a;
    for (a = 1; a < argc; ++a) {
        int rot, i;
        const char *str = argv[a];
        size_t len = strlen(str);
        str = str + len - 6;
        memcpy(key, str, 3);
        memcpy(code, str + 3, 3);
        result[3] = key[3] = code[3] = 0;
        rot = atoi(key);
        for (i = 0; i != 3; ++i) {
            result[(i + rot) % 3] = ((code[i] + 10 - key[i]) % 10) + '0';
        }
        printf("%s %s\n", argv[a], result);
    }
    return 0;
}