#include <stdio.h>
#include <string.h>
#include "crc16tab.h"


/*
*    Calculates CRC
*
*    Copyright (c) 2022 - 2023 R.J. van der Putten, Leiden, Holland, 
*    rob at sput dot nl.
* 
*    This program is free software; you can redistribute it and/or modify
*    it under the terms of the GNU General Public License version 3 as
*    published by the Free Software Foundation.
* 
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU General Public License for more details.
*/


int main(void)
{
    char line[4096];
    unsigned char t;
    int i, len;
    unsigned int r;

    memset(line, 0, 4096);

    while (fgets(line + 2, 4088, stdin)) {
	i = 0;
	/*  Cleanup  */
	len = strlen(line) - 1;
	if (line[len] == 10) {
	    line[len] = 0;
	    len--;
	}
	if (line[len] == 13) {
	    line[len] = 0;
	    len--;
	}
	len++;
	/*  Pad for length of CRC  */
	line[len] = 0;
	len++;
	line[len] = 0;
	len++;

	t = 0;

	r = 0xFFFF;

	while (i < len) {
	    /*  Shift CRC width - 8  */
	    t = (r >> 8) & 0xFF;
	    r = (r << 8) | (unsigned char) line[i];
	    r ^= crctab[t];
	    r = r & 0xFFFF;
	    i++;
	}

	printf("Crc: %04X\n", r);
    }

    return(0);
}