/*
 *  spreadspace avr utils
 *
 *
 *  Copyright (C) 2012 Christian Pointner <equinox@spreadspace.org>
 *
 *  This file is part of spreadspace avr utils.
 *
 *  spreadspace avr utils is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  any later version.
 *
 *  spreadspace avr utils 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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with spreadspace avr utils. If not, see <http://www.gnu.org/licenses/>.
 */

#include <ctype.h>
#include <stdio.h>

#define MAX_KEY_LEN 7

char generate_csum(char* key)
{
  return 0xFF;
}

int main(int argc, char* argv[])
{
  char* line = NULL;
  size_t len = 0;

  for(;;) {
    ssize_t ret = getline(&line, &len, stdin);
    if(ret <= 0) return 0;

    int i;
    for(i=0; i<len; ++i) {
      if(!isxdigit(line[i])) {
        line[i] = 0;
        break;
      }
    }
    if(i & 1 || i == 0 || i > MAX_KEY_LEN*2) {
      fprintf(stderr, "ignoring invalid key (odd number of digits or empty string or too long): %s\n", line);
      continue;
    }
    char key[MAX_KEY_LEN+1];
    int j;
    char tmp[3];
    tmp[2] = 0;
    for(j = 0; j<(i/2); ++j) {
      tmp[0] = line[j*2];
      tmp[1] = line[j*2 + 1];
      key[j] = (char)strtoul(tmp, NULL, 16);
    }
    for(j=i/2; j < MAX_KEY_LEN; ++j) {
      key[j] = 0;
    }
    key[MAX_KEY_LEN] = generate_csum(key);
    ret = fwrite(key, MAX_KEY_LEN+1, 1, stdout);
  }

  return 0;
}