Unique Candidate Identifier check digit calculator.

uci.c

// ============================================================================
//        Copyright (c) 2010-2011 Graham Edgecombe. All Rights Reserved.       
//              Unique Candidate Identifier Check Digit Calculator             
// ============================================================================

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

#define CENTRE_LEN 5
#define BOARD_LEN 1
#define YEAR_LEN 2
#define CANDIDATE_LEN 4
#define CHECK_LEN 1

#define UCI_LEN (CENTRE_LEN + BOARD_LEN + YEAR_LEN + CANDIDATE_LEN + CHECK_LEN)

#define UCI_STR_LEN (UCI_LEN + 4)

#define PRODUCT 16
#define DIVISOR 17

struct uci
{
  char centre[CENTRE_LEN + 1];
  char board[BOARD_LEN + 1];
  char year[YEAR_LEN + 1];
  char candidate[CANDIDATE_LEN + 1];
};

char uci_char_to_num(char c, bool letters)
{
  if (c >= '0' && c <= '9')
    return c - '0';
  else if (c >= 'A' && c <= 'I')
    return c - 'A';
  else if (letters)
    if (c == 'J' || c == 'Q' || c == 'X')
      return 10;
    else if (c == 'K' || c == 'R' || c == 'Y')
      return 11;
    else if (c == 'L' || c == 'S' || c == 'Z')
      return 12;
    else if (c == 'M' || c == 'T')
      return 13;
    else if (c == 'N' || c == 'U')
      return 14;
    else if (c == 'O' || c == 'V')
      return 15;
    else if (c == 'P' || c == 'W')
      return 16;
  return 0;
};

char uci_check_digit(struct uci *u)
{
  unsigned char values[UCI_LEN - CHECK_LEN];
  int offset = 0;

  for (int i = 0; i < CENTRE_LEN; i++)
    values[offset++] = uci_char_to_num(u->centre[i], i < 2);

  for (int i = 0; i < BOARD_LEN; i++)
    values[offset++] = uci_char_to_num(u->board[i], true);

  for (int i = 0; i < YEAR_LEN; i++)
    values[offset++] = uci_char_to_num(u->year[i], false);

  for (int i = 0; i < CANDIDATE_LEN; i++)
    values[offset++] = uci_char_to_num(u->candidate[i], false);

  unsigned int sum = 0;
  for (int i = 0; i < (UCI_LEN - CHECK_LEN); i++)
    sum += (PRODUCT - i) * values[i];

  int remainder = sum % DIVISOR;

  if (remainder < 8)
    return 'A' + remainder;
  else if (remainder < 10)
    return 'K' + remainder - 8;
  else if (remainder == 11)
    return 'R';
  else if (remainder == 12)
    return 'T';
  else
    return 'V' + remainder - 13;
}

void uci_str(char *str, struct uci *u)
{
  char check = uci_check_digit(u);
  sprintf(str, "UCI%s%s%s%s%c", u->centre, u->board, u->year, u->candidate, check);
}

int main(int argc, char **argv)
{
  struct uci u;

  sprintf(u.centre, "68199");
  sprintf(u.board, "0");
  sprintf(u.year, "01");
  sprintf(u.candidate, "2058");

  char str[UCI_STR_LEN];
  uci_str((char *) &str, &u);

  printf("%s\n", str);

  return 0;
}