// lotto2.c  rolf.freitag at email.de 2000
// For producing random Lotto numbers (1..49) which are really equally distributed.
// Todo: Buffering +qsort of each row of numbers.

#include <stdio.h>
#include <iso646.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

// simple version number
#define SOFTWARE_VERSION_NUMBER 1.0

int
main (const int argc, const char * const argv[])
{
  int i = 0;
  unsigned char i1 = 0, i2 = 0;
  unsigned long int lc = 0;
  unsigned char c7[7] = { 0 };
  FILE *ifp = NULL, *ofp = NULL;
  char inname[0x100] = "/dev/urandom";            // input file name
  char outname[0x100] = "./lotto2.out";           // output file name

  if ( (argc>1) and not strncmp (argv[1], "-V", 123) )
  {
    fprintf (stdout, "%s version %.1f\n", argv[0], SOFTWARE_VERSION_NUMBER);
    exit ( (2 == argc) ? 0 : -1);
  }
  ifp = fopen (inname, "rb");
  if (ifp == NULL)
  {
    fprintf (stderr, "\a\ncan't open %s ", inname);
    perror("\n error \n");
    exit (errno);                                 // missing output file
  }
  ofp = fopen (outname, "w");
  if (ofp == NULL)
  {
    fprintf (stderr, "\a\ncan't open %s ", outname);
    perror("\n error \n");
    exit (errno);                                 // missing output file
  }
  fprintf (ofp, "True random Lotto numbers (1..49).\n");
  for (i = 0; i < 59 * 3 * 7; i++)                /* 59 lines with 3 times 6 numbers */
  {
    i2 = 0;
    while (i2 == 0)                               // while no usable random number
    {
      fscanf (ifp, "%c", &i1);                    // read a true random byte
      if (i1 <= 244)
      {
        i2 = i1 / 5 + 1;                          /* 0 <= i1 <= 244 implies  1 <= i2 <= 49 */
        /* this loop is done approx. 1,045 times  */
        for (i1 = 0; i1 < lc % 7; i1++)           /* avoid two times the same number in a row of 7 numbers */
          if (c7[i1] == i2)                       /* same number */
        {
          i2 = 0;
          break;                                  /* not the same number */
        }
        else
          c7[lc % 7] = i2;                        /* Store the actual and valid value to avoid two times the same number. */
      }
    }                                             /* while, a true random Lotto number has been prduced  */
    if (lc % 7 != 0)                              // 6 numbers
      if (i2 > 9)
        fprintf (ofp, "%u ", i2);
    else
      fprintf (ofp, " %u ", i2);
    else
      fprintf (ofp, "  ");
    fflush (ofp);
    lc++;
    if (lc % 7 == 0)
    {
      fprintf (ofp, "\t");
      for (i1 = 0; i1 < 7; i1++)
        c7[i1] = 0;
      if (lc % 3 == 0)                            /* x % 7 = 0 u. x % 3 = 0 implies x % 21 = 0 */
        fprintf (ofp, "\n");                      /* line end */
    }
  }                                               /* for */
  fclose (ifp);
  return (0);
}