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0.5.12.2 Source Code

int r[100]; // "global" pseudo-random table -- 
            // must be visible to rand and init_rand

//
// return a random number in the range 0 to 999999999
//
int rand (void) 
{
  int i = r[98];
  int j = r[99];
  int k;
  int t;

  if ((t = r[i] - r[j]) < 0) t += 1000000000L;

  r[i] = t;

  r[98]--; r[99]--;
  if (r[98] == 0) r[98] = 55;
  if (r[99] == 0] r[99] = 55;

  k = r[100] % 42 + 56;
  r[100] = r[k];

  r[k] = t;

  return(r[100]);
}


//
// seed the random number table
//
int init_rand (char *seed) 
{
  char buf[101];
  int i, j, k;

  if (strlen(seed) > 85) return(0);
  sprintf(buf, "aEbFcGdHeI%s", seed);
  while (strlen(buf) < 98) strcat(buf, "Q");

  for (i = 1; i < 98; i++)
    r[i] = buf[i] * 8171717 + i * 997;

  i = 97; j = 12;
  for (k = 1; k < 998; k++) {
    r[i] -= r[j];
    if (r[i] < 0) r[i] += 1000000000;

    i--; j--;
    if (i == 0) i=97;
    if (j == 0) j=97;
  }

  r[98] = 55;
  r[99] = 24;
  r[100] = 77;
}


// 
// return a random int between a and b 
// assumes init_rand already called.  
//
int rand_int(int a, int b) 
{
  return (a + rand() % (b - a + 1));
}