date and time created 88/07/22 16:08:01 by bostic

[unix-history] / usr / src / games / rogue / random.c

#ifndef lint
static char sccsid[] = "@(#)random.c    5.1 (Berkeley) %G%";
#endif /* not lint */

static long rntb[32] = {
                3, 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342, 
       0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb, 0x7449e56b,
       0xbeb1dbb0, 0xab5c5918, 0x946554fd, 0x8c2e680f, 0xeb3d799f,
       0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88, 0xe369735d,
       0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc, 
       0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e,
       0x8999220b, 0x27fb47b9
};

static long *fptr = &rntb[4];
static long *rptr = &rntb[1];
static long *state = &rntb[1];
static int rand_type = 3;
static int rand_deg = 31;
static int rand_sep = 3;
static long *end_ptr = &rntb[32];

srrandom(x)
int x;
{
       register int i;
       long rrandom();

       state[0] = (long) x;
       if (rand_type != 0) {
               for (i = 1; i < rand_deg; i++) {
                       state[i] = 1103515245 * state[i - 1] + 12345;
               }
               fptr = &state[rand_sep];
               rptr = &state[0];
               for (i = 0; i < 10 * rand_deg; i++) {
                       (void) rrandom();
               }
       }
}

long
rrandom()
{
       long i;
       
       if (rand_type == 0) {
               i = state[0] = (state[0]*1103515245 + 12345) & 0x7fffffff;
       } else {
               *fptr += *rptr;
               i = (*fptr >> 1) & 0x7fffffff;
               if (++fptr >= end_ptr) {
                       fptr = state;
                       ++rptr;
               } else {
                       if (++rptr >= end_ptr) {
                               rptr = state;
                       }
               }
       }
       return(i);
}

get_rand(x, y)
register int x, y;
{
       register int r, t;
       long lr;

       if (x > y) {
               t = y;
               y = x;
               x = t;
       }
       lr = rrandom();
       lr &= (long) 0x00003fff;
       r = (int) lr;
       r = (r % ((y - x) + 1)) + x;
       return(r);
}

rand_percent(percentage)
register int percentage;
{
       return(get_rand(1, 100) <= percentage);
}

coin_toss()
{

       return(((rrandom() & 01) ? 1 : 0));
}