/*
* random:
*
* If we are using the trivial TYPE_0 R.N.G., just do the old linear
* congruential bit. Otherwise, we do our fancy trinomial stuff, which is
* the same in all the other cases due to all the global variables that have
* been set up. The basic operation is to add the number at the rear pointer
* into the one at the front pointer. Then both pointers are advanced to
* the next location cyclically in the table. The value returned is the sum
* generated, reduced to 31 bits by throwing away the "least random" low bit.
*
* Note: the code takes advantage of the fact that both the front and
* rear pointers can't wrap on the same call by not testing the rear
* pointer if the front one has wrapped.
*
* Returns a 31-bit random number.
*/
long
random(void)
{
uint32_t i;
uint32_t *f, *r;
if (rand_type == TYPE_0) {
i = state[0];
state[0] = i = good_rand(i);
} else {
/*
* Use local variables rather than static variables for speed.
*/
f = fptr; r = rptr;
*f += *r;
i = *f >> 1; /* chucking least random bit */
if (++f >= end_ptr) {
f = state;
++r;
}
else if (++r >= end_ptr) {
r = state;
}
fptr = f; rptr = r;
}
return ((long)i);
}
void
VRND_SeedTestable(unsigned int x)
{
int i, lim;
state[0] = (uint32_t)x;
for (i = 1; i < rand_deg; i++)
state[i] = good_rand(state[i - 1]);
fptr = &state[rand_sep];
rptr = &state[0];
lim = 10 * rand_deg;
for (i = 0; i < lim; i++)
(void)VRND_RandomTestable();
}
/*
* srandom:
*
* Initialize the random number generator based on the given seed. If the
* type is the trivial no-state-information type, just remember the seed.
* Otherwise, initializes state[] based on the given "seed" via a linear
* congruential generator. Then, the pointers are set to known locations
* that are exactly rand_sep places apart. Lastly, it cycles the state
* information a given number of times to get rid of any initial dependencies
* introduced by the L.C.R.N.G. Note that the initialization of randtbl[]
* for default usage relies on values produced by this routine.
*/
void
srandom(unsigned int x)
{
int i, lim;
state[0] = (uint32_t)x;
if (rand_type == TYPE_0)
lim = NSHUFF;
else {
for (i = 1; i < rand_deg; i++)
state[i] = good_rand(state[i - 1]);
fptr = &state[rand_sep];
rptr = &state[0];
lim = 10 * rand_deg;
}
for (i = 0; i < lim; i++)
(void)random();
}
