From:	"Damian Yerrick" <die DOT spammers AT pineight DOT 8m DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Saving random seed, and Allegro
Date:	Tue, 31 Aug 1999 23:58:31 -0500
Organization:	Rose-Hulman Institute of Technology
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Nate Eldredge <neldredge AT hmc DOT edu> wrote in message
news:37CC9150 DOT 2BFD0245 AT hmc DOT edu...
> Tom Morton wrote:
> >
> > Hello fellow human beings,
> >
> > I'm writing a game with allegro and djgpp and it requires a random
> > number generator that can have it's seed saved and changed. Until
> > now I have been using the rand() and srand() functions but I need
> > to be able to store the state of the random number generator.

Easy. Use this pseudorandom number function (adapted
from the ANSI standard for C rand() ) and two accessors:

/**** cut ****/

static int curSeed = 1;

/* MyRandom()
 * Returns a random number from 0 to 32,767.
 */
int MyRandom(void)
{
  curSeed = (curSeed * 1103515245) + 12345;
  return (curSeed & 0x7fff0000) >> 16;
}

/* SetSeed()
 * Replaces srand(). Sets the seed for MyRandom().
 */
void SetSeed(int seed)
{
  curSeed = seed;
}

/* GetSeed()
 * Returns the current seed for MyRandom() so it can be saved.
 */
int GetSeed(void)
{
  return curSeed;
}

/**** and paste ****/

If you are using Allegro's install_timer(), an initial seed can be obtained
by
    SetSeed(retrace_count);

Assuming you have a struct or class with a member
randSeed, and you have an instance thereof called myState:
To save the seed,
    myState.randSeed = GetSeed();
To restore the seed,
    SetSeed(myState.randSeed);

> Nate Eldredge
> neldredge AT hmc DOT edu

Damian Yerrick
http://come.to/yerrick

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