/******************************  pmrandom.h  ***************************

  Purpose:	Implement a random-number generator package for this program.

  Provenance:	Written and tested by Q. Chen and E. Fox, March 1991.
  		Edited by S. Wartik, April 1991.

  Notes:	It is assumed that the C data type "int" can store
  		32-bit quantities.
**/

#include "pmrandom.h"

static int seed = DEFAULT_SEED;     /* The seed of the random number generator.	*/

/*************************************************************************

	setseed(int)

   Returns:	int

   Purpose:	Set the seed for the random number generator.

   Plan:	Uses a formula suggested by Park and Miller.  See above.

   Notes:	None.
**/

void setseed( new_seed )
    int	new_seed;
{
	int	low, high, test;

    if ( (new_seed < 1) || (new_seed > 2147483646) )
	new_seed = DEFAULT_SEED;
    high = new_seed / 127773;		/* 127773 = 2147483647 div 16807 */
    low  = new_seed % 127773;
    test = 16807 * low - 2836 * high;	/* 2836 = 2147483647 mod 16807   */
    seed = ( test > 0 ) ? test : test + 2147483647;
}


/*************************************************************************

	   pmrandom()

   Returns:	void

   Purpose:	Return the next random number in the sequence.

   Plan:	Uses the formula:

		    f() = ( 16807 * seed ) mod 2147483647.

		The value of "seed" must be within [1, ..., 2147483646].

   Notes:	None.
**/

int pmrandom()
{
    int	tmp = seed;

    setseed(seed);
    return(tmp);
}

/***********************************************************************

  	getseed()

  Returns:	int

  Purpose:	Get the current value of the seed.

  Notes:	None.
**/

int getseed()
{
    return (seed);
}