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/*
* random.c
*
* Z-machine random number generator
*
*/
#include "frotz.h"
static long A = 1;
static interval = 0;
static counter = 0;
/*
* seed_random
*
* Set the seed value for the random number generator.
*
*/
void seed_random (int value)
{
if (value == 0) { /* ask interface for seed value */
A = os_random_seed ();
interval = 0;
} else if (value < 1000) { /* special seed value */
counter = 0;
interval = value;
} else { /* standard seed value */
A = value;
interval = 0;
}
}/* seed_random */
/*
* z_random, store a random number or set the random number seed.
*
* zargs[0] = range (positive) or seed value (negative)
*
*/
void z_random ()
{
if ((short) zargs[0] <= 0) { /* set random seed */
seed_random (- (short) zargs[0]);
store (0);
} else { /* generate random number */
zword result;
if (interval != 0) { /* ...in special mode */
result = counter++;
if (counter == interval) counter = 0;
} else { /* ...in standard mode */
A = 0x015a4e35L * A + 1;
result = (A >> 16) & 0x7fff;
}
store ((zword) (result % zargs[0] + 1));
}
}/* z_random */
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