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