83 lines
2.0 KiB
C
83 lines
2.0 KiB
C
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/*
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* Random number generator is:
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*
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* Copyright 1988 by Rayan S. Zachariassen, all rights reserved.
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* This will be free software, but only when it is finished.
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*
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* Used in ntp by permission of the author. If copyright is
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* annoying to you, read no further. Instead, look up the reference,
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* write me an equivalent to this and send it back to me.
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*/
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/*
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* Random number generator; see Knuth Vol 2. 2nd ed. p.27 (section 3.2.2)
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*/
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#include "ntp_stdlib.h"
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extern time_t time P((time_t *loc));
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/*
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* 55 random numbers, not all even. Note we don't initialize ran_y
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* directly since I have had thoughts of putting this in an EPROM
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*/
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static time_t ran_y[55];
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static time_t init_ran_y[55] = {
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1860909544, 231033423, 437666411, 1349655137, 2014584962,
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504613712, 656256107, 1246027206, 573713775, 643466871,
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540235388, 1630565153, 443649364, 729302839, 1933991552,
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944681982, 949111118, 406212522, 1065063137, 1712954727,
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73280612, 787623973, 1874130997, 801658492, 73395958,
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739165367, 596047144, 490055249, 1131094323, 662727104,
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483614097, 844520219, 893760527, 921280508, 46691708,
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760861842, 1425894220, 702947816, 2006889048, 1999607995,
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1346414687, 399640789, 1482689501, 1790064052, 1128943628,
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1269197405, 587262386, 2078054746, 1675409928, 1652325524,
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1643525825, 1748690540, 292465849, 1370173174, 402865384
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};
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static int ran_j;
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static int ran_k;
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/*
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* ranp2 - return a random integer in the range 0 .. (1 << m) - 1
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*/
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u_long
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ranp2(
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int m
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)
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{
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time_t r;
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ran_y[ran_k] += ran_y[ran_j]; /* overflow does a mod */
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r = ran_y[ran_k];
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if (ran_k-- == 0)
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ran_k = 54;
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if (ran_j-- == 0)
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ran_j = 54;
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return (u_long)(r & ((1 << m ) - 1));
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}
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/*
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* init_random - do initialization of random number routine
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*/
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void
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init_random(void)
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{
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register int i;
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register time_t now;
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ran_j = 23;
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ran_k = 54;
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/*
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* Randomize the seed array some more. The time of day
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* should be initialized by now.
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*/
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now = time((time_t *)0) | 01;
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for (i = 0; i < 55; ++i)
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ran_y[i] = now * init_ran_y[i]; /* overflow does a mod */
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}
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