33 lines
808 B
C
33 lines
808 B
C
/*
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* This file is part of the UCB release of Plan 9. It is subject to the license
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* terms in the LICENSE file found in the top-level directory of this
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* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
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* part of the UCB release of Plan 9, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms contained
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* in the LICENSE file.
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*/
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#include <u.h>
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#include <libc.h>
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uint32_t
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jehanne_ntruerand(uint32_t n)
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{
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uint32_t m, r;
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/*
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* set m to the one less than the maximum multiple of n <= 2^32,
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* so we want a random number <= m.
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*/
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if(n > (1UL<<31))
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m = n-1;
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else
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/* 2^32 - 2^32%n - 1 = (2^32 - 1) - (2*(2^31%n))%n */
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m = 0xFFFFFFFFUL - (2*((1UL<<31)%n))%n;
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while((r = jehanne_truerand()) > m)
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;
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return r%n;
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}
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