24 lines
371 B
C
24 lines
371 B
C
#include <u.h>
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#include <libc.h>
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ulong
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ntruerand(ulong n)
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{
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ulong 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 = truerand()) > m)
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;
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return r%n;
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}
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