Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>

ulong
ntruerand(ulong n)
{
        ulong m, r;

        /*
         * set m to the one less than the maximum multiple of n <= 2^32,
         * so we want a random number <= m.
         */
        if(n > (1UL<<31))
                m = n-1;
        else
                /* 2^32 - 2^32%n - 1 = (2^32 - 1) - (2*(2^31%n))%n */
                m = 0xFFFFFFFFUL - (2*((1UL<<31)%n))%n;

        while((r = truerand()) > m)
                ;

        return r%n;
}