ref: 53fa826a8a695bcfade5c47f636f719c71e96b98
dir: /sys/src/libc/port/ntruerand.c/
#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; }