1 #include <u.h> 2 #include <libc.h> 3 4 ulong ntruerand(ulong n)5ntruerand(ulong n) 6 { 7 ulong m, r; 8 9 /* 10 * set m to the one less than the maximum multiple of n <= 2^32, 11 * so we want a random number <= m. 12 */ 13 if(n > (1UL<<31)) 14 m = n-1; 15 else 16 /* 2^32 - 2^32%n - 1 = (2^32 - 1) - (2*(2^31%n))%n */ 17 m = 0xFFFFFFFFUL - (2*((1UL<<31)%n))%n; 18 19 while((r = truerand()) > m) 20 ; 21 22 return r%n; 23 } 24