1 0fc65b37 2004-03-21 devnull #include <u.h>
 2 0fc65b37 2004-03-21 devnull #include <libc.h>
 3 0fc65b37 2004-03-21 devnull #include <libsec.h>
 4 0fc65b37 2004-03-21 devnull 
 5 0fc65b37 2004-03-21 devnull #define Maxrand	((1UL<<31)-1)
 6 0fc65b37 2004-03-21 devnull 
 7 0fc65b37 2004-03-21 devnull ulong
 8 0fc65b37 2004-03-21 devnull nfastrand(ulong n)
 9 0fc65b37 2004-03-21 devnull {
10 0fc65b37 2004-03-21 devnull 	ulong m, r;
11 fa325e9b 2020-01-10 cross 
12 0fc65b37 2004-03-21 devnull 	/*
13 0fc65b37 2004-03-21 devnull 	 * set m to the maximum multiple of n <= 2^31-1
14 0fc65b37 2004-03-21 devnull 	 * so we want a random number < m.
15 0fc65b37 2004-03-21 devnull 	 */
16 0fc65b37 2004-03-21 devnull 	if(n > Maxrand)
17 0fc65b37 2004-03-21 devnull 		sysfatal("nfastrand: n too large");
18 0fc65b37 2004-03-21 devnull 
19 0fc65b37 2004-03-21 devnull 	m = Maxrand - Maxrand % n;
20 0fc65b37 2004-03-21 devnull 	while((r = fastrand()) >= m)
21 0fc65b37 2004-03-21 devnull 		;
22 0fc65b37 2004-03-21 devnull 	return r%n;
23 0fc65b37 2004-03-21 devnull }