conterm/libsec/nfastrand.c
Russ Cox 934846f35c a
2005-08-08 12:50:13 +00:00

24 lines
327 B
C

#include <u.h>
#include <libc.h>
#include <libsec.h>
#define Maxrand ((1UL<<31)-1)
ulong
nfastrand(ulong n)
{
ulong m, r;
/*
* set m to the maximum multiple of n <= 2^31-1
* so we want a random number < m.
*/
if(n > Maxrand)
abort();
m = Maxrand - Maxrand % n;
while((r = fastrand()) >= m)
;
return r%n;
}