shithub: drawterm

ref: a85fefcc920f837ce3a8e0010cfd09cf0b3523ce
dir: /libsec/nfastrand.c/

View raw version 
#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;
}