a

libsec/nfastrand.c

@@ -0,0 +1,23 @@
+#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;
+}