From: Chris Torek <torek@ucbvax.Berkeley.EDU>
Date: Wed, 24 Jun 1992 16:08:54 +0000 (-0800)
Subject: date and time created 92/06/24 01:08:54 by torek
X-Git-Tag: BSD-4_4-Snapshot-Development~6477
X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/commitdiff_plain/a4681977c1301612ed75f7f63095e8431bfbf5b7

date and time created 92/06/24 01:08:54 by torek

SCCS-vsn: sys/libkern/random.c 7.1
---

diff --git a/usr/src/sys/libkern/random.c b/usr/src/sys/libkern/random.c
new file mode 100644
index 0000000000..6c25d70ff6
--- /dev/null
+++ b/usr/src/sys/libkern/random.c
@@ -0,0 +1,37 @@
+/*-
+ * Copyright (c) 1992 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * %sccs.include.redist.c%
+ *
+ *	@(#)random.c	7.1 (Berkeley) %G%
+ */
+
+#include "libkern.h"
+
+/*
+ * Pseudo-random number generator for randomizing the profiling clock,
+ * and whatever else we might use it for.  The result is uniform on
+ * [0, 2^31 - 1].
+ */
+u_long
+random()
+{
+	static u_long randseed = 1;
+	register long x, hi, lo, t;
+
+	/*
+	 * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
+	 * From "Random number generators: good ones are hard to find",
+	 * Park and Miller, Communications of the ACM, vol. 31, no. 10,
+	 * October 1988, p. 1195.
+	 */
+	x = randseed;
+	hi = x / 127773;
+	lo = x % 127773;
+	t = 16807 * lo - 2836 * hi;
+	if (t <= 0)
+		t += 0x7fffffff;
+	randseed = t;
+	return (t);
+}