BSD 4.4 Lite Kernel Sources

1 files changed, 63 insertions, 0 deletions

diff --git a/sys/libkern/random.c b/sys/libkern/random.c
new file mode 100644
index 0000000..5153124
--- /dev/null
+++ b/sys/libkern/random.c
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+/*-
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)random.c	8.1 (Berkeley) 6/10/93
+ */
+
+#include <libkern/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);
+}