xnu-2050.9.2.tar.gz

[apple/xnu.git] / bsd / libkern / random.c

diff --git a/bsd/libkern/random.c b/bsd/libkern/random.c
index aed1b355b176c9f942f863cb128ec3677a5983ef..070080f90afe102c541498ef29634f06297703d6 100644 (file)
--- a/bsd/libkern/random.c
+++ b/bsd/libkern/random.c
@@ -1,23 +1,29 @@
 /*
  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
- * The contents of this file constitute Original Code as defined in and
- * are subject to the Apple Public Source License Version 1.1 (the
- * "License").  You may not use this file except in compliance with the
- * License.  Please obtain a copy of the License at
- * http://www.apple.com/publicsource and read it before using this file.
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
  * 
- * This Original Code and all software distributed under the License are
- * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
- * License for the specific language governing rights and limitations
- * under the License.
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
  * 
- * @APPLE_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 /*-
  * Copyright (c) 1992, 1993
@@ -54,50 +60,21 @@
  *     @(#)random.c    8.1 (Berkeley) 6/10/93
  */
 
-/*
- * Modification History
- *
- * Feb 22, 1999        Dieter Siegmund (dieter@apple.com)
- * - the first time, set the random seed to the microsecond time value
- *   to make the random numbers less predictable
- */
+#include <sys/types.h>
+#include <sys/random.h>
 #include <libkern/libkern.h>
-#include <sys/time.h>
+#include <dev/random/randomdev.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()
+u_int32_t
+random(void)
 {
-       static int first = 1;
-       static u_long randseed = 1;
-
-       register long x, hi, lo, t;
-
-       if (first) {
-           struct timeval tv;
-           microtime(&tv);
-           randseed = tv.tv_usec;
-           if(!randseed)
-               randseed=1;
-           first = 0;
-       }
-
-       /*
-        * 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);
+       /* Zero all but bottom 31 bits, also works for 64-bit longs */
+       u_int32_t mask = (u_int32_t)-1 >> ((sizeof(u_int32_t) * 8) - 31);
+       return (mask & RandomULong());
 }
+