diff options
Diffstat (limited to 'usr/src/boot/libsa/random.c')
| -rw-r--r-- | usr/src/boot/libsa/random.c | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/usr/src/boot/libsa/random.c b/usr/src/boot/libsa/random.c new file mode 100644 index 0000000000..1547078b42 --- /dev/null +++ b/usr/src/boot/libsa/random.c @@ -0,0 +1,68 @@ +/* + * 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. 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 <sys/cdefs.h> + +#include <sys/types.h> + +static ulong_t randseed = 1; + +void +srandom(ulong_t seed) +{ + randseed = seed; +} + +/* + * 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]. + */ +ulong_t +random(void) +{ + 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); +} |