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Diffstat (limited to 'lib/stdlib/rand.c')
-rw-r--r-- | lib/stdlib/rand.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/lib/stdlib/rand.c b/lib/stdlib/rand.c new file mode 100644 index 000000000..59cb79631 --- /dev/null +++ b/lib/stdlib/rand.c @@ -0,0 +1,65 @@ +/*- + * Portions Copyright (c) 2010, Intel Corporation. All rights reserved.<BR> + * Copyright (c) 1990, 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. + * 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. + * + */ +//__FBSDID("$FreeBSD: src/lib/libc/stdlib/rand.c,v 1.17.2.1.2.1 2009/10/25 01:10:29 kensmith Exp $"); +#include <stdlib.h> + +static unsigned int next = 1; + +/** Compute a pseudo-random number. + * + * Compute x = (7^5 * x) mod (2^31 - 1) + * without overflowing 31 bits: + * (2^31 - 1) = 127773 * (7^5) + 2836 + * 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. +**/ +int +rand() +{ + int hi, lo, x; + + /* Can't be initialized with 0, so use another value. */ + if (next == 0) + next = 123459876; + hi = next / 127773; + lo = next % 127773; + x = 16807 * lo - 2836 * hi; + if (x < 0) + x += 0x7fffffff; + return ((next = x) % ((unsigned int)RAND_MAX + 1)); +} + +void +srand(unsigned int seed) +{ + next = (unsigned int)seed; +} |