From 293cb0eab638c682e951e68c404dc214772539c2 Mon Sep 17 00:00:00 2001 From: AptRock327 Date: Tue, 7 May 2024 21:46:45 +0200 Subject: libc: stdlib: POSIX-compliant randomness This commit implements two functions: rand(), and srand() which together allow for the generation of pseudorandom numbers. Signed-off-by: AptRock327 Signed-off-by: Ian Moffett --- lib/libc/src/stdlib/rand.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 lib/libc/src/stdlib/rand.c (limited to 'lib/libc/src') diff --git a/lib/libc/src/stdlib/rand.c b/lib/libc/src/stdlib/rand.c new file mode 100644 index 0000000..8a0899f --- /dev/null +++ b/lib/libc/src/stdlib/rand.c @@ -0,0 +1,63 @@ +/* + * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team. + * 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 Hyra 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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. + */ + +#include + +/* linear feedback shift register - static global variable */ +static unsigned int lfsr = 0; + +/* + * Sets the global LFSR to a provided seed + * + * @seed: Seed that will be used for random number generation + */ +void +srand(unsigned int seed) +{ + lfsr = seed; +} + +/* + * Generates a random number between 0 and RAND_MAX + * + * Returns random number (unsigned int) between 0 and RAND_MAX + */ +unsigned int +rand(void) +{ + unsigned int intResult = 0; + unsigned int bitResult; + for(int i = 0; i < 32; i++) { + bitResult = lfsr % 2; + intResult |= (bitResult << i); + lfsr >>= 1; + lfsr |= ((bitResult ^ (lfsr % 2)) << 31); + } + return intResult; +} -- cgit v1.2.3