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f590145ed3
On POSIX systems, add also clock() to the seed + use as a source also /dev/random if available.
115 lines
3.2 KiB
C
115 lines
3.2 KiB
C
/**
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* @file utils/random.c
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* @author Martin Pulec <martin.pulec@cesnet.cz>
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*/
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/*
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* Copyright (c) 2023 CESNET, z. s. p. o.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, is permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of CESNET nor the names of its contributors may be
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* used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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* EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* @file
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* @note
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* Remarks (possible improvements):
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* - lbl_random reads from '/dev/urandom' instead if available (so Linux only)
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* and HAVE_DEV_URANDOM defined (which isn't)
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* - init_rng() in rtp.c used also hostname for seeding (but there may not be
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* reasonable value, eg. '::1' if no host given to rcvr)
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*/
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#ifndef _WIN32
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#include <stdio.h>
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#include <unistd.h>
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#endif
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#define _CRT_RAND_S // request rand_s (Win)
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#include <stdlib.h>
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#include "random.h"
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#include "tv.h"
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/**
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* @note
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* Windows rand_s() is not supposed to be seeded
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* @remark
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* thread-safe
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*/
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void
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ug_rand_init(void)
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{
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#ifndef _WIN32
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unsigned seed =
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(getpid() * 42) ^ (unsigned) get_time_in_ns() ^ (unsigned) clock();
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FILE *dev_r = fopen("/dev/random", "rb");
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if (dev_r != NULL) {
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unsigned seed_dev_r = 0;
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if (fread(&seed_dev_r, sizeof seed_dev_r, 1, dev_r) == 1) {
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seed ^= seed_dev_r;
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}
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fclose(dev_r);
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}
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srandom(seed);
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#endif
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}
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/**
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* @returns pseudorandom number in interval [0, 2^32-1]
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*
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* @remark
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* thread-safe
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*/
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uint32_t
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ug_rand(void)
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{
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#ifdef _WIN32
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uint32_t ret = 0;
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rand_s(&ret);
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#else
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uint32_t ret = (uint32_t) random() << 1;
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ret |= random() & 0x1;
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#endif
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return ret;
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}
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/**
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* Behaves similarly to drand48()
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*
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* uses only 2^32 values from the interval (drand48 may use 48 bits)
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*
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* @returns val in interval [0.0, 1.0)
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*
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* @remark
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* thread-safe
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*/
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double
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ug_drand()
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{
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return ug_rand() / (UINT32_MAX + 1.0);
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}
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