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/*
* Copyright 2017 Timothy Arceri
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*/
#if defined(__linux__)
#include <sys/file.h>
#include <unistd.h>
#else
#include <time.h>
#endif
#include "rand_xor.h"
/* Super fast random number generator.
*
* This rand_xorshift128plus function by Sebastiano Vigna belongs
* to the public domain.
*/
uint64_t
rand_xorshift128plus(uint64_t *seed)
{
uint64_t *s = seed;
uint64_t s1 = s[0];
const uint64_t s0 = s[1];
s[0] = s0;
s1 ^= s1 << 23;
s[1] = s1 ^ s0 ^ (s1 >> 18) ^ (s0 >> 5);
return s[1] + s0;
}
void
s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed)
{
if (!randomised_seed)
goto fixed_seed;
#if defined(__linux__)
int fd = open("/dev/urandom", O_RDONLY);
if (fd < 0)
goto fixed_seed;
size_t seed_size = sizeof(uint64_t) * 2;
if (read(fd, seed, seed_size) != seed_size) {
close(fd);
goto fixed_seed;
}
close(fd);
return;
#else
seed[0] = 0x3bffb83978e24f88;
seed[1] = time(NULL);
return;
#endif
fixed_seed:
/* Fallback to a fixed seed */
seed[0] = 0x3bffb83978e24f88;
seed[1] = 0x9238d5d56c71cd35;
}
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