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