123 lines
3.7 KiB
C++
123 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Contributor(s):
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* Copyright (C) 2012 Tino Kluge <tino.kluge@hrz.tu-chemnitz.de>
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*/
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#include <comphelper/random.hxx>
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#include <sal/log.hxx>
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#include <assert.h>
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#include <time.h>
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#include <mutex>
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#include <random>
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#include <rtl/random.h>
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#include <stdexcept>
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#if defined HAVE_VALGRIND_HEADERS
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#include <valgrind/memcheck.h>
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#endif
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// this is nothing but a simple wrapper around
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// the std::random generators
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namespace comphelper::rng
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{
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// underlying random number generator
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// std::mt19937 implements the Mersenne twister algorithm which
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// is fast and has good statistical properties, it produces integers
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// in the range of [0, 2^32-1] internally
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// memory requirement: 625*sizeof(uint32_t)
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// http://en.wikipedia.org/wiki/Mersenne_twister
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#define STD_RNG_ALGO std::mt19937
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namespace
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{
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struct RandomNumberGenerator
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{
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std::mutex mutex;
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STD_RNG_ALGO global_rng;
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RandomNumberGenerator() { reseed(); }
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void reseed()
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{
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// make RR easier to use, breaks easily without the RNG being repeatable
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bool bRepeatable = (getenv("SAL_RAND_REPEATABLE") != nullptr) || (getenv("RR") != nullptr);
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// valgrind on some platforms (e.g.Ubuntu16.04) does not support the new Intel RDRAND instructions,
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// which leads to "Illegal Opcode" errors, so just turn off randomness.
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#if defined HAVE_VALGRIND_HEADERS
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if (RUNNING_ON_VALGRIND)
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bRepeatable = true;
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#endif
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if (bRepeatable)
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{
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global_rng.seed(42);
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return;
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}
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size_t seed = 0;
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if (rtl_random_getBytes(nullptr, &seed, sizeof(seed)) != rtl_Random_E_None)
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seed = 0;
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// initialises the state of the global random number generator
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// should only be called once.
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// (note, a few std::variate_generator<> (like normal) have their
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// own state which would need a reset as well to guarantee identical
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// sequence of numbers, e.g. via myrand.distribution().reset())
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global_rng.seed(seed ^ time(nullptr));
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}
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};
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RandomNumberGenerator& GetTheRandomNumberGenerator()
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{
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static RandomNumberGenerator RANDOM;
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return RANDOM;
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}
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}
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void reseed() { GetTheRandomNumberGenerator().reseed(); }
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// uniform ints [a,b] distribution
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int uniform_int_distribution(int a, int b)
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{
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std::uniform_int_distribution<int> dist(a, b);
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auto& gen = GetTheRandomNumberGenerator();
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std::scoped_lock<std::mutex> g(gen.mutex);
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return dist(gen.global_rng);
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}
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// uniform ints [a,b] distribution
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unsigned int uniform_uint_distribution(unsigned int a, unsigned int b)
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{
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std::uniform_int_distribution<unsigned int> dist(a, b);
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auto& gen = GetTheRandomNumberGenerator();
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std::scoped_lock<std::mutex> g(gen.mutex);
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return dist(gen.global_rng);
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}
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// uniform size_t [a,b] distribution
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size_t uniform_size_distribution(size_t a, size_t b)
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{
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std::uniform_int_distribution<size_t> dist(a, b);
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auto& gen = GetTheRandomNumberGenerator();
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std::scoped_lock<std::mutex> g(gen.mutex);
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return dist(gen.global_rng);
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}
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// uniform size_t [a,b) distribution
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double uniform_real_distribution(double a, double b)
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{
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assert(a < b);
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std::uniform_real_distribution<double> dist(a, b);
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auto& gen = GetTheRandomNumberGenerator();
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std::scoped_lock<std::mutex> g(gen.mutex);
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return dist(gen.global_rng);
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}
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} // namespace
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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