59 lines
1.6 KiB
C++
59 lines
1.6 KiB
C++
/*
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* Copyright 2003-2021 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef MPD_LAZY_RANDOM_ENGINE_HXX
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#define MPD_LAZY_RANDOM_ENGINE_HXX
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#include <cassert>
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#include <optional>
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#include <random>
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/**
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* A random engine that will be created and seeded on demand.
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*/
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class LazyRandomEngine {
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std::optional<std::mt19937> engine;
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public:
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typedef std::mt19937::result_type result_type;
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LazyRandomEngine() : engine(std::nullopt) {}
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LazyRandomEngine(const LazyRandomEngine &other) = delete;
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LazyRandomEngine &operator=(const LazyRandomEngine &other) = delete;
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/**
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* Create and seed the real engine. Call this before any
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* other method.
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*/
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void AutoCreate();
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static constexpr result_type min() { return std::mt19937::min(); }
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static constexpr result_type max() { return std::mt19937::max(); }
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result_type operator()() {
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assert(engine);
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return engine->operator()();
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}
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};
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#endif
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