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