aboutsummaryrefslogtreecommitdiffstats
path: root/src/util/LazyRandomEngine.hxx
blob: 4156b3bb1e3993b46d43d5a497e5270a8f41e4b9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
/*
 * Copyright (C) 2003-2014 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 "check.h"

#include <random>

#include <assert.h>

/**
 * 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