MPD  0.20.18
LazyRandomEngine.hxx
Go to the documentation of this file.
1 /*
2  * Copyright 2003-2017 The Music Player Daemon Project
3  * http://www.musicpd.org
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; either version 2 of the License, or
8  * (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License along
16  * with this program; if not, write to the Free Software Foundation, Inc.,
17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18  */
19 
20 #ifndef MPD_LAZY_RANDOM_ENGINE_HXX
21 #define MPD_LAZY_RANDOM_ENGINE_HXX
22 
23 #include "check.h"
24 
25 #include <random>
26 
27 #include <assert.h>
28 
33  std::mt19937 *engine;
34 
35 public:
36  typedef std::mt19937::result_type result_type;
37 
38  LazyRandomEngine():engine(nullptr) {}
40  delete engine;
41  }
42 
43  LazyRandomEngine(const LazyRandomEngine &other) = delete;
44  LazyRandomEngine &operator=(const LazyRandomEngine &other) = delete;
45 
50  void AutoCreate();
51 
52  static constexpr result_type min() {
53  return std::mt19937::min();
54  }
55 
56  static constexpr result_type max() {
57  return std::mt19937::max();
58  }
59 
61  assert(engine != nullptr);
62 
63  return engine->operator()();
64  }
65 };
66 
67 #endif
void AutoCreate()
Create and seed the real engine.
static constexpr result_type max()
result_type operator()()
LazyRandomEngine & operator=(const LazyRandomEngine &other)=delete
static constexpr result_type min()
std::mt19937::result_type result_type
A random engine that will be created and seeded on demand.