diff options
Diffstat (limited to 'src/util')
-rw-r--r-- | src/util/LazyRandomEngine.cxx | 31 | ||||
-rw-r--r-- | src/util/LazyRandomEngine.hxx | 67 |
2 files changed, 98 insertions, 0 deletions
diff --git a/src/util/LazyRandomEngine.cxx b/src/util/LazyRandomEngine.cxx new file mode 100644 index 000000000..0f90ebb2e --- /dev/null +++ b/src/util/LazyRandomEngine.cxx @@ -0,0 +1,31 @@ +/* + * Copyright (C) 2003-2013 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. + */ + +#include "config.h" +#include "LazyRandomEngine.hxx" + +void +LazyRandomEngine::AutoCreate() +{ + if (engine != nullptr) + return; + + std::random_device rd; + engine = new std::mt19937(rd()); +} diff --git a/src/util/LazyRandomEngine.hxx b/src/util/LazyRandomEngine.hxx new file mode 100644 index 000000000..8afe1d1c0 --- /dev/null +++ b/src/util/LazyRandomEngine.hxx @@ -0,0 +1,67 @@ +/* + * Copyright (C) 2003-2013 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(); + + result_type min() const { + return engine->min(); + } + + result_type max() const { + return engine->max(); + } + + result_type operator()() { + assert(engine != nullptr); + + return engine->operator()(); + } +}; + +#endif |