149 lines
4.9 KiB
C++
149 lines
4.9 KiB
C++
////////////////////////////////////////////////////////////
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//
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// SFML - Simple and Fast Multimedia Library
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// Copyright (C) 2007-2017 Laurent Gomila (laurent@sfml-dev.org)
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//
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// This software is provided 'as-is', without any express or implied warranty.
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// In no event will the authors be held liable for any damages arising from the use of this software.
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//
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// Permission is granted to anyone to use this software for any purpose,
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// including commercial applications, and to alter it and redistribute it freely,
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// subject to the following restrictions:
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//
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// 1. The origin of this software must not be misrepresented;
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// you must not claim that you wrote the original software.
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// If you use this software in a product, an acknowledgment
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// in the product documentation would be appreciated but is not required.
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//
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// 2. Altered source versions must be plainly marked as such,
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// and must not be misrepresented as being the original software.
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//
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// 3. This notice may not be removed or altered from any source distribution.
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//
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////////////////////////////////////////////////////////////
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#ifndef SFML_MUTEX_HPP
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#define SFML_MUTEX_HPP
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////////////////////////////////////////////////////////////
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// Headers
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////////////////////////////////////////////////////////////
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#include <SFML/System/Export.hpp>
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#include <SFML/System/NonCopyable.hpp>
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namespace sf
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{
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namespace priv
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{
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class MutexImpl;
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}
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////////////////////////////////////////////////////////////
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/// \brief Blocks concurrent access to shared resources
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/// from multiple threads
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///
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////////////////////////////////////////////////////////////
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class SFML_SYSTEM_API Mutex : NonCopyable
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{
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public:
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////////////////////////////////////////////////////////////
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/// \brief Default constructor
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///
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////////////////////////////////////////////////////////////
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Mutex();
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////////////////////////////////////////////////////////////
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/// \brief Destructor
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///
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////////////////////////////////////////////////////////////
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~Mutex();
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////////////////////////////////////////////////////////////
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/// \brief Lock the mutex
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///
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/// If the mutex is already locked in another thread,
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/// this call will block the execution until the mutex
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/// is released.
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///
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/// \see unlock
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///
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////////////////////////////////////////////////////////////
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void lock();
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////////////////////////////////////////////////////////////
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/// \brief Unlock the mutex
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///
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/// \see lock
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///
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////////////////////////////////////////////////////////////
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void unlock();
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private:
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////////////////////////////////////////////////////////////
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// Member data
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////////////////////////////////////////////////////////////
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priv::MutexImpl* m_mutexImpl; ///< OS-specific implementation
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};
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} // namespace sf
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#endif // SFML_MUTEX_HPP
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////////////////////////////////////////////////////////////
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/// \class sf::Mutex
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/// \ingroup system
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///
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/// Mutex stands for "MUTual EXclusion". A mutex is a
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/// synchronization object, used when multiple threads are involved.
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///
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/// When you want to protect a part of the code from being accessed
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/// simultaneously by multiple threads, you typically use a
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/// mutex. When a thread is locked by a mutex, any other thread
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/// trying to lock it will be blocked until the mutex is released
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/// by the thread that locked it. This way, you can allow only
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/// one thread at a time to access a critical region of your code.
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///
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/// Usage example:
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/// \code
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/// Database database; // this is a critical resource that needs some protection
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/// sf::Mutex mutex;
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///
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/// void thread1()
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/// {
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/// mutex.lock(); // this call will block the thread if the mutex is already locked by thread2
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/// database.write(...);
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/// mutex.unlock(); // if thread2 was waiting, it will now be unblocked
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/// }
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///
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/// void thread2()
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/// {
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/// mutex.lock(); // this call will block the thread if the mutex is already locked by thread1
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/// database.write(...);
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/// mutex.unlock(); // if thread1 was waiting, it will now be unblocked
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/// }
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/// \endcode
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///
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/// Be very careful with mutexes. A bad usage can lead to bad problems,
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/// like deadlocks (two threads are waiting for each other and the
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/// application is globally stuck).
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///
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/// To make the usage of mutexes more robust, particularly in
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/// environments where exceptions can be thrown, you should
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/// use the helper class sf::Lock to lock/unlock mutexes.
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///
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/// SFML mutexes are recursive, which means that you can lock
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/// a mutex multiple times in the same thread without creating
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/// a deadlock. In this case, the first call to lock() behaves
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/// as usual, and the following ones have no effect.
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/// However, you must call unlock() exactly as many times as you
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/// called lock(). If you don't, the mutex won't be released.
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///
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/// \see sf::Lock
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///
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////////////////////////////////////////////////////////////
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