1 /* Copyright (c) 2006-2020. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #ifndef SIMGRID_S4U_SEMAPHORE_HPP
7 #define SIMGRID_S4U_SEMAPHORE_HPP
9 #include <simgrid/forward.h>
10 #include <simgrid/simix.h>
15 /** @brief A classical semaphore, but blocking in the simulation world
18 * It is strictly impossible to use a real semaphore, such as
19 * `sem_init <http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_init.html>`_,
20 * because it would block the whole simulation.
21 * Instead, you should use the present class, that offers a very similar interface.
23 * An example is available in Section :ref:`s4u_ex_IPC`.
25 * As for any S4U object, you can use the :ref:`RAII idiom <s4u_raii>` for memory management of semaphores.
26 * Use :cpp:func:`create() <simgrid::s4u::Mutex::create()>` to get a :cpp:type:`simgrid::s4u::SemaphorePtr` to a newly
27 * created semaphore, that will get automatically freed when the variable goes out of scope.
31 class XBT_PUBLIC Semaphore {
33 std::atomic_int_fast32_t refcount_{0};
35 friend void intrusive_ptr_add_ref(Semaphore* sem);
36 friend void intrusive_ptr_release(Semaphore* sem);
39 explicit Semaphore(unsigned int initial_capacity);
43 Semaphore(Semaphore const&) = delete; // No copy constructor. Use SemaphorePtr instead
44 Semaphore& operator=(Semaphore const&) = delete; // No direct assignment either. Use SemaphorePtr instead
47 /** Constructs a new semaphore */
48 static SemaphorePtr create(unsigned int initial_capacity);
51 int acquire_timeout(double timeout);
58 } // namespace simgrid
60 #endif /* SIMGRID_S4U_SEMAPHORE_HPP */