1 /* Copyright (c) 2006-2023. 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>
11 namespace simgrid::s4u {
13 /** @brief A classical semaphore, but blocking in the simulation world
16 * It is strictly impossible to use a real semaphore, such as
17 * `sem_init <http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_init.html>`_,
18 * because it would block the whole simulation.
19 * Instead, you should use the present class, that offers a very similar interface.
21 * An example is available in Section :ref:`s4u_ex_IPC`.
23 * As for any S4U object, you can use the :ref:`RAII idiom <s4u_raii>` for memory management of semaphores.
24 * Use :cpp:func:`create() <simgrid::s4u::Mutex::create()>` to get a :cpp:type:`simgrid::s4u::SemaphorePtr` to a newly
25 * created semaphore, that will get automatically freed when the variable goes out of scope.
29 class XBT_PUBLIC Semaphore {
31 friend kernel::activity::SemaphoreImpl;
32 friend XBT_PUBLIC void kernel::activity::intrusive_ptr_release(kernel::activity::SemaphoreImpl* sem);
35 kernel::activity::SemaphoreImpl* const pimpl_;
37 friend XBT_PUBLIC void intrusive_ptr_add_ref(const Semaphore* sem);
38 friend XBT_PUBLIC void intrusive_ptr_release(const Semaphore* sem);
40 explicit Semaphore(kernel::activity::SemaphoreImpl* sem) : pimpl_(sem) {}
41 ~Semaphore() = default;
43 Semaphore(Semaphore const&) = delete; // No copy constructor. Use SemaphorePtr instead
44 Semaphore& operator=(Semaphore const&) = delete; // No direct assignment either. Use SemaphorePtr instead
48 /** \static Constructs a new semaphore */
49 static SemaphorePtr create(unsigned int initial_capacity);
52 /** Returns true if there was a timeout */
53 bool acquire_timeout(double timeout);
55 int get_capacity() const;
56 bool would_block() const;
59 } // namespace simgrid::s4u
61 #endif /* SIMGRID_S4U_SEMAPHORE_HPP */