std::counting_semaphore, std::binary_semaphore
From cppreference.com
| Defined in header <semaphore>
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| template< std::ptrdiff_t LeastMaxValue = /* implementation-defined */ > class counting_semaphore; |
(1) | (since C++20) |
| using binary_semaphore = std::counting_semaphore<1>; |
(2) | (since C++20) |
1) A
counting_semaphore is a lightweight synchronization primitive that can control access to a shared resource. Unlike a std::mutex, a counting_semaphore allows more than one concurrent access to the same resource, for at least LeastMaxValue concurrent accessors. The program is ill-formed if LeastMaxValue is negative.2)
binary_semaphore is an alias for specialization of std::counting_semaphore with LeastMaxValue being 1. Implementations may implement binary_semaphore more efficiently than the default implementation of std::counting_semaphore.A counting_semaphore contains an internal counter initialized by the constructor. This counter is decremented by calls to acquire() and related methods, and is incremented by calls to release(). When the counter is zero, acquire() blocks until the counter is incremented, but try_acquire() does not block; try_acquire_for() and try_acquire_until() block until the counter is incremented or a timeout is reached.
Similar to std::condition_variable::wait(), counting_semaphore's try_acquire() can spuriously fail.
Specializations of std::counting_semaphore are not DefaultConstructible, CopyConstructible,