std::latch
From cppreference.com
C++
Concurrency support library
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
std::latch
| Member functions | ||||
| Constants | ||||
Defined in header <latch>
|
||
class latch; |
(since C++20) | |
The latch class is a downward counter of type
std::ptrdiff_t
Concurrent invocations of the member functions of std::latch, except for the destructor, do not introduce data races.
Data Members
| Name | Definition |
std::ptrdiff_t counter
|
the internal counter (exposition-only member object* |
Member functions
constructs a latch (public member function) |
|
destroys the latch (public member function) |
|
operator= [deleted] |
latch is not assignable (public member function) |
| decrements the counter in a non-blocking manner (public member function) |
|
| tests if the internal counter equals zero (public member function) |
|
| blocks until the counter reaches zero (public member function) |
|
| decrements the counter and blocks until it reaches zero (public member function) |
|
Constants | |
|
[static] |
the maximum value of counter supported by the implementation (public static member function) |
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_latch |
201907L |
(C++20) | std::latch
|
Example
Run this code
#include <functional> #include <iostream> #include <latch> #include <string> #include <thread> struct Job { const std::string name; std::string product{"not worked"}; std::thread action{}; }; int main() { Job jobs[]{{"Annika"}, {"Buru"}, {"Chuck"}}; std::latch work_done{std::size(jobs)}; std::latch start_clean_up{1}; auto work = [&](Job& my_job) { my_job.product = my_job.name + " worked"; work_done.count_down(); start_clean_up.wait(); my_job.product = my_job.name + " cleaned"; }; std::cout << "Work is starting... "; for (auto& job : jobs) job.action = std::thread{work, std::ref(job)}; work_done.wait(); std::cout << "done:\n"; for (auto const& job : jobs) std::cout << " " << job.product << '\n'; std::cout << "Workers are cleaning up... "; start_clean_up.count_down(); for (auto& job : jobs) job.action.join(); std::cout << "done:\n"; for (auto const& job : jobs) std::cout << " " << job.product << '\n'; }
Output:
Work is starting... done: Annika worked Buru worked Chuck worked Workers are cleaning up... done: Annika cleaned Buru cleaned Chuck cleaned
See also
|
(C++20)
|
reusable thread barrier (class template) |