78 lines
1.5 KiB
C++
78 lines
1.5 KiB
C++
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#pragma once
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// use tf::Latch
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#include <condition_variable>
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#include <limits>
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#include <mutex>
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namespace tf {
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class Latch {
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private:
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std::ptrdiff_t _counter;
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mutable std::condition_variable _cv;
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mutable std::mutex _mutex;
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public:
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static constexpr ptrdiff_t (max)() noexcept
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{
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return (std::numeric_limits<ptrdiff_t>::max)();
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}
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explicit Latch(std::ptrdiff_t expected)
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: _counter(expected)
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{
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assert(0 <= expected && expected < (max)());
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}
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~Latch() = default;
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Latch(const Latch&) = delete;
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Latch& operator=(const Latch&) = delete;
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void count_down(std::ptrdiff_t update = 1)
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{
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std::lock_guard<decltype(_mutex)> lk(_mutex);
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assert(0 <= update && update <= _counter);
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_counter -= update;
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if (_counter == 0) {
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_cv.notify_all();
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}
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}
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bool try_wait() const noexcept
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{
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std::lock_guard<decltype(_mutex)> lk(_mutex);
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// no spurious failure
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return (_counter == 0);
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}
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void wait() const
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{
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std::unique_lock<decltype(_mutex)> lk(_mutex);
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while (_counter != 0) {
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_cv.wait(lk);
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}
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}
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void arrive_and_wait(std::ptrdiff_t update = 1)
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{
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std::unique_lock<decltype(_mutex)> lk(_mutex);
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// equivalent to { count_down(update); wait(); }
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assert(0 <= update && update <= _counter);
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_counter -= update;
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if (_counter == 0) {
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_cv.notify_all();
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}
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while (_counter != 0) {
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_cv.wait(lk);
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}
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}
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};
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} // namespace tf -------------------------------------------------------------
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