semaphore.hpp

#ifndef SEMAPHORE_DEF
#define SEMAPHORE_DEF
 
#include <mutex>
#include <condition_variable>
 
class semaphore {
private:
    std::mutex mutex_;
    std::condition_variable condition_;
    unsigned long count_ = 0; // Initialized as locked.
 
public:
    void notify() {
        std::lock_guard<decltype(mutex_)> lock(mutex_);
        ++count_;
        condition_.notify_one();
    }
 
    void wait() {
        std::unique_lock<decltype(mutex_)> lock(mutex_);
        while (!count_) { // Handle spurious wake-ups.
            condition_.wait(lock);
        }
        --count_;
    }
 
    bool try_wait() {
        std::lock_guard<decltype(mutex_)> lock(mutex_);
        if (count_) {
            --count_;
            return true;
        }
        return false;
    }
};
 
#endif