semaphore.h

 
#pragma once
 
#include <condition_variable>
#include <mutex>
 
namespace xrpl {
 
template <class Mutex, class CondVar>
class basic_semaphore
{
private:
    Mutex m_mutex;
    CondVar m_cond;
    std::size_t m_count;
 
public:
    using size_type = std::size_t;
 
    explicit basic_semaphore(size_type count = 0) : m_count(count)
    {
    }
 
    void
    notify()
    {
        std::lock_guard lock{m_mutex};
        ++m_count;
        m_cond.notify_one();
    }
 
    void
    wait()
    {
        std::unique_lock lock{m_mutex};
        while (m_count == 0)
            m_cond.wait(lock);
        --m_count;
    }
 
    bool
    try_wait()
    {
        std::lock_guard lock{m_mutex};
        if (m_count == 0)
            return false;
        --m_count;
        return true;
    }
};
 
using semaphore = basic_semaphore<std::mutex, std::condition_variable>;
 
}  // namespace xrpl