Semaphore.hpp

#pragma once

#include <atomic>
#include <mutex>

namespace samchon
{
namespace library
{
    class Semaphore
    {
    private:
        size_t capacity_;

        /* ====================================================
            VARIABLES FOR LOCK
        ==================================================== */
        size_t acquired_;

        std::mutex count_mtx;

        std::mutex mtx;

    public:
        Semaphore(size_t capacity = 2)
        {
            this->acquired_ = 0;
            this->capacity_ = capacity;
        };

        void setCapacity(size_t val)
        {
            std::unique_lock<std::mutex> uk(count_mtx);

            this->capacity_ = val;
        };

        /* ====================================================
            GETTERS
        ==================================================== */
        auto capacity() const -> size_t
        {
            return capacity_;
        };

        auto acquired() const -> size_t
        {
            return acquired_;
        };

        /* ====================================================
            LOCKERS
        ==================================================== */
        void acquire()
        {
            std::unique_lock<std::mutex> uk(count_mtx);

            if (++acquired_ == capacity_)
            {
                uk.unlock();
                mtx.lock();
            }
        };

        auto tryAcquire() -> bool
        {
            std::unique_lock<std::mutex> uk(count_mtx);

            if (acquired_ == capacity_)
                return false;
            else
            {
                if (++acquired_ >= capacity_)
                    return mtx.try_lock();

                return true;
            }
        };

        void release()
        {
            std::unique_lock<std::mutex> uk(count_mtx);

            if (acquired_ != 0 && --acquired_ == capacity_ - 1)
                mtx.unlock();
        };
    };
};
};

#include <samchon/library/UniqueAcquire.hpp>
#include <samchon/library/SharedAcquire.hpp>