VulcanoLE/headers/VUtils/Storage/SafeQueue.h

#pragma once

#include <utility>
#include <atomic>
#include <queue>
#include <condition_variable>
#include <optional>
#include <cassert>
namespace VUtils {
    template<typename T>
    struct SafeQueue {
        explicit SafeQueue(size_t maxSize = -1UL) : m_maxSize(maxSize), m_end(false) {};

        void push(const T &t);

        void push(T &&t);

        void close();

        void clear();

        std::optional<T> pop();

        std::optional<T> waitAndPop();

        bool isClosed();

        int size();

    private:
        std::queue<T> m_que;
        std::mutex m_mtx;
        std::condition_variable m_cvEmpty, m_cvFull;
        const size_t m_maxSize;
        std::atomic<bool> m_end;
    };

    template<typename T>
    void SafeQueue<T>::push(const T &t) {
        std::unique_lock<std::mutex> lck(m_mtx);
        while (m_que.size() == m_maxSize && !m_end) {
            // we dont wait! we return false because queue is full...
            m_cvFull.wait(lck);
        }
        assert(!m_end);
        m_que.push(std::move(t));
        m_cvEmpty.notify_one();
    }

    template<typename T>
    void SafeQueue<T>::push(T &&t) {
        std::unique_lock<std::mutex> lck(m_mtx);
        while (m_que.size() == m_maxSize && !m_end)
            m_cvFull.wait(lck);
        assert(!m_end);
        m_que.push(std::move(t));
        m_cvEmpty.notify_one();
    }

    template<typename T>
    void SafeQueue<T>::close() {
        m_end = true;
        std::lock_guard<std::mutex> lck(m_mtx);
        m_cvEmpty.notify_all();
        m_cvFull.notify_all();
    }

    template<typename T>
    std::optional<T> SafeQueue<T>::pop() {
        std::unique_lock<std::mutex> lck(m_mtx);
        if (m_que.empty() || m_end) return {};
        T t = std::move(m_que.front());
        m_que.pop();
        m_cvFull.notify_one();
        return t;
    }

    template<typename T>
    std::optional<T> SafeQueue<T>::waitAndPop() {
        std::unique_lock<std::mutex> lck(m_mtx);
        while (m_que.empty() && !m_end)
            m_cvEmpty.wait(lck);
        if (m_que.empty() || m_end) return {};
        T t = std::move(m_que.front());
        m_que.pop();
        m_cvFull.notify_one();
        return t;
    }

    template<typename T>
    void SafeQueue<T>::clear() {
        std::unique_lock<std::mutex> lck(m_mtx);
        std::queue<T> empty;
        std::swap(m_que, empty);
        m_cvEmpty.notify_all();
        m_cvFull.notify_all();
    }

    template<typename T>
    bool SafeQueue<T>::isClosed() {
        return m_end;
    }

    template<typename T>
    int SafeQueue<T>::size() {
        return m_que.size();
    }
}