Merge "LocklessQueue cleanup" into main

 */

#pragma once

#include <atomic>

#include <optional>

template <typename T>

// Single consumer multi producer stack. We can understand the two operations independently to see

// Single consumer multi producer queue. We can understand the two operations independently to see

// why they are without race condition.

//

// push is responsible for maintaining a linked list stored in mPush, and called from multiple

// then store the list and pop one element.

//

// If we already had something in the pop list we just pop directly.

template <typename T>

class LocklessQueue {

public:

    class Entry {

    public:

        T mValue;

        std::atomic<Entry*> mNext;

        Entry(T value) : mValue(value) {}

    };

    std::atomic<Entry*> mPush = nullptr;

    std::atomic<Entry*> mPop = nullptr;

    bool isEmpty() { return (mPush.load() == nullptr) && (mPop.load() == nullptr); }

    void push(T value) {

        Entry* entry = new Entry(value);

        Entry* entry = new Entry(std::move(value));

        Entry* previousHead = mPush.load(/*std::memory_order_relaxed*/);

        do {

            entry->mNext = previousHead;

        } while (!mPush.compare_exchange_weak(previousHead, entry)); /*std::memory_order_release*/

    }

    std::optional<T> pop() {

        Entry* popped = mPop.load(/*std::memory_order_acquire*/);

        if (popped) {

            // Single consumer so this is fine

            mPop.store(popped->mNext /* , std::memory_order_release */);

            auto value = popped->mValue;

            auto value = std::move(popped->mValue);

            delete popped;

            return std::move(value);

            return value;

        } else {

            Entry* grabbedList = mPush.exchange(nullptr /* , std::memory_order_acquire */);

            if (!grabbedList) return std::nullopt;

                grabbedList = next;

            }

            mPop.store(popped /* , std::memory_order_release */);

            auto value = grabbedList->mValue;

            auto value = std::move(grabbedList->mValue);

            delete grabbedList;

            return std::move(value);

            return value;

        }

    }

private:

    class Entry {

    public:

        T mValue;

        std::atomic<Entry*> mNext;

        Entry(T value) : mValue(value) {}

    };

    std::atomic<Entry*> mPush = nullptr;

    std::atomic<Entry*> mPop = nullptr;

};