LinkedStack.h

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// Copyright 2024 libsese
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#pragma once
 
#include <atomic>
 
namespace sese::concurrent {
 
// GCOVR_EXCL_START
 
template<class T>
class LinkedStack {
    struct Node {
        T value;
        std::atomic<Node *> next{nullptr};
    };
 
    std::atomic<Node *> root{nullptr};
 
public:
    ~LinkedStack() {
        auto p_node = root.load();
        while (p_node) {
            auto p_next = p_node->next.load();
            delete p_node;
            p_node = p_next;
        }
    }
 
    void push(const T &value) {
        auto new_node = new Node;
        new_node->value = value;
 
        Node *current_root;
        while (true) {
            current_root = root.load();
            new_node->next.store(current_root);
            if (root.compare_exchange_weak(current_root, new_node)) {
                break;
            }
        }
    }
 
    bool pop(T &value) {
        Node *old_root;
        Node *new_root;
        while (true) {
            old_root = root.load();
            if (old_root == nullptr) {
                return false;
            }
            new_root = old_root->next.load();
            if (root.compare_exchange_weak(old_root, new_root)) {
                break;
            }
        }
        value = old_root->value;
        delete old_root;
        return true;
    }
 
    bool empty() {
        return root.load() == nullptr;
    }
};
 
// GCOVR_EXCL_STOP
 
} // namespace sese::concurrent