threadsafequeue.h

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/* Conquer Space
 * Copyright (C) 2021-2025 Conquer Space
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
#pragma once
 
#include <mutex>
#include <queue>
 
namespace cqsp::engine {
template <typename T>
class ThreadsafeQueue {
    std::queue<T> queue_;
    mutable std::mutex mutex_;
 
    // Moved out of public interface to prevent races between this
    // and pop().
    bool empty() const { return queue_.empty(); }
 
 public:
    ThreadsafeQueue() = default;
    ThreadsafeQueue(const ThreadsafeQueue<T>&) = delete;
    ThreadsafeQueue& operator=(const ThreadsafeQueue<T>&) = delete;
 
    ThreadsafeQueue(ThreadsafeQueue<T>&& other) {
        std::lock_guard<std::mutex> lock(mutex_);
        queue_ = std::move(other.queue_);
    }
 
    virtual ~ThreadsafeQueue() {}
 
    unsigned long size() const {
        std::lock_guard<std::mutex> lock(mutex_);
        return queue_.size();
    }
 
    std::optional<T> pop() {
        std::lock_guard<std::mutex> lock(mutex_);
        if (queue_.empty()) {
            return {};
        }
        T tmp = queue_.front();
        queue_.pop();
        return tmp;
    }
 
    void push(const T& item) {
        std::lock_guard<std::mutex> lock(mutex_);
        queue_.push(item);
    }
};
}  // namespace cqsp::engine