async_worker.h

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// BSD 3-Clause License
// Copyright (c) 2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#pragma once
 
#include "jthread_compat.h"
 
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <functional>
#include <memory>
#include <mutex>
#include <queue>
#include <thread>
 
namespace kcenon::logger::async {
 
using task_type = std::function<void()>;
 
class async_worker {
public:
    explicit async_worker(std::size_t queue_size = 8192);
 
    ~async_worker();
 
    // Non-copyable, non-movable (owns thread resource)
    async_worker(const async_worker&) = delete;
    async_worker& operator=(const async_worker&) = delete;
    async_worker(async_worker&&) = delete;
    async_worker& operator=(async_worker&&) = delete;
 
    void start();
 
    void stop();
 
    bool enqueue(task_type task);
 
    void flush();
 
    [[nodiscard]] bool is_running() const noexcept;
 
    [[nodiscard]] std::size_t pending_count() const;
 
    [[nodiscard]] std::size_t capacity() const noexcept;
 
    [[nodiscard]] std::uint64_t dropped_count() const noexcept;
 
private:
#if LOGGER_HAS_JTHREAD
    void worker_loop(std::stop_token stop_token);
#else
    void worker_loop(simple_stop_source& stop);
#endif
 
    void drain_queue();
 
private:
    const std::size_t queue_size_;          
    std::queue<task_type> queue_;           
    mutable std::mutex queue_mutex_;        
 
#if LOGGER_HAS_JTHREAD
    std::condition_variable_any queue_cv_;  
#else
    std::condition_variable queue_cv_;      
#endif
 
    compat_jthread worker_thread_;          
    std::atomic<bool> running_{false};      
    std::atomic<std::uint64_t> dropped_count_{0};  
};
 
} // namespace kcenon::logger::async