tec_thread_pool.hpp

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// Time-stamp: <Last changed 2026-02-20 16:04:44 by magnolia>
/*----------------------------------------------------------------------
------------------------------------------------------------------------
Copyright (c) 2020-2026 The Emacs Cat (https://github.com/olddeuteronomy/tec).
 
   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 <cstddef>
#include <thread>
#include <atomic>
#include <functional>
#include <mutex>
#include <condition_variable>
#include <vector>
#include <queue>
 
#include "tec/tec_def.hpp"  // IWYU pragma: keep
#include "tec/tec_trace.hpp"
 
 
namespace tec {
 
class ThreadPool {
public:
    using TaskFunc = std::function<void()>;
 
protected:
    size_t num_threads_; 
    std::vector<std::thread> workers_; 
    std::queue<TaskFunc> tasks_; 
    std::mutex queue_mutex_; 
    std::condition_variable condition_; 
    std::atomic<bool> stop_; 
 
public:
    explicit ThreadPool(size_t num_threads)
        : num_threads_(num_threads)
        , stop_(false)
    {
        TEC_ENTER("ThreadPool::ThreadPool");
        //
        // Register thread workers.
        //
        for (size_t i = 0; i < num_threads; ++i) {
            workers_.emplace_back([this] {
                while (true) {
                    TaskFunc task;
                    {
                        std::unique_lock<std::mutex> lock(queue_mutex_);
                        condition_.wait(lock, [this] {
                            return stop_ || !tasks_.empty();
                        });
 
                        if (stop_ && tasks_.empty())
                            return;
 
                        task = std::move(tasks_.front());
                        tasks_.pop();
                    }
 
                    if (task) {
                        task();
                    }
                }
            });
        }
        TEC_TRACE("Thread pool created with {} workers.", num_threads_);
    }
 
    constexpr size_t get_num_threads() {
        return num_threads_;
    }
 
    virtual ~ThreadPool() {
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            stop_ = true;
        }
        condition_.notify_all();
        for (std::thread& worker : workers_) {
            if (worker.joinable())
                worker.join();
        }
    }
 
    template<class F>
    void enqueue(F&& task) {
        {
            std::unique_lock<std::mutex> lock(queue_mutex_);
            tasks_.emplace(std::forward<F>(task));
        }
        condition_.notify_one();
    }
};
 
} // namespace tec