IOThread.hpp

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// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2026 Caleb Buahin
//
// 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.

 
#ifndef OPENSWMM_ENGINE_IO_THREAD_HPP
#define OPENSWMM_ENGINE_IO_THREAD_HPP
 
#include "WriteTask.hpp"
 
#include <thread>
#include <mutex>
#include <condition_variable>
#include <queue>
#include <atomic>
#include <functional>
 
namespace openswmm {
 
class PluginFactory;

class IOThread {
public:
    static constexpr std::size_t DEFAULT_QUEUE_CAPACITY = 8;

    explicit IOThread(PluginFactory& factory,
                      std::size_t capacity = DEFAULT_QUEUE_CAPACITY);
 
    ~IOThread();
 
    // Non-copyable, non-movable (owns a thread)
    IOThread(const IOThread&) = delete;
    IOThread& operator=(const IOThread&) = delete;
 
    // -----------------------------------------------------------------------
    // Control
    // -----------------------------------------------------------------------

    void start();

    void post(SimulationSnapshot snap);

    void stop();
 
    // -----------------------------------------------------------------------
    // Diagnostics
    // -----------------------------------------------------------------------

    bool running() const noexcept { return running_.load(std::memory_order_relaxed); }

    int tasks_completed() const noexcept { return tasks_completed_.load(std::memory_order_relaxed); }

    int last_error() const noexcept { return last_error_.load(std::memory_order_relaxed); }
 
private:
    void run();  
 
    PluginFactory&           factory_;
    const std::size_t        capacity_;
 
    std::thread              thread_;
    std::queue<WriteTask>    queue_;
    std::mutex               mutex_;
    std::condition_variable  cv_not_full_;   
    std::condition_variable  cv_not_empty_;  
    std::atomic<bool>        stop_flag_      {false};
    std::atomic<bool>        running_        {false};
    std::atomic<int>         tasks_completed_{0};
    std::atomic<int>         last_error_     {0};
    int                      next_sequence_  = 0;
};
 
} /* namespace openswmm */
 
#endif /* OPENSWMM_ENGINE_IO_THREAD_HPP */