multihreadosm

#include <fstream>
#include <iostream>
#include <vector>
#include <string>
#include <future>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <osmium/io/any_input.hpp>
#include <osmium/handler.hpp>
#include <osmium/visitor.hpp>

class WayData {
public:
    osmium::object_id_type id;
    std::vector<std::pair<double, double>> nodes; // Store lon, lat pairs
    std::string name;

    WayData(const osmium::Way& way) {
        id = way.id();
        for (const auto& node : way.nodes()) {
            if (node.location().valid()) {
                nodes.emplace_back(node.lon(), node.lat());
            }
        }
        const char* name_tag = way.tags()["name"];
        if (name_tag) {
            name = name_tag;
        }
    }
};

std::string process_way(const WayData& wayData) {
    std::string feature = "{ \"type\": \"Feature\", \"properties\": { \"id\": \"" + std::to_string(wayData.id) + "\", ";

    if (!wayData.name.empty()) {
        feature += "\"name\": \"" + wayData.name + "\", ";
    }

    feature += "\"geometry\": { \"type\": \"LineString\", \"coordinates\": [";
    for (const auto& node : wayData.nodes) {
        feature += "[" + std::to_string(node.first) + ", " + std::to_string(node.second) + "],";
    }

    if (feature.back() == ',') {
        feature.pop_back();
    }

    feature += "] } }";
    return feature;
}

class ThreadPool {
public:
    ThreadPool(size_t threads) : stop(false) {
        for(size_t i = 0; i < threads; ++i)
            workers.emplace_back([this] {
                while(true) {
                    std::function<void()> task;
                    {
                        std::unique_lock<std::mutex> lock(this->queue_mutex);
                        this->condition.wait(lock, [this]{ return this->stop || !this->tasks.empty(); });
                        if(this->stop && this->tasks.empty())
                            return;
                        task = std::move(this->tasks.front());
                        this->tasks.pop();
                    }
                    task();
                }
            });
    }

    ~ThreadPool() {
        {
            std::unique_lock<std::mutex> lock(queue_mutex);
            stop = true;
        }
        condition.notify_all();
        for(std::thread &worker: workers)
            worker.join();
    }

    template<class F, class... Args>
    auto enqueue(F&& f, Args&&... args)
        -> std::future<typename std::result_of<F(Args...)>::type> {
        using return_type = typename std::result_of<F(Args...)>::type;

        auto task = std::make_shared< std::packaged_task<return_type()> >(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...)
        );

        std::future<return_type> res = task->get_future();
        {
            std::unique_lock<std::mutex> lock(queue_mutex);
            if(stop)
                throw std::runtime_error("enqueue on stopped ThreadPool");

            tasks.emplace([task](){ (*task)(); });
        }
        condition.notify_one();
        return res;
    }

private:
    std::vector< std::thread > workers;
    std::queue< std::function<void()> > tasks;

    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;
};

int main(int argc, char* argv[]) {
    int num_threads = std::thread::hardware_concurrency();
    std::string input_file_name;

    for (int i = 1; i < argc; ++i) {
        std::string arg = argv[i];
        if (arg == "-j" && i + 1 < argc) {
            num_threads = std::stoi(argv[++i]);
        } else {
            input_file_name = argv[i];
        }
    }

    if (input_file_name.empty()) {
        std::cerr << "Usage: " << argv[0] << " [-j num_threads] OSM_FILE.osm.pbf" << std::endl;
        return 1;
    }

    osmium::io::File input_file(input_file_name);
    osmium::io::Reader reader(input_file);

    ThreadPool pool(num_threads);
    std::vector<std::future<std::string>> results;

    while (osmium::memory::Buffer buffer = reader.read()) {
        for (const auto& way : buffer.select<osmium::Way>()) {
            WayData wayData(way);
            results.emplace_back(pool.enqueue(process_way, wayData));
        }
    }

    std::vector<std::string> features;
    for (auto& result : results) {
        std::string feature = result.get();
        if (!feature.empty()) {
            features.push_back(feature);
        }
    }

    std::ofstream file("output.geojson");
    file << "{ \"type\": \"FeatureCollection\", \"features\": [";
    for (const auto& feature : features) {
        file << feature << ",";
    }
    if (!features.empty()) {
        file.seekp(-1, std::ios_base::end);
    }
    file << "] }";
    file.close();

    reader.close();
}