c++ 线程安全map

#include <iostream>
#include <map>
#include <shared_mutex>
#include <thread>

template <typename Key, typename Value>
class ThreadSafeMap {
public:
    void insert(const Key& key, const Value& value) {
        std::unique_lock<std::shared_mutex> lock(mutex_);
        map_[key] = value;
    }

    bool find(const Key& key, Value& value) const {
        std::shared_lock<std::shared_mutex> lock(mutex_);
        auto it = map_.find(key);
        if (it != map_.end()) {
            value = it->second;
            return true;
        }
        return false;
    }

private:
    mutable std::shared_mutex mutex_;
    std::map<Key, Value> map_;
};

void writer(ThreadSafeMap<int, std::string>& map, int key, const std::string& value) {
    map.insert(key, value);
}

void reader(const ThreadSafeMap<int, std::string>& map, int key) {
    std::string value;
    if (map.find(key, value)) {
        std::cout << "Key " << key << " has value " << value << std::endl;
    } else {
        std::cout << "Key " << key << " not found" << std::endl;
    }
}

int main() {
    ThreadSafeMap<int, std::string> map;

    std::thread t1(writer, std::ref(map), 1, "one");
    std::thread t2(reader, std::ref(map), 1);
    std::thread t3(writer, std::ref(map), 2, "two");
    std::thread t4(reader, std::ref(map), 2);

    t1.join();
    t2.join();
    t3.join();
    t4.join();

    return 0;
}