利用C++实现一个线程安全的map

#include <map>
#include <mutex>
#include <vector>
#include <initializer_list>

template<typename K, typename V>
class ThreadSafeMap {
public:
    ThreadSafeMap() {}

    ThreadSafeMap(std::initializer_list<std::pair<K, V>> init_list) {
        for (auto& pair : init_list) {
            map_[pair.first] = pair.second;
        }
    }

    V& operator[](const K& key) {
        std::lock_guard<std::mutex> lock(mutex_);
        return map_[key];
    }

    bool insert(const K& key, const V& value) {
        std::lock_guard<std::mutex> lock(mutex_);
        auto result = map_.insert(std::make_pair(key, value));
        return result.second;
    }

    bool erase(const K& key) {
        std::lock_guard<std::mutex> lock(mutex_);
        return map_.erase(key);
    }

    bool contains(const K& key) const {
        std::lock_guard<std::mutex> lock(mutex_);
        return map_.find(key) != map_.end();
    }

    size_t size() const {
        std::lock_guard<std::mutex> lock(mutex_);
        return map_.size();
    }

    std::vector<K> keys() const {
        std::lock_guard<std::mutex> lock(mutex_);
        std::vector<K> result;
        for (auto& pair : map_) {
            result.push_back(pair.first);
        }
        return result;
    }

private:
    std::map<K, V> map_;
    mutable std::mutex mutex_;
};

ThreadSafeMap<int, std::string> map{{1, "one"}, {2, "two"}, {3, "three"}};

// 使用[]运算符来访问和修改map中的元素
map[1] = "ONE";
map[4] = "four";
std::cout << map[1] << std::endl; // 输出 "ONE"

// 使用insert方法插入新元素
map.insert(5, "five");

// 使用erase方法删除元素
map.erase(2);

// 使用contains方法判断是否包含某个元素
if (map.contains(1)) {
    std::cout << "Map contains key 1" << std::endl;
}

// 使用size方法获取元素个数
std::cout << "Map size: " << map.size() << std::endl;

// 使用keys方法获取所有key
auto keys = map.keys();
for (auto& key : keys) {
    std::cout << key << std::endl;
}