concurrent_hashmap.h

#ifndef WEB_SERVER_CONCURRENT_HASHMAP_H
#define WEB_SERVER_CONCURRENT_HASHMAP_H

#include <unordered_map>
#include <mutex>
#include <shared_mutex>

using std::unordered_map;
using std::shared_mutex, std::shared_lock, std::unique_lock;

template<class K, class V>
class concurrent_hashmap {
public:
    int count(K key);
    V get(K key);
    void set(K key, V value);
    void erase(K key);
private:
    unordered_map<K, V> data;
    mutable shared_mutex mutex;
};

template<class K, class V>
int concurrent_hashmap<K, V>::count(K key) {
    shared_lock<shared_mutex> lock(this->mutex);
    return this->data.count(key);
}

template<class K, class V>
V concurrent_hashmap<K, V>::get(K key) {
    shared_lock<shared_mutex> lock(this->mutex);
    return this->data[key];
}

template<class K, class V>
void concurrent_hashmap<K, V>::set(K key, V value) {
    unique_lock<shared_mutex> lock(this->mutex);
    this->data[key] = value;
}

template<class K, class V>
void concurrent_hashmap<K, V>::erase(K key) {
    unique_lock<shared_mutex> lock(this->mutex);
    if (this->data.count(key)) {
        this->data.erase(key);
    }
}

#endif //WEB_SERVER_CONCURRENT_HASHMAP_H