cache: Introduce StringCache, switch to unordered_map, default to memory cache if fs cache dir not given

cache/mapcache.h

@@ -5,12 +5,13 @@
 #include <shared_mutex>
 #include <optional>
 #include <string>
+#include "icache.h"
 
 /* Thread-Safe Key-Value store */
 template <class T> class MapCache
 {
   private:
-	std::map<std::string, T> cache;
+	std::unordered_map<std::string, T> cache;
 	mutable std::shared_mutex sharedMutex;
 
   public:
@@ -34,6 +35,53 @@ template <class T> class MapCache
 		std::lock_guard<std::shared_mutex> lock{sharedMutex};
 		this->cache.clear();
 	}
+
+	void remove(const std::string &key)
+	{
+		std::lock_guard<std::shared_mutex> lock{sharedMutex};
+		this->cache.erase(key);
+	}
+
+	void removePrefix(const std::string &key)
+	{
+		std::lock_guard<std::shared_mutex> lock{sharedMutex};
+		std::erase_if(this->cache, [key](const auto &item)
+		{
+			auto const& [k, v] = item;
+			return k.starts_with(std::string_view(key));
+		});
+	}
+
+};
+
+
+class StringCache : public MapCache<std::string>, public ICache
+{
+	virtual std::optional<std::string> get(std::string_view key) const override
+	{
+		return MapCache<std::string>::find(std::string(key));
+	}
+
+	virtual void put(std::string_view key, std::string val) override
+	{
+		MapCache<std::string>::set(std::string(key), val);
+	}
+
+	virtual void remove(std::string_view key) override
+	{
+		MapCache<std::string>::remove(std::string(key));
+	}
+
+	virtual void removePrefix(std::string_view prefix)
+	{
+		MapCache<std::string>::removePrefix(std::string(prefix));
+	}
+
+	virtual void clear() override
+	{
+		MapCache<std::string>::clear();
+	}
+
 };
 
 #endif // MAPCACHE_H