factory.h

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#ifndef GEOGRAM_BASIC_FACTORY
#define GEOGRAM_BASIC_FACTORY
 
#include <geogram/basic/memory.h>
#include <geogram/basic/counted.h>
#include <string>
#include <map>
#include <vector>
#include <typeinfo>
 
namespace GEO {
 
    class GEOGRAM_API InstanceRepo {
    public:
    typedef Counted Instance;
 
    template <class InstanceType>
    static InstanceType& instance() {
        const std::string name = typeid(InstanceType).name();
        Instance* instance = get(name);
        if(instance == nullptr) {
            instance = new InstanceType;
            add(name, instance);
        }
        return *static_cast<InstanceType*>(instance);
    }
 
    private:
    static void add(const std::string& name, Instance* instance);
 
    static Instance* get(const std::string& name);
    };
 
    /**************************************************************************/
 
    template <class FactoryCreator>
    class Factory : public InstanceRepo::Instance {
    public:
        typedef typename FactoryCreator::CreatorType CreatorType;
 
        template <class ConcreteType>
        static void register_creator(const std::string& name) {
            Factory& self = instance();
            self.registry_[name] =
                FactoryCreator::template create<ConcreteType>;
        }
 
        static CreatorType find_creator(const std::string& name) {
            Factory& self = instance();
            auto i = self.registry_.find(name);
            return i == self.registry_.end() ? nullptr : i->second;
        }
 
        static void list_creators(std::vector<std::string>& names) {
            Factory& self = instance();
            for(auto& it : self.registry_) {
                names.push_back(it.first);
            }
        }
 
        static bool has_creator(const std::string& name) {
            Factory& self = instance();
            for(auto& it : self.registry_) {
                if(it.first == name) {
                    return true;
                }
            }
            return false;
        }
 
        template <class ConcreteType>
        struct RegisterCreator {
            RegisterCreator(const std::string& name) {
                Factory::template register_creator<ConcreteType>(name);
            }
        };
 
    protected:
        ~Factory() override {
        }
 
    private:
        static inline Factory& instance() {
            return InstanceRepo::instance<Factory>();
        }
 
        typedef std::map<std::string, CreatorType> Registry;
        Registry registry_;
    };
 
    template <class Type>
    struct FactoryCreator0 {
        typedef Type* (* CreatorType)();
 
        template <class ConcreteType>
        static Type* create() {
            return new ConcreteType;
        }
    };
 
    template <class Type>
    class Factory0 : public Factory<FactoryCreator0<Type> > {
        typedef Factory<FactoryCreator0<Type> > BaseClass;
 
    public:
        static Type* create_object(const std::string& name) {
            typename BaseClass::CreatorType creator =
                BaseClass::find_creator(name);
            return creator == nullptr ? nullptr : (* creator)();
        }
    };
 
    template <class Type, class Param1>
    struct FactoryCreator1 {
        typedef Type* (* CreatorType)(const Param1&);
 
        template <class ConcreteType>
        static Type* create(const Param1& param1) {
            return new ConcreteType(param1);
        }
    };
 
    template <class Type, class Param1>
    class Factory1 : public Factory<FactoryCreator1<Type, Param1> > {
        typedef Factory<FactoryCreator1<Type, Param1> > BaseClass;
 
    public:
        static Type* create_object(const std::string& name, const Param1& param1) {
            typename BaseClass::CreatorType creator =
                BaseClass::find_creator(name);
            return creator == nullptr ? nullptr : (* creator)(param1);
        }
    };
 
#define geo_register_creator(FactoryType, ConcreteType, name)           \
    static FactoryType::RegisterCreator<ConcreteType>                   \
    CPP_CONCAT(Factory_register_creator_, __LINE__) (name);             \
    geo_argused(CPP_CONCAT(Factory_register_creator_, __LINE__))
}
 
#endif