clonable.hpp

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#ifndef FSTCLONABLE_H
#define FSTCLONABLE_H
 /* 
=========================================================================
Copyright and license:
  * FST4 software (with the exception of any bundled or externally linked
    third-party components) is Copyright (C) 2000-present Institute of
    Information Theory and Automation of the Czech Academy of Sciences (UTIA).
  * FST4 is free software: you can redistribute it and/or modify it under
    the terms of the GNU Affero General Public License as published by the
    Free Software Foundation, version 3. The full text of the license is in
    the file LICENSE in the distribution root and at
    https://www.gnu.org/licenses/agpl-3.0.html.
  * FST4 is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public
    License for more details.
  * Closed-source use without the AGPL's copyleft obligations requires a
    commercial license from UTIA; in case of interest write to
    utia@utia.cas.cz. LICENSING.md in the distribution root explains both
    options, the contributor license agreement that every contribution
    requires, and the contacts (technical questions and pull requests:
    somol@utia.cas.cz, with "FST" in the subject line).
========================================================================== */
 
#include <cassert>
#include <iostream>
#include <memory>
#include <typeinfo>
#include <type_traits> // for the contract static_asserts in Clonable_Impl
#include "error.hpp"
#include "global.hpp"
 
/*============== Template parameter type naming conventions ==============
--------- Numeric types: -------------------------------------------------
DATATYPE - data sample values - usually real numbers (but may be integers
          in text processing etc.)
REALTYPE - must be real numbers - for representing intermediate results of 
          calculations like mean, covariance etc.
IDXTYPE - index values for enumeration of data samples - (nonnegative) integers, 
          extent depends on numbers of samples in data
DIMTYPE - index values for enumeration of features (dimensions), or classes (not 
          class sizes) - (nonnegative) integers, usually lower extent than IDXTYPE, 
          but be aware of expressions like _classes*_features*_features ! 
          in linearized representations of feature matrices for all classes
BINTYPE - feature selection marker type - represents ca. <10 different feature 
          states (selected, deselected, sel./desel. temporarily 1st nested loop, 2nd...)
RETURNTYPE - criterion value: real value, but may be extended in future to support 
          multiple values 
--------- Class types: ---------------------------------------------------
SUBSET       - class of class type Subset 
CLASSIFIER   - class implementing interface defined in abstract class Classifier 
EVALUATOR    - class implementing interface defined in abstract class Sequential_Step 
DISTANCE     - class implementing interface defined in abstract class Distance 
DATAACCESSOR - class implementing interface defined in abstract class Data_Accessor 
INTERVALCONTAINER - class of class type Data_Intervaller 
CONTAINER    - STL container of class type Data_Interval  
========================================================================== */
 
namespace FST {
 
class Clonable;
 
std::ostream& operator<<(std::ostream& os, const Clonable& cl);
  
class Clonable { // abstract class
        friend std::ostream& operator<<(std::ostream& os, const Clonable& cl);
public:
        Clonable(): _clone(false), _sharing(false) {}
        virtual ~Clonable() {}

        virtual Clonable* clone() const =0;

        virtual Clonable* sharing_clone() const =0;

        virtual Clonable* stateless_clone() const =0;

        bool is_clone() const {return _clone;}
        bool is_sharing() const {return _sharing;} 
        bool is_sharing_clone() const {return _sharing && _clone;} 
 
        virtual std::ostream& print(std::ostream& os) const {return os;} 
protected:
        void set_cloned(const bool cloned=true) {_clone=cloned;} 
        void set_sharing(const bool sharing=true) {_sharing=sharing;} 
        void set_sharing_cloned(const bool cloned=true, const bool sharing=true) {_clone=cloned; _sharing=sharing;} 
private:
        bool _clone;
        bool _sharing; 
};

inline std::ostream& operator<<(std::ostream& os, const Clonable& cl) {
        return cl.print(os);
}

enum CloneKind {
        CLONE_INHERIT,      
        CLONE_THROW,        
        CLONE_DEEP,         
        CLONE_WEAK,         
        CLONE_WEAK_SHARING, 
        CLONE_TO_STATELESS  
};

template<class Derived, class Base,
         CloneKind DEEP_KIND = CLONE_DEEP,
         CloneKind SHARING_KIND = CLONE_INHERIT,
         CloneKind STATELESS_KIND = CLONE_INHERIT>
class Clonable_Impl : public Base {
        static_assert(std::is_base_of<Clonable,Base>::value,
                      "Clonable_Impl: Base must derive from Clonable (family-base contract)");
public:
        Base* clone() const override {return make<DEEP_KIND,SLOT_CLONE>();} 
        Base* sharing_clone() const override {return make<SHARING_KIND,SLOT_SHARING>();} 
        Base* stateless_clone() const override {return make<STATELESS_KIND,SLOT_STATELESS>();} 
protected:
        using Base::Base; 
private:
        enum Slot {SLOT_CLONE, SLOT_SHARING, SLOT_STATELESS}; 

        const Derived& self() const {
                assert(typeid(*this)==typeid(Derived)); // a more-derived class is missing its own Clonable_Impl layer (would slice)
                return static_cast<const Derived&>(*this);
        }

        template<CloneKind K, Slot S> Base* make() const {
                static_assert(std::is_base_of<Clonable_Impl,Derived>::value,
                              "Clonable_Impl: Derived must derive from its own Clonable_Impl (CRTP contract)");
                if constexpr(K==CLONE_DEEP) {
                        Derived *c=new Derived(self()); c->set_cloned(); return c;
                } else if constexpr(K==CLONE_WEAK) {
                        Derived *c=new Derived(self(),0); c->set_cloned(); return c;
                } else if constexpr(K==CLONE_WEAK_SHARING) {
                        Derived *c=new Derived(self(),0); c->set_sharing_cloned(); return c;
                } else if constexpr(K==CLONE_TO_STATELESS) {
                        return this->stateless_clone();
                } else if constexpr(K==CLONE_THROW) {
                        throw fst_error("Clonable_Impl: this clone kind is not supported by this class.");
                } else {
                        // CLONE_INHERIT defers to the Base body, which by family convention throws; the
                        // casts are unreachable at runtime and exist only to satisfy the return type
                        if constexpr(S==SLOT_CLONE) return static_cast<Base*>(Base::clone());
                        else if constexpr(S==SLOT_SHARING) return static_cast<Base*>(Base::sharing_clone());
                        else return static_cast<Base*>(Base::stateless_clone());
                }
        }
};

template<class T>
std::unique_ptr<T> clone_unique(const T& src) {
        return std::unique_ptr<T>(static_cast<T*>(src.clone()));
}

template<class T>
std::unique_ptr<T> sharing_clone_unique(const T& src) {
        return std::unique_ptr<T>(static_cast<T*>(src.sharing_clone()));
}

template<class T>
std::unique_ptr<T> stateless_clone_unique(const T& src) {
        return std::unique_ptr<T>(static_cast<T*>(src.stateless_clone()));
}
 
} // namespace
#endif // FSTCLONABLE_H ///:~