libpEpDatatypes/src/wrapper.hh

// This file is under GNU General Public License 3.0
// see LICENSE.txt

#ifndef LIBPEPDATATYPES_WRAPPER_HH
#define LIBPEPDATATYPES_WRAPPER_HH

#include <initializer_list>
#include <iterator>

namespace pEp
{

template<class T>
class Wrapper
{
public:
    typedef T c_type;

    template<class... Args>
    Wrapper(Args... args) : value{ this->_new(args...) } {}
    
    // no implicit copying... (yet?)
    Wrapper(const Wrapper<T>&) = delete;
    void operator=(const Wrapper<T>&) = delete;
    
    // must be implemented separately for each T
    Wrapper(Wrapper<T>&& victim);
    Wrapper<T>& operator=(Wrapper<T>&& victim);
    
    ~Wrapper();

    Wrapper<T> copy() const;
    
    bool operator==(const Wrapper<T>& b) const
    {
        return value==b.value;
    }
    
    bool operator!=(const Wrapper<T>& b) const
    {
        return value!=b.value;
    }

private:
    // must be defined for each wrapped type:
    template<class... Args>
    T _new(Args...);

    T value;
};


// many wrapped datatypes are pointers, we can generalize a lot for them:
template<class T>
class Wrapper<T*>
{
public:
    typedef T* c_type;

    Wrapper() : value{nullptr} {}

    template<class... Args>
    Wrapper(Args... args) : value{ this->_new(args...) } {}

    // move is easy, efficient and generic:
    Wrapper(Wrapper<T*>&& victim) noexcept
    : value{ victim.value}
    {
        victim.value = nullptr;
    }
    
    Wrapper<T*>& operator=(Wrapper<T*>&& victim) noexcept
    {
        _free(value);
        value = victim.value;
        victim.value = nullptr;
        return *this;
    }

    Wrapper(const Wrapper<T*>& orig)
    : value{ orig.copy_out() }
    {}
    
    Wrapper<T*>& operator=(const Wrapper<T*>& orig)
    {
        if(&orig == this) return *this;
        _free(value);
        value = orig.copy_out();
        return *this;
    }
    
    ~Wrapper()
    {
        _free(value);
    }
    
    bool operator==(const Wrapper<T*>& b) const
    {
        return value==b.value;
    }
    
    bool operator!=(const Wrapper<T*>& b) const
    {
        return value!=b.value;
    }
    
    const T* operator->() const { return value; }
    const T* get() const { return value; }
    
    // dangerous!
    T* operator->() { return value; }
    T* get() { return value;}
    
    T*  move_out()       { T* r = value; value=nullptr; return r;}
    
    // only implemented for the datatypes where necessay.
    // other implementations can follow if necessary.
    T*  copy_out() const;

protected:

    Wrapper(T* _value) : value{_value} {}

    // must be defined for each wrapped type:
    template<class... Args>
    T* _new(Args...);
    
    void _free(T*);

    T* value;
};



// Wraps single-linked lists and provides an interface compatible
// to std::forward_list
template<class T, class Element>
class ListWrapper;


template<class T, class Element>
class ListWrapper<T*, Element> : public Wrapper<T*>
{
public:
    typedef Wrapper<T*> Base;
    typedef ListWrapper<T*, Element> LW;

    static Element T::* const Value; // to access the current value
    
    // does not own the *value
    class iterator : public std::iterator< std::forward_iterator_tag, Element, ptrdiff_t>
    {
    public:
    
        iterator() = default;
        
        iterator operator++() { return (value ? value = value->next : value); }
        Element  operator*()  { return value->*LW::Value; }
        Element  operator->() { return value->*LW::Value; }
        bool     operator==(const iterator& other) const { return value == other.value; }
        bool     operator!=(const iterator& other) const { return value != other.value; }

    private:
        iterator(T* _t) : value{_t} {}
        T* value = nullptr;
        friend class ListWrapper<T*, Element>;
    };
    
    
    using Base::value;
    
    ListWrapper() : Base() {}
    
    ListWrapper(const std::initializer_list<pEp::Wrapper<Element>>& i);
    ListWrapper(const std::initializer_list<Element>& i);
    
    iterator begin()     { return iterator{value}; }
    iterator end() const { return iterator{}; }
    int  size()    const;
    bool empty()   const;
    
    void erase(const iterator& it);
    void clear();
    void push_back(Element&&);
    void push_back(Wrapper<Element>&&);
};

} // end of namespace pEp

#endif // LIBPEPDATATYPES_WRAPPER_HH