handle.h

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/***************************************************************************************************
 * Copyright 2022 NVIDIA Corporation. All rights reserved.
 **************************************************************************************************/

#ifndef MI_BASE_HANDLE_H
#define MI_BASE_HANDLE_H

#include <mi/base/assert.h>
#include <mi/base/config.h> // for MI_CXX_FEATURE_RVALUE_REFERENCES
#include <mi/base/iinterface.h>

#ifdef __cpp_variadic_templates
#include <utility>
#endif


namespace mi {
namespace base {

// Helper type to define Dup_interface
struct Dup_interface_helper {};

typedef const Dup_interface_helper* Dup_interface;

static const Dup_interface DUP_INTERFACE = 0;

template <class Interface>
class Handle
{
public:
    typedef Handle<Interface> Self;

    typedef Interface Interface_type;

    // STL iterator inspired typedef names

    typedef Interface  value_type;

    typedef Difference difference_type;

    typedef Interface* pointer;

    typedef Interface& reference;

private:
    template <typename I2> friend class Handle;

    // Pointer to underlying interface, can be \c NULL
    Interface* m_iptr;

public:
    Handle() : m_iptr( 0) { }

    explicit Handle( Interface* ptr) : m_iptr( ptr) { }

    Handle( Interface* ptr, Dup_interface)
      : m_iptr( ptr)
    {
        if( m_iptr)
            m_iptr->retain();
    }

    Handle( const Self& other)
      : m_iptr( other.m_iptr)
    {
        if( m_iptr)
            m_iptr->retain();
    }

    template <class Interface2>
    Handle( const Handle<Interface2>& other)
      : m_iptr( other.get())
    {
        if( m_iptr)
            m_iptr->retain();
    }

#ifdef MI_CXX_FEATURE_RVALUE_REFERENCES
    Handle( Self&& other)
      : m_iptr( other.m_iptr)
    {
        other.m_iptr = 0;
    }

    template <class Interface2>
    Handle( Handle<Interface2>&& other)
      : m_iptr( other.m_iptr)
    {
        other.m_iptr = 0;
    }
#endif

    void swap( Self& other)
    {
        Interface* tmp_iptr = m_iptr;
        m_iptr = other.m_iptr;
        other.m_iptr = tmp_iptr;
    }

    Self& operator=( const Self& other)
    {
        Self( other).swap( *this);
        return *this;
    }

    template <class Interface2>
    Self& operator=( const Handle<Interface2>& other)
    {
        Self( other).swap( *this);
        return *this;
    }

#ifdef MI_CXX_FEATURE_RVALUE_REFERENCES
    Self& operator=( Self&& other)
    {
        if( this != &other) {
            if( m_iptr)
                m_iptr->release();
            m_iptr = other.m_iptr;
            other.m_iptr = 0;
        }
        return *this;
    }

    template <class Interface2>
    Self& operator=( Handle<Interface2>&& other)
    {
        if( m_iptr)
            m_iptr->release();
        m_iptr = other.m_iptr;
        other.m_iptr = 0;

        return *this;
    }
#endif

    Self& operator=( Interface* ptr)
    {
        Self( ptr).swap( *this);
        return *this;
    }

    void reset()
    {
        if( m_iptr) {
            m_iptr->release();
            m_iptr = 0;
        }
    }

    ~Handle()
    {
        if( m_iptr)
            m_iptr->release();
    }

    bool is_valid_interface() const { return m_iptr != 0; }

    Interface* get() const { return  m_iptr; }

    Interface* extract()
    {
        Interface* ptr = m_iptr;
        m_iptr = 0;
        return ptr;
    }

#ifdef __cpp_variadic_templates
    template <typename... T>
    Self& emplace(T&&... args)
    {
        return emplace<Interface>(std::forward<T>(args)...);
    }

    template <typename Impl, typename... T>
    Self& emplace(T&&... args)
    {
        reset();
        m_iptr = new Impl(std::forward<T>(args)...);
        return *this;
    }
#endif

    Interface& operator*() const
    {
        mi_base_assert_msg( is_valid_interface(), "precondition");
        return *m_iptr;
    }

    Interface* operator->() const
    {
        mi_base_assert_msg( is_valid_interface(), "precondition");
        return m_iptr;
    }

    template <class New_interface>
    Handle<New_interface> get_interface() const
    {
        if( !is_valid_interface())
            return Handle<New_interface>( 0);
        return Handle<New_interface>( static_cast< New_interface*>(
            m_iptr->get_interface( typename New_interface::IID())));
    }

    typedef bool (Handle::*bool_conversion_support)() const;

    operator bool_conversion_support() const
    {
        return is_valid_interface() ? &Handle<Interface>::is_valid_interface : 0;
    }

    friend bool operator==( const Handle<Interface>& lhs, const Interface* rhs)
    {
        return lhs.get() == rhs;
    }

    friend bool operator==( const Interface* lhs, const Handle<Interface>& rhs)
    {
        return lhs == rhs.get();
    }

    friend bool operator!=( const Handle<Interface>& lhs, const Interface* rhs)
    {
        return !( lhs == rhs);
    }

    friend bool operator!=( const Interface* lhs, const Handle<Interface>& rhs) {
        return !( lhs == rhs);
    }
};

template <class Interface1, class Interface2>
inline bool operator==( const Handle<Interface1>& lhs, const Handle<Interface2>& rhs)
{
    return lhs.get() == rhs.get();
}

template <class Interface1, class Interface2>
inline bool operator!=( const Handle<Interface1>& lhs, const Handle<Interface2>& rhs)
{
    return !( lhs == rhs);
}

template <class Interface>
inline Handle<Interface> make_handle( Interface* iptr)
{
    return Handle<Interface>( iptr);
}

template <class Interface>
inline Handle<Interface> make_handle_dup( Interface* iptr)
{
    return Handle<Interface>( iptr, DUP_INTERFACE);
}

#ifdef __cpp_variadic_templates
template <typename Impl, typename... T>
inline Handle<Impl> construct_handle(T&&... args)
{
    return Handle<Impl>{new Impl(std::forward<T>(args)...)};
}

#endif

 // end group mi_base_iinterface

} // namespace base
} // namespace mi

#endif // MI_BASE_HANDLE_H