comptr.h

/*
**  UICore
**  Copyright (c) 1997-2015 The UICore Team
**
**  This software is provided 'as-is', without any express or implied
**  warranty.  In no event will the authors be held liable for any damages
**  arising from the use of this software.
**
**  Permission is granted to anyone to use this software for any purpose,
**  including commercial applications, and to alter it and redistribute it
**  freely, subject to the following restrictions:
**
**  1. The origin of this software must not be misrepresented; you must not
**     claim that you wrote the original software. If you use this software
**     in a product, an acknowledgment in the product documentation would be
**     appreciated but is not required.
**  2. Altered source versions must be plainly marked as such, and must not be
**     misrepresented as being the original software.
**  3. This notice may not be removed or altered from any source distribution.
**
**  Note: Some of the libraries UICore may link to may have additional
**  requirements or restrictions.
**
**  File Author(s):
**
**    Magnus Norddahl
*/

#pragma once

namespace uicore
{
    template <typename Type>
    class ComPtr
    {
    public:
        ComPtr() : ptr(0) { }
        explicit ComPtr(Type *ptr) : ptr(ptr) { }
        ComPtr(const ComPtr &copy) : ptr(copy.ptr) { if (ptr) ptr->AddRef(); }
        ~ComPtr() { clear(); }
        ComPtr &operator =(const ComPtr &copy)
        {
            if (this == &copy)
                return *this;
            if (copy.ptr)
                copy.ptr->AddRef();
            if (ptr)
                ptr->Release();
            ptr = copy.ptr;
            return *this;
        }

        template<typename That>
        explicit ComPtr(const ComPtr<That> &that)
            : ptr(static_cast<Type*>(that.ptr))
        {
            if (ptr)
                ptr->AddRef();
        }

        bool operator ==(const ComPtr &other) const { return ptr == other.ptr; }
        bool operator !=(const ComPtr &other) const { return ptr != other.ptr; }
        bool operator <(const ComPtr &other) const { return ptr < other.ptr; }
        bool operator <=(const ComPtr &other) const { return ptr <= other.ptr; }
        bool operator >(const ComPtr &other) const { return ptr > other.ptr; }
        bool operator >=(const ComPtr &other) const { return ptr >= other.ptr; }

        // const does not exist in COM, so we drop the const qualifier on returned objects to avoid needing mutable variables elsewhere

        Type * const operator ->() const { return const_cast<Type*>(ptr); }
        Type *operator ->() { return ptr; }
        operator Type *() const { return const_cast<Type*>(ptr); }
        operator bool() const { return ptr != 0; }

        bool is_null() const { return ptr == 0; }
        void clear() { if (ptr) ptr->Release(); ptr = 0; }
        Type *get() const { return const_cast<Type*>(ptr); }
        Type **output_variable() { clear(); return &ptr; }

        Type *ptr;
    };
}