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/*
Minetest
Copyright (C) 2018 numzero, Lobachevskiy Vitaliy <numzer0@yandex.ru>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
This program 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#pragma once
#include <type_traits>
#include "irrlichttypes.h"
#include "IReferenceCounted.h"
/** Shared pointer for IrrLicht objects.
*
* It should only be used for user-managed objects, i.e. those created with
* the @c new operator or @c create* functions, like:
* `irr_ptr<scene::IMeshBuffer> buf{new scene::SMeshBuffer()};`
* The reference counting is *not* balanced as new objects have reference
* count set to one, and the @c irr_ptr constructor (and @c reset) assumes
* ownership of that reference.
*
* It shouldn’t be used for engine-managed objects, including those created
* with @c addTexture and similar methods. Constructing @c irr_ptr directly
* from such object is a bug and may lead to a crash. Indirect construction
* is possible though; see the @c grab free function for details and use cases.
*/
template <class ReferenceCounted,
class = typename std::enable_if<std::is_base_of<IReferenceCounted,
ReferenceCounted>::value>::type>
class irr_ptr
{
ReferenceCounted *value = nullptr;
public:
irr_ptr() {}
irr_ptr(std::nullptr_t) noexcept {}
irr_ptr(const irr_ptr &b) noexcept { grab(b.get()); }
irr_ptr(irr_ptr &&b) noexcept { reset(b.release()); }
template <typename B, class = typename std::enable_if<std::is_convertible<B *,
ReferenceCounted *>::value>::type>
irr_ptr(const irr_ptr<B> &b) noexcept
{
grab(b.get());
}
template <typename B, class = typename std::enable_if<std::is_convertible<B *,
ReferenceCounted *>::value>::type>
irr_ptr(irr_ptr<B> &&b) noexcept
{
reset(b.release());
}
/** Constructs a shared pointer out of a plain one to control object lifetime.
* @param object The object, usually returned by some @c create* function.
* @note Move semantics: reference counter is *not* increased.
* @warning Never wrap any @c add* function with this!
*/
explicit irr_ptr(ReferenceCounted *object) noexcept { reset(object); }
~irr_ptr() { reset(); }
irr_ptr &operator=(const irr_ptr &b) noexcept
{
grab(b.get());
return *this;
}
irr_ptr &operator=(irr_ptr &&b) noexcept
{
reset(b.release());
return *this;
}
template <typename B, class = typename std::enable_if<std::is_convertible<B *,
ReferenceCounted *>::value>::type>
irr_ptr &operator=(const irr_ptr<B> &b) noexcept
{
grab(b.get());
return *this;
}
template <typename B, class = typename std::enable_if<std::is_convertible<B *,
ReferenceCounted *>::value>::type>
irr_ptr &operator=(irr_ptr<B> &&b) noexcept
{
reset(b.release());
return *this;
}
ReferenceCounted &operator*() const noexcept { return *value; }
ReferenceCounted *operator->() const noexcept { return value; }
explicit operator ReferenceCounted *() const noexcept { return value; }
explicit operator bool() const noexcept { return !!value; }
/** Returns the stored pointer.
*/
ReferenceCounted *get() const noexcept { return value; }
/** Returns the stored pointer, erasing it from this class.
* @note Move semantics: reference counter is not changed.
*/
ReferenceCounted *release() noexcept
{
ReferenceCounted *object = value;
value = nullptr;
return object;
}
/** Drops stored pointer replacing it with the given one.
* @note Move semantics: reference counter is *not* increased.
*/
void reset(ReferenceCounted *object = nullptr) noexcept
{
if (value)
value->drop();
value = object;
}
/** Drops stored pointer replacing it with the given one.
* @note Copy semantics: reference counter *is* increased.
*/
void grab(ReferenceCounted *object) noexcept
{
if (object)
object->grab();
reset(object);
}
};
// clang-format off
// ^ dislikes long lines
/** Constructs a shared pointer as a *secondary* reference to an object
*
* This function is intended to make a temporary reference to an object which
* is owned elsewhere so that it is not destroyed too early. To acheive that
* it does balanced reference counting, i.e. reference count is increased
* in this function and decreased when the returned pointer is destroyed.
*/
template <class ReferenceCounted>
irr_ptr<ReferenceCounted> grab(ReferenceCounted *object) noexcept
{
irr_ptr<ReferenceCounted> ptr;
ptr.grab(object);
return ptr;
}
template <typename ReferenceCounted>
bool operator==(const irr_ptr<ReferenceCounted> &a, const irr_ptr<ReferenceCounted> &b) noexcept
{
return a.get() == b.get();
}
template <typename ReferenceCounted>
bool operator==(const irr_ptr<ReferenceCounted> &a, const ReferenceCounted *b) noexcept
{
return a.get() == b;
}
template <typename ReferenceCounted>
bool operator==(const ReferenceCounted *a, const irr_ptr<ReferenceCounted> &b) noexcept
{
return a == b.get();
}
template <typename ReferenceCounted>
bool operator!=(const irr_ptr<ReferenceCounted> &a, const irr_ptr<ReferenceCounted> &b) noexcept
{
return a.get() != b.get();
}
template <typename ReferenceCounted>
bool operator!=(const irr_ptr<ReferenceCounted> &a, const ReferenceCounted *b) noexcept
{
return a.get() != b;
}
template <typename ReferenceCounted>
bool operator!=(const ReferenceCounted *a, const irr_ptr<ReferenceCounted> &b) noexcept
{
return a != b.get();
}
// clang-format on
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