minetest/irr/include/irr_ptr.h
2024-09-18 12:19:40 +02:00

207 lines
6.0 KiB
C++
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

/*
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 <utility>
namespace irr { class IReferenceCounted; }
/** 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 shouldnt 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 irr_ptr
{
ReferenceCounted *value = nullptr;
public:
irr_ptr() noexcept = default;
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,
std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
irr_ptr(const irr_ptr<B> &b) noexcept
{
grab(b.get());
}
template <typename B,
std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
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,
std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
irr_ptr &operator=(const irr_ptr<B> &b) noexcept
{
grab(b.get());
return *this;
}
template <typename B,
std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
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
{
static_assert(std::is_base_of_v<irr::IReferenceCounted, ReferenceCounted>,
"Class is not an IReferenceCounted");
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
{
static_assert(std::is_base_of_v<irr::IReferenceCounted, ReferenceCounted>,
"Class is not an IReferenceCounted");
if (object)
object->grab();
reset(object);
}
};
/** 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 achieve 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>
[[nodiscard]]
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();
}
/** Same as std::make_unique<T>, but for irr_ptr.
*/
template <class T, class... Args>
irr_ptr<T> make_irr(Args&&... args)
{
return irr_ptr<T>(new T(std::forward<Args>(args)...));
}