Add Irrlicht-specific smart pointer (#6814)

1 files changed, 137 insertions, 0 deletions

diff --git a/src/irr_ptr.h b/src/irr_ptr.h
new file mode 100644
index 000000000..5022adb9d
--- /dev/null
+++ b/src/irr_ptr.h
@@ -0,0 +1,137 @@
+/*
+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()};`
+ *
+ * It should *never* be used for engine-managed objects, including
+ * those created with @c addTexture and similar methods.
+ */
+template <class ReferenceCounted,
+		class = typename std::enable_if<std::is_base_of<IReferenceCounted,
+				ReferenceCounted>::value>::type>
+class irr_ptr
+{
+	ReferenceCounted *value = nullptr;
+
+	/** Drops stored pointer replacing it with the given one.
+	 * @note Copy semantics: reference counter *is* increased.
+	 */
+	void grab(ReferenceCounted *object)
+	{
+		if (object)
+			object->grab();
+		reset(object);
+	}
+
+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
+	 * @note Move semantics: reference counter is *not* increased.
+	 */
+	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;
+	}
+};