Fuck git

external/parallel-rdp/parallel-rdp-standalone/util/intrusive.hpp

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+/* Copyright (c) 2017-2023 Hans-Kristian Arntzen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <utility>
+#include <memory>
+#include <atomic>
+#include <type_traits>
+
+namespace Util
+{
+class SingleThreadCounter
+{
+public:
+	inline void add_ref()
+	{
+		count++;
+	}
+
+	inline bool release()
+	{
+		return --count == 0;
+	}
+
+private:
+	uint32_t count = 1;
+};
+
+class MultiThreadCounter
+{
+public:
+	MultiThreadCounter()
+	{
+		count.store(1, std::memory_order_relaxed);
+	}
+
+	inline void add_ref()
+	{
+		count.fetch_add(1, std::memory_order_relaxed);
+	}
+
+	inline bool release()
+	{
+		auto result = count.fetch_sub(1, std::memory_order_acq_rel);
+		return result == 1;
+	}
+
+private:
+	std::atomic_uint32_t count;
+};
+
+template <typename T>
+class IntrusivePtr;
+
+template <typename T, typename Deleter = std::default_delete<T>, typename ReferenceOps = SingleThreadCounter>
+class IntrusivePtrEnabled
+{
+public:
+	using IntrusivePtrType = IntrusivePtr<T>;
+	using EnabledBase = T;
+	using EnabledDeleter = Deleter;
+	using EnabledReferenceOp = ReferenceOps;
+
+	void release_reference()
+	{
+		if (reference_count.release())
+			Deleter()(static_cast<T *>(this));
+	}
+
+	void add_reference()
+	{
+		reference_count.add_ref();
+	}
+
+	IntrusivePtrEnabled() = default;
+
+	IntrusivePtrEnabled(const IntrusivePtrEnabled &) = delete;
+
+	void operator=(const IntrusivePtrEnabled &) = delete;
+
+protected:
+	Util::IntrusivePtr<T> reference_from_this();
+
+private:
+	ReferenceOps reference_count;
+};
+
+template <typename T>
+class IntrusivePtr
+{
+public:
+	template <typename U>
+	friend class IntrusivePtr;
+
+	IntrusivePtr() = default;
+
+	explicit IntrusivePtr(T *handle)
+		: data(handle)
+	{
+	}
+
+	T &operator*()
+	{
+		return *data;
+	}
+
+	const T &operator*() const
+	{
+		return *data;
+	}
+
+	T *operator->()
+	{
+		return data;
+	}
+
+	const T *operator->() const
+	{
+		return data;
+	}
+
+	explicit operator bool() const
+	{
+		return data != nullptr;
+	}
+
+	bool operator==(const IntrusivePtr &other) const
+	{
+		return data == other.data;
+	}
+
+	bool operator!=(const IntrusivePtr &other) const
+	{
+		return data != other.data;
+	}
+
+	T *get()
+	{
+		return data;
+	}
+
+	const T *get() const
+	{
+		return data;
+	}
+
+	void reset()
+	{
+		using ReferenceBase = IntrusivePtrEnabled<
+				typename T::EnabledBase,
+				typename T::EnabledDeleter,
+				typename T::EnabledReferenceOp>;
+
+		// Static up-cast here to avoid potential issues with multiple intrusive inheritance.
+		// Also makes sure that the pointer type actually inherits from this type.
+		if (data)
+			static_cast<ReferenceBase *>(data)->release_reference();
+		data = nullptr;
+	}
+
+	template <typename U>
+	IntrusivePtr &operator=(const IntrusivePtr<U> &other)
+	{
+		static_assert(std::is_base_of<T, U>::value,
+		              "Cannot safely assign downcasted intrusive pointers.");
+
+		using ReferenceBase = IntrusivePtrEnabled<
+				typename T::EnabledBase,
+				typename T::EnabledDeleter,
+				typename T::EnabledReferenceOp>;
+
+		reset();
+		data = static_cast<T *>(other.data);
+
+		// Static up-cast here to avoid potential issues with multiple intrusive inheritance.
+		// Also makes sure that the pointer type actually inherits from this type.
+		if (data)
+			static_cast<ReferenceBase *>(data)->add_reference();
+		return *this;
+	}
+
+	IntrusivePtr &operator=(const IntrusivePtr &other)
+	{
+		using ReferenceBase = IntrusivePtrEnabled<
+				typename T::EnabledBase,
+				typename T::EnabledDeleter,
+				typename T::EnabledReferenceOp>;
+
+		if (this != &other)
+		{
+			reset();
+			data = other.data;
+			if (data)
+				static_cast<ReferenceBase *>(data)->add_reference();
+		}
+		return *this;
+	}
+
+	template <typename U>
+	IntrusivePtr(const IntrusivePtr<U> &other)
+	{
+		*this = other;
+	}
+
+	IntrusivePtr(const IntrusivePtr &other)
+	{
+		*this = other;
+	}
+
+	~IntrusivePtr()
+	{
+		reset();
+	}
+
+	template <typename U>
+	IntrusivePtr &operator=(IntrusivePtr<U> &&other) noexcept
+	{
+		reset();
+		data = other.data;
+		other.data = nullptr;
+		return *this;
+	}
+
+	IntrusivePtr &operator=(IntrusivePtr &&other) noexcept
+	{
+		if (this != &other)
+		{
+			reset();
+			data = other.data;
+			other.data = nullptr;
+		}
+		return *this;
+	}
+
+	template <typename U>
+	IntrusivePtr(IntrusivePtr<U> &&other) noexcept
+	{
+		*this = std::move(other);
+	}
+
+	template <typename U>
+	IntrusivePtr(IntrusivePtr &&other) noexcept
+	{
+		*this = std::move(other);
+	}
+
+	T *release() &
+	{
+		T *ret = data;
+		data = nullptr;
+		return ret;
+	}
+
+	T *release() &&
+	{
+		T *ret = data;
+		data = nullptr;
+		return ret;
+	}
+
+private:
+	T *data = nullptr;
+};
+
+template <typename T, typename Deleter, typename ReferenceOps>
+IntrusivePtr<T> IntrusivePtrEnabled<T, Deleter, ReferenceOps>::reference_from_this()
+{
+	add_reference();
+	return IntrusivePtr<T>(static_cast<T *>(this));
+}
+
+template <typename Derived>
+using DerivedIntrusivePtrType = IntrusivePtr<Derived>;
+
+template <typename T, typename... P>
+DerivedIntrusivePtrType<T> make_handle(P &&... p)
+{
+	return DerivedIntrusivePtrType<T>(new T(std::forward<P>(p)...));
+}
+
+template <typename Base, typename Derived, typename... P>
+typename Base::IntrusivePtrType make_derived_handle(P &&... p)
+{
+	return typename Base::IntrusivePtrType(new Derived(std::forward<P>(p)...));
+}
+
+template <typename T>
+using ThreadSafeIntrusivePtrEnabled = IntrusivePtrEnabled<T, std::default_delete<T>, MultiThreadCounter>;
+}