self_list.h

/**************************************************************************/
/*  self_list.h                                                           */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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/* 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    */
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/* included in all copies or substantial portions of the Software.        */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
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#pragma once

#include "core/error/error_macros.h"
#include "core/templates/sort_list.h"
#include "core/typedefs.h"

template <typename T>
class SelfList {
public:
	class List {
		SelfList<T> *_first = nullptr;
		SelfList<T> *_last = nullptr;

	public:
		void add(SelfList<T> *p_elem) {
			ERR_FAIL_COND(p_elem->_root);

			p_elem->_root = this;
			p_elem->_next = _first;
			p_elem->_prev = nullptr;

			if (_first) {
				_first->_prev = p_elem;

			} else {
				_last = p_elem;
			}

			_first = p_elem;
		}

		void add_last(SelfList<T> *p_elem) {
			ERR_FAIL_COND(p_elem->_root);

			p_elem->_root = this;
			p_elem->_next = nullptr;
			p_elem->_prev = _last;

			if (_last) {
				_last->_next = p_elem;

			} else {
				_first = p_elem;
			}

			_last = p_elem;
		}

		void remove(SelfList<T> *p_elem) {
			ERR_FAIL_COND(p_elem->_root != this);
			if (p_elem->_next) {
				p_elem->_next->_prev = p_elem->_prev;
			}

			if (p_elem->_prev) {
				p_elem->_prev->_next = p_elem->_next;
			}

			if (_first == p_elem) {
				_first = p_elem->_next;
			}

			if (_last == p_elem) {
				_last = p_elem->_prev;
			}

			p_elem->_next = nullptr;
			p_elem->_prev = nullptr;
			p_elem->_root = nullptr;
		}

		void clear() {
			while (_first) {
				remove(_first);
			}
		}

		void sort() {
			sort_custom<Comparator<T>>();
		}

		template <typename C>
		void sort_custom() {
			if (_first == _last) {
				return;
			}

			struct PtrComparator {
				C compare;
				_FORCE_INLINE_ bool operator()(const T *p_a, const T *p_b) const { return compare(*p_a, *p_b); }
			};
			using Element = SelfList<T>;
			SortList<Element, T *, &Element::_self, &Element::_prev, &Element::_next, PtrComparator> sorter;
			sorter.sort(_first, _last);
		}

		_FORCE_INLINE_ SelfList<T> *first() { return _first; }
		_FORCE_INLINE_ const SelfList<T> *first() const { return _first; }

		// Forbid copying, which has broken behavior.
		void operator=(const List &) = delete;

		_FORCE_INLINE_ List() {}
		_FORCE_INLINE_ ~List() {
			// A self list must be empty on destruction.
			DEV_ASSERT(_first == nullptr);
		}
	};

private:
	List *_root = nullptr;
	T *_self = nullptr;
	SelfList<T> *_next = nullptr;
	SelfList<T> *_prev = nullptr;

public:
	_FORCE_INLINE_ bool in_list() const { return _root; }
	_FORCE_INLINE_ void remove_from_list() {
		if (_root) {
			_root->remove(this);
		}
	}
	_FORCE_INLINE_ SelfList<T> *next() { return _next; }
	_FORCE_INLINE_ SelfList<T> *prev() { return _prev; }
	_FORCE_INLINE_ const SelfList<T> *next() const { return _next; }
	_FORCE_INLINE_ const SelfList<T> *prev() const { return _prev; }
	_FORCE_INLINE_ T *self() const { return _self; }

	// Forbid copying, which has broken behavior.
	void operator=(const SelfList<T> &) = delete;

	_FORCE_INLINE_ SelfList(T *p_self) {
		_self = p_self;
	}

	_FORCE_INLINE_ ~SelfList() {
		if (_root) {
			_root->remove(this);
		}
	}
};