/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <andrea@suse.de>
  (C) 2002  David Woodhouse <dwmw2@infradead.org>
  (C) 2012  Michel Lespinasse <walken@google.com>


  linux/include/linux/rbtree_augmented.h
*/

#ifndef _LINUX_RBTREE_AUGMENTED_H
#define _LINUX_RBTREE_AUGMENTED_H

#include "rbtree.h"

/*
 * Please note - only struct rb_augment_callbacks and the prototypes for
 * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
 * The rest are implementation details you are not expected to depend on.
 *
 * See Documentation/core-api/rbtree.rst for documentation and samples.
 */

struct rb_augment_callbacks
{
	void (*propagate)(struct rb_node *node, struct rb_node *stop);
	void (*copy)(struct rb_node *old, struct rb_node *new_node);
	void (*rotate)(struct rb_node *old, struct rb_node *new_node);
};

extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
								  void (*augment_rotate)(struct rb_node *old, struct rb_node *new_node));

/*
 * Fixup the rbtree and update the augmented information when rebalancing.
 *
 * On insertion, the user must update the augmented information on the path
 * leading to the inserted node, then call rb_link_node() as usual and
 * rb_insert_augmented() instead of the usual rb_insert_color() call.
 * If rb_insert_augmented() rebalances the rbtree, it will callback into
 * a user provided function to update the augmented information on the
 * affected subtrees.
 */
static inline void
rb_insert_augmented(struct rb_node *node, struct rb_root *root,
					const struct rb_augment_callbacks *augment)
{
	__rb_insert_augmented(node, root, augment->rotate);
}

static inline void
rb_insert_augmented_cached(struct rb_node *node,
						   struct rb_root_cached *root, bool newleft,
						   const struct rb_augment_callbacks *augment)
{
	if (newleft)
		root->rb_leftmost = node;
	rb_insert_augmented(node, &root->rb_root, augment);
}

/*
 * Template for declaring augmented rbtree callbacks (generic case)
 *
 * RBSTATIC:    'static' or empty
 * RBNAME:      name of the rb_augment_callbacks structure
 * RBSTRUCT:    struct type of the tree nodes
 * RBFIELD:     name of struct rb_node field within RBSTRUCT
 * RBAUGMENTED: name of field within RBSTRUCT holding data for subtree
 * RBCOMPUTE:   name of function that recomputes the RBAUGMENTED data
 */

#define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,                          \
							 RBSTRUCT, RBFIELD, RBAUGMENTED, RBCOMPUTE) \
	static inline void                                                  \
		RBNAME##_propagate(struct rb_node *rb, struct rb_node *stop)    \
	{                                                                   \
		while (rb != stop)                                              \
		{                                                               \
			RBSTRUCT *node = rb_entry(rb, RBSTRUCT, RBFIELD);           \
			if (RBCOMPUTE(node, true))                                  \
				break;                                                  \
			rb = rb_parent(&node->RBFIELD);                             \
		}                                                               \
	}                                                                   \
	static inline void                                                  \
		RBNAME##_copy(struct rb_node *rb_old, struct rb_node *rb_new)   \
	{                                                                   \
		RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD);            \
		RBSTRUCT *new_node = rb_entry(rb_new, RBSTRUCT, RBFIELD);       \
		new_node->RBAUGMENTED = old->RBAUGMENTED;                       \
	}                                                                   \
	static void                                                         \
		RBNAME##_rotate(struct rb_node *rb_old, struct rb_node *rb_new) \
	{                                                                   \
		RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD);            \
		RBSTRUCT *new_node = rb_entry(rb_new, RBSTRUCT, RBFIELD);       \
		new_node->RBAUGMENTED = old->RBAUGMENTED;                       \
		RBCOMPUTE(old, false);                                          \
	}                                                                   \
	RBSTATIC const struct rb_augment_callbacks RBNAME = {               \
		.propagate = RBNAME##_propagate,                                \
		.copy = RBNAME##_copy,                                          \
		.rotate = RBNAME##_rotate};

/*
 * Template for declaring augmented rbtree callbacks,
 * computing RBAUGMENTED scalar as max(RBCOMPUTE(node)) for all subtree nodes.
 *
 * RBSTATIC:    'static' or empty
 * RBNAME:      name of the rb_augment_callbacks structure
 * RBSTRUCT:    struct type of the tree nodes
 * RBFIELD:     name of struct rb_node field within RBSTRUCT
 * RBTYPE:      type of the RBAUGMENTED field
 * RBAUGMENTED: name of RBTYPE field within RBSTRUCT holding data for subtree
 * RBCOMPUTE:   name of function that returns the per-node RBTYPE scalar
 */

#define RB_DECLARE_CALLBACKS_MAX(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,    \
								 RBTYPE, RBAUGMENTED, RBCOMPUTE)         \
	static inline bool RBNAME##_compute_max(RBSTRUCT *node, bool exit)   \
	{                                                                    \
		RBSTRUCT *child;                                                 \
		RBTYPE max = RBCOMPUTE(node);                                    \
		if (node->RBFIELD.rb_left)                                       \
		{                                                                \
			child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD);  \
			if (child->RBAUGMENTED > max)                                \
				max = child->RBAUGMENTED;                                \
		}                                                                \
		if (node->RBFIELD.rb_right)                                      \
		{                                                                \
			child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD); \
			if (child->RBAUGMENTED > max)                                \
				max = child->RBAUGMENTED;                                \
		}                                                                \
		if (exit && node->RBAUGMENTED == max)                            \
			return true;                                                 \
		node->RBAUGMENTED = max;                                         \
		return false;                                                    \
	}                                                                    \
	RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,                               \
						 RBSTRUCT, RBFIELD, RBAUGMENTED, RBNAME##_compute_max)

#define RB_RED 0
#define RB_BLACK 1

#define __rb_parent(pc) ((struct rb_node *)(pc & ~3))

#define __rb_color(pc) ((pc) & 1)
#define __rb_is_black(pc) __rb_color(pc)
#define __rb_is_red(pc) (!__rb_color(pc))
#define rb_color(rb) __rb_color((rb)->__rb_parent_color)
#define rb_is_red(rb) __rb_is_red((rb)->__rb_parent_color)
#define rb_is_black(rb) __rb_is_black((rb)->__rb_parent_color)

static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
	rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
}

static inline void rb_set_parent_color(struct rb_node *rb,
									   struct rb_node *p, int color)
{
	rb->__rb_parent_color = (unsigned long)p | color;
}

static inline void
__rb_change_child(struct rb_node *old, struct rb_node *new_node,
				  struct rb_node *parent, struct rb_root *root)
{
	if (parent)
	{
		if (parent->rb_left == old)
			parent->rb_left = new_node;
		else
			parent->rb_right = new_node;
	}
	else
		root->rb_node = new_node;
}

extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
							 void (*augment_rotate)(struct rb_node *old, struct rb_node *new_node));

static inline struct rb_node *
__rb_erase_augmented(struct rb_node *node, struct rb_root *root,
					 const struct rb_augment_callbacks *augment)
{
	struct rb_node *child = node->rb_right;
	struct rb_node *tmp = node->rb_left;
	struct rb_node *parent, *rebalance;
	unsigned long pc;

	if (!tmp)
	{
		/*
		 * Case 1: node to erase has no more than 1 child (easy!)
		 *
		 * Note that if there is one child it must be red due to 5)
		 * and node must be black due to 4). We adjust colors locally
		 * so as to bypass __rb_erase_color() later on.
		 */
		pc = node->__rb_parent_color;
		parent = __rb_parent(pc);
		__rb_change_child(node, child, parent, root);
		if (child)
		{
			child->__rb_parent_color = pc;
			rebalance = NULL;
		}
		else
			rebalance = __rb_is_black(pc) ? parent : NULL;
		tmp = parent;
	}
	else if (!child)
	{
		/* Still case 1, but this time the child is node->rb_left */
		tmp->__rb_parent_color = pc = node->__rb_parent_color;
		parent = __rb_parent(pc);
		__rb_change_child(node, tmp, parent, root);
		rebalance = NULL;
		tmp = parent;
	}
	else
	{
		struct rb_node *successor = child, *child2;

		tmp = child->rb_left;
		if (!tmp)
		{
			/*
			 * Case 2: node's successor is its right child
			 *
			 *    (n)          (s)
			 *    / \          / \
			 *  (x) (s)  ->  (x) (c)
			 *        \
			 *        (c)
			 */
			parent = successor;
			child2 = successor->rb_right;

			augment->copy(node, successor);
		}
		else
		{
			/*
			 * Case 3: node's successor is leftmost under
			 * node's right child subtree
			 *
			 *    (n)          (s)
			 *    / \          / \
			 *  (x) (y)  ->  (x) (y)
			 *      /            /
			 *    (p)          (p)
			 *    /            /
			 *  (s)          (c)
			 *    \
			 *    (c)
			 */
			do
			{
				parent = successor;
				successor = tmp;
				tmp = tmp->rb_left;
			} while (tmp);
			child2 = successor->rb_right;
			parent->rb_left = child2;
			successor->rb_right = child;
			rb_set_parent(child, successor);

			augment->copy(node, successor);
			augment->propagate(parent, successor);
		}

		tmp = node->rb_left;
		successor->rb_left = tmp;
		rb_set_parent(tmp, successor);

		pc = node->__rb_parent_color;
		tmp = __rb_parent(pc);
		__rb_change_child(node, successor, tmp, root);

		if (child2)
		{
			rb_set_parent_color(child2, parent, RB_BLACK);
			rebalance = NULL;
		}
		else
		{
			rebalance = rb_is_black(successor) ? parent : NULL;
		}
		successor->__rb_parent_color = pc;
		tmp = successor;
	}

	augment->propagate(tmp, NULL);
	return rebalance;
}

static inline void
rb_erase_augmented(struct rb_node *node, struct rb_root *root,
				   const struct rb_augment_callbacks *augment)
{
	struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
	if (rebalance)
		__rb_erase_color(rebalance, root, augment->rotate);
}

static inline void
rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
						  const struct rb_augment_callbacks *augment)
{
	if (root->rb_leftmost == node)
		root->rb_leftmost = rb_next(node);
	rb_erase_augmented(node, &root->rb_root, augment);
}

#endif /* _LINUX_RBTREE_AUGMENTED_H */
