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/* 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 <linux/compiler.h>
#include <linux/rbtree.h>
#include <linux/rcupdate.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);
void (*rotate)(struct rb_node *old, struct rb_node *new);
};
extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
/*
* 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);
}
static __always_inline struct rb_node *
rb_add_augmented_cached(struct rb_node *node, struct rb_root_cached *tree,
bool (*less)(struct rb_node *, const struct rb_node *),
const struct rb_augment_callbacks *augment)
{
struct rb_node **link = &tree->rb_root.rb_node;
struct rb_node *parent = NULL;
bool leftmost = true;
while (*link) {
parent = *link;
if (less(node, parent)) {
link = &parent->rb_left;
} else {
link = &parent->rb_right;
leftmost = false;
}
}
rb_link_node(node, parent, link);
augment->propagate(parent, NULL); /* suboptimal */
rb_insert_augmented_cached(node, tree, leftmost, augment);
return leftmost ? node : NULL;
}
/*
* 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 = rb_entry(rb_new, RBSTRUCT, RBFIELD); \
new->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 = rb_entry(rb_new, RBSTRUCT, RBFIELD); \
new->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,
struct rb_node *parent, struct rb_root *root)
{
if (parent) {
if (parent->rb_left == old)
WRITE_ONCE(parent->rb_left, new);
else
WRITE_ONCE(parent->rb_right, new);
} else
WRITE_ONCE(root->rb_node, new);
}
static inline void
__rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
struct rb_node *parent, struct rb_root *root)
{
if (parent) {
if (parent->rb_left == old)
rcu_assign_pointer(parent->rb_left, new);
else
rcu_assign_pointer(parent->rb_right, new);
} else
rcu_assign_pointer(root->rb_node, new);
}
extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
static __always_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;
WRITE_ONCE(parent->rb_left, child2);
WRITE_ONCE(successor->rb_right, child);
rb_set_parent(child, successor);
augment->copy(node, successor);
augment->propagate(parent, successor);
}
tmp = node->rb_left;
WRITE_ONCE(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 __always_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 __always_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 */