Quelle rbtree_augmented.h Sprache: C

/* 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 */

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