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lib/rbtree.c
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1da177e4c Linux-2.6.12-rc2 |
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/* Red Black Trees (C) 1999 Andrea Arcangeli <andrea@suse.de> (C) 2002 David Woodhouse <dwmw2@infradead.org> |
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(C) 2012 Michel Lespinasse <walken@google.com> |
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This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA linux/lib/rbtree.c */ |
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#include <linux/rbtree_augmented.h> |
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#include <linux/export.h> |
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/* * red-black trees properties: http://en.wikipedia.org/wiki/Rbtree * * 1) A node is either red or black * 2) The root is black * 3) All leaves (NULL) are black * 4) Both children of every red node are black * 5) Every simple path from root to leaves contains the same number * of black nodes. * * 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two * consecutive red nodes in a path and every red node is therefore followed by * a black. So if B is the number of black nodes on every simple path (as per * 5), then the longest possible path due to 4 is 2B. * * We shall indicate color with case, where black nodes are uppercase and red |
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* nodes will be lowercase. Unknown color nodes shall be drawn as red within * parentheses and have some accompanying text comment. |
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*/ |
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/* * Notes on lockless lookups: * * All stores to the tree structure (rb_left and rb_right) must be done using * WRITE_ONCE(). And we must not inadvertently cause (temporary) loops in the * tree structure as seen in program order. * * These two requirements will allow lockless iteration of the tree -- not * correct iteration mind you, tree rotations are not atomic so a lookup might * miss entire subtrees. * * But they do guarantee that any such traversal will only see valid elements * and that it will indeed complete -- does not get stuck in a loop. * * It also guarantees that if the lookup returns an element it is the 'correct' * one. But not returning an element does _NOT_ mean it's not present. * * NOTE: * * Stores to __rb_parent_color are not important for simple lookups so those * are left undone as of now. Nor did I check for loops involving parent * pointers. */ |
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static inline void rb_set_black(struct rb_node *rb) { rb->__rb_parent_color |= RB_BLACK; } |
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static inline struct rb_node *rb_red_parent(struct rb_node *red) { return (struct rb_node *)red->__rb_parent_color; } |
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/* * Helper function for rotations: * - old's parent and color get assigned to new * - old gets assigned new as a parent and 'color' as a color. */ static inline void __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new, struct rb_root *root, int color) { struct rb_node *parent = rb_parent(old); new->__rb_parent_color = old->__rb_parent_color; rb_set_parent_color(old, new, color); |
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__rb_change_child(old, new, parent, root); |
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} |
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static __always_inline void __rb_insert(struct rb_node *node, struct rb_root *root, |
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bool newleft, struct rb_node **leftmost, |
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) |
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{ |
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struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; |
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|
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if (newleft) *leftmost = node; |
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while (true) { /* |
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* Loop invariant: node is red. |
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*/ |
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if (unlikely(!parent)) { /* * The inserted node is root. Either this is the * first node, or we recursed at Case 1 below and * are no longer violating 4). */ |
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rb_set_parent_color(node, NULL, RB_BLACK); |
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break; |
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} /* * If there is a black parent, we are done. * Otherwise, take some corrective action as, * per 4), we don't want a red root or two * consecutive red nodes. */ if(rb_is_black(parent)) |
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break; |
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gparent = rb_red_parent(parent); |
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tmp = gparent->rb_right; if (parent != tmp) { /* parent == gparent->rb_left */ |
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if (tmp && rb_is_red(tmp)) { /* |
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* Case 1 - node's uncle is red (color flips). |
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* * G g * / \ / \ * p u --> P U * / / |
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* n n |
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* * However, since g's parent might be red, and * 4) does not allow this, we need to recurse * at g. */ rb_set_parent_color(tmp, gparent, RB_BLACK); rb_set_parent_color(parent, gparent, RB_BLACK); node = gparent; parent = rb_parent(node); rb_set_parent_color(node, parent, RB_RED); continue; |
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} |
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tmp = parent->rb_right; if (node == tmp) { |
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/* |
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* Case 2 - node's uncle is black and node is * the parent's right child (left rotate at parent). |
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* * G G * / \ / \ * p U --> n U * \ / * n p * * This still leaves us in violation of 4), the * continuation into Case 3 will fix that. */ |
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tmp = node->rb_left; WRITE_ONCE(parent->rb_right, tmp); WRITE_ONCE(node->rb_left, parent); |
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if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); rb_set_parent_color(parent, node, RB_RED); |
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augment_rotate(parent, node); |
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parent = node; |
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tmp = node->rb_right; |
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} |
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/* |
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* Case 3 - node's uncle is black and node is * the parent's left child (right rotate at gparent). |
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* * G P * / \ / \ * p U --> n g * / \ * n U */ |
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WRITE_ONCE(gparent->rb_left, tmp); /* == parent->rb_right */ WRITE_ONCE(parent->rb_right, gparent); |
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if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); |
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augment_rotate(gparent, parent); |
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break; |
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} else { |
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tmp = gparent->rb_left; if (tmp && rb_is_red(tmp)) { /* Case 1 - color flips */ rb_set_parent_color(tmp, gparent, RB_BLACK); rb_set_parent_color(parent, gparent, RB_BLACK); node = gparent; parent = rb_parent(node); rb_set_parent_color(node, parent, RB_RED); continue; |
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} |
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tmp = parent->rb_left; if (node == tmp) { |
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/* Case 2 - right rotate at parent */ |
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tmp = node->rb_right; WRITE_ONCE(parent->rb_left, tmp); WRITE_ONCE(node->rb_right, parent); |
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if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); rb_set_parent_color(parent, node, RB_RED); |
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augment_rotate(parent, node); |
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parent = node; |
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tmp = node->rb_left; |
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} |
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/* Case 3 - left rotate at gparent */ |
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WRITE_ONCE(gparent->rb_right, tmp); /* == parent->rb_left */ WRITE_ONCE(parent->rb_left, gparent); |
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if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); |
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augment_rotate(gparent, parent); |
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break; |
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} } |
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} |
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/* * Inline version for rb_erase() use - we want to be able to inline * and eliminate the dummy_rotate callback there */ static __always_inline void ____rb_erase_color(struct rb_node *parent, struct rb_root *root, |
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) |
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{ |
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struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; |
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|
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while (true) { /* |
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* Loop invariants: * - node is black (or NULL on first iteration) * - node is not the root (parent is not NULL) * - All leaf paths going through parent and node have a * black node count that is 1 lower than other leaf paths. |
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*/ |
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sibling = parent->rb_right; if (node != sibling) { /* node == parent->rb_left */ |
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if (rb_is_red(sibling)) { /* * Case 1 - left rotate at parent * * P S * / \ / \ * N s --> p Sr * / \ / \ * Sl Sr N Sl */ |
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tmp1 = sibling->rb_left; WRITE_ONCE(parent->rb_right, tmp1); WRITE_ONCE(sibling->rb_left, parent); |
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rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); |
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augment_rotate(parent, sibling); |
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sibling = tmp1; |
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} |
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tmp1 = sibling->rb_right; if (!tmp1 || rb_is_black(tmp1)) { tmp2 = sibling->rb_left; if (!tmp2 || rb_is_black(tmp2)) { /* * Case 2 - sibling color flip * (p could be either color here) * * (p) (p) * / \ / \ * N S --> N s * / \ / \ * Sl Sr Sl Sr * |
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* This leaves us violating 5) which * can be fixed by flipping p to black * if it was red, or by recursing at p. * p is red when coming from Case 1. |
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*/ rb_set_parent_color(sibling, parent, RB_RED); |
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if (rb_is_red(parent)) rb_set_black(parent); else { node = parent; parent = rb_parent(node); if (parent) continue; } break; |
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} |
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/* * Case 3 - right rotate at sibling * (p could be either color here) * * (p) (p) * / \ / \ |
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* N S --> N sl |
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* / \ \ |
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* sl Sr S |
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* \ * Sr |
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* * Note: p might be red, and then both * p and sl are red after rotation(which * breaks property 4). This is fixed in * Case 4 (in __rb_rotate_set_parents() * which set sl the color of p * and set p RB_BLACK) * * (p) (sl) * / \ / \ * N sl --> P S * \ / \ * S N Sr * \ * Sr |
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*/ |
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tmp1 = tmp2->rb_right; WRITE_ONCE(sibling->rb_left, tmp1); WRITE_ONCE(tmp2->rb_right, sibling); WRITE_ONCE(parent->rb_right, tmp2); |
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if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); |
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augment_rotate(sibling, tmp2); |
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tmp1 = sibling; sibling = tmp2; |
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} |
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/* * Case 4 - left rotate at parent + color flips * (p and sl could be either color here. * After rotation, p becomes black, s acquires * p's color, and sl keeps its color) * * (p) (s) * / \ / \ * N S --> P Sr * / \ / \ * (sl) sr N (sl) */ |
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tmp2 = sibling->rb_left; WRITE_ONCE(parent->rb_right, tmp2); WRITE_ONCE(sibling->rb_left, parent); |
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rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); __rb_rotate_set_parents(parent, sibling, root, RB_BLACK); |
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augment_rotate(parent, sibling); |
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break; |
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} else { |
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sibling = parent->rb_left; if (rb_is_red(sibling)) { /* Case 1 - right rotate at parent */ |
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tmp1 = sibling->rb_right; WRITE_ONCE(parent->rb_left, tmp1); WRITE_ONCE(sibling->rb_right, parent); |
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rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); |
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augment_rotate(parent, sibling); |
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sibling = tmp1; |
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} |
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tmp1 = sibling->rb_left; if (!tmp1 || rb_is_black(tmp1)) { tmp2 = sibling->rb_right; if (!tmp2 || rb_is_black(tmp2)) { /* Case 2 - sibling color flip */ rb_set_parent_color(sibling, parent, RB_RED); |
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if (rb_is_red(parent)) rb_set_black(parent); else { node = parent; parent = rb_parent(node); if (parent) continue; } break; |
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} |
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/* Case 3 - left rotate at sibling */ |
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tmp1 = tmp2->rb_left; WRITE_ONCE(sibling->rb_right, tmp1); WRITE_ONCE(tmp2->rb_left, sibling); WRITE_ONCE(parent->rb_left, tmp2); |
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if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); |
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augment_rotate(sibling, tmp2); |
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tmp1 = sibling; sibling = tmp2; |
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} |
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/* Case 4 - right rotate at parent + color flips */ |
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tmp2 = sibling->rb_right; WRITE_ONCE(parent->rb_left, tmp2); WRITE_ONCE(sibling->rb_right, parent); |
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rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); __rb_rotate_set_parents(parent, sibling, root, RB_BLACK); |
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augment_rotate(parent, sibling); |
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break; |
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} } |
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} |
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/* Non-inline version for rb_erase_augmented() use */ void __rb_erase_color(struct rb_node *parent, struct rb_root *root, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { ____rb_erase_color(parent, root, augment_rotate); } |
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EXPORT_SYMBOL(__rb_erase_color); |
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/* * Non-augmented rbtree manipulation functions. * * We use dummy augmented callbacks here, and have the compiler optimize them * out of the rb_insert_color() and rb_erase() function definitions. */ static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {} static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {} static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {} static const struct rb_augment_callbacks dummy_callbacks = { |
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.propagate = dummy_propagate, .copy = dummy_copy, .rotate = dummy_rotate |
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}; void rb_insert_color(struct rb_node *node, struct rb_root *root) { |
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__rb_insert(node, root, false, NULL, dummy_rotate); |
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} EXPORT_SYMBOL(rb_insert_color); void rb_erase(struct rb_node *node, struct rb_root *root) { |
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struct rb_node *rebalance; |
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rebalance = __rb_erase_augmented(node, root, NULL, &dummy_callbacks); |
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if (rebalance) ____rb_erase_color(rebalance, root, dummy_rotate); |
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} EXPORT_SYMBOL(rb_erase); |
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void rb_insert_color_cached(struct rb_node *node, struct rb_root_cached *root, bool leftmost) { __rb_insert(node, &root->rb_root, leftmost, &root->rb_leftmost, dummy_rotate); } EXPORT_SYMBOL(rb_insert_color_cached); void rb_erase_cached(struct rb_node *node, struct rb_root_cached *root) { struct rb_node *rebalance; rebalance = __rb_erase_augmented(node, &root->rb_root, &root->rb_leftmost, &dummy_callbacks); if (rebalance) ____rb_erase_color(rebalance, &root->rb_root, dummy_rotate); } EXPORT_SYMBOL(rb_erase_cached); |
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/* * Augmented rbtree manipulation functions. * * This instantiates the same __always_inline functions as in the non-augmented * case, but this time with user-defined callbacks. */ void __rb_insert_augmented(struct rb_node *node, struct rb_root *root, |
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bool newleft, struct rb_node **leftmost, |
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { |
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__rb_insert(node, root, newleft, leftmost, augment_rotate); |
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} EXPORT_SYMBOL(__rb_insert_augmented); |
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/* * This function returns the first node (in sort order) of the tree. */ |
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struct rb_node *rb_first(const struct rb_root *root) |
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{ struct rb_node *n; n = root->rb_node; if (!n) return NULL; while (n->rb_left) n = n->rb_left; return n; } EXPORT_SYMBOL(rb_first); |
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struct rb_node *rb_last(const struct rb_root *root) |
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{ struct rb_node *n; n = root->rb_node; if (!n) return NULL; while (n->rb_right) n = n->rb_right; return n; } EXPORT_SYMBOL(rb_last); |
f4b477c47 rbtree: add const... |
509 |
struct rb_node *rb_next(const struct rb_node *node) |
1da177e4c Linux-2.6.12-rc2 |
510 |
{ |
55a981027 [RBTREE] Merge co... |
511 |
struct rb_node *parent; |
4c199a93a rbtree: empty nod... |
512 |
if (RB_EMPTY_NODE(node)) |
10fd48f23 [PATCH] rbtree: f... |
513 |
return NULL; |
7ce6ff9e5 rbtree: coding st... |
514 515 516 517 |
/* * If we have a right-hand child, go down and then left as far * as we can. */ |
1da177e4c Linux-2.6.12-rc2 |
518 |
if (node->rb_right) { |
cd9e61ed1 rbtree: cache lef... |
519 |
node = node->rb_right; |
1da177e4c Linux-2.6.12-rc2 |
520 521 |
while (node->rb_left) node=node->rb_left; |
f4b477c47 rbtree: add const... |
522 |
return (struct rb_node *)node; |
1da177e4c Linux-2.6.12-rc2 |
523 |
} |
7ce6ff9e5 rbtree: coding st... |
524 525 526 527 528 529 530 |
/* * No right-hand children. Everything down and left is smaller than us, * so any 'next' node must be in the general direction of our parent. * Go up the tree; any time the ancestor is a right-hand child of its * parent, keep going up. First time it's a left-hand child of its * parent, said parent is our 'next' node. */ |
55a981027 [RBTREE] Merge co... |
531 532 |
while ((parent = rb_parent(node)) && node == parent->rb_right) node = parent; |
1da177e4c Linux-2.6.12-rc2 |
533 |
|
55a981027 [RBTREE] Merge co... |
534 |
return parent; |
1da177e4c Linux-2.6.12-rc2 |
535 536 |
} EXPORT_SYMBOL(rb_next); |
f4b477c47 rbtree: add const... |
537 |
struct rb_node *rb_prev(const struct rb_node *node) |
1da177e4c Linux-2.6.12-rc2 |
538 |
{ |
55a981027 [RBTREE] Merge co... |
539 |
struct rb_node *parent; |
4c199a93a rbtree: empty nod... |
540 |
if (RB_EMPTY_NODE(node)) |
10fd48f23 [PATCH] rbtree: f... |
541 |
return NULL; |
7ce6ff9e5 rbtree: coding st... |
542 543 544 545 |
/* * If we have a left-hand child, go down and then right as far * as we can. */ |
1da177e4c Linux-2.6.12-rc2 |
546 |
if (node->rb_left) { |
cd9e61ed1 rbtree: cache lef... |
547 |
node = node->rb_left; |
1da177e4c Linux-2.6.12-rc2 |
548 549 |
while (node->rb_right) node=node->rb_right; |
f4b477c47 rbtree: add const... |
550 |
return (struct rb_node *)node; |
1da177e4c Linux-2.6.12-rc2 |
551 |
} |
7ce6ff9e5 rbtree: coding st... |
552 553 554 555 |
/* * No left-hand children. Go up till we find an ancestor which * is a right-hand child of its parent. */ |
55a981027 [RBTREE] Merge co... |
556 557 |
while ((parent = rb_parent(node)) && node == parent->rb_left) node = parent; |
1da177e4c Linux-2.6.12-rc2 |
558 |
|
55a981027 [RBTREE] Merge co... |
559 |
return parent; |
1da177e4c Linux-2.6.12-rc2 |
560 561 562 563 564 565 |
} EXPORT_SYMBOL(rb_prev); void rb_replace_node(struct rb_node *victim, struct rb_node *new, struct rb_root *root) { |
55a981027 [RBTREE] Merge co... |
566 |
struct rb_node *parent = rb_parent(victim); |
1da177e4c Linux-2.6.12-rc2 |
567 |
|
c1adf2005 Introduce rb_repl... |
568 569 |
/* Copy the pointers/colour from the victim to the replacement */ *new = *victim; |
1da177e4c Linux-2.6.12-rc2 |
570 |
/* Set the surrounding nodes to point to the replacement */ |
1da177e4c Linux-2.6.12-rc2 |
571 |
if (victim->rb_left) |
55a981027 [RBTREE] Merge co... |
572 |
rb_set_parent(victim->rb_left, new); |
1da177e4c Linux-2.6.12-rc2 |
573 |
if (victim->rb_right) |
55a981027 [RBTREE] Merge co... |
574 |
rb_set_parent(victim->rb_right, new); |
c1adf2005 Introduce rb_repl... |
575 576 577 578 579 580 581 582 |
__rb_change_child(victim, new, parent, root); } EXPORT_SYMBOL(rb_replace_node); void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new, struct rb_root *root) { struct rb_node *parent = rb_parent(victim); |
1da177e4c Linux-2.6.12-rc2 |
583 584 585 |
/* Copy the pointers/colour from the victim to the replacement */ *new = *victim; |
c1adf2005 Introduce rb_repl... |
586 587 588 589 590 591 592 593 594 595 596 597 |
/* Set the surrounding nodes to point to the replacement */ if (victim->rb_left) rb_set_parent(victim->rb_left, new); if (victim->rb_right) rb_set_parent(victim->rb_right, new); /* Set the parent's pointer to the new node last after an RCU barrier * so that the pointers onwards are seen to be set correctly when doing * an RCU walk over the tree. */ __rb_change_child_rcu(victim, new, parent, root); |
1da177e4c Linux-2.6.12-rc2 |
598 |
} |
c1adf2005 Introduce rb_repl... |
599 |
EXPORT_SYMBOL(rb_replace_node_rcu); |
9dee5c515 rbtree: add posto... |
600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 |
static struct rb_node *rb_left_deepest_node(const struct rb_node *node) { for (;;) { if (node->rb_left) node = node->rb_left; else if (node->rb_right) node = node->rb_right; else return (struct rb_node *)node; } } struct rb_node *rb_next_postorder(const struct rb_node *node) { const struct rb_node *parent; if (!node) return NULL; parent = rb_parent(node); /* If we're sitting on node, we've already seen our children */ if (parent && node == parent->rb_left && parent->rb_right) { /* If we are the parent's left node, go to the parent's right * node then all the way down to the left */ return rb_left_deepest_node(parent->rb_right); } else /* Otherwise we are the parent's right node, and the parent * should be next */ return (struct rb_node *)parent; } EXPORT_SYMBOL(rb_next_postorder); struct rb_node *rb_first_postorder(const struct rb_root *root) { if (!root->rb_node) return NULL; return rb_left_deepest_node(root->rb_node); } EXPORT_SYMBOL(rb_first_postorder); |