/* Red Black Trees (C) 1999 Andrea Arcangeli <andrea@suse.de> (C) 2002 David Woodhouse <dwmw2@infradead.org> (C) 2012 Michel Lespinasse <walken@google.com> 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*/ #include <linux/rbtree_augmented.h>#include <linux/export.h> /* * 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 * nodes will be lowercase. Unknown color nodes shall be drawn as red within * parentheses and have some accompanying text comment. */ static inline void rb_set_black(struct rb_node *rb){ rb->__rb_parent_color |= RB_BLACK;} static inline struct rb_node *rb_red_parent(struct rb_node *red){ return (struct rb_node *)red->__rb_parent_color;} /* * 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); __rb_change_child(old, new, parent, root);} static __always_inline void__rb_insert(struct rb_node *node, struct rb_root *root, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)){ struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; while (true) { /* * Loop invariant: node is red * * If there is a black parent, we are done. * Otherwise, take some corrective action as we don't * want a red root or two consecutive red nodes. */ if (!parent) { rb_set_parent_color(node, NULL, RB_BLACK); break; } else if (rb_is_black(parent)) break; gparent = rb_red_parent(parent); tmp = gparent->rb_right; if (parent != tmp) { /* parent == gparent->rb_left */ if (tmp && rb_is_red(tmp)) { /* * Case 1 - color flips * * G g * / \ / \ * p u --> P U * / / * n N * * 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; } tmp = parent->rb_right; if (node == tmp) { /* * Case 2 - left rotate at parent * * G G * / \ / \ * p U --> n U * \ / * n p * * This still leaves us in violation of 4), the * continuation into Case 3 will fix that. */ parent->rb_right = tmp = node->rb_left; node->rb_left = parent; if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); rb_set_parent_color(parent, node, RB_RED); augment_rotate(parent, node); parent = node; tmp = node->rb_right; } /* * Case 3 - right rotate at gparent * * G P * / \ / \ * p U --> n g * / \ * n U */ gparent->rb_left = tmp; /* == parent->rb_right */ parent->rb_right = gparent; if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); augment_rotate(gparent, parent); break; } else { 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; } tmp = parent->rb_left; if (node == tmp) { /* Case 2 - right rotate at parent */ parent->rb_left = tmp = node->rb_right; node->rb_right = parent; if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); rb_set_parent_color(parent, node, RB_RED); augment_rotate(parent, node); parent = node; tmp = node->rb_left; } /* Case 3 - left rotate at gparent */ gparent->rb_right = tmp; /* == parent->rb_left */ parent->rb_left = gparent; if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); augment_rotate(gparent, parent); break; } }} /* * 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, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)){ struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; while (true) { /* * 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. */ sibling = parent->rb_right; if (node != sibling) { /* node == parent->rb_left */ if (rb_is_red(sibling)) { /* * Case 1 - left rotate at parent * * P S * / \ / \ * N s --> p Sr * / \ / \ * Sl Sr N Sl */ parent->rb_right = tmp1 = sibling->rb_left; sibling->rb_left = parent; rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); augment_rotate(parent, sibling); sibling = tmp1; } 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 * * 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. */ rb_set_parent_color(sibling, parent, RB_RED); if (rb_is_red(parent)) rb_set_black(parent); else { node = parent; parent = rb_parent(node); if (parent) continue; } break; } /* * Case 3 - right rotate at sibling * (p could be either color here) * * (p) (p) * / \ / \ * N S --> N Sl * / \ \ * sl Sr s * \ * Sr */ sibling->rb_left = tmp1 = tmp2->rb_right; tmp2->rb_right = sibling; parent->rb_right = tmp2; if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); augment_rotate(sibling, tmp2); tmp1 = sibling; sibling = tmp2; } /* * 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) */ parent->rb_right = tmp2 = sibling->rb_left; sibling->rb_left = parent; rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); __rb_rotate_set_parents(parent, sibling, root, RB_BLACK); augment_rotate(parent, sibling); break; } else { sibling = parent->rb_left; if (rb_is_red(sibling)) { /* Case 1 - right rotate at parent */ parent->rb_left = tmp1 = sibling->rb_right; sibling->rb_right = parent; rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); augment_rotate(parent, sibling); sibling = tmp1; } 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); if (rb_is_red(parent)) rb_set_black(parent); else { node = parent; parent = rb_parent(node); if (parent) continue; } break; } /* Case 3 - right rotate at sibling */ sibling->rb_right = tmp1 = tmp2->rb_left; tmp2->rb_left = sibling; parent->rb_left = tmp2; if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); augment_rotate(sibling, tmp2); tmp1 = sibling; sibling = tmp2; } /* Case 4 - left rotate at parent + color flips */ parent->rb_left = tmp2 = sibling->rb_right; sibling->rb_right = parent; rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); __rb_rotate_set_parents(parent, sibling, root, RB_BLACK); augment_rotate(parent, sibling); break; } }} /* 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);}EXPORT_SYMBOL(__rb_erase_color); /* * 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 = { dummy_propagate, dummy_copy, dummy_rotate}; void rb_insert_color(struct rb_node *node, struct rb_root *root){ __rb_insert(node, root, dummy_rotate);}EXPORT_SYMBOL(rb_insert_color); void rb_erase(struct rb_node *node, struct rb_root *root){ struct rb_node *rebalance; rebalance = __rb_erase_augmented(node, root, &dummy_callbacks); if (rebalance) ____rb_erase_color(rebalance, root, dummy_rotate);}EXPORT_SYMBOL(rb_erase); /* * 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, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)){ __rb_insert(node, root, augment_rotate);}EXPORT_SYMBOL(__rb_insert_augmented); /* * This function returns the first node (in sort order) of the tree. */struct rb_node *rb_first(const struct rb_root *root){ 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); struct rb_node *rb_last(const struct rb_root *root){ 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); struct rb_node *rb_next(const struct rb_node *node){ struct rb_node *parent; if (RB_EMPTY_NODE(node)) return NULL; /* * If we have a right-hand child, go down and then left as far * as we can. */ if (node->rb_right) { node = node->rb_right; while (node->rb_left) node=node->rb_left; return (struct rb_node *)node; } /* * 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. */ while ((parent = rb_parent(node)) && node == parent->rb_right) node = parent; return parent;}EXPORT_SYMBOL(rb_next); struct rb_node *rb_prev(const struct rb_node *node){ struct rb_node *parent; if (RB_EMPTY_NODE(node)) return NULL; /* * If we have a left-hand child, go down and then right as far * as we can. */ if (node->rb_left) { node = node->rb_left; while (node->rb_right) node=node->rb_right; return (struct rb_node *)node; } /* * No left-hand children. Go up till we find an ancestor which * is a right-hand child of its parent. */ while ((parent = rb_parent(node)) && node == parent->rb_left) node = parent; Lines 1–500 of 560. Load more
/* Red Black Trees (C) 1999 Andrea Arcangeli <andrea@suse.de> (C) 2002 David Woodhouse <dwmw2@infradead.org> (C) 2012 Michel Lespinasse <walken@google.com> 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 */ #include <linux/rbtree_augmented.h> #include <linux/export.h> /* * 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 * nodes will be lowercase. Unknown color nodes shall be drawn as red within * parentheses and have some accompanying text comment. */ static inline void rb_set_black(struct rb_node *rb) { rb->__rb_parent_color |= RB_BLACK; } static inline struct rb_node *rb_red_parent(struct rb_node *red) { return (struct rb_node *)red->__rb_parent_color; } /* * 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); __rb_change_child(old, new, parent, root); } static __always_inline void __rb_insert(struct rb_node *node, struct rb_root *root, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; while (true) { /* * Loop invariant: node is red * * If there is a black parent, we are done. * Otherwise, take some corrective action as we don't * want a red root or two consecutive red nodes. */ if (!parent) { rb_set_parent_color(node, NULL, RB_BLACK); break; } else if (rb_is_black(parent)) break; gparent = rb_red_parent(parent); tmp = gparent->rb_right; if (parent != tmp) { /* parent == gparent->rb_left */ if (tmp && rb_is_red(tmp)) { /* * Case 1 - color flips * * G g * / \ / \ * p u --> P U * / / * n N * * 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; } tmp = parent->rb_right; if (node == tmp) { /* * Case 2 - left rotate at parent * * G G * / \ / \ * p U --> n U * \ / * n p * * This still leaves us in violation of 4), the * continuation into Case 3 will fix that. */ parent->rb_right = tmp = node->rb_left; node->rb_left = parent; if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); rb_set_parent_color(parent, node, RB_RED); augment_rotate(parent, node); parent = node; tmp = node->rb_right; } /* * Case 3 - right rotate at gparent * * G P * / \ / \ * p U --> n g * / \ * n U */ gparent->rb_left = tmp; /* == parent->rb_right */ parent->rb_right = gparent; if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); augment_rotate(gparent, parent); break; } else { 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; } tmp = parent->rb_left; if (node == tmp) { /* Case 2 - right rotate at parent */ parent->rb_left = tmp = node->rb_right; node->rb_right = parent; if (tmp) rb_set_parent_color(tmp, parent, RB_BLACK); rb_set_parent_color(parent, node, RB_RED); augment_rotate(parent, node); parent = node; tmp = node->rb_left; } /* Case 3 - left rotate at gparent */ gparent->rb_right = tmp; /* == parent->rb_left */ parent->rb_left = gparent; if (tmp) rb_set_parent_color(tmp, gparent, RB_BLACK); __rb_rotate_set_parents(gparent, parent, root, RB_RED); augment_rotate(gparent, parent); break; } } } /* * 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, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; while (true) { /* * 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. */ sibling = parent->rb_right; if (node != sibling) { /* node == parent->rb_left */ if (rb_is_red(sibling)) { /* * Case 1 - left rotate at parent * * P S * / \ / \ * N s --> p Sr * / \ / \ * Sl Sr N Sl */ parent->rb_right = tmp1 = sibling->rb_left; sibling->rb_left = parent; rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); augment_rotate(parent, sibling); sibling = tmp1; } 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 * * 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. */ rb_set_parent_color(sibling, parent, RB_RED); if (rb_is_red(parent)) rb_set_black(parent); else { node = parent; parent = rb_parent(node); if (parent) continue; } break; } /* * Case 3 - right rotate at sibling * (p could be either color here) * * (p) (p) * / \ / \ * N S --> N Sl * / \ \ * sl Sr s * \ * Sr */ sibling->rb_left = tmp1 = tmp2->rb_right; tmp2->rb_right = sibling; parent->rb_right = tmp2; if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); augment_rotate(sibling, tmp2); tmp1 = sibling; sibling = tmp2; } /* * 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) */ parent->rb_right = tmp2 = sibling->rb_left; sibling->rb_left = parent; rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); __rb_rotate_set_parents(parent, sibling, root, RB_BLACK); augment_rotate(parent, sibling); break; } else { sibling = parent->rb_left; if (rb_is_red(sibling)) { /* Case 1 - right rotate at parent */ parent->rb_left = tmp1 = sibling->rb_right; sibling->rb_right = parent; rb_set_parent_color(tmp1, parent, RB_BLACK); __rb_rotate_set_parents(parent, sibling, root, RB_RED); augment_rotate(parent, sibling); sibling = tmp1; } 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); if (rb_is_red(parent)) rb_set_black(parent); else { node = parent; parent = rb_parent(node); if (parent) continue; } break; } /* Case 3 - right rotate at sibling */ sibling->rb_right = tmp1 = tmp2->rb_left; tmp2->rb_left = sibling; parent->rb_left = tmp2; if (tmp1) rb_set_parent_color(tmp1, sibling, RB_BLACK); augment_rotate(sibling, tmp2); tmp1 = sibling; sibling = tmp2; } /* Case 4 - left rotate at parent + color flips */ parent->rb_left = tmp2 = sibling->rb_right; sibling->rb_right = parent; rb_set_parent_color(tmp1, sibling, RB_BLACK); if (tmp2) rb_set_parent(tmp2, parent); __rb_rotate_set_parents(parent, sibling, root, RB_BLACK); augment_rotate(parent, sibling); break; } } } /* 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); } EXPORT_SYMBOL(__rb_erase_color); /* * 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 = { dummy_propagate, dummy_copy, dummy_rotate }; void rb_insert_color(struct rb_node *node, struct rb_root *root) { __rb_insert(node, root, dummy_rotate); } EXPORT_SYMBOL(rb_insert_color); void rb_erase(struct rb_node *node, struct rb_root *root) { struct rb_node *rebalance; rebalance = __rb_erase_augmented(node, root, &dummy_callbacks); if (rebalance) ____rb_erase_color(rebalance, root, dummy_rotate); } EXPORT_SYMBOL(rb_erase); /* * 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, void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) { __rb_insert(node, root, augment_rotate); } EXPORT_SYMBOL(__rb_insert_augmented); /* * This function returns the first node (in sort order) of the tree. */ struct rb_node *rb_first(const struct rb_root *root) { 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); struct rb_node *rb_last(const struct rb_root *root) { 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); struct rb_node *rb_next(const struct rb_node *node) { struct rb_node *parent; if (RB_EMPTY_NODE(node)) return NULL; /* * If we have a right-hand child, go down and then left as far * as we can. */ if (node->rb_right) { node = node->rb_right; while (node->rb_left) node=node->rb_left; return (struct rb_node *)node; } /* * 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. */ while ((parent = rb_parent(node)) && node == parent->rb_right) node = parent; return parent; } EXPORT_SYMBOL(rb_next); struct rb_node *rb_prev(const struct rb_node *node) { struct rb_node *parent; if (RB_EMPTY_NODE(node)) return NULL; /* * If we have a left-hand child, go down and then right as far * as we can. */ if (node->rb_left) { node = node->rb_left; while (node->rb_right) node=node->rb_right; return (struct rb_node *)node; } /* * No left-hand children. Go up till we find an ancestor which * is a right-hand child of its parent. */ while ((parent = rb_parent(node)) && node == parent->rb_left) node = parent;