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Diffstat (limited to 'src/libbasic/c-rbtree.h')
| -rw-r--r-- | src/libbasic/c-rbtree.h | 297 |
1 files changed, 0 insertions, 297 deletions
diff --git a/src/libbasic/c-rbtree.h b/src/libbasic/c-rbtree.h deleted file mode 100644 index 20c5515ca1..0000000000 --- a/src/libbasic/c-rbtree.h +++ /dev/null @@ -1,297 +0,0 @@ -#pragma once - -/*** - This file is part of systemd. See COPYING for details. - - systemd is free software; you can redistribute it and/or modify it - under the terms of the GNU Lesser General Public License as published by - the Free Software Foundation; either version 2.1 of the License, or - (at your option) any later version. - - systemd 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 - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public License - along with systemd; If not, see <http://www.gnu.org/licenses/>. -***/ - -/* - * Standalone Red-Black-Tree Implementation in Standard ISO-C11 - * - * This header provides an RB-Tree API, that is fully implemented in ISO-C11 - * and has no external dependencies. Furthermore, tree traversal, memory - * allocations, and key comparisons a fully in control of the API user. The - * implementation only provides the RB-Tree specific rebalancing and coloring. - * - * A tree is represented by the "CRBTree" structure. It contains a *singly* - * field, which is a pointer to the root node. If NULL, the tree is empty. If - * non-NULL, there is at least a single element in the tree. - * - * Each node of the tree is represented by the "CRBNode" structure. It has - * three fields. The @left and @right members can be accessed by the API user - * directly to traverse the tree. The third member is an implementation detail - * and encodes the parent pointer and color of the node. - * API users are required to embed the CRBNode object into their own objects - * and then use offsetof() (i.e., container_of() and friends) to turn CRBNode - * pointers into pointers to their own structure. - */ - -#ifdef __cplusplus -extern "C" { -#endif - -typedef struct CRBNode CRBNode; -typedef struct CRBTree CRBTree; - -/** - * struct CRBNode - Node of a Red-Black Tree - * @__parent_and_color: internal state - * @left: left child, or NULL - * @right: right child, or NULL - * - * Each node in an RB-Tree must embed an CRBNode object. This object contains - * pointers to its left and right child, which can be freely accessed by the - * API user at any time. They are NULL, if the node does not have a left/right - * child. - * - * The @__parent_and_color field must never be accessed directly. It encodes - * the pointer to the parent node, and the color of the node. Use the accessor - * functions instead. - * - * There is no reason to initialize a CRBNode object before linking it. - * However, if you need a boolean state that tells you whether the node is - * linked or not, you should initialize the node via c_rbnode_init() or - * C_RBNODE_INIT. - */ -struct CRBNode { - CRBNode *__parent_and_color; - CRBNode *left; - CRBNode *right; -}; - -#define C_RBNODE_INIT(_var) { .__parent_and_color = &(_var) } - -CRBNode *c_rbnode_leftmost(CRBNode *n); -CRBNode *c_rbnode_rightmost(CRBNode *n); -CRBNode *c_rbnode_next(CRBNode *n); -CRBNode *c_rbnode_prev(CRBNode *n); - -/** - * struct CRBTree - Red-Black Tree - * @root: pointer to the root node, or NULL - * - * Each Red-Black Tree is rooted in an CRBTree object. This object contains a - * pointer to the root node of the tree. The API user is free to access the - * @root member at any time, and use it to traverse the tree. - * - * To initialize an RB-Tree, set it to NULL / all zero. - */ -struct CRBTree { - CRBNode *root; -}; - -CRBNode *c_rbtree_first(CRBTree *t); -CRBNode *c_rbtree_last(CRBTree *t); - -void c_rbtree_add(CRBTree *t, CRBNode *p, CRBNode **l, CRBNode *n); -void c_rbtree_remove(CRBTree *t, CRBNode *n); - -/** - * c_rbnode_init() - mark a node as unlinked - * @n: node to operate on - * - * This marks the node @n as unlinked. The node will be set to a valid state - * that can never happen if the node is linked in a tree. Furthermore, this - * state is fully known to the implementation, and as such handled gracefully - * in all cases. - * - * You are *NOT* required to call this on your node. c_rbtree_add() can handle - * uninitialized nodes just fine. However, calling this allows to use - * c_rbnode_is_linked() to check for the state of a node. Furthermore, - * iterators and accessors can be called on initialized (yet unlinked) nodes. - * - * Use the C_RBNODE_INIT macro if you want to initialize static variables. - */ -static inline void c_rbnode_init(CRBNode *n) { - *n = (CRBNode)C_RBNODE_INIT(*n); -} - -/** - * c_rbnode_is_linked() - check whether a node is linked - * @n: node to check, or NULL - * - * This checks whether the passed node is linked. If you pass NULL, or if the - * node is not linked into a tree, this will return false. Otherwise, this - * returns true. - * - * Note that you must have either linked the node or initialized it, before - * calling this function. Never call this function on uninitialized nodes. - * Furthermore, removing a node via c_rbtree_remove() does *NOT* mark the node - * as unlinked. You have to call c_rbnode_init() yourself after removal, or use - * the c_rbtree_remove_init() helper. - * - * Return: true if the node is linked, false if not. - */ -static inline _Bool c_rbnode_is_linked(CRBNode *n) { - return n && n->__parent_and_color != n; -} - -/** - * c_rbnode_parent() - return parent pointer - * @n node to access - * - * This returns a pointer to the parent of the given node @n. If @n does not - * have a parent, NULL is returned. If @n is not linked, @n itself is returned. - * - * You should not call this on unlinked or uninitialized nodes! If you do, you - * better know how its semantics. - * - * Return: Pointer to parent. - */ -static inline CRBNode *c_rbnode_parent(CRBNode *n) { - return (CRBNode*)((unsigned long)n->__parent_and_color & ~1UL); -} - -/** - * c_rbtree_remove_init() - safely remove node from tree and reinitialize it - * @t: tree to operate on - * @n: node to remove, or NULL - * - * This is almost the same as c_rbtree_remove(), but extends it slightly, to be - * more convenient to use in many cases: - * - if @n is unlinked or NULL, this is a no-op - * - @n is reinitialized after being removed - */ -static inline void c_rbtree_remove_init(CRBTree *t, CRBNode *n) { - if (c_rbnode_is_linked(n)) { - c_rbtree_remove(t, n); - c_rbnode_init(n); - } -} - -/** - * CRBCompareFunc - compare a node to a key - * @t: tree where the node is linked to - * @k: key to compare - * @n: node to compare - * - * If you use the tree-traversal helpers (which are optional), you need to - * provide this callback so they can compare nodes in a tree to the key you - * look for. - * - * The tree @t is provided as optional context to this callback. The key you - * look for is provided as @k, the current node that should be compared to is - * provided as @n. This function should work like strcmp(), that is, return -1 - * if @key orders before @n, 0 if both compare equal, and 1 if it orders after - * @n. - */ -typedef int (*CRBCompareFunc) (CRBTree *t, void *k, CRBNode *n); - -/** - * c_rbtree_find_node() - find node - * @t: tree to search through - * @f: comparison function - * @k: key to search for - * - * This searches through @t for a node that compares equal to @k. The function - * @f must be provided by the caller, which is used to compare nodes to @k. See - * the documentation of CRBCompareFunc for details. - * - * If there are multiple entries that compare equal to @k, this will return a - * pseudo-randomly picked node. If you need stable lookup functions for trees - * where duplicate entries are allowed, you better code your own lookup. - * - * Return: Pointer to matching node, or NULL. - */ -static inline CRBNode *c_rbtree_find_node(CRBTree *t, CRBCompareFunc f, const void *k) { - CRBNode *i; - - assert(t); - assert(f); - - i = t->root; - while (i) { - int v = f(t, (void *)k, i); - if (v < 0) - i = i->left; - else if (v > 0) - i = i->right; - else - return i; - } - - return NULL; -} - -/** - * c_rbtree_find_entry() - find entry - * @_t: tree to search through - * @_f: comparison function - * @_k: key to search for - * @_t: type of the structure that embeds the nodes - * @_o: name of the node-member in type @_t - * - * This is very similar to c_rbtree_find_node(), but instead of returning a - * pointer to the CRBNode, it returns a pointer to the surrounding object. This - * object must embed the CRBNode object. The type of the surrounding object - * must be given as @_t, and the name of the embedded CRBNode member as @_o. - * - * See c_rbtree_find_node() for more details. - * - * Return: Pointer to found entry, NULL if not found. - */ -#define c_rbtree_find_entry(_m, _f, _k, _t, _o) \ - ((_t *)(((char *)c_rbtree_find_node((_m), (_f), (_k)) ?: \ - (char *)NULL + offsetof(_t, _o)) - offsetof(_t, _o))) - -/** - * c_rbtree_find_slot() - find slot to insert new node - * @t: tree to search through - * @f: comparison function - * @k: key to search for - * @p: output storage for parent pointer - * - * This searches through @t just like c_rbtree_find_node() does. However, - * instead of returning a pointer to a node that compares equal to @k, this - * searches for a slot to insert a node with key @k. A pointer to the slot is - * returned, and a pointer to the parent of the slot is stored in @p. Both - * can be passed directly to c_rbtree_add(), together with your node to insert. - * - * If there already is a node in the tree, that compares equal to @k, this will - * return NULL and store the conflicting node in @p. In all other cases, - * this will return a pointer (non-NULL) to the empty slot to insert the node - * at. @p will point to the parent node of that slot. - * - * If you want trees that allow duplicate nodes, you better code your own - * insertion function. - * - * Return: Pointer to slot to insert node, or NULL on conflicts. - */ -static inline CRBNode **c_rbtree_find_slot(CRBTree *t, CRBCompareFunc f, const void *k, CRBNode **p) { - CRBNode **i; - - assert(t); - assert(f); - assert(p); - - i = &t->root; - *p = NULL; - while (*i) { - int v = f(t, (void *)k, *i); - *p = *i; - if (v < 0) - i = &(*i)->left; - else if (v > 0) - i = &(*i)->right; - else - return NULL; - } - - return i; -} - -#ifdef __cplusplus -} -#endif |