2 * avl_tree.h - intrusive, nonrecursive AVL tree data structure (self-balancing
3 * binary search tree), header file
5 * The following copying information applies to this specific source code file:
7 * Written in 2014-2016 by Eric Biggers <ebiggers3@gmail.com>
9 * To the extent possible under law, the author(s) have dedicated all copyright
10 * and related and neighboring rights to this software to the public domain
11 * worldwide via the Creative Commons Zero 1.0 Universal Public Domain
12 * Dedication (the "CC0").
14 * This software is distributed in the hope that it will be useful, but WITHOUT
15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
16 * FOR A PARTICULAR PURPOSE. See the CC0 for more details.
18 * You should have received a copy of the CC0 along with this software; if not
19 * see <http://creativecommons.org/publicdomain/zero/1.0/>.
25 #include "wimlib/types.h"
26 #define AVL_INLINE forceinline
28 /* Node in an AVL tree. Embed this in some other data structure. */
29 struct avl_tree_node {
31 /* Pointer to left child or NULL */
32 struct avl_tree_node *left;
34 /* Pointer to right child or NULL */
35 struct avl_tree_node *right;
37 /* Pointer to parent combined with the balance factor. This saves 4 or
38 * 8 bytes of memory depending on the CPU architecture.
40 * Low 2 bits: One greater than the balance factor of this subtree,
41 * which is equal to height(right) - height(left). The mapping is:
48 * The rest of the bits are the pointer to the parent node. It must be
49 * 4-byte aligned, and it will be NULL if this is the root node and
50 * therefore has no parent. */
51 uintptr_t parent_balance;
54 /* Cast an AVL tree node to the containing data structure. */
55 #define avl_tree_entry(entry, type, member) \
56 ((type*) ((char *)(entry) - offsetof(type, member)))
58 /* Returns a pointer to the parent of the specified AVL tree node, or NULL if it
59 * is already the root of the tree. */
60 static AVL_INLINE struct avl_tree_node *
61 avl_get_parent(const struct avl_tree_node *node)
63 return (struct avl_tree_node *)(node->parent_balance & ~3);
66 /* (Internal use only) */
68 avl_tree_rebalance_after_insert(struct avl_tree_node **root_ptr,
69 struct avl_tree_node *inserted);
72 * Looks up an item in the specified AVL tree.
75 * Pointer to the root of the AVL tree. (This can be NULL --- that just
76 * means the tree is empty.)
79 * First argument to pass to the comparison callback. This generally
80 * should be a pointer to an object equal to the one being searched for.
83 * Comparison callback. Must return < 0, 0, or > 0 if the first argument
84 * is less than, equal to, or greater than the second argument,
85 * respectively. The first argument will be @cmp_ctx and the second
86 * argument will be a pointer to the AVL tree node of an item in the tree.
88 * Returns a pointer to the AVL tree node of the resulting item, or NULL if the
93 * struct int_wrapper {
95 * struct avl_tree_node index_node;
98 * static int _avl_cmp_int_to_node(const void *intptr,
99 * const struct avl_tree_node *nodeptr)
101 * int n1 = *(const int *)intptr;
102 * int n2 = avl_tree_entry(nodeptr, struct int_wrapper, index_node)->data;
111 * bool contains_int(struct avl_tree_node *root, int n)
113 * struct avl_tree_node *result;
115 * result = avl_tree_lookup(root, &n, _avl_cmp_int_to_node);
116 * return result ? true : false;
119 static AVL_INLINE struct avl_tree_node *
120 avl_tree_lookup(const struct avl_tree_node *root,
122 int (*cmp)(const void *, const struct avl_tree_node *))
124 const struct avl_tree_node *cur = root;
127 int res = (*cmp)(cmp_ctx, cur);
135 return (struct avl_tree_node*)cur;
138 /* Same as avl_tree_lookup(), but uses a more specific type for the comparison
139 * function. Specifically, with this function the item being searched for is
140 * expected to be in the same format as those already in the tree, with an
141 * embedded 'struct avl_tree_node'. */
142 static AVL_INLINE struct avl_tree_node *
143 avl_tree_lookup_node(const struct avl_tree_node *root,
144 const struct avl_tree_node *node,
145 int (*cmp)(const struct avl_tree_node *,
146 const struct avl_tree_node *))
148 return avl_tree_lookup(root,
150 (int (*) (const void *,
151 const struct avl_tree_node *))cmp);
155 * Inserts an item into the specified AVL tree.
158 * Location of the AVL tree's root pointer. Indirection is needed because
159 * the root node may change as a result of rotations caused by the
160 * insertion. Initialize *root_ptr to NULL for an empty tree.
163 * Pointer to the `struct avl_tree_node' embedded in the item to insert.
164 * No members in it need be pre-initialized, although members in the
165 * containing structure should be pre-initialized so that @cmp can use them
169 * Comparison callback. Must return < 0, 0, or > 0 if the first argument
170 * is less than, equal to, or greater than the second argument,
171 * respectively. The first argument will be @item and the second
172 * argument will be a pointer to an AVL tree node embedded in some
173 * previously-inserted item to which @item is being compared.
175 * If no item in the tree is comparatively equal (via @cmp) to @item, inserts
176 * @item and returns NULL. Otherwise does nothing and returns a pointer to the
177 * AVL tree node embedded in the previously-inserted item which compared equal
182 * struct int_wrapper {
184 * struct avl_tree_node index_node;
187 * #define GET_DATA(i) avl_tree_entry((i), struct int_wrapper, index_node)->data
189 * static int _avl_cmp_ints(const struct avl_tree_node *node1,
190 * const struct avl_tree_node *node2)
192 * int n1 = GET_DATA(node1);
193 * int n2 = GET_DATA(node2);
202 * bool insert_int(struct avl_tree_node **root_ptr, int data)
204 * struct int_wrapper *i = malloc(sizeof(struct int_wrapper));
206 * if (avl_tree_insert(root_ptr, &i->index_node, _avl_cmp_ints)) {
214 static AVL_INLINE struct avl_tree_node *
215 avl_tree_insert(struct avl_tree_node **root_ptr,
216 struct avl_tree_node *item,
217 int (*cmp)(const struct avl_tree_node *,
218 const struct avl_tree_node *))
220 struct avl_tree_node **cur_ptr = root_ptr, *cur = NULL;
225 res = (*cmp)(item, cur);
227 cur_ptr = &cur->left;
229 cur_ptr = &cur->right;
234 item->parent_balance = (uintptr_t)cur | 1;
235 avl_tree_rebalance_after_insert(root_ptr, item);
239 /* Removes an item from the specified AVL tree.
240 * See implementation for details. */
242 avl_tree_remove(struct avl_tree_node **root_ptr, struct avl_tree_node *node);
244 /* Nonrecursive AVL tree traversal functions */
246 extern struct avl_tree_node *
247 avl_tree_first_in_order(const struct avl_tree_node *root);
249 extern struct avl_tree_node *
250 avl_tree_last_in_order(const struct avl_tree_node *root);
252 extern struct avl_tree_node *
253 avl_tree_next_in_order(const struct avl_tree_node *node);
255 extern struct avl_tree_node *
256 avl_tree_prev_in_order(const struct avl_tree_node *node);
258 extern struct avl_tree_node *
259 avl_tree_first_in_postorder(const struct avl_tree_node *root);
261 extern struct avl_tree_node *
262 avl_tree_next_in_postorder(const struct avl_tree_node *prev,
263 const struct avl_tree_node *prev_parent);
266 * Iterate through the nodes in an AVL tree in sorted order.
267 * You may not modify the tree during the iteration.
270 * Variable that will receive a pointer to each struct inserted into the
273 * Root of the AVL tree.
275 * Type of *child_struct.
277 * Member of @struct_name type that is the AVL tree node.
281 * struct int_wrapper {
283 * struct avl_tree_node index_node;
286 * void print_ints(struct avl_tree_node *root)
288 * struct int_wrapper *i;
290 * avl_tree_for_each_in_order(i, root, struct int_wrapper, index_node)
291 * printf("%d\n", i->data);
294 #define avl_tree_for_each_in_order(child_struct, root, \
295 struct_name, struct_member) \
296 for (struct avl_tree_node *_cur = \
297 avl_tree_first_in_order(root); \
298 _cur && ((child_struct) = \
299 avl_tree_entry(_cur, struct_name, \
300 struct_member), 1); \
301 _cur = avl_tree_next_in_order(_cur))
304 * Like avl_tree_for_each_in_order(), but uses the reverse order.
306 #define avl_tree_for_each_in_reverse_order(child_struct, root, \
307 struct_name, struct_member) \
308 for (struct avl_tree_node *_cur = \
309 avl_tree_last_in_order(root); \
310 _cur && ((child_struct) = \
311 avl_tree_entry(_cur, struct_name, \
312 struct_member), 1); \
313 _cur = avl_tree_prev_in_order(_cur))
316 * Like avl_tree_for_each_in_order(), but iterates through the nodes in
317 * postorder, so the current node may be deleted or freed.
319 #define avl_tree_for_each_in_postorder(child_struct, root, \
320 struct_name, struct_member) \
321 for (struct avl_tree_node *_cur = \
322 avl_tree_first_in_postorder(root), *_parent; \
323 _cur && ((child_struct) = \
324 avl_tree_entry(_cur, struct_name, \
326 && (_parent = avl_get_parent(_cur), 1); \
327 _cur = avl_tree_next_in_postorder(_cur, _parent))
329 #endif /* _AVL_TREE_H_ */