src/cx/tree.h@13068743197f
src/cx/tree.h
Mon, 19 Feb 2024 22:08:09 +0100
- author
- Mike Becker <universe@uap-core.de>
- date
- Mon, 19 Feb 2024 22:08:09 +0100
- changeset 835
- 13068743197f
- parent 833
- 5c926801f052
- child 840
- 4f02995ce44e
- permissions
- -rw-r--r--
set tree iterator stack pointer to NULL on dispose to avoid accidental double-frees
1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
3 *
4 * Copyright 2024 Mike Becker, Olaf Wintermann All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28 /**
29 * \file tree.h
30 * \brief Interface for tree implementations.
31 * \author Mike Becker
32 * \author Olaf Wintermann
33 * \copyright 2-Clause BSD License
34 */
36 #ifndef UCX_TREE_H
37 #define UCX_TREE_H
39 #include "common.h"
41 #include "iterator.h"
43 #ifdef __cplusplus
44 extern "C" {
45 #endif
47 /**
48 * Tree iterator.
49 *
50 * This iterator is not position-aware in a strict sense, as it does not assume a particular order of elements in the
51 * tree. However, the iterator keeps track of the number of nodes it has passed in a counter variable.
52 * Each node, regardless of the number of passes, is counted only once.
53 *
54 * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
55 * underlying data structure is mutated by other means than this iterator (e.g. elements added or removed),
56 * the iterator becomes invalid (regardless of what cxIteratorValid() returns).
57 *
58 * @see CxIterator
59 */
60 typedef struct cx_tree_iterator_s {
61 /**
62 * The base properties of this iterator.
63 */
64 struct cx_iterator_base_s base;
65 /**
66 * Set to true, when the iterator shall visit a node again
67 * when all it's children have been processed.
68 */
69 bool visit_on_exit;
70 /**
71 * True, if this iterator is currently leaving the node.
72 */
73 bool exiting;
74 /**
75 * Offset in the node struct for the children linked list.
76 */
77 off_t loc_children;
78 /**
79 * Offset in the node struct for the next pointer.
80 */
81 off_t loc_next;
82 /**
83 * The total number of distinct nodes that have been passed so far.
84 */
85 size_t counter;
86 /**
87 * The currently observed node.
88 *
89 * This is the same what cxIteratorCurrent() would return.
90 */
91 void *node;
92 /**
93 * Internal stack.
94 * Will be automatically freed once the iterator becomes invalid.
95 *
96 * If you want to discard the iterator before, you need to manually
97 * call cxTreeIteratorDispose().
98 */
99 void **stack;
100 /**
101 * Internal capacity of the stack.
102 */
103 size_t stack_capacity;
104 union {
105 /**
106 * Internal stack size.
107 */
108 size_t stack_size;
109 /**
110 * The current depth in the tree.
111 */
112 size_t depth;
113 };
114 } CxTreeIterator;
116 /**
117 * Releases internal memory of the given tree iterator.
118 * @param iter the iterator
119 */
120 static inline void cxTreeIteratorDispose(CxTreeIterator *iter) {
121 free(iter->stack);
122 iter->stack = NULL;
123 }
125 /**
126 * Links a node to a (new) parent.
127 *
128 * If the node has already a parent, it is unlinked, first.
129 * If the parent has children already, the node is prepended to the list
130 * of all currently existing children.
131 *
132 * @param parent the parent node
133 * @param node the node that shall be linked
134 * @param loc_parent offset in the node struct for the parent pointer
135 * @param loc_children offset in the node struct for the children linked list
136 * @param loc_prev offset in the node struct for the prev pointer
137 * @param loc_next offset in the node struct for the next pointer
138 * @see cx_tree_unlink()
139 */
140 __attribute__((__nonnull__))
141 void cx_tree_link(
142 void * restrict parent,
143 void * restrict node,
144 ptrdiff_t loc_parent,
145 ptrdiff_t loc_children,
146 ptrdiff_t loc_prev,
147 ptrdiff_t loc_next
148 );
150 /**
151 * Unlinks a node from its parent.
152 *
153 * If the node has no parent, this function does nothing.
154 *
155 * @param node the node that shall be unlinked from its parent
156 * @param loc_parent offset in the node struct for the parent pointer
157 * @param loc_children offset in the node struct for the children linked list
158 * @param loc_prev offset in the node struct for the prev pointer
159 * @param loc_next offset in the node struct for the next pointer
160 * @see cx_tree_link()
161 */
162 __attribute__((__nonnull__))
163 void cx_tree_unlink(
164 void *node,
165 ptrdiff_t loc_parent,
166 ptrdiff_t loc_children,
167 ptrdiff_t loc_prev,
168 ptrdiff_t loc_next
169 );
171 /**
172 * Function pointer for a search function.
173 *
174 * A function of this kind shall check if the specified \p node
175 * contains the given \p data or if one of the children might contain
176 * the data.
177 *
178 * The function should use the returned integer to indicate how close the
179 * match is, where a negative number means that it does not match at all.
180 *
181 * For example if a tree stores file path information, a node that is
182 * describing a parent directory of a filename that is searched, shall
183 * return a positive number to indicate that a child node might contain the
184 * searched item. On the other hand, if the node denotes a path that is not a
185 * prefix of the searched filename, the function would return -1 to indicate
186 * that * the search does not need to be continued in that branch.
187 *
188 * @param node the node that is currently investigated
189 * @param data the data that is searched for
190 *
191 * @return 0 if the node contains the data,
192 * positive if one of the children might contain the data,
193 * negative if neither the node, nor the children contains the data
194 */
195 typedef int (*cx_tree_search_func)(void const *node, void const* data);
198 /**
199 * Searches for data in a tree.
200 *
201 * When the data cannot be found exactly, the search function might return a
202 * closest result which might be a good starting point for adding a new node
203 * to the tree.
204 *
205 * Depending on the tree structure it is not necessarily guaranteed that the
206 * "closest" match is uniquely defined. This function will search for a node
207 * with the best match according to the \p sfunc (meaning: the return value of
208 * \p sfunc which is closest to zero). If that is also ambiguous, an arbitrary
209 * node matching the criteria is returned.
210 *
211 * @param root the root node
212 * @param data the data to search for
213 * @param sfunc the search function
214 * @param result where the result shall be stored
215 * @param loc_children offset in the node struct for the children linked list
216 * @param loc_next offset in the node struct for the next pointer
217 * @return zero if the node was found exactly, positive if a node was found that
218 * could contain the node (but doesn't right now), negative if the tree does not
219 * contain any node that might be related to the searched data
220 */
221 __attribute__((__nonnull__))
222 int cx_tree_search(
223 void const *root,
224 void const *data,
225 cx_tree_search_func sfunc,
226 void **result,
227 ptrdiff_t loc_children,
228 ptrdiff_t loc_next
229 );
231 /**
232 * Creates an iterator for a tree with the specified root node.
233 *
234 * @note A tree iterator needs to maintain a stack of visited nodes, which is allocated using stdlib malloc().
235 * When the iterator becomes invalid, this memory is automatically released. However, if you wish to cancel the
236 * iteration before the iterator becomes invalid by itself, you MUST call cxTreeIteratorDispose() manually to release
237 * the memory.
238 *
239 * @remark At the moment, the returned iterator does not support cxIteratorFlagRemoval().
240 *
241 * @param root the root node
242 * @param visit_on_exit set to true, when the iterator shall visit a node again after processing all children
243 * @param loc_children offset in the node struct for the children linked list
244 * @param loc_next offset in the node struct for the next pointer
245 * @return the new tree iterator
246 * @see cxTreeIteratorDispose()
247 */
248 __attribute__((__nonnull__))
249 CxTreeIterator cx_tree_iterator(
250 void *root,
251 bool visit_on_exit,
252 ptrdiff_t loc_children,
253 ptrdiff_t loc_next
254 );
256 #ifdef __cplusplus
257 } // extern "C"
258 #endif
260 #endif //UCX_TREE_H
