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 #include "cx/tree.h"
30
31 #include "cx/array_list.h"
32
33 #include <assert.h>
34
35 #define CX_TREE_PTR(cur, off) (*(void**)(((char*)(cur))+(off)))
36 #define CX_TREE_PTR(cur, off) (*(void**)(((char*)(cur))+(off)))
37 #define tree_parent(node) CX_TREE_PTR(node, loc_parent)
38 #define tree_children(node) CX_TREE_PTR(node, loc_children)
39 #define tree_prev(node) CX_TREE_PTR(node, loc_prev)
40 #define tree_next(node) CX_TREE_PTR(node, loc_next)
41
42 void cx_tree_link(
43 void *restrict parent,
44 void *restrict node,
45 ptrdiff_t loc_parent,
46 ptrdiff_t loc_children,
47 ptrdiff_t loc_prev,
48 ptrdiff_t loc_next
49 ) {
50 void *current_parent = tree_parent(node);
51 if (current_parent == parent) return;
52 if (current_parent != NULL) {
53 cx_tree_unlink(node, loc_parent, loc_children,
54 loc_prev, loc_next);
55 }
56
57 if (tree_children(parent) == NULL) {
58 tree_children(parent) = node;
59 } else {
60 void *children = tree_children(parent);
61 tree_prev(children) = node;
62 tree_next(node) = children;
63 tree_children(parent) = node;
64 }
65 tree_parent(node) = parent;
66 }
67
68 void cx_tree_unlink(
69 void *node,
70 ptrdiff_t loc_parent,
71 ptrdiff_t loc_children,
72 ptrdiff_t loc_prev,
73 ptrdiff_t loc_next
74 ) {
75 if (tree_parent(node) == NULL) return;
76
77 void *left = tree_prev(node);
78 void *right = tree_next(node);
79 assert(left == NULL || tree_children(tree_parent(node)) != node);
80 if (left == NULL) {
81 tree_children(tree_parent(node)) = right;
82 } else {
83 tree_next(left) = right;
84 }
85 if (right != NULL) tree_prev(right) = left;
86 tree_parent(node) = NULL;
87 tree_prev(node) = NULL;
88 tree_next(node) = NULL;
89 }
90
91 int cx_tree_search(
92 void const *root,
93 void const *data,
94 cx_tree_search_func sfunc,
95 void **result,
96 ptrdiff_t loc_children,
97 ptrdiff_t loc_next
98 ) {
99 int ret;
100 *result = NULL;
101
102 // shortcut: compare root before doing anything else
103 ret = sfunc(root, data);
104 if (ret < 0) {
105 return ret;
106 } else if (ret == 0 || tree_children(root) == NULL) {
107 *result = (void*)root;
108 return ret;
109 }
110
111 // create a working stack
112 CX_ARRAY_DECLARE(void const*, work);
113 cx_array_initialize(work, 32);
114
115 // add the children of root to the working stack
116 {
117 void *c = tree_children(root);
118 while (c != NULL) {
119 cx_array_simple_add(work, c);
120 c = tree_next(c);
121 }
122 }
123
124 // remember a candidate for adding the data
125 // also remember the exact return code from sfunc
126 void *candidate = NULL;
127 int ret_candidate = -1;
128
129 // process the working stack
130 while (work_size > 0) {
131 // pop element
132 void const *node = work[--work_size];
133
134 // apply the search function
135 ret = sfunc(node, data);
136
137 if (ret == 0) {
138 // if found, exit the search
139 *result = (void*) node;
140 work_size = 0;
141 break;
142 } else if (ret > 0) {
143 // if children might contain the data, add them to the stack
144 void *c = tree_children(node);
145 while (c != NULL) {
146 cx_array_simple_add(work, c);
147 c = tree_next(c);
148 }
149
150 // remember this node in case no child is suitable
151 if (ret_candidate < 0 || ret < ret_candidate) {
152 candidate = (void *) node;
153 ret_candidate = ret;
154 }
155 }
156 }
157
158 // not found, but was there a candidate?
159 if (ret != 0 && candidate != NULL) {
160 ret = ret_candidate;
161 *result = candidate;
162 }
163
164 // free the working queue and return
165 free(work);
166 return ret;
167 }
168
169 static bool cx_tree_iter_valid(void const *it) {
170 struct cx_tree_iterator_s const *iter = it;
171 return iter->node != NULL;
172 }
173
174 static void *cx_tree_iter_current(void const *it) {
175 struct cx_tree_iterator_s const *iter = it;
176 return iter->node;
177 }
178
179 static void cx_tree_iter_next(void *it) {
180 struct cx_tree_iterator_s *iter = it;
181 ptrdiff_t const loc_next = iter->loc_next;
182 ptrdiff_t const loc_children = iter->loc_children;
183
184 void *children;
185
186 // check if we are currently exiting or entering nodes
187 if (iter->exiting) {
188 children = NULL;
189 // skipping on exit is pointless, just clear the flag
190 iter->skip = false;
191 } else {
192 if (iter->skip) {
193 // skip flag is set, pretend that there are no children
194 iter->skip = false;
195 children = NULL;
196 } else {
197 // try to enter the children (if any)
198 children = tree_children(iter->node);
199 }
200 }
201
202 if (children == NULL) {
203 // search for the next node
204 void *next;
205 cx_tree_iter_search_next:
206 // check if there is a sibling
207 if (iter->exiting) {
208 next = iter->node_next;
209 } else {
210 next = tree_next(iter->node);
211 iter->node_next = next;
212 }
213 if (next == NULL) {
214 // no sibling, we are done with this node and exit
215 if (iter->visit_on_exit && !iter->exiting) {
216 // iter is supposed to visit the node again
217 iter->exiting = true;
218 } else {
219 iter->exiting = false;
220 if (iter->depth == 1) {
221 // there is no parent - we have iterated the entire tree
222 // invalidate the iterator and free the node stack
223 iter->node = iter->node_next = NULL;
224 iter->stack_capacity = iter->depth = 0;
225 free(iter->stack);
226 iter->stack = NULL;
227 } else {
228 // the parent node can be obtained from the top of stack
229 // this way we can avoid the loc_parent in the iterator
230 iter->depth--;
231 iter->node = iter->stack[iter->depth - 1];
232 // retry with the parent node to find a sibling
233 goto cx_tree_iter_search_next;
234 }
235 }
236 } else {
237 if (iter->visit_on_exit && !iter->exiting) {
238 // iter is supposed to visit the node again
239 iter->exiting = true;
240 } else {
241 iter->exiting = false;
242 // move to the sibling
243 iter->counter++;
244 iter->node = next;
245 // new top of stack is the sibling
246 iter->stack[iter->depth - 1] = next;
247 }
248 }
249 } else {
250 // node has children, push the first child onto the stack and enter it
251 cx_array_simple_add(iter->stack, children);
252 iter->node = children;
253 iter->counter++;
254 }
255 }
256
257 CxTreeIterator cx_tree_iterator(
258 void *root,
259 bool visit_on_exit,
260 ptrdiff_t loc_children,
261 ptrdiff_t loc_next
262 ) {
263 CxTreeIterator iter;
264 iter.loc_children = loc_children;
265 iter.loc_next = loc_next;
266 iter.visit_on_exit = visit_on_exit;
267
268 // allocate stack
269 iter.stack_capacity = 16;
270 iter.stack = malloc(sizeof(void *) * 16);
271 iter.depth = 0;
272
273 // visit the root node
274 iter.node = root;
275 iter.node_next = NULL;
276 iter.counter = 1;
277 iter.depth = 1;
278 iter.stack[0] = root;
279 iter.exiting = false;
280 iter.skip = false;
281
282 // assign base iterator functions
283 iter.base.mutating = false;
284 iter.base.remove = false;
285 iter.base.current_impl = NULL;
286 iter.base.valid = cx_tree_iter_valid;
287 iter.base.next = cx_tree_iter_next;
288 iter.base.current = cx_tree_iter_current;
289
290 return iter;
291 }
292
293 static bool cx_tree_visitor_valid(void const *it) {
294 struct cx_tree_visitor_s const *iter = it;
295 return iter->node != NULL;
296 }
297
298 static void *cx_tree_visitor_current(void const *it) {
299 struct cx_tree_visitor_s const *iter = it;
300 return iter->node;
301 }
302
303 __attribute__((__nonnull__))
304 static void cx_tree_visitor_enqueue_siblings(
305 struct cx_tree_visitor_s *iter, void *node, ptrdiff_t loc_next) {
306 node = tree_next(node);
307 while (node != NULL) {
308 struct cx_tree_visitor_queue_s *q;
309 q = malloc(sizeof(struct cx_tree_visitor_queue_s));
310 q->depth = iter->queue_last->depth;
311 q->node = node;
312 iter->queue_last->next = q;
313 iter->queue_last = q;
314 node = tree_next(node);
315 }
316 iter->queue_last->next = NULL;
317 }
318
319 static void cx_tree_visitor_next(void *it) {
320 struct cx_tree_visitor_s *iter = it;
321 ptrdiff_t const loc_next = iter->loc_next;
322 ptrdiff_t const loc_children = iter->loc_children;
323
324 // add the children of the current node to the queue
325 // unless the skip flag is set
326 void *children;
327 if (iter->skip) {
328 iter->skip = false;
329 children = NULL;
330 } else {
331 children = tree_children(iter->node);
332 }
333 if (children != NULL) {
334 struct cx_tree_visitor_queue_s *q;
335 q = malloc(sizeof(struct cx_tree_visitor_queue_s));
336 q->depth = iter->depth + 1;
337 q->node = children;
338 if (iter->queue_last == NULL) {
339 assert(iter->queue_next == NULL);
340 iter->queue_next = q;
341 } else {
342 iter->queue_last->next = q;
343 }
344 iter->queue_last = q;
345 cx_tree_visitor_enqueue_siblings(iter, children, loc_next);
346 }
347
348 // check if there is a next node
349 if (iter->queue_next == NULL) {
350 iter->node = NULL;
351 return;
352 }
353
354 // dequeue the next node
355 iter->node = iter->queue_next->node;
356 iter->depth = iter->queue_next->depth;
357 {
358 struct cx_tree_visitor_queue_s *q = iter->queue_next;
359 iter->queue_next = q->next;
360 if (iter->queue_next == NULL) {
361 assert(iter->queue_last == q);
362 iter->queue_last = NULL;
363 }
364 free(q);
365 }
366
367 // increment the node counter
368 iter->counter++;
369 }
370
371 CxTreeVisitor cx_tree_visitor(
372 void *root,
373 ptrdiff_t loc_children,
374 ptrdiff_t loc_next
375 ) {
376 CxTreeVisitor iter;
377 iter.loc_children = loc_children;
378 iter.loc_next = loc_next;
379
380 // allocate stack
381 iter.depth = 0;
382
383 // visit the root node
384 iter.node = root;
385 iter.counter = 1;
386 iter.depth = 1;
387 iter.skip = false;
388 iter.queue_next = NULL;
389 iter.queue_last = NULL;
390
391 // assign base iterator functions
392 iter.base.mutating = false;
393 iter.base.remove = false;
394 iter.base.current_impl = NULL;
395 iter.base.valid = cx_tree_visitor_valid;
396 iter.base.next = cx_tree_visitor_next;
397 iter.base.current = cx_tree_visitor_current;
398
399 return iter;
400 }
401
402