Thu, 15 Feb 2024 21:54:43 +0100
add cx_tree_search() - relates to #165
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
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27 */
29 #include "cx/tree.h"
31 #include "cx/array_list.h"
33 #include <assert.h>
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)
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 }
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 }
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;
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 }
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;
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 }
111 // create a working stack
112 size_t work_cap = 32;
113 size_t work_size = 0;
114 void const **work = malloc(sizeof(void*) * work_cap);
115 #define work_add(node) cx_array_add(&work, &work_size, &work_cap, \
116 sizeof(void*), &(node), cx_array_default_reallocator)
118 // add the children of root to the working stack
119 {
120 void *c = tree_children(root);
121 while (c != NULL) {
122 work_add(c);
123 c = tree_next(c);
124 }
125 }
127 // remember a candidate for adding the data
128 // also remember the exact return code from sfunc
129 void *candidate = NULL;
130 int ret_candidate = -1;
132 // process the working stack
133 while (work_size > 0) {
134 // pop element
135 void const *node = work[--work_size];
137 // apply the search function
138 ret = sfunc(node, data);
140 if (ret == 0) {
141 // if found, exit the search
142 *result = (void*) node;
143 work_size = 0;
144 break;
145 } else if (ret > 0) {
146 // if children might contain the data, add them to the stack
147 void *c = tree_children(node);
148 while (c != NULL) {
149 work_add(c);
150 c = tree_next(c);
151 }
153 // remember this node in case no child is suitable
154 if (ret_candidate < 0 || ret < ret_candidate) {
155 candidate = (void *) node;
156 ret_candidate = ret;
157 }
158 }
159 }
161 // not found, but was there a candidate?
162 if (ret != 0 && candidate != NULL) {
163 ret = ret_candidate;
164 *result = candidate;
165 }
167 // free the working queue and return
168 #undef workq_add
169 free(work);
170 return ret;
171 }