src/cx/iterator.h@ac5e7f789048
src/cx/iterator.h
Sat, 26 Nov 2022 16:58:41 +0100
- author
- Mike Becker <universe@uap-core.de>
- date
- Sat, 26 Nov 2022 16:58:41 +0100
- changeset 630
- ac5e7f789048
- parent 628
- 1e2be40f0cb5
- child 641
- d402fead3386
- permissions
- -rw-r--r--
separate iterators and mutating iterators
Trade tons of code duplication for const-correctness.
1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
3 *
4 * Copyright 2021 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 iterator.h
30 * \brief Interface for iterator implementations.
31 * \author Mike Becker
32 * \author Olaf Wintermann
33 * \version 3.0
34 * \copyright 2-Clause BSD License
35 */
37 #ifndef UCX_ITERATOR_H
38 #define UCX_ITERATOR_H
40 #include "common.h"
42 /**
43 * The base of mutating and non-mutating iterators.
44 */
45 struct cx_iterator_base_s {
46 /**
47 * True iff the iterator points to valid data.
48 */
49 __attribute__ ((__nonnull__))
50 bool (*valid)(void const *);
52 /**
53 * Returns a pointer to the current element.
54 */
55 __attribute__ ((__nonnull__))
56 void *(*current)(void const *);
58 /**
59 * Advances the iterator.
60 */
61 __attribute__ ((__nonnull__))
62 void (*next)(void *);
64 /**
65 * Flag current element for removal, if possible.
66 */
67 __attribute__ ((__nonnull__))
68 bool (*flag_removal)(void *);
70 /**
71 * Indicates whether this iterator is muting.
72 */
73 bool mutating;
75 /**
76 * Internal flag for removing the current element when advancing.
77 */
78 bool remove;
79 };
81 /**
82 * Internal iterator struct - use CxMutIterator.
83 */
84 struct cx_mut_iterator_s {
86 /**
87 * The base properties of this iterator.
88 */
89 struct cx_iterator_base_s base;
91 /**
92 * Handle for the current element, if required.
93 */
94 void *elem_handle;
96 /**
97 * Handle for the source collection, if any.
98 */
99 void *src_handle;
101 /**
102 * Field for storing a key-value pair.
103 * May be used by iterators that iterate over k/v-collections.
104 */
105 struct {
106 /**
107 * A pointer to the key.
108 */
109 void const *key;
110 /**
111 * A pointer to the value.
112 */
113 void *value;
114 } kv_data;
116 /**
117 * Field for storing a slot number.
118 * May be used by iterators that iterate over multi-bucket collections.
119 */
120 size_t slot;
122 /**
123 * If the iterator is position-aware, contains the index of the element in the underlying collection.
124 * Otherwise, this field is usually uninitialized.
125 */
126 size_t index;
127 };
129 /**
130 * Mutating iterator value type.
131 *
132 * An iterator points to a certain element in an (possibly unbounded) chain of elements.
133 * Iterators that are based on collections (which have a defined "first" element), are supposed
134 * to be "position-aware", which means that they keep track of the current index within the collection.
135 *
136 * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
137 * iterator is based on a collection and the underlying collection is mutated by other means than this iterator
138 * (e.g. elements added or removed), the iterator becomes invalid (regardless of what cxIteratorValid() returns)
139 * and MUST be re-obtained from the collection.
140 *
141 * @see CxIterator
142 */
143 typedef struct cx_mut_iterator_s CxMutIterator;
145 /**
146 * Internal iterator struct - use CxIterator.
147 */
148 struct cx_iterator_s {
150 /**
151 * The base properties of this iterator.
152 */
153 struct cx_iterator_base_s base;
155 /**
156 * Handle for the current element, if required.
157 */
158 void *elem_handle;
160 /**
161 * Handle for the source collection, if any.
162 */
163 void const *src_handle;
165 /**
166 * Field for storing a key-value pair.
167 * May be used by iterators that iterate over k/v-collections.
168 */
169 struct {
170 /**
171 * A pointer to the key.
172 */
173 void const *key;
174 /**
175 * A pointer to the value.
176 */
177 void *value;
178 } kv_data;
180 /**
181 * Field for storing a slot number.
182 * May be used by iterators that iterate over multi-bucket collections.
183 */
184 size_t slot;
186 /**
187 * If the iterator is position-aware, contains the index of the element in the underlying collection.
188 * Otherwise, this field is usually uninitialized.
189 */
190 size_t index;
191 };
193 /**
194 * Iterator value type.
195 * An iterator points to a certain element in an (possibly unbounded) chain of elements.
196 * Iterators that are based on collections (which have a defined "first" element), are supposed
197 * to be "position-aware", which means that they keep track of the current index within the collection.
198 *
199 * @note Objects that are pointed to by an iterator are always mutable through that iterator. However,
200 * this iterator cannot mutate the collection itself (add or remove elements) and any mutation of the
201 * collection by other means make this iterator invalid (regardless of what cxIteratorValid() returns).
202 *
203 * @see CxMutIterator
204 */
205 typedef struct cx_iterator_s CxIterator;
207 /**
208 * Checks if the iterator points to valid data.
209 *
210 * This is especially false for past-the-end iterators.
211 *
212 * @param iter the iterator
213 * @return true iff the iterator points to valid data
214 */
215 #define cxIteratorValid(iter) (iter).base.valid(&(iter))
217 /**
218 * Returns a pointer to the current element.
219 *
220 * The behavior is undefined if this iterator is invalid.
221 *
222 * @param iter the iterator
223 * @return a pointer to the current element
224 */
225 #define cxIteratorCurrent(iter) (iter).base.current(&iter)
227 /**
228 * Advances the iterator to the next element.
229 *
230 * @param iter the iterator
231 */
232 #define cxIteratorNext(iter) (iter).base.next(&iter)
234 /**
235 * Flags the current element for removal.
236 *
237 * @param iter the iterator
238 * @return false if this iterator cannot remove the element
239 */
240 #define cxIteratorFlagRemoval(iter) (iter).base.flag_removal(&iter)
242 /**
243 * Loops over an iterator.
244 * @param type the type of the elements
245 * @param elem the name of the iteration variable
246 * @param iter the iterator
247 */
248 #define cx_foreach(type, elem, iter) \
249 for (type elem; cxIteratorValid(iter) && (elem = (type)cxIteratorCurrent(iter)) != NULL ; cxIteratorNext(iter))
251 #endif // UCX_ITERATOR_H
