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 */
36
37 #ifndef UCX_ITERATOR_H
38 #define UCX_ITERATOR_H
39
40 #include "common.h"
41
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 *);
51
52 /**
53 * Returns a pointer to the current element.
54 *
55 * When valid returns false, the behavior of this function is undefined.
56 */
57 __attribute__ ((__nonnull__))
58 void *(*current)(void const *);
59
60 /**
61 * Original implementation in case the function needs to be wrapped.
62 */
63 __attribute__ ((__nonnull__))
64 void *(*current_impl)(void const *);
65
66 /**
67 * Advances the iterator.
68 *
69 * When valid returns false, the behavior of this function is undefined.
70 */
71 __attribute__ ((__nonnull__))
72 void (*next)(void *);
73
74 /**
75 * Flag current element for removal, if possible.
76 *
77 * When valid returns false, the behavior of this function is undefined.
78 */
79 __attribute__ ((__nonnull__))
80 bool (*flag_removal)(void *);
81
82 /**
83 * Indicates whether this iterator may remove elements.
84 */
85 bool mutating;
86
87 /**
88 * Internal flag for removing the current element when advancing.
89 */
90 bool remove;
91 };
92
93 /**
94 * Internal iterator struct - use CxMutIterator.
95 */
96 struct cx_mut_iterator_s {
97
98 /**
99 * The base properties of this iterator.
100 */
101 struct cx_iterator_base_s base;
102
103 /**
104 * Handle for the current element, if required.
105 */
106 void *elem_handle;
107
108 /**
109 * Handle for the source collection, if any.
110 */
111 void *src_handle;
112
113 /**
114 * Field for storing a key-value pair.
115 * May be used by iterators that iterate over k/v-collections.
116 */
117 struct {
118 /**
119 * A pointer to the key.
120 */
121 void const *key;
122 /**
123 * A pointer to the value.
124 */
125 void *value;
126 } kv_data;
127
128 /**
129 * Field for storing a slot number.
130 * May be used by iterators that iterate over multi-bucket collections.
131 */
132 size_t slot;
133
134 /**
135 * If the iterator is position-aware, contains the index of the element in the underlying collection.
136 * Otherwise, this field is usually uninitialized.
137 */
138 size_t index;
139 };
140
141 /**
142 * Mutating iterator value type.
143 *
144 * An iterator points to a certain element in an (possibly unbounded) chain of elements.
145 * Iterators that are based on collections (which have a defined "first" element), are supposed
146 * to be "position-aware", which means that they keep track of the current index within the collection.
147 *
148 * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
149 * iterator is based on a collection and the underlying collection is mutated by other means than this iterator
150 * (e.g. elements added or removed), the iterator becomes invalid (regardless of what cxIteratorValid() returns)
151 * and MUST be re-obtained from the collection.
152 *
153 * @see CxIterator
154 */
155 typedef struct cx_mut_iterator_s CxMutIterator;
156
157 /**
158 * Internal iterator struct - use CxIterator.
159 */
160 struct cx_iterator_s {
161
162 /**
163 * The base properties of this iterator.
164 */
165 struct cx_iterator_base_s base;
166
167 /**
168 * Handle for the current element, if required.
169 */
170 void *elem_handle;
171
172 /**
173 * Handle for the source collection, if any.
174 */
175 void const *src_handle;
176
177 /**
178 * Field for storing a key-value pair.
179 * May be used by iterators that iterate over k/v-collections.
180 */
181 struct {
182 /**
183 * A pointer to the key.
184 */
185 void const *key;
186 /**
187 * A pointer to the value.
188 */
189 void *value;
190 } kv_data;
191
192 /**
193 * Field for storing a slot number.
194 * May be used by iterators that iterate over multi-bucket collections.
195 */
196 size_t slot;
197
198 /**
199 * If the iterator is position-aware, contains the index of the element in the underlying collection.
200 * Otherwise, this field is usually uninitialized.
201 */
202 size_t index;
203 };
204
205 /**
206 * Iterator value type.
207 * An iterator points to a certain element in a (possibly unbounded) chain of elements.
208 * Iterators that are based on collections (which have a defined "first" element), are supposed
209 * to be "position-aware", which means that they keep track of the current index within the collection.
210 *
211 * @note Objects that are pointed to by an iterator are always mutable through that iterator. However,
212 * this iterator cannot mutate the collection itself (add or remove elements) and any mutation of the
213 * collection by other means makes this iterator invalid (regardless of what cxIteratorValid() returns).
214 *
215 * @see CxMutIterator
216 */
217 typedef struct cx_iterator_s CxIterator;
218
219 /**
220 * Checks if the iterator points to valid data.
221 *
222 * This is especially false for past-the-end iterators.
223 *
224 * @param iter the iterator
225 * @return true iff the iterator points to valid data
226 */
227 #define cxIteratorValid(iter) (iter).base.valid(&(iter))
228
229 /**
230 * Returns a pointer to the current element.
231 *
232 * The behavior is undefined if this iterator is invalid.
233 *
234 * @param iter the iterator
235 * @return a pointer to the current element
236 */
237 #define cxIteratorCurrent(iter) (iter).base.current(&iter)
238
239 /**
240 * Advances the iterator to the next element.
241 *
242 * @param iter the iterator
243 */
244 #define cxIteratorNext(iter) (iter).base.next(&iter)
245
246 /**
247 * Flags the current element for removal.
248 *
249 * @param iter the iterator
250 * @return false if this iterator cannot remove the element
251 */
252 #define cxIteratorFlagRemoval(iter) (iter).base.flag_removal(&iter)
253
254 /**
255 * Loops over an iterator.
256 * @param type the type of the elements
257 * @param elem the name of the iteration variable
258 * @param iter the iterator
259 */
260 #define cx_foreach(type, elem, iter) \
261 for (type elem; cxIteratorValid(iter) && (elem = (type)cxIteratorCurrent(iter)) != NULL ; cxIteratorNext(iter))
262
263 #endif // UCX_ITERATOR_H
264