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comparison: ucx/cx/iterator.h

ucx/cx/iterator.h

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

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