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 * \copyright 2-Clause BSD License
34 */
35
36 #ifndef UCX_ITERATOR_H
37 #define UCX_ITERATOR_H
38
39 #include "common.h"
40
41 struct cx_iterator_base_s {
42 /**
43 * True iff the iterator points to valid data.
44 */
45 __attribute__ ((__nonnull__))
46 bool (*valid)(void const *);
47
48 /**
49 * Returns a pointer to the current element.
50 *
51 * When valid returns false, the behavior of this function is undefined.
52 */
53 __attribute__ ((__nonnull__))
54 void *(*current)(void const *);
55
56 /**
57 * Original implementation in case the function needs to be wrapped.
58 */
59 __attribute__ ((__nonnull__))
60 void *(*current_impl)(void const *);
61
62 /**
63 * Advances the iterator.
64 *
65 * When valid returns false, the behavior of this function is undefined.
66 */
67 __attribute__ ((__nonnull__))
68 void (*next)(void *);
69 /**
70 * Indicates whether this iterator may remove elements.
71 */
72 bool mutating;
73 /**
74 * Internal flag for removing the current element when advancing.
75 */
76 bool remove;
77 };
78
79 /**
80 * Declares base attributes for an iterator.
81 */
82 #define CX_ITERATOR_BASE struct cx_iterator_base_s base
83
84 /**
85 * Internal iterator struct - use CxIterator.
86 */
87 struct cx_iterator_s {
88 CX_ITERATOR_BASE;
89
90 /**
91 * Handle for the current element.
92 */
93 void *elem_handle;
94
95 /**
96 * Handle for the source collection, if any.
97 */
98 union {
99 /**
100 * Access for mutating iterators.
101 */
102 void *m;
103 /**
104 * Access for normal iterators.
105 */
106 void const *c;
107 } src_handle;
108
109 /**
110 * Field for storing a key-value pair.
111 * May be used by iterators that iterate over k/v-collections.
112 */
113 struct {
114 /**
115 * A pointer to the key.
116 */
117 void const *key;
118 /**
119 * A pointer to the value.
120 */
121 void *value;
122 } kv_data;
123
124 /**
125 * Field for storing a slot number.
126 * May be used by iterators that iterate over multi-bucket collections.
127 */
128 size_t slot;
129
130 /**
131 * If the iterator is position-aware, contains the index of the element in the underlying collection.
132 * Otherwise, this field is usually uninitialized.
133 */
134 size_t index;
135
136 /**
137 * The size of an individual element.
138 */
139 size_t elem_size;
140
141 /**
142 * May contain the total number of elements, if known.
143 * Shall be set to \c SIZE_MAX when the total number is unknown during iteration.
144 */
145 size_t elem_count;
146 };
147
148 /**
149 * Iterator type.
150 *
151 * An iterator points to a certain element in a (possibly unbounded) chain of elements.
152 * Iterators that are based on collections (which have a defined "first" element), are supposed
153 * to be "position-aware", which means that they keep track of the current index within the collection.
154 *
155 * @note Objects that are pointed to by an iterator are always mutable through that iterator. However,
156 * any concurrent mutation of the collection other than by this iterator makes this iterator invalid
157 * and it must not be used anymore.
158 */
159 typedef struct cx_iterator_s CxIterator;
160
161 /**
162 * Checks if the iterator points to valid data.
163 *
164 * This is especially false for past-the-end iterators.
165 *
166 * @param iter the iterator
167 * @return true iff the iterator points to valid data
168 */
169 #define cxIteratorValid(iter) (iter).base.valid(&(iter))
170
171 /**
172 * Returns a pointer to the current element.
173 *
174 * The behavior is undefined if this iterator is invalid.
175 *
176 * @param iter the iterator
177 * @return a pointer to the current element
178 */
179 #define cxIteratorCurrent(iter) (iter).base.current(&iter)
180
181 /**
182 * Advances the iterator to the next element.
183 *
184 * @param iter the iterator
185 */
186 #define cxIteratorNext(iter) (iter).base.next(&iter)
187
188 /**
189 * Flags the current element for removal, if this iterator is mutating.
190 *
191 * @param iter the iterator
192 */
193 #define cxIteratorFlagRemoval(iter) (iter).base.remove |= (iter).base.mutating
194
195 /**
196 * Loops over an iterator.
197 * @param type the type of the elements
198 * @param elem the name of the iteration variable
199 * @param iter the iterator
200 */
201 #define cx_foreach(type, elem, iter) \
202 for (type elem; cxIteratorValid(iter) && (elem = (type)cxIteratorCurrent(iter)) != NULL ; cxIteratorNext(iter))
203
204
205 /**
206 * Creates an iterator for the specified plain array.
207 *
208 * The \p array can be \c NULL in which case the iterator will be immediately
209 * initialized such that #cxIteratorValid() returns \c false.
210 *
211 *
212 * @param array a pointer to the array (can be \c NULL)
213 * @param elem_size the size of one array element
214 * @param elem_count the number of elements in the array
215 * @return an iterator for the specified array
216 */
217 __attribute__((__warn_unused_result__))
218 CxIterator cxIterator(
219 void const *array,
220 size_t elem_size,
221 size_t elem_count
222 );
223
224 /**
225 * Creates a mutating iterator for the specified plain array.
226 *
227 * While the iterator is in use, the array may only be altered by removing
228 * elements through #cxIteratorFlagRemoval(). Every other change to the array
229 * will bring this iterator to an undefined state.
230 *
231 * When \p remove_keeps_order is set to \c false, removing an element will only
232 * move the last element to the position of the removed element, instead of
233 * moving all subsequent elements by one. Usually, when the order of elements is
234 * not important, this parameter should be set to \c false.
235 *
236 * The \p array can be \c NULL in which case the iterator will be immediately
237 * initialized such that #cxIteratorValid() returns \c false.
238 *
239 *
240 * @param array a pointer to the array (can be \c NULL)
241 * @param elem_size the size of one array element
242 * @param elem_count the number of elements in the array
243 * @param remove_keeps_order \c true if the order of elements must be preserved
244 * when removing an element
245 * @return an iterator for the specified array
246 */
247 __attribute__((__warn_unused_result__))
248 CxIterator cxMutIterator(
249 void *array,
250 size_t elem_size,
251 size_t elem_count,
252 bool remove_keeps_order
253 );
254
255 #endif // UCX_ITERATOR_H
256