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)(const void *);
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)(const void *);
55
56 /**
57 * Original implementation in case the function needs to be wrapped.
58 */
59 __attribute__ ((__nonnull__))
60 void *(*current_impl)(const void *);
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 * Must be the first member of an iterator structure.
82 */
83 #define CX_ITERATOR_BASE struct cx_iterator_base_s base
84
85 /**
86 * Internal iterator struct - use CxIterator.
87 */
88 struct cx_iterator_s {
89 CX_ITERATOR_BASE;
90
91 /**
92 * Handle for the current element.
93 */
94 void *elem_handle;
95
96 /**
97 * Handle for the source collection, if any.
98 */
99 union {
100 /**
101 * Access for mutating iterators.
102 */
103 void *m;
104 /**
105 * Access for normal iterators.
106 */
107 const void *c;
108 } src_handle;
109
110 /**
111 * Field for storing a key-value pair.
112 * May be used by iterators that iterate over k/v-collections.
113 */
114 struct {
115 /**
116 * A pointer to the key.
117 */
118 const void *key;
119 /**
120 * A pointer to the value.
121 */
122 void *value;
123 } kv_data;
124
125 /**
126 * Field for storing a slot number.
127 * May be used by iterators that iterate over multi-bucket collections.
128 */
129 size_t slot;
130
131 /**
132 * If the iterator is position-aware, contains the index of the element in the underlying collection.
133 * Otherwise, this field is usually uninitialized.
134 */
135 size_t index;
136
137 /**
138 * The size of an individual element.
139 */
140 size_t elem_size;
141
142 /**
143 * May contain the total number of elements, if known.
144 * Shall be set to \c SIZE_MAX when the total number is unknown during iteration.
145 */
146 size_t elem_count;
147 };
148
149 /**
150 * Iterator type.
151 *
152 * An iterator points to a certain element in a (possibly unbounded) chain of elements.
153 * Iterators that are based on collections (which have a defined "first" element), are supposed
154 * to be "position-aware", which means that they keep track of the current index within the collection.
155 *
156 * @note Objects that are pointed to by an iterator are always mutable through that iterator. However,
157 * any concurrent mutation of the collection other than by this iterator makes this iterator invalid
158 * and it must not be used anymore.
159 */
160 typedef struct cx_iterator_s CxIterator;
161
162 /**
163 * Checks if the iterator points to valid data.
164 *
165 * This is especially false for past-the-end iterators.
166 *
167 * @param iter the iterator
168 * @return true iff the iterator points to valid data
169 */
170 #define cxIteratorValid(iter) (iter).base.valid(&(iter))
171
172 /**
173 * Returns a pointer to the current element.
174 *
175 * The behavior is undefined if this iterator is invalid.
176 *
177 * @param iter the iterator
178 * @return a pointer to the current element
179 */
180 #define cxIteratorCurrent(iter) (iter).base.current(&iter)
181
182 /**
183 * Advances the iterator to the next element.
184 *
185 * @param iter the iterator
186 */
187 #define cxIteratorNext(iter) (iter).base.next(&iter)
188
189 /**
190 * Flags the current element for removal, if this iterator is mutating.
191 *
192 * @param iter the iterator
193 */
194 #define cxIteratorFlagRemoval(iter) (iter).base.remove |= (iter).base.mutating
195
196 /**
197 * Obtains a reference to an arbitrary iterator.
198 *
199 * This is useful for APIs that expect some iterator as an argument.
200 *
201 * @param iter the iterator
202 */
203 #define cxIteratorRef(iter) &((iter).base)
204
205 /**
206 * Loops over an iterator.
207 * @param type the type of the elements
208 * @param elem the name of the iteration variable
209 * @param iter the iterator
210 */
211 #define cx_foreach(type, elem, iter) \
212 for (type elem; cxIteratorValid(iter) && (elem = (type)cxIteratorCurrent(iter)) != NULL ; cxIteratorNext(iter))
213
214
215 /**
216 * Creates an iterator for the specified plain array.
217 *
218 * The \p array can be \c NULL in which case the iterator will be immediately
219 * initialized such that #cxIteratorValid() returns \c false.
220 *
221 *
222 * @param array a pointer to the array (can be \c NULL)
223 * @param elem_size the size of one array element
224 * @param elem_count the number of elements in the array
225 * @return an iterator for the specified array
226 */
227 __attribute__((__warn_unused_result__))
228 CxIterator cxIterator(
229 const void *array,
230 size_t elem_size,
231 size_t elem_count
232 );
233
234 /**
235 * Creates a mutating iterator for the specified plain array.
236 *
237 * While the iterator is in use, the array may only be altered by removing
238 * elements through #cxIteratorFlagRemoval(). Every other change to the array
239 * will bring this iterator to an undefined state.
240 *
241 * When \p remove_keeps_order is set to \c false, removing an element will only
242 * move the last element to the position of the removed element, instead of
243 * moving all subsequent elements by one. Usually, when the order of elements is
244 * not important, this parameter should be set to \c false.
245 *
246 * The \p array can be \c NULL in which case the iterator will be immediately
247 * initialized such that #cxIteratorValid() returns \c false.
248 *
249 *
250 * @param array a pointer to the array (can be \c NULL)
251 * @param elem_size the size of one array element
252 * @param elem_count the number of elements in the array
253 * @param remove_keeps_order \c true if the order of elements must be preserved
254 * when removing an element
255 * @return an iterator for the specified array
256 */
257 __attribute__((__warn_unused_result__))
258 CxIterator cxMutIterator(
259 void *array,
260 size_t elem_size,
261 size_t elem_count,
262 bool remove_keeps_order
263 );
264
265 #endif // UCX_ITERATOR_H
266