src/cx/iterator.h

Sun, 01 May 2022 10:39:13 +0200

author
Mike Becker <universe@uap-core.de>
date
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child 551
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fix regression: nitems adjusted at the wrong location

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1 /*
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2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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3 *
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4 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
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5 *
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6 * Redistribution and use in source and binary forms, with or without
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7 * modification, are permitted provided that the following conditions are met:
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8 *
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9 * 1. Redistributions of source code must retain the above copyright
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10 * notice, this list of conditions and the following disclaimer.
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11 *
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12 * 2. Redistributions in binary form must reproduce the above copyright
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13 * notice, this list of conditions and the following disclaimer in the
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14 * documentation and/or other materials provided with the distribution.
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15 *
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16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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26 * POSSIBILITY OF SUCH DAMAGE.
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27 */
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28 /**
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29 * \file iterator.h
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30 * \brief Interface for iterator implementations.
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31 * \author Mike Becker
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32 * \author Olaf Wintermann
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33 * \version 3.0
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34 * \copyright 2-Clause BSD License
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35 */
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36
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37 #ifndef UCX_ITERATOR_H
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38 #define UCX_ITERATOR_H
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39
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40 #include "common.h"
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41
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42 /**
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43 * Internal iterator struct - use CxIterator.
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44 */
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45 struct cx_iterator_s {
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46 /**
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47 * True iff the iterator points to valid data.
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48 */
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49 bool (*valid)(struct cx_iterator_s const *) __attribute__ ((__nonnull__));
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50
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51 /**
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52 * Returns a pointer to the current element.
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53 */
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54 void *(*current)(struct cx_iterator_s const *) __attribute__ ((__nonnull__));
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55
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56 /**
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57 * Advances the iterator.
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58 */
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59 void (*next)(struct cx_iterator_s *) __attribute__ ((__nonnull__));
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60
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61 /**
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62 * Handle for the current element, if required.
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63 */
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64 void *elem_handle;
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65
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66 /**
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67 * Handle for the source collection, if any.
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68 */
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69 void *src_handle;
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70
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71 /**
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72 * If the iterator is position-aware, contains the index of the element in the underlying collection.
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73 * Otherwise, this field is usually uninitialized.
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74 */
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75 size_t index;
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76
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77 /**
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78 * Users may set this to true, if the current element shall be removed from the underlying collection
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79 * when the iterator advances.
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80 * Has no effect on iterators that are not based on a collection.
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81 */
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82 bool remove;
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83 };
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84
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85 /**
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86 * Iterator value type.
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87 * An iterator points to a certain element in an (possibly unbounded) chain of elements.
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88 * Iterators that are based on collections (which have a defined "first" element), are supposed
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89 * to be "position-aware", which means that they keep track of the current index within the collection.
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90 *
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91 * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
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92 * iterator is based on a collection and the underlying collection is mutated (elements added or removed),
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93 * the iterator becomes invalid (regardless of what cxIteratorValid() returns) and MUST be re-obtained
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94 * from the collection.
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95 */
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96 typedef struct cx_iterator_s CxIterator;
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97
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98 /**
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99 * Checks if the iterator points to valid data.
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100 *
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101 * This is especially false for past-the-end iterators.
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102 *
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103 * @param iter a pointer to the iterator
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104 * @return true iff the iterator points to valid data
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105 */
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106 __attribute__ ((__nonnull__))
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107 static inline bool cxIteratorValid(CxIterator const *iter) {
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108 return iter->valid(iter);
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109 }
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110
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111 /**
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112 * Returns a pointer to the current element.
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113 *
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114 * The behavior is undefined if this iterator is invalid.
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115 *
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116 * @param iter a pointer to the iterator
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117 * @return a pointer to the current element
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118 */
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119 __attribute__ ((__nonnull__))
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120 static inline void *cxIteratorCurrent(CxIterator const *iter) {
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121 return iter->current(iter);
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122 }
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123
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124 /**
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125 * Advances the iterator to the next element.
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126 *
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127 * @param iter a pointer to the iterator
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128 */
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129 __attribute__ ((__nonnull__))
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130 static inline void cxIteratorNext(CxIterator *iter) {
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131 iter->next(iter);
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132 }
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133
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134 /**
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135 * Loops over an iterator.
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136 * @param type the type of the elements
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137 * @param elem the name of the iteration variable
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138 * @param iter the iterator
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139 */
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140 #define cx_foreach(type, elem, iter) \
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141 for (type elem; cxIteratorValid(&iter) && (elem = (type)cxIteratorCurrent(&iter)) != NULL ; cxIteratorNext(&iter)) // NOLINT(bugprone-macro-parentheses)
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142
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143 #endif /* UCX_ITERATOR_H */

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