1 /*
2  *  Copyright (c) 2020, The OpenThread Authors.
3  *  All rights reserved.
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6  *  modification, are permitted provided that the following conditions are met:
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8  *     notice, this list of conditions and the following disclaimer.
9  *  2. Redistributions in binary form must reproduce the above copyright
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11  *     documentation and/or other materials provided with the distribution.
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14  *     derived from this software without specific prior written permission.
15  *
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27  */
28 
29 /**
30  * @file
31  *   This file includes definitions for a generic item-pointer iterator class.
32  */
33 
34 #ifndef ITERATOR_UTILS_HPP_
35 #define ITERATOR_UTILS_HPP_
36 
37 namespace ot {
38 
39 /**
40  * @addtogroup core-iterator-utils
41  *
42  * @brief
43  *   This module includes definitions for OpenThread generic item-pointer iterator class.
44  *
45  * @{
46  *
47  */
48 
49 /**
50  * This template class is used as a base class for those item-pointer iterators.
51  *
52  * These iterators have common methods and operators like `Advance()` and `++` and hold a pointer to the
53  * object.
54  *
55  * Users of this class should follow CRTP-style inheritance, i.e., `IteratorType` class itself should publicly inherit
56  * from `ItemPtrIterator<ItemType, IteratorType>`.
57  *
58  * @tparam  ItemType      The type of the object that the iterator points to.
59  * @tparam  IteratorType  The Iterator class that inherits this class. The class MUST have a method `Advance()` which
60  *                        moves the pointer to the next. `Advance()` SHALL NOT be called when `IsDone()` is `true` and
61  *                        would set the pointer to `nullptr` when there's no more elements.
62  *
63  */
64 template <typename ItemType, typename IteratorType> class ItemPtrIterator
65 {
66 public:
67     /**
68      * This method indicates whether there are no more items to be accessed (iterator has reached the end).
69      *
70      * @retval TRUE   There are no more items to be accessed (iterator has reached the end).
71      * @retval FALSE  The current item is valid.
72      *
73      */
IsDone(void) const74     bool IsDone(void) const { return mItem == nullptr; }
75 
76     /**
77      * This method overloads `++` operator (pre-increment) to advance the iterator.
78      *
79      * The iterator is moved to point to the next item using IteratorType's `Advance` method.
80      * If there are no more items, the iterator becomes empty (i.e., `operator*` returns `nullptr` and `IsDone()`
81      * returns `true`).
82      *
83      */
operator ++(void)84     void operator++(void) { static_cast<IteratorType *>(this)->Advance(); }
85 
86     /**
87      * This method overloads `++` operator (post-increment) to advance the iterator.
88      *
89      * The iterator is moved to point to the next item using IteratorType's `Advance` method.
90      * If there are no more items, the iterator becomes empty (i.e., `operator*` returns `nullptr` and `IsDone()`
91      * returns `true`).
92      *
93      */
operator ++(int)94     void operator++(int) { static_cast<IteratorType *>(this)->Advance(); }
95 
96     /**
97      * This method overloads the `*` dereference operator and gets a reference to then item to which the iterator is
98      * currently pointing.
99      *
100      * This method MUST be used when the iterator is not empty/finished (i.e., `IsDone()` returns `false`).
101      *
102      * @returns A reference to the item currently pointed by the iterator.
103      *
104      */
operator *(void)105     ItemType &operator*(void) { return *mItem; }
106 
107     /**
108      * This method overloads the `->` dereference operator and gets a pointer to the item to which the iterator is
109      * currently pointing.
110      *
111      * @returns A pointer to the item associated with the iterator, or `nullptr` if iterator is empty/done.
112      *
113      */
operator ->(void)114     ItemType *operator->(void) { return mItem; }
115 
116     /**
117      * This method overloads operator `==` to evaluate whether or not two `Iterator` instances point to the same
118      * item.
119      *
120      * @param[in]  aOther  The other `Iterator` to compare with.
121      *
122      * @retval TRUE   If the two `Iterator` objects point to the same item or both are done.
123      * @retval FALSE  If the two `Iterator` objects do not point to the same item.
124      *
125      */
operator ==(const IteratorType & aOther) const126     bool operator==(const IteratorType &aOther) const { return mItem == aOther.mItem; }
127 
128     /**
129      * This method overloads operator `!=` to evaluate whether or not two `Iterator` instances point to the same
130      * child entry.
131      *
132      * @param[in]  aOther  The other `Iterator` to compare with.
133      *
134      * @retval TRUE   If the two `Iterator` objects do not point to the same item.
135      * @retval FALSE  If the two `Iterator` objects point to the same item or both are done.
136      *
137      */
operator !=(const IteratorType & aOther) const138     bool operator!=(const IteratorType &aOther) const { return mItem != aOther.mItem; }
139 
140 protected:
141     /**
142      * Default constructor
143      *
144      */
ItemPtrIterator(void)145     ItemPtrIterator(void)
146         : mItem(nullptr)
147     {
148     }
149 
150     /**
151      * Constructor with an Item pointer.
152      *
153      */
ItemPtrIterator(ItemType * item)154     explicit ItemPtrIterator(ItemType *item)
155         : mItem(item)
156     {
157     }
158 
159     ItemType *mItem;
160 };
161 
162 /**
163  * @}
164  *
165  */
166 
167 } // namespace ot
168 
169 #endif // ITERATOR_UTILS_HPP_
170