/src/gdal/port/cpl_enumerate.h
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1 | | /****************************************************************************** |
2 | | * |
3 | | * Project: CPL - Common Portability Library |
4 | | * Purpose: Collection enumerator |
5 | | * Author: Even Rouault, even.rouault at spatialys.com |
6 | | * |
7 | | ****************************************************************************** |
8 | | * Copyright (c) 2025, Even Rouault <even.rouault at spatialys.com> |
9 | | * |
10 | | * SPDX-License-Identifier: MIT |
11 | | ****************************************************************************/ |
12 | | |
13 | | #ifndef CPL_ENUMERATE_H |
14 | | #define CPL_ENUMERATE_H |
15 | | |
16 | | #include <cstddef> // size_t |
17 | | #include <iterator> // std::begin(), std::end() |
18 | | #include <utility> // std::declval(), std::pair |
19 | | |
20 | | namespace cpl |
21 | | { |
22 | | |
23 | | //! @cond Doxygen_Suppress |
24 | | |
25 | | template <class T> class Enumerator |
26 | | { |
27 | | public: |
28 | | using TIter = decltype(std::begin(std::declval<T &>())); |
29 | | |
30 | | class iterator |
31 | | { |
32 | | public: |
33 | 0 | explicit inline iterator(const TIter &it) : m_iter(it) |
34 | 0 | { |
35 | 0 | } |
36 | | |
37 | | inline bool operator==(const iterator &other) const |
38 | | { |
39 | | return m_iter == other.m_iter; |
40 | | } |
41 | | |
42 | | inline bool operator!=(const iterator &other) const |
43 | 0 | { |
44 | 0 | return m_iter != other.m_iter; |
45 | 0 | } |
46 | | |
47 | | inline iterator &operator++() |
48 | 0 | { |
49 | 0 | ++m_index; |
50 | 0 | ++m_iter; |
51 | 0 | return *this; |
52 | 0 | } |
53 | | |
54 | | inline iterator operator++(int) |
55 | | { |
56 | | iterator before = *this; |
57 | | ++(*this); |
58 | | return before; |
59 | | } |
60 | | |
61 | | inline auto operator*() const |
62 | 0 | { |
63 | 0 | return std::pair<size_t, decltype(*m_iter) &>(m_index, *m_iter); |
64 | 0 | } |
65 | | |
66 | | private: |
67 | | TIter m_iter; |
68 | | size_t m_index = 0; |
69 | | }; |
70 | | |
71 | 0 | explicit inline Enumerator(T &iterable) : m_iterable(iterable) |
72 | 0 | { |
73 | 0 | } |
74 | | |
75 | | inline iterator begin() const |
76 | 0 | { |
77 | 0 | return iterator(std::begin(m_iterable)); |
78 | 0 | } |
79 | | |
80 | | inline iterator end() const |
81 | 0 | { |
82 | | // We could initialize the m_index to SIZE_T_MAX, but this does not |
83 | | // really matter as iterator comparison is done on the underlying |
84 | | // iterator and not the index. |
85 | 0 | return iterator(std::end(m_iterable)); |
86 | 0 | } |
87 | | |
88 | | private: |
89 | | T &m_iterable; |
90 | | }; |
91 | | |
92 | | //! @endcond |
93 | | |
94 | | /** Function returning an eumerator whose values are |
95 | | * a std::pair of (index: size_t, value: iterable::value_type). |
96 | | * |
97 | | * This is similar to Python enumerate() function and C++23 |
98 | | * std::ranges::enumerate() (https://en.cppreference.com/w/cpp/ranges/enumerate_view.html) |
99 | | * |
100 | | * \since GDAL 3.13 |
101 | | */ |
102 | | template <class T> inline auto enumerate(T &iterable) |
103 | 0 | { |
104 | 0 | return Enumerator<T>(iterable); |
105 | 0 | } |
106 | | |
107 | | } // namespace cpl |
108 | | |
109 | | #endif |