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36 * \brief Defines helper types for class enumerations.
38 * These helper types facilitate iterating over class enums, and
39 * maintaining a type-safe and value-safe matching list of names. The
40 * code is closely based on the public-domain code by Guilherme
41 * R. Lampert, found in commit c94c18a of
42 * https://github.com/glampert/enum_helpers/blob/master/enum_helpers.hpp
45 * NOTE This functionality only works for enumerations of monotonically
46 * increasing values, starting with the value zero.
56 * EnumerationWrapper<Foo> iter;
60 * // 'c' is a constant from Foo
63 * const EnumerationArray<Foo, std::string> fooStrings = { { "Bar", "Baz", "Fooz" } };
65 * for (Foo c : keysOf(fooStrings))
67 * print(fooStrings[c]);
70 * ArrayRef<const std::string> namesRef(fooStrings);
72 * \author Mark Abraham <mark.j.abraham@gmail.com>
74 * \ingroup module_utility
76 #ifndef GMX_UTILITY_ENUMHELPERS_H
77 #define GMX_UTILITY_ENUMHELPERS_H
82 #include <type_traits>
84 #include "gromacs/utility/gmxassert.h"
90 * \brief Allows iterating sequential enumerators.
92 * You can also provide an increment step > 1 if each constant is
93 * spaced by a larger value. Terminating constant is assumed to be a
94 * 'Count' member, which is never iterated. A different name for the
95 * terminating constant can also be specified on declaration.
97 * NOTE This functionality only works for enumerations of monotonically
98 * increasing values, starting with the value zero.
100 * See file documentation for usage example.
102 * \tparam EnumType The enum (class) type.
103 * \tparam Last Last constant or number thereof (assumes a default 'Count' member).
104 * \tparam Step Step increment.
106 template<typename EnumType, EnumType Last = EnumType::Count, unsigned int Step = 1>
107 class EnumerationIterator final
110 //! Convenience alias
111 using IntegerType = std::underlying_type_t<EnumType>;
113 /*! \name Iterator type traits
114 * Satisfies the requirements for STL forward iterator.
117 using iterator_category = std::forward_iterator_tag;
118 using value_type = EnumType;
119 using difference_type = std::ptrdiff_t;
120 using pointer = EnumType*;
121 using reference = EnumType&;
124 constexpr EnumerationIterator() noexcept : m_current{ 0 } // Assumes 0 is the first constant
128 constexpr EnumerationIterator(const EnumType index) noexcept :
129 m_current(static_cast<IntegerType>(index))
132 //! Pre-increment operator
133 EnumerationIterator operator++()
138 //! Post-increment operator
139 EnumerationIterator operator++(int)
141 EnumerationIterator old_val{ *this };
145 //! Dereference operator
146 EnumType operator*() const
148 GMX_ASSERT(m_current < static_cast<IntegerType>(Last), "dereferencing out of range");
149 return static_cast<EnumType>(m_current);
153 //! Comparision operators
154 bool operator==(const EnumerationIterator other) const noexcept
156 return m_current == other.m_current;
158 bool operator!=(const EnumerationIterator other) const noexcept
160 return m_current != other.m_current;
162 bool operator<(const EnumerationIterator other) const noexcept
164 return m_current < other.m_current;
166 bool operator>(const EnumerationIterator other) const noexcept
168 return m_current > other.m_current;
170 bool operator<=(const EnumerationIterator other) const noexcept
172 return m_current <= other.m_current;
174 bool operator>=(const EnumerationIterator other) const noexcept
176 return m_current >= other.m_current;
181 IntegerType m_current;
185 * \brief Allows constructing iterators for looping over sequential enumerators.
187 * These are particularly useful for range-based for statements.
189 * You can also provide an increment step > 1 if each constant is
190 * spaced by a larger value. Terminating constant is assumed to be a
191 * 'Count' member, which is never iterated. A different name for the
192 * terminating constant can also be specified on declaration.
194 * See file documentation for usage example.
196 * \tparam EnumType The enum (class) type.
197 * \tparam Last Last constant or number thereof (assumes a default 'Count' member).
198 * \tparam Step Step increment.
200 template<typename EnumType, EnumType Last = EnumType::Count, unsigned int Step = 1>
201 class EnumerationWrapper final
204 //! Convenience alias.
205 using IteratorType = EnumerationIterator<EnumType, Last, Step>;
207 //! Functions required for range-based for statements to work.
209 IteratorType begin() const { return IteratorType{}; }
210 IteratorType end() const { return IteratorType{ Last }; }
215 * \brief Wrapper for a C-style array with size and indexing defined
216 * by an enum. Useful for declaring arrays of enum names for debug
217 * or other printing. An ArrayRef<DataType> may be constructed from
218 * an object of this type.
220 * See file documentation for usage example.
222 * \tparam EnumType The enum (class) type.
223 * \tparam DataType Type of the data stored in the array.
224 * \tparam ArraySize Size in entries of the array.
226 template<typename EnumType, // The enum (class) type.
227 typename DataType, // Type of the data stored in the array.
228 EnumType ArraySize = EnumType::Count // Size in entries of the array.
230 struct EnumerationArray final
232 //! Convenience alias
233 using EnumerationWrapperType = EnumerationWrapper<EnumType, ArraySize>;
235 /*! \brief Data for names.
237 * Data is kept public so we can use direct aggregate
238 * initialization just like in a plain C-style array. */
239 DataType m_elements[std::size_t(ArraySize)];
241 //! Returns an object that provides iterators over the keys.
242 static constexpr EnumerationWrapperType keys() { return EnumerationWrapperType{}; }
243 //! Returns the size of the enumeration.
244 static constexpr std::size_t size() { return std::size_t(ArraySize); }
247 //! Array access with asserts:
248 DataType& operator[](const std::size_t index)
250 GMX_ASSERT(index < size(), "index out of range");
251 return m_elements[index];
253 const DataType& operator[](const std::size_t index) const
255 GMX_ASSERT(index < size(), "index out of range");
256 return m_elements[index];
259 DataType& operator[](const EnumType index)
261 GMX_ASSERT(std::size_t(index) < size(), "index out of range");
262 return m_elements[std::size_t(index)];
264 const DataType& operator[](const EnumType index) const
266 GMX_ASSERT(std::size_t(index) < size(), "index out of range");
267 return m_elements[std::size_t(index)];
272 //! Range iterators (unchecked)
273 using iterator = DataType*;
274 using const_iterator = const DataType*;
275 using reverse_iterator = std::reverse_iterator<iterator>;
276 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
280 //! Getters for forward iterators for ranges
281 iterator begin() { return &m_elements[0]; }
282 iterator end() { return &m_elements[size()]; }
283 const_iterator begin() const { return &m_elements[0]; }
284 const_iterator end() const { return &m_elements[size()]; }
288 //! Getters for reverse iterators for ranges
289 reverse_iterator rbegin() { return reverse_iterator{ end() }; }
290 reverse_iterator rend() { return reverse_iterator{ begin() }; }
291 const_reverse_iterator rbegin() const { return const_reverse_iterator{ end() }; }
292 const_reverse_iterator rend() const { return const_reverse_iterator{ begin() }; }
296 //! Pointers (unchecked)
297 using pointer = DataType*;
298 using const_pointer = const DataType*;
301 //! Returns a const raw pointer to the contents of the array.
302 const_pointer data() const { return &m_elements[0]; }
303 //! Returns a raw pointer to the contents of the array.
304 pointer data() { return &m_elements[0]; }
307 /*! \brief Returns an object that provides iterators over the keys
308 * associated with \c EnumerationArrayType.
310 * This helper function is useful in contexts where there is an object
311 * of an EnumerationArray, and we want to use a range-based for loop
312 * over the keys associated with it, and it would be inconvenient to
313 * use the very word EnumerationArray<...> type, nor introduce a using
314 * statement for this purpose. It is legal in C++ to call a static
315 * member function (such as keys()) via an object rather than the
316 * type, but clang-tidy warns about that. So instead we make available
317 * a free function that calls that static method. */
318 template<typename EnumerationArrayType>
319 typename EnumerationArrayType::EnumerationWrapperType keysOf(const EnumerationArrayType& /* arrayObject */)
321 return EnumerationArrayType::keys();