gprofng: fix build with -mx32
[binutils-gdb/blckswan.git] / gdbsupport / array-view.h
blobe9e4d542fffb558c7122852fe8a1dac030da379e
1 /* Copyright (C) 2017-2022 Free Software Foundation, Inc.
3 This file is part of GDB.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 #ifndef COMMON_ARRAY_VIEW_H
19 #define COMMON_ARRAY_VIEW_H
21 #include "traits.h"
22 #include <algorithm>
23 #include <type_traits>
25 /* An array_view is an abstraction that provides a non-owning view
26 over a sequence of contiguous objects.
28 A way to put it is that array_view is to std::vector (and
29 std::array and built-in arrays with rank==1) like std::string_view
30 is to std::string.
32 The main intent of array_view is to use it as function input
33 parameter type, making it possible to pass in any sequence of
34 contiguous objects, irrespective of whether the objects live on the
35 stack or heap and what actual container owns them. Implicit
36 construction from the element type is supported too, making it easy
37 to call functions that expect an array of elements when you only
38 have one element (usually on the stack). For example:
40 struct A { .... };
41 void function (gdb::array_view<A> as);
43 std::vector<A> std_vec = ...;
44 std::array<A, N> std_array = ...;
45 A array[] = {...};
46 A elem;
48 function (std_vec);
49 function (std_array);
50 function (array);
51 function (elem);
53 Views can be either mutable or const. A const view is simply
54 created by specifying a const T as array_view template parameter,
55 in which case operator[] of non-const array_view objects ends up
56 returning const references. Making the array_view itself const is
57 analogous to making a pointer itself be const. I.e., disables
58 re-seating the view/pointer.
60 Since array_view objects are small (pointer plus size), and
61 designed to be trivially copyable, they should generally be passed
62 around by value.
64 You can find unit tests covering the whole API in
65 unittests/array-view-selftests.c. */
67 namespace gdb {
69 template <typename T>
70 class array_view
72 /* True iff decayed T is the same as decayed U. E.g., we want to
73 say that 'T&' is the same as 'const T'. */
74 template <typename U>
75 using IsDecayedT = typename std::is_same<typename std::decay<T>::type,
76 typename std::decay<U>::type>;
78 /* True iff decayed T is the same as decayed U, and 'U *' is
79 implicitly convertible to 'T *'. This is a requirement for
80 several methods. */
81 template <typename U>
82 using DecayedConvertible = gdb::And<IsDecayedT<U>,
83 std::is_convertible<U *, T *>>;
85 public:
86 using value_type = T;
87 using reference = T &;
88 using const_reference = const T &;
89 using size_type = size_t;
91 /* Default construction creates an empty view. */
92 constexpr array_view () noexcept
93 : m_array (nullptr), m_size (0)
96 /* Create an array view over a single object of the type of an
97 array_view element. The created view as size==1. This is
98 templated on U to allow constructing a array_view<const T> over a
99 (non-const) T. The "convertible" requirement makes sure that you
100 can't create an array_view<T> over a const T. */
101 template<typename U,
102 typename = Requires<DecayedConvertible<U>>>
103 constexpr array_view (U &elem) noexcept
104 : m_array (&elem), m_size (1)
107 /* Same as above, for rvalue references. */
108 template<typename U,
109 typename = Requires<DecayedConvertible<U>>>
110 constexpr array_view (U &&elem) noexcept
111 : m_array (&elem), m_size (1)
114 /* Create an array view from a pointer to an array and an element
115 count. */
116 template<typename U,
117 typename = Requires<DecayedConvertible<U>>>
118 constexpr array_view (U *array, size_t size) noexcept
119 : m_array (array), m_size (size)
122 /* Create an array view from a range. This is templated on both U
123 an V to allow passing in a mix of 'const T *' and 'T *'. */
124 template<typename U, typename V,
125 typename = Requires<DecayedConvertible<U>>,
126 typename = Requires<DecayedConvertible<V>>>
127 constexpr array_view (U *begin, V *end) noexcept
128 : m_array (begin), m_size (end - begin)
131 /* Create an array view from an array. */
132 template<typename U, size_t Size,
133 typename = Requires<DecayedConvertible<U>>>
134 constexpr array_view (U (&array)[Size]) noexcept
135 : m_array (array), m_size (Size)
138 /* Create an array view from a contiguous container. E.g.,
139 std::vector and std::array. */
140 template<typename Container,
141 typename = Requires<gdb::Not<IsDecayedT<Container>>>,
142 typename
143 = Requires<DecayedConvertible
144 <typename std::remove_pointer
145 <decltype (std::declval<Container> ().data ())
146 >::type>>,
147 typename
148 = Requires<std::is_convertible
149 <decltype (std::declval<Container> ().size ()),
150 size_type>>>
151 constexpr array_view (Container &&c) noexcept
152 : m_array (c.data ()), m_size (c.size ())
155 /* Observer methods. Some of these can't be constexpr until we
156 require C++14. */
157 /*constexpr14*/ T *data () noexcept { return m_array; }
158 constexpr const T *data () const noexcept { return m_array; }
160 /*constexpr14*/ T *begin () noexcept { return m_array; }
161 constexpr const T *begin () const noexcept { return m_array; }
163 /*constexpr14*/ T *end () noexcept { return m_array + m_size; }
164 constexpr const T *end () const noexcept { return m_array + m_size; }
166 /*constexpr14*/ reference operator[] (size_t index) noexcept
168 #if defined(_GLIBCXX_DEBUG)
169 gdb_assert (index < m_size);
170 #endif
171 return m_array[index];
173 constexpr const_reference operator[] (size_t index) const noexcept
175 #if defined(_GLIBCXX_DEBUG) && __cplusplus >= 201402L
176 gdb_assert (index < m_size);
177 #endif
178 return m_array[index];
181 constexpr size_type size () const noexcept { return m_size; }
182 constexpr bool empty () const noexcept { return m_size == 0; }
184 /* Slice an array view. */
186 /* Return a new array view over SIZE elements starting at START. */
187 constexpr array_view<T> slice (size_type start, size_type size) const noexcept
189 #if defined(_GLIBCXX_DEBUG) && __cplusplus >= 201402L
190 gdb_assert (start + size <= m_size);
191 #endif
192 return {m_array + start, size};
195 /* Return a new array view over all the elements after START,
196 inclusive. */
197 constexpr array_view<T> slice (size_type start) const noexcept
199 #if defined(_GLIBCXX_DEBUG) && __cplusplus >= 201402L
200 gdb_assert (start <= m_size);
201 #endif
202 return {m_array + start, size () - start};
205 private:
206 T *m_array;
207 size_type m_size;
210 /* Copy the contents referenced by the array view SRC to the array view DEST.
212 The two array views must have the same length. */
214 template <typename U, typename T>
215 void copy (gdb::array_view<U> src, gdb::array_view<T> dest)
217 gdb_assert (dest.size () == src.size ());
218 if (dest.data () < src.data ())
219 std::copy (src.begin (), src.end (), dest.begin ());
220 else if (dest.data () > src.data ())
221 std::copy_backward (src.begin (), src.end (), dest.end ());
224 /* Compare LHS and RHS for (deep) equality. That is, whether LHS and
225 RHS have the same sizes, and whether each pair of elements of LHS
226 and RHS at the same position compares equal. */
228 template <typename T>
229 bool
230 operator== (const gdb::array_view<T> &lhs, const gdb::array_view<T> &rhs)
232 if (lhs.size () != rhs.size ())
233 return false;
235 for (size_t i = 0; i < lhs.size (); i++)
236 if (!(lhs[i] == rhs[i]))
237 return false;
239 return true;
242 /* Compare two array_views for inequality. */
244 template <typename T>
245 bool
246 operator!= (const gdb::array_view<T> &lhs, const gdb::array_view<T> &rhs)
248 return !(lhs == rhs);
251 /* Create an array view from a pointer to an array and an element
252 count.
254 This is useful as alternative to constructing an array_view using
255 brace initialization when the size variable you have handy is of
256 signed type, since otherwise without an explicit cast the code
257 would be ill-formed.
259 For example, with:
261 extern void foo (int, int, gdb::array_view<value *>);
263 value *args[2];
264 int nargs;
265 foo (1, 2, {values, nargs});
267 You'd get:
269 source.c:10: error: narrowing conversion of ‘nargs’ from ‘int’ to
270 ‘size_t {aka long unsigned int}’ inside { } [-Werror=narrowing]
272 You could fix it by writing the somewhat distracting explicit cast:
274 foo (1, 2, {values, (size_t) nargs});
276 Or by instantiating an array_view explicitly:
278 foo (1, 2, gdb::array_view<value *>(values, nargs));
280 Or, better, using make_array_view, which has the advantage of
281 inferring the arrav_view element's type:
283 foo (1, 2, gdb::make_array_view (values, nargs));
286 template<typename U>
287 constexpr inline array_view<U>
288 make_array_view (U *array, size_t size) noexcept
290 return {array, size};
293 } /* namespace gdb */
295 #endif