1 | // The -*- C++ -*- type traits classes for internal use in libstdc++ |
2 | |
3 | // Copyright (C) 2000-2018 Free Software Foundation, Inc. |
4 | // |
5 | // This file is part of the GNU ISO C++ Library. This library is free |
6 | // software; you can redistribute it and/or modify it under the |
7 | // terms of the GNU General Public License as published by the |
8 | // Free Software Foundation; either version 3, or (at your option) |
9 | // any later version. |
10 | |
11 | // This library is distributed in the hope that it will be useful, |
12 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
14 | // GNU General Public License for more details. |
15 | |
16 | // Under Section 7 of GPL version 3, you are granted additional |
17 | // permissions described in the GCC Runtime Library Exception, version |
18 | // 3.1, as published by the Free Software Foundation. |
19 | |
20 | // You should have received a copy of the GNU General Public License and |
21 | // a copy of the GCC Runtime Library Exception along with this program; |
22 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
23 | // <http://www.gnu.org/licenses/>. |
24 | |
25 | /** @file bits/cpp_type_traits.h |
26 | * This is an internal header file, included by other library headers. |
27 | * Do not attempt to use it directly. @headername{ext/type_traits} |
28 | */ |
29 | |
30 | // Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr> |
31 | |
32 | #ifndef _CPP_TYPE_TRAITS_H |
33 | #define _CPP_TYPE_TRAITS_H 1 |
34 | |
35 | #pragma GCC system_header |
36 | |
37 | #include <bits/c++config.h> |
38 | |
39 | // |
40 | // This file provides some compile-time information about various types. |
41 | // These representations were designed, on purpose, to be constant-expressions |
42 | // and not types as found in <bits/type_traits.h>. In particular, they |
43 | // can be used in control structures and the optimizer hopefully will do |
44 | // the obvious thing. |
45 | // |
46 | // Why integral expressions, and not functions nor types? |
47 | // Firstly, these compile-time entities are used as template-arguments |
48 | // so function return values won't work: We need compile-time entities. |
49 | // We're left with types and constant integral expressions. |
50 | // Secondly, from the point of view of ease of use, type-based compile-time |
51 | // information is -not- *that* convenient. On has to write lots of |
52 | // overloaded functions and to hope that the compiler will select the right |
53 | // one. As a net effect, the overall structure isn't very clear at first |
54 | // glance. |
55 | // Thirdly, partial ordering and overload resolution (of function templates) |
56 | // is highly costly in terms of compiler-resource. It is a Good Thing to |
57 | // keep these resource consumption as least as possible. |
58 | // |
59 | // See valarray_array.h for a case use. |
60 | // |
61 | // -- Gaby (dosreis@cmla.ens-cachan.fr) 2000-03-06. |
62 | // |
63 | // Update 2005: types are also provided and <bits/type_traits.h> has been |
64 | // removed. |
65 | // |
66 | |
67 | extern "C++" { |
68 | |
69 | namespace std _GLIBCXX_VISIBILITY(default) |
70 | { |
71 | _GLIBCXX_BEGIN_NAMESPACE_VERSION |
72 | |
73 | struct __true_type { }; |
74 | struct __false_type { }; |
75 | |
76 | template<bool> |
77 | struct __truth_type |
78 | { typedef __false_type __type; }; |
79 | |
80 | template<> |
81 | struct __truth_type<true> |
82 | { typedef __true_type __type; }; |
83 | |
84 | // N.B. The conversions to bool are needed due to the issue |
85 | // explained in c++/19404. |
86 | template<class _Sp, class _Tp> |
87 | struct __traitor |
88 | { |
89 | enum { __value = bool(_Sp::__value) || bool(_Tp::__value) }; |
90 | typedef typename __truth_type<__value>::__type __type; |
91 | }; |
92 | |
93 | // Compare for equality of types. |
94 | template<typename, typename> |
95 | struct __are_same |
96 | { |
97 | enum { __value = 0 }; |
98 | typedef __false_type __type; |
99 | }; |
100 | |
101 | template<typename _Tp> |
102 | struct __are_same<_Tp, _Tp> |
103 | { |
104 | enum { __value = 1 }; |
105 | typedef __true_type __type; |
106 | }; |
107 | |
108 | // Holds if the template-argument is a void type. |
109 | template<typename _Tp> |
110 | struct __is_void |
111 | { |
112 | enum { __value = 0 }; |
113 | typedef __false_type __type; |
114 | }; |
115 | |
116 | template<> |
117 | struct __is_void<void> |
118 | { |
119 | enum { __value = 1 }; |
120 | typedef __true_type __type; |
121 | }; |
122 | |
123 | // |
124 | // Integer types |
125 | // |
126 | template<typename _Tp> |
127 | struct __is_integer |
128 | { |
129 | enum { __value = 0 }; |
130 | typedef __false_type __type; |
131 | }; |
132 | |
133 | // Thirteen specializations (yes there are eleven standard integer |
134 | // types; <em>long long</em> and <em>unsigned long long</em> are |
135 | // supported as extensions). Up to four target-specific __int<N> |
136 | // types are supported as well. |
137 | template<> |
138 | struct __is_integer<bool> |
139 | { |
140 | enum { __value = 1 }; |
141 | typedef __true_type __type; |
142 | }; |
143 | |
144 | template<> |
145 | struct __is_integer<char> |
146 | { |
147 | enum { __value = 1 }; |
148 | typedef __true_type __type; |
149 | }; |
150 | |
151 | template<> |
152 | struct __is_integer<signed char> |
153 | { |
154 | enum { __value = 1 }; |
155 | typedef __true_type __type; |
156 | }; |
157 | |
158 | template<> |
159 | struct __is_integer<unsigned char> |
160 | { |
161 | enum { __value = 1 }; |
162 | typedef __true_type __type; |
163 | }; |
164 | |
165 | # ifdef _GLIBCXX_USE_WCHAR_T |
166 | template<> |
167 | struct __is_integer<wchar_t> |
168 | { |
169 | enum { __value = 1 }; |
170 | typedef __true_type __type; |
171 | }; |
172 | # endif |
173 | |
174 | #if __cplusplus >= 201103L |
175 | template<> |
176 | struct __is_integer<char16_t> |
177 | { |
178 | enum { __value = 1 }; |
179 | typedef __true_type __type; |
180 | }; |
181 | |
182 | template<> |
183 | struct __is_integer<char32_t> |
184 | { |
185 | enum { __value = 1 }; |
186 | typedef __true_type __type; |
187 | }; |
188 | #endif |
189 | |
190 | template<> |
191 | struct __is_integer<short> |
192 | { |
193 | enum { __value = 1 }; |
194 | typedef __true_type __type; |
195 | }; |
196 | |
197 | template<> |
198 | struct __is_integer<unsigned short> |
199 | { |
200 | enum { __value = 1 }; |
201 | typedef __true_type __type; |
202 | }; |
203 | |
204 | template<> |
205 | struct __is_integer<int> |
206 | { |
207 | enum { __value = 1 }; |
208 | typedef __true_type __type; |
209 | }; |
210 | |
211 | template<> |
212 | struct __is_integer<unsigned int> |
213 | { |
214 | enum { __value = 1 }; |
215 | typedef __true_type __type; |
216 | }; |
217 | |
218 | template<> |
219 | struct __is_integer<long> |
220 | { |
221 | enum { __value = 1 }; |
222 | typedef __true_type __type; |
223 | }; |
224 | |
225 | template<> |
226 | struct __is_integer<unsigned long> |
227 | { |
228 | enum { __value = 1 }; |
229 | typedef __true_type __type; |
230 | }; |
231 | |
232 | template<> |
233 | struct __is_integer<long long> |
234 | { |
235 | enum { __value = 1 }; |
236 | typedef __true_type __type; |
237 | }; |
238 | |
239 | template<> |
240 | struct __is_integer<unsigned long long> |
241 | { |
242 | enum { __value = 1 }; |
243 | typedef __true_type __type; |
244 | }; |
245 | |
246 | #define __INT_N(TYPE) \ |
247 | template<> \ |
248 | struct __is_integer<TYPE> \ |
249 | { \ |
250 | enum { __value = 1 }; \ |
251 | typedef __true_type __type; \ |
252 | }; \ |
253 | template<> \ |
254 | struct __is_integer<unsigned TYPE> \ |
255 | { \ |
256 | enum { __value = 1 }; \ |
257 | typedef __true_type __type; \ |
258 | }; |
259 | |
260 | #ifdef __GLIBCXX_TYPE_INT_N_0 |
261 | __INT_N(__GLIBCXX_TYPE_INT_N_0) |
262 | #endif |
263 | #ifdef __GLIBCXX_TYPE_INT_N_1 |
264 | __INT_N(__GLIBCXX_TYPE_INT_N_1) |
265 | #endif |
266 | #ifdef __GLIBCXX_TYPE_INT_N_2 |
267 | __INT_N(__GLIBCXX_TYPE_INT_N_2) |
268 | #endif |
269 | #ifdef __GLIBCXX_TYPE_INT_N_3 |
270 | __INT_N(__GLIBCXX_TYPE_INT_N_3) |
271 | #endif |
272 | |
273 | #undef __INT_N |
274 | |
275 | // |
276 | // Floating point types |
277 | // |
278 | template<typename _Tp> |
279 | struct __is_floating |
280 | { |
281 | enum { __value = 0 }; |
282 | typedef __false_type __type; |
283 | }; |
284 | |
285 | // three specializations (float, double and 'long double') |
286 | template<> |
287 | struct __is_floating<float> |
288 | { |
289 | enum { __value = 1 }; |
290 | typedef __true_type __type; |
291 | }; |
292 | |
293 | template<> |
294 | struct __is_floating<double> |
295 | { |
296 | enum { __value = 1 }; |
297 | typedef __true_type __type; |
298 | }; |
299 | |
300 | template<> |
301 | struct __is_floating<long double> |
302 | { |
303 | enum { __value = 1 }; |
304 | typedef __true_type __type; |
305 | }; |
306 | |
307 | // |
308 | // Pointer types |
309 | // |
310 | template<typename _Tp> |
311 | struct __is_pointer |
312 | { |
313 | enum { __value = 0 }; |
314 | typedef __false_type __type; |
315 | }; |
316 | |
317 | template<typename _Tp> |
318 | struct __is_pointer<_Tp*> |
319 | { |
320 | enum { __value = 1 }; |
321 | typedef __true_type __type; |
322 | }; |
323 | |
324 | // |
325 | // An arithmetic type is an integer type or a floating point type |
326 | // |
327 | template<typename _Tp> |
328 | struct __is_arithmetic |
329 | : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> > |
330 | { }; |
331 | |
332 | // |
333 | // A scalar type is an arithmetic type or a pointer type |
334 | // |
335 | template<typename _Tp> |
336 | struct __is_scalar |
337 | : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> > |
338 | { }; |
339 | |
340 | // |
341 | // For use in std::copy and std::find overloads for streambuf iterators. |
342 | // |
343 | template<typename _Tp> |
344 | struct __is_char |
345 | { |
346 | enum { __value = 0 }; |
347 | typedef __false_type __type; |
348 | }; |
349 | |
350 | template<> |
351 | struct __is_char<char> |
352 | { |
353 | enum { __value = 1 }; |
354 | typedef __true_type __type; |
355 | }; |
356 | |
357 | #ifdef _GLIBCXX_USE_WCHAR_T |
358 | template<> |
359 | struct __is_char<wchar_t> |
360 | { |
361 | enum { __value = 1 }; |
362 | typedef __true_type __type; |
363 | }; |
364 | #endif |
365 | |
366 | template<typename _Tp> |
367 | struct __is_byte |
368 | { |
369 | enum { __value = 0 }; |
370 | typedef __false_type __type; |
371 | }; |
372 | |
373 | template<> |
374 | struct __is_byte<char> |
375 | { |
376 | enum { __value = 1 }; |
377 | typedef __true_type __type; |
378 | }; |
379 | |
380 | template<> |
381 | struct __is_byte<signed char> |
382 | { |
383 | enum { __value = 1 }; |
384 | typedef __true_type __type; |
385 | }; |
386 | |
387 | template<> |
388 | struct __is_byte<unsigned char> |
389 | { |
390 | enum { __value = 1 }; |
391 | typedef __true_type __type; |
392 | }; |
393 | |
394 | #if __cplusplus >= 201703L |
395 | enum class byte : unsigned char; |
396 | |
397 | template<> |
398 | struct __is_byte<byte> |
399 | { |
400 | enum { __value = 1 }; |
401 | typedef __true_type __type; |
402 | }; |
403 | #endif // C++17 |
404 | |
405 | // |
406 | // Move iterator type |
407 | // |
408 | template<typename _Tp> |
409 | struct __is_move_iterator |
410 | { |
411 | enum { __value = 0 }; |
412 | typedef __false_type __type; |
413 | }; |
414 | |
415 | // Fallback implementation of the function in bits/stl_iterator.h used to |
416 | // remove the move_iterator wrapper. |
417 | template<typename _Iterator> |
418 | inline _Iterator |
419 | __miter_base(_Iterator __it) |
420 | { return __it; } |
421 | |
422 | _GLIBCXX_END_NAMESPACE_VERSION |
423 | } // namespace |
424 | } // extern "C++" |
425 | |
426 | #endif //_CPP_TYPE_TRAITS_H |
427 | |