1 | // The -*- C++ -*- type traits classes for internal use in libstdc++ |
2 | |
3 | // Copyright (C) 2000-2019 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. One 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 ([email protected]) 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 | #ifdef _GLIBCXX_USE_CHAR8_T |
175 | template<> |
176 | struct __is_integer<char8_t> |
177 | { |
178 | enum { __value = 1 }; |
179 | typedef __true_type __type; |
180 | }; |
181 | #endif |
182 | |
183 | #if __cplusplus >= 201103L |
184 | template<> |
185 | struct __is_integer<char16_t> |
186 | { |
187 | enum { __value = 1 }; |
188 | typedef __true_type __type; |
189 | }; |
190 | |
191 | template<> |
192 | struct __is_integer<char32_t> |
193 | { |
194 | enum { __value = 1 }; |
195 | typedef __true_type __type; |
196 | }; |
197 | #endif |
198 | |
199 | template<> |
200 | struct __is_integer<short> |
201 | { |
202 | enum { __value = 1 }; |
203 | typedef __true_type __type; |
204 | }; |
205 | |
206 | template<> |
207 | struct __is_integer<unsigned short> |
208 | { |
209 | enum { __value = 1 }; |
210 | typedef __true_type __type; |
211 | }; |
212 | |
213 | template<> |
214 | struct __is_integer<int> |
215 | { |
216 | enum { __value = 1 }; |
217 | typedef __true_type __type; |
218 | }; |
219 | |
220 | template<> |
221 | struct __is_integer<unsigned int> |
222 | { |
223 | enum { __value = 1 }; |
224 | typedef __true_type __type; |
225 | }; |
226 | |
227 | template<> |
228 | struct __is_integer<long> |
229 | { |
230 | enum { __value = 1 }; |
231 | typedef __true_type __type; |
232 | }; |
233 | |
234 | template<> |
235 | struct __is_integer<unsigned long> |
236 | { |
237 | enum { __value = 1 }; |
238 | typedef __true_type __type; |
239 | }; |
240 | |
241 | template<> |
242 | struct __is_integer<long long> |
243 | { |
244 | enum { __value = 1 }; |
245 | typedef __true_type __type; |
246 | }; |
247 | |
248 | template<> |
249 | struct __is_integer<unsigned long long> |
250 | { |
251 | enum { __value = 1 }; |
252 | typedef __true_type __type; |
253 | }; |
254 | |
255 | #define __INT_N(TYPE) \ |
256 | template<> \ |
257 | struct __is_integer<TYPE> \ |
258 | { \ |
259 | enum { __value = 1 }; \ |
260 | typedef __true_type __type; \ |
261 | }; \ |
262 | template<> \ |
263 | struct __is_integer<unsigned TYPE> \ |
264 | { \ |
265 | enum { __value = 1 }; \ |
266 | typedef __true_type __type; \ |
267 | }; |
268 | |
269 | #ifdef __GLIBCXX_TYPE_INT_N_0 |
270 | __INT_N(__GLIBCXX_TYPE_INT_N_0) |
271 | #endif |
272 | #ifdef __GLIBCXX_TYPE_INT_N_1 |
273 | __INT_N(__GLIBCXX_TYPE_INT_N_1) |
274 | #endif |
275 | #ifdef __GLIBCXX_TYPE_INT_N_2 |
276 | __INT_N(__GLIBCXX_TYPE_INT_N_2) |
277 | #endif |
278 | #ifdef __GLIBCXX_TYPE_INT_N_3 |
279 | __INT_N(__GLIBCXX_TYPE_INT_N_3) |
280 | #endif |
281 | |
282 | #undef __INT_N |
283 | |
284 | // |
285 | // Floating point types |
286 | // |
287 | template<typename _Tp> |
288 | struct __is_floating |
289 | { |
290 | enum { __value = 0 }; |
291 | typedef __false_type __type; |
292 | }; |
293 | |
294 | // three specializations (float, double and 'long double') |
295 | template<> |
296 | struct __is_floating<float> |
297 | { |
298 | enum { __value = 1 }; |
299 | typedef __true_type __type; |
300 | }; |
301 | |
302 | template<> |
303 | struct __is_floating<double> |
304 | { |
305 | enum { __value = 1 }; |
306 | typedef __true_type __type; |
307 | }; |
308 | |
309 | template<> |
310 | struct __is_floating<long double> |
311 | { |
312 | enum { __value = 1 }; |
313 | typedef __true_type __type; |
314 | }; |
315 | |
316 | // |
317 | // Pointer types |
318 | // |
319 | template<typename _Tp> |
320 | struct __is_pointer |
321 | { |
322 | enum { __value = 0 }; |
323 | typedef __false_type __type; |
324 | }; |
325 | |
326 | template<typename _Tp> |
327 | struct __is_pointer<_Tp*> |
328 | { |
329 | enum { __value = 1 }; |
330 | typedef __true_type __type; |
331 | }; |
332 | |
333 | // |
334 | // An arithmetic type is an integer type or a floating point type |
335 | // |
336 | template<typename _Tp> |
337 | struct __is_arithmetic |
338 | : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> > |
339 | { }; |
340 | |
341 | // |
342 | // A scalar type is an arithmetic type or a pointer type |
343 | // |
344 | template<typename _Tp> |
345 | struct __is_scalar |
346 | : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> > |
347 | { }; |
348 | |
349 | // |
350 | // For use in std::copy and std::find overloads for streambuf iterators. |
351 | // |
352 | template<typename _Tp> |
353 | struct __is_char |
354 | { |
355 | enum { __value = 0 }; |
356 | typedef __false_type __type; |
357 | }; |
358 | |
359 | template<> |
360 | struct __is_char<char> |
361 | { |
362 | enum { __value = 1 }; |
363 | typedef __true_type __type; |
364 | }; |
365 | |
366 | #ifdef _GLIBCXX_USE_WCHAR_T |
367 | template<> |
368 | struct __is_char<wchar_t> |
369 | { |
370 | enum { __value = 1 }; |
371 | typedef __true_type __type; |
372 | }; |
373 | #endif |
374 | |
375 | template<typename _Tp> |
376 | struct __is_byte |
377 | { |
378 | enum { __value = 0 }; |
379 | typedef __false_type __type; |
380 | }; |
381 | |
382 | template<> |
383 | struct __is_byte<char> |
384 | { |
385 | enum { __value = 1 }; |
386 | typedef __true_type __type; |
387 | }; |
388 | |
389 | template<> |
390 | struct __is_byte<signed char> |
391 | { |
392 | enum { __value = 1 }; |
393 | typedef __true_type __type; |
394 | }; |
395 | |
396 | template<> |
397 | struct __is_byte<unsigned char> |
398 | { |
399 | enum { __value = 1 }; |
400 | typedef __true_type __type; |
401 | }; |
402 | |
403 | #if __cplusplus >= 201703L |
404 | enum class byte : unsigned char; |
405 | |
406 | template<> |
407 | struct __is_byte<byte> |
408 | { |
409 | enum { __value = 1 }; |
410 | typedef __true_type __type; |
411 | }; |
412 | #endif // C++17 |
413 | |
414 | // |
415 | // Move iterator type |
416 | // |
417 | template<typename _Tp> |
418 | struct __is_move_iterator |
419 | { |
420 | enum { __value = 0 }; |
421 | typedef __false_type __type; |
422 | }; |
423 | |
424 | // Fallback implementation of the function in bits/stl_iterator.h used to |
425 | // remove the move_iterator wrapper. |
426 | template<typename _Iterator> |
427 | inline _Iterator |
428 | __miter_base(_Iterator __it) |
429 | { return __it; } |
430 | |
431 | _GLIBCXX_END_NAMESPACE_VERSION |
432 | } // namespace |
433 | } // extern "C++" |
434 | |
435 | #endif //_CPP_TYPE_TRAITS_H |
436 | |