libstdc++
char_traits.h
Go to the documentation of this file.
1 // Character Traits for use by standard string and iostream -*- C++ -*-
2 
3 // Copyright (C) 1997-2015 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/char_traits.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{string}
28  */
29 
30 //
31 // ISO C++ 14882: 21 Strings library
32 //
33 
34 #ifndef _CHAR_TRAITS_H
35 #define _CHAR_TRAITS_H 1
36 
37 #pragma GCC system_header
38 
39 #include <bits/stl_algobase.h> // std::copy, std::fill_n
40 #include <bits/postypes.h> // For streampos
41 #include <cwchar> // For WEOF, wmemmove, wmemset, etc.
42 
43 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46 
47  /**
48  * @brief Mapping from character type to associated types.
49  *
50  * @note This is an implementation class for the generic version
51  * of char_traits. It defines int_type, off_type, pos_type, and
52  * state_type. By default these are unsigned long, streamoff,
53  * streampos, and mbstate_t. Users who need a different set of
54  * types, but who don't need to change the definitions of any function
55  * defined in char_traits, can specialize __gnu_cxx::_Char_types
56  * while leaving __gnu_cxx::char_traits alone. */
57  template<typename _CharT>
58  struct _Char_types
59  {
60  typedef unsigned long int_type;
61  typedef std::streampos pos_type;
62  typedef std::streamoff off_type;
63  typedef std::mbstate_t state_type;
64  };
65 
66 
67  /**
68  * @brief Base class used to implement std::char_traits.
69  *
70  * @note For any given actual character type, this definition is
71  * probably wrong. (Most of the member functions are likely to be
72  * right, but the int_type and state_type typedefs, and the eof()
73  * member function, are likely to be wrong.) The reason this class
74  * exists is so users can specialize it. Classes in namespace std
75  * may not be specialized for fundamental types, but classes in
76  * namespace __gnu_cxx may be.
77  *
78  * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.character_types
79  * for advice on how to make use of this class for @a unusual character
80  * types. Also, check out include/ext/pod_char_traits.h.
81  */
82  template<typename _CharT>
83  struct char_traits
84  {
85  typedef _CharT char_type;
86  typedef typename _Char_types<_CharT>::int_type int_type;
87  typedef typename _Char_types<_CharT>::pos_type pos_type;
88  typedef typename _Char_types<_CharT>::off_type off_type;
89  typedef typename _Char_types<_CharT>::state_type state_type;
90 
91  static void
92  assign(char_type& __c1, const char_type& __c2)
93  { __c1 = __c2; }
94 
95  static _GLIBCXX_CONSTEXPR bool
96  eq(const char_type& __c1, const char_type& __c2)
97  { return __c1 == __c2; }
98 
99  static _GLIBCXX_CONSTEXPR bool
100  lt(const char_type& __c1, const char_type& __c2)
101  { return __c1 < __c2; }
102 
103  static int
104  compare(const char_type* __s1, const char_type* __s2, std::size_t __n);
105 
106  static std::size_t
107  length(const char_type* __s);
108 
109  static const char_type*
110  find(const char_type* __s, std::size_t __n, const char_type& __a);
111 
112  static char_type*
113  move(char_type* __s1, const char_type* __s2, std::size_t __n);
114 
115  static char_type*
116  copy(char_type* __s1, const char_type* __s2, std::size_t __n);
117 
118  static char_type*
119  assign(char_type* __s, std::size_t __n, char_type __a);
120 
121  static _GLIBCXX_CONSTEXPR char_type
122  to_char_type(const int_type& __c)
123  { return static_cast<char_type>(__c); }
124 
125  static _GLIBCXX_CONSTEXPR int_type
126  to_int_type(const char_type& __c)
127  { return static_cast<int_type>(__c); }
128 
129  static _GLIBCXX_CONSTEXPR bool
130  eq_int_type(const int_type& __c1, const int_type& __c2)
131  { return __c1 == __c2; }
132 
133  static _GLIBCXX_CONSTEXPR int_type
134  eof()
135  { return static_cast<int_type>(_GLIBCXX_STDIO_EOF); }
136 
137  static _GLIBCXX_CONSTEXPR int_type
138  not_eof(const int_type& __c)
139  { return !eq_int_type(__c, eof()) ? __c : to_int_type(char_type()); }
140  };
141 
142  template<typename _CharT>
143  int
144  char_traits<_CharT>::
145  compare(const char_type* __s1, const char_type* __s2, std::size_t __n)
146  {
147  for (std::size_t __i = 0; __i < __n; ++__i)
148  if (lt(__s1[__i], __s2[__i]))
149  return -1;
150  else if (lt(__s2[__i], __s1[__i]))
151  return 1;
152  return 0;
153  }
154 
155  template<typename _CharT>
156  std::size_t
157  char_traits<_CharT>::
158  length(const char_type* __p)
159  {
160  std::size_t __i = 0;
161  while (!eq(__p[__i], char_type()))
162  ++__i;
163  return __i;
164  }
165 
166  template<typename _CharT>
167  const typename char_traits<_CharT>::char_type*
168  char_traits<_CharT>::
169  find(const char_type* __s, std::size_t __n, const char_type& __a)
170  {
171  for (std::size_t __i = 0; __i < __n; ++__i)
172  if (eq(__s[__i], __a))
173  return __s + __i;
174  return 0;
175  }
176 
177  template<typename _CharT>
178  typename char_traits<_CharT>::char_type*
179  char_traits<_CharT>::
180  move(char_type* __s1, const char_type* __s2, std::size_t __n)
181  {
182  return static_cast<_CharT*>(__builtin_memmove(__s1, __s2,
183  __n * sizeof(char_type)));
184  }
185 
186  template<typename _CharT>
187  typename char_traits<_CharT>::char_type*
188  char_traits<_CharT>::
189  copy(char_type* __s1, const char_type* __s2, std::size_t __n)
190  {
191  // NB: Inline std::copy so no recursive dependencies.
192  std::copy(__s2, __s2 + __n, __s1);
193  return __s1;
194  }
195 
196  template<typename _CharT>
197  typename char_traits<_CharT>::char_type*
198  char_traits<_CharT>::
199  assign(char_type* __s, std::size_t __n, char_type __a)
200  {
201  // NB: Inline std::fill_n so no recursive dependencies.
202  std::fill_n(__s, __n, __a);
203  return __s;
204  }
205 
206 _GLIBCXX_END_NAMESPACE_VERSION
207 } // namespace
208 
209 namespace std _GLIBCXX_VISIBILITY(default)
210 {
211 _GLIBCXX_BEGIN_NAMESPACE_VERSION
212 
213  // 21.1
214  /**
215  * @brief Basis for explicit traits specializations.
216  *
217  * @note For any given actual character type, this definition is
218  * probably wrong. Since this is just a thin wrapper around
219  * __gnu_cxx::char_traits, it is possible to achieve a more
220  * appropriate definition by specializing __gnu_cxx::char_traits.
221  *
222  * See https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.character_types
223  * for advice on how to make use of this class for @a unusual character
224  * types. Also, check out include/ext/pod_char_traits.h.
225  */
226  template<class _CharT>
227  struct char_traits : public __gnu_cxx::char_traits<_CharT>
228  { };
229 
230 
231  /// 21.1.3.1 char_traits specializations
232  template<>
233  struct char_traits<char>
234  {
235  typedef char char_type;
236  typedef int int_type;
237  typedef streampos pos_type;
238  typedef streamoff off_type;
239  typedef mbstate_t state_type;
240 
241  static void
242  assign(char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
243  { __c1 = __c2; }
244 
245  static _GLIBCXX_CONSTEXPR bool
246  eq(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
247  { return __c1 == __c2; }
248 
249  static _GLIBCXX_CONSTEXPR bool
250  lt(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
251  {
252  // LWG 467.
253  return (static_cast<unsigned char>(__c1)
254  < static_cast<unsigned char>(__c2));
255  }
256 
257  static int
258  compare(const char_type* __s1, const char_type* __s2, size_t __n)
259  {
260  if (__n == 0)
261  return 0;
262  return __builtin_memcmp(__s1, __s2, __n);
263  }
264 
265  static size_t
266  length(const char_type* __s)
267  { return __builtin_strlen(__s); }
268 
269  static const char_type*
270  find(const char_type* __s, size_t __n, const char_type& __a)
271  {
272  if (__n == 0)
273  return 0;
274  return static_cast<const char_type*>(__builtin_memchr(__s, __a, __n));
275  }
276 
277  static char_type*
278  move(char_type* __s1, const char_type* __s2, size_t __n)
279  {
280  if (__n == 0)
281  return __s1;
282  return static_cast<char_type*>(__builtin_memmove(__s1, __s2, __n));
283  }
284 
285  static char_type*
286  copy(char_type* __s1, const char_type* __s2, size_t __n)
287  {
288  if (__n == 0)
289  return __s1;
290  return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n));
291  }
292 
293  static char_type*
294  assign(char_type* __s, size_t __n, char_type __a)
295  {
296  if (__n == 0)
297  return __s;
298  return static_cast<char_type*>(__builtin_memset(__s, __a, __n));
299  }
300 
301  static _GLIBCXX_CONSTEXPR char_type
302  to_char_type(const int_type& __c) _GLIBCXX_NOEXCEPT
303  { return static_cast<char_type>(__c); }
304 
305  // To keep both the byte 0xff and the eof symbol 0xffffffff
306  // from ending up as 0xffffffff.
307  static _GLIBCXX_CONSTEXPR int_type
308  to_int_type(const char_type& __c) _GLIBCXX_NOEXCEPT
309  { return static_cast<int_type>(static_cast<unsigned char>(__c)); }
310 
311  static _GLIBCXX_CONSTEXPR bool
312  eq_int_type(const int_type& __c1, const int_type& __c2) _GLIBCXX_NOEXCEPT
313  { return __c1 == __c2; }
314 
315  static _GLIBCXX_CONSTEXPR int_type
316  eof() _GLIBCXX_NOEXCEPT
317  { return static_cast<int_type>(_GLIBCXX_STDIO_EOF); }
318 
319  static _GLIBCXX_CONSTEXPR int_type
320  not_eof(const int_type& __c) _GLIBCXX_NOEXCEPT
321  { return (__c == eof()) ? 0 : __c; }
322  };
323 
324 
325 #ifdef _GLIBCXX_USE_WCHAR_T
326  /// 21.1.3.2 char_traits specializations
327  template<>
328  struct char_traits<wchar_t>
329  {
330  typedef wchar_t char_type;
331  typedef wint_t int_type;
332  typedef streamoff off_type;
333  typedef wstreampos pos_type;
334  typedef mbstate_t state_type;
335 
336  static void
337  assign(char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
338  { __c1 = __c2; }
339 
340  static _GLIBCXX_CONSTEXPR bool
341  eq(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
342  { return __c1 == __c2; }
343 
344  static _GLIBCXX_CONSTEXPR bool
345  lt(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
346  { return __c1 < __c2; }
347 
348  static int
349  compare(const char_type* __s1, const char_type* __s2, size_t __n)
350  {
351  if (__n == 0)
352  return 0;
353  return wmemcmp(__s1, __s2, __n);
354  }
355 
356  static size_t
357  length(const char_type* __s)
358  { return wcslen(__s); }
359 
360  static const char_type*
361  find(const char_type* __s, size_t __n, const char_type& __a)
362  {
363  if (__n == 0)
364  return 0;
365  return wmemchr(__s, __a, __n);
366  }
367 
368  static char_type*
369  move(char_type* __s1, const char_type* __s2, size_t __n)
370  {
371  if (__n == 0)
372  return __s1;
373  return wmemmove(__s1, __s2, __n);
374  }
375 
376  static char_type*
377  copy(char_type* __s1, const char_type* __s2, size_t __n)
378  {
379  if (__n == 0)
380  return __s1;
381  return wmemcpy(__s1, __s2, __n);
382  }
383 
384  static char_type*
385  assign(char_type* __s, size_t __n, char_type __a)
386  {
387  if (__n == 0)
388  return __s;
389  return wmemset(__s, __a, __n);
390  }
391 
392  static _GLIBCXX_CONSTEXPR char_type
393  to_char_type(const int_type& __c) _GLIBCXX_NOEXCEPT
394  { return char_type(__c); }
395 
396  static _GLIBCXX_CONSTEXPR int_type
397  to_int_type(const char_type& __c) _GLIBCXX_NOEXCEPT
398  { return int_type(__c); }
399 
400  static _GLIBCXX_CONSTEXPR bool
401  eq_int_type(const int_type& __c1, const int_type& __c2) _GLIBCXX_NOEXCEPT
402  { return __c1 == __c2; }
403 
404  static _GLIBCXX_CONSTEXPR int_type
405  eof() _GLIBCXX_NOEXCEPT
406  { return static_cast<int_type>(WEOF); }
407 
408  static _GLIBCXX_CONSTEXPR int_type
409  not_eof(const int_type& __c) _GLIBCXX_NOEXCEPT
410  { return eq_int_type(__c, eof()) ? 0 : __c; }
411  };
412 #endif //_GLIBCXX_USE_WCHAR_T
413 
414 _GLIBCXX_END_NAMESPACE_VERSION
415 } // namespace
416 
417 #if ((__cplusplus >= 201103L) \
418  && defined(_GLIBCXX_USE_C99_STDINT_TR1))
419 
420 #include <cstdint>
421 
422 namespace std _GLIBCXX_VISIBILITY(default)
423 {
424 _GLIBCXX_BEGIN_NAMESPACE_VERSION
425 
426  template<>
427  struct char_traits<char16_t>
428  {
429  typedef char16_t char_type;
430  typedef uint_least16_t int_type;
431  typedef streamoff off_type;
432  typedef u16streampos pos_type;
433  typedef mbstate_t state_type;
434 
435  static void
436  assign(char_type& __c1, const char_type& __c2) noexcept
437  { __c1 = __c2; }
438 
439  static constexpr bool
440  eq(const char_type& __c1, const char_type& __c2) noexcept
441  { return __c1 == __c2; }
442 
443  static constexpr bool
444  lt(const char_type& __c1, const char_type& __c2) noexcept
445  { return __c1 < __c2; }
446 
447  static int
448  compare(const char_type* __s1, const char_type* __s2, size_t __n)
449  {
450  for (size_t __i = 0; __i < __n; ++__i)
451  if (lt(__s1[__i], __s2[__i]))
452  return -1;
453  else if (lt(__s2[__i], __s1[__i]))
454  return 1;
455  return 0;
456  }
457 
458  static size_t
459  length(const char_type* __s)
460  {
461  size_t __i = 0;
462  while (!eq(__s[__i], char_type()))
463  ++__i;
464  return __i;
465  }
466 
467  static const char_type*
468  find(const char_type* __s, size_t __n, const char_type& __a)
469  {
470  for (size_t __i = 0; __i < __n; ++__i)
471  if (eq(__s[__i], __a))
472  return __s + __i;
473  return 0;
474  }
475 
476  static char_type*
477  move(char_type* __s1, const char_type* __s2, size_t __n)
478  {
479  if (__n == 0)
480  return __s1;
481  return (static_cast<char_type*>
482  (__builtin_memmove(__s1, __s2, __n * sizeof(char_type))));
483  }
484 
485  static char_type*
486  copy(char_type* __s1, const char_type* __s2, size_t __n)
487  {
488  if (__n == 0)
489  return __s1;
490  return (static_cast<char_type*>
491  (__builtin_memcpy(__s1, __s2, __n * sizeof(char_type))));
492  }
493 
494  static char_type*
495  assign(char_type* __s, size_t __n, char_type __a)
496  {
497  for (size_t __i = 0; __i < __n; ++__i)
498  assign(__s[__i], __a);
499  return __s;
500  }
501 
502  static constexpr char_type
503  to_char_type(const int_type& __c) noexcept
504  { return char_type(__c); }
505 
506  static constexpr int_type
507  to_int_type(const char_type& __c) noexcept
508  { return int_type(__c); }
509 
510  static constexpr bool
511  eq_int_type(const int_type& __c1, const int_type& __c2) noexcept
512  { return __c1 == __c2; }
513 
514  static constexpr int_type
515  eof() noexcept
516  { return static_cast<int_type>(-1); }
517 
518  static constexpr int_type
519  not_eof(const int_type& __c) noexcept
520  { return eq_int_type(__c, eof()) ? 0 : __c; }
521  };
522 
523  template<>
524  struct char_traits<char32_t>
525  {
526  typedef char32_t char_type;
527  typedef uint_least32_t int_type;
528  typedef streamoff off_type;
529  typedef u32streampos pos_type;
530  typedef mbstate_t state_type;
531 
532  static void
533  assign(char_type& __c1, const char_type& __c2) noexcept
534  { __c1 = __c2; }
535 
536  static constexpr bool
537  eq(const char_type& __c1, const char_type& __c2) noexcept
538  { return __c1 == __c2; }
539 
540  static constexpr bool
541  lt(const char_type& __c1, const char_type& __c2) noexcept
542  { return __c1 < __c2; }
543 
544  static int
545  compare(const char_type* __s1, const char_type* __s2, size_t __n)
546  {
547  for (size_t __i = 0; __i < __n; ++__i)
548  if (lt(__s1[__i], __s2[__i]))
549  return -1;
550  else if (lt(__s2[__i], __s1[__i]))
551  return 1;
552  return 0;
553  }
554 
555  static size_t
556  length(const char_type* __s)
557  {
558  size_t __i = 0;
559  while (!eq(__s[__i], char_type()))
560  ++__i;
561  return __i;
562  }
563 
564  static const char_type*
565  find(const char_type* __s, size_t __n, const char_type& __a)
566  {
567  for (size_t __i = 0; __i < __n; ++__i)
568  if (eq(__s[__i], __a))
569  return __s + __i;
570  return 0;
571  }
572 
573  static char_type*
574  move(char_type* __s1, const char_type* __s2, size_t __n)
575  {
576  if (__n == 0)
577  return __s1;
578  return (static_cast<char_type*>
579  (__builtin_memmove(__s1, __s2, __n * sizeof(char_type))));
580  }
581 
582  static char_type*
583  copy(char_type* __s1, const char_type* __s2, size_t __n)
584  {
585  if (__n == 0)
586  return __s1;
587  return (static_cast<char_type*>
588  (__builtin_memcpy(__s1, __s2, __n * sizeof(char_type))));
589  }
590 
591  static char_type*
592  assign(char_type* __s, size_t __n, char_type __a)
593  {
594  for (size_t __i = 0; __i < __n; ++__i)
595  assign(__s[__i], __a);
596  return __s;
597  }
598 
599  static constexpr char_type
600  to_char_type(const int_type& __c) noexcept
601  { return char_type(__c); }
602 
603  static constexpr int_type
604  to_int_type(const char_type& __c) noexcept
605  { return int_type(__c); }
606 
607  static constexpr bool
608  eq_int_type(const int_type& __c1, const int_type& __c2) noexcept
609  { return __c1 == __c2; }
610 
611  static constexpr int_type
612  eof() noexcept
613  { return static_cast<int_type>(-1); }
614 
615  static constexpr int_type
616  not_eof(const int_type& __c) noexcept
617  { return eq_int_type(__c, eof()) ? 0 : __c; }
618  };
619 
620 _GLIBCXX_END_NAMESPACE_VERSION
621 } // namespace
622 
623 #endif
624 
625 #endif // _CHAR_TRAITS_H
std::char_traits
Basis for explicit traits specializations.
Definition: char_traits.h:227
std::fpos
Class representing stream positions.
Definition: postypes.h:112
__gnu_cxx
GNU extensions for public use.
__gnu_cxx::char_traits
Base class used to implement std::char_traits.
Definition: char_traits.h:83
std::streamoff
long long streamoff
Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
Definition: postypes.h:94
__gnu_cxx::_Char_types
Mapping from character type to associated types.
Definition: char_traits.h:58
std
ISO C++ entities toplevel namespace is std.