libstdc++
sso_string_base.h
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1 // Short-string-optimized versatile string base -*- C++ -*-
2 
3 // Copyright (C) 2005-2025 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 ext/sso_string_base.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{ext/vstring.h}
28  */
29 
30 #ifndef _SSO_STRING_BASE_H
31 #define _SSO_STRING_BASE_H 1
32 
33 #include <bits/requires_hosted.h> // GNU extensions are currently omitted
34 
35 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
36 {
37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
38 
39  template<typename _CharT, typename _Traits, typename _Alloc>
40  class __sso_string_base
41  : protected __vstring_utility<_CharT, _Traits, _Alloc>
42  {
43  public:
44  typedef _Traits traits_type;
45  typedef typename _Traits::char_type value_type;
46 
47  typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base;
48  typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type;
49  typedef typename _CharT_alloc_type::size_type size_type;
50 
51  private:
52  // Data Members:
53  typename _Util_Base::template _Alloc_hider<_CharT_alloc_type>
54  _M_dataplus;
55  size_type _M_string_length;
56 
57  enum { _S_local_capacity = 15 };
58 
59  union
60  {
61  _CharT _M_local_data[_S_local_capacity + 1];
62  size_type _M_allocated_capacity;
63  };
64 
65  void
66  _M_data(_CharT* __p)
67  { _M_dataplus._M_p = __p; }
68 
69  void
70  _M_length(size_type __length)
71  { _M_string_length = __length; }
72 
73  void
74  _M_capacity(size_type __capacity)
75  { _M_allocated_capacity = __capacity; }
76 
77  bool
78  _M_is_local() const
79  { return _M_data() == _M_local_data; }
80 
81  // Create & Destroy
82  _CharT*
83  _M_create(size_type&, size_type);
84 
85  void
86  _M_dispose()
87  {
88  if (!_M_is_local())
89  _M_destroy(_M_allocated_capacity);
90  }
91 
92  void
93  _M_destroy(size_type __size) throw()
94  { _M_get_allocator().deallocate(_M_data(), __size + 1); }
95 
96  // _M_construct_aux is used to implement the 21.3.1 para 15 which
97  // requires special behaviour if _InIterator is an integral type
98  template<typename _InIterator>
99  void
100  _M_construct_aux(_InIterator __beg, _InIterator __end,
101  std::__false_type)
102  {
104  _Tag;
105  _M_construct(__beg, __end, _Tag());
106  }
107 
108  // _GLIBCXX_RESOLVE_LIB_DEFECTS
109  // 438. Ambiguity in the "do the right thing" clause
110  template<typename _Integer>
111  void
112  _M_construct_aux(_Integer __beg, _Integer __end, std::__true_type)
113  { _M_construct_aux_2(static_cast<size_type>(__beg), __end); }
114 
115  void
116  _M_construct_aux_2(size_type __req, _CharT __c)
117  { _M_construct(__req, __c); }
118 
119  template<typename _InIterator>
120  void
121  _M_construct(_InIterator __beg, _InIterator __end)
122  {
123  typedef typename std::__is_integer<_InIterator>::__type _Integral;
124  _M_construct_aux(__beg, __end, _Integral());
125  }
126 
127  // For Input Iterators, used in istreambuf_iterators, etc.
128  template<typename _InIterator>
129  void
130  _M_construct(_InIterator __beg, _InIterator __end,
132 
133  // For forward_iterators up to random_access_iterators, used for
134  // string::iterator, _CharT*, etc.
135  template<typename _FwdIterator>
136  void
137  _M_construct(_FwdIterator __beg, _FwdIterator __end,
139 
140  void
141  _M_construct(size_type __req, _CharT __c);
142 
143  public:
144  size_type
145  _M_max_size() const
146  {
147  typedef __alloc_traits<_CharT_alloc_type> _ATraits;
148  return (_ATraits::max_size(_M_get_allocator()) - 1) / 2;
149  }
150 
151  _CharT*
152  _M_data() const
153  { return _M_dataplus._M_p; }
154 
155  size_type
156  _M_length() const
157  { return _M_string_length; }
158 
159  size_type
160  _M_capacity() const
161  {
162  return _M_is_local() ? size_type(_S_local_capacity)
163  : _M_allocated_capacity;
164  }
165 
166  bool
167  _M_is_shared() const
168  { return false; }
169 
170  void
171  _M_set_leaked() { }
172 
173  void
174  _M_leak() { }
175 
176  void
177  _M_set_length(size_type __n)
178  {
179  _M_length(__n);
180  traits_type::assign(_M_data()[__n], _CharT());
181  }
182 
183  __sso_string_base()
184  : _M_dataplus(_M_local_data)
185  { _M_set_length(0); }
186 
187  __sso_string_base(const _Alloc& __a);
188 
189  __sso_string_base(const __sso_string_base& __rcs);
190 
191 #if __cplusplus >= 201103L
192  __sso_string_base(__sso_string_base&& __rcs);
193 #endif
194 
195  __sso_string_base(size_type __n, _CharT __c, const _Alloc& __a);
196 
197  template<typename _InputIterator>
198  __sso_string_base(_InputIterator __beg, _InputIterator __end,
199  const _Alloc& __a);
200 
201  ~__sso_string_base()
202  { _M_dispose(); }
203 
204  _CharT_alloc_type&
205  _M_get_allocator()
206  { return _M_dataplus; }
207 
208  const _CharT_alloc_type&
209  _M_get_allocator() const
210  { return _M_dataplus; }
211 
212  void
213  _M_swap(__sso_string_base& __rcs);
214 
215  void
216  _M_assign(const __sso_string_base& __rcs);
217 
218  void
219  _M_reserve(size_type __res);
220 
221  void
222  _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
223  size_type __len2);
224 
225  void
226  _M_erase(size_type __pos, size_type __n);
227 
228  void
229  _M_clear()
230  { _M_set_length(0); }
231 
232  bool
233  _M_compare(const __sso_string_base&) const
234  { return false; }
235  };
236 
237  template<typename _CharT, typename _Traits, typename _Alloc>
238  void
239  __sso_string_base<_CharT, _Traits, _Alloc>::
240  _M_swap(__sso_string_base& __rcs)
241  {
242  if (this == &__rcs)
243  return;
244 
245  // _GLIBCXX_RESOLVE_LIB_DEFECTS
246  // 431. Swapping containers with unequal allocators.
247  std::__alloc_swap<_CharT_alloc_type>::_S_do_it(_M_get_allocator(),
248  __rcs._M_get_allocator());
249 
250  if (_M_is_local())
251  if (__rcs._M_is_local())
252  {
253  if (_M_length() && __rcs._M_length())
254  {
255  _CharT __tmp_data[_S_local_capacity + 1];
256  traits_type::copy(__tmp_data, __rcs._M_local_data,
257  _S_local_capacity + 1);
258  traits_type::copy(__rcs._M_local_data, _M_local_data,
259  _S_local_capacity + 1);
260  traits_type::copy(_M_local_data, __tmp_data,
261  _S_local_capacity + 1);
262  }
263  else if (__rcs._M_length())
264  {
265  traits_type::copy(_M_local_data, __rcs._M_local_data,
266  _S_local_capacity + 1);
267  _M_length(__rcs._M_length());
268  __rcs._M_set_length(0);
269  return;
270  }
271  else if (_M_length())
272  {
273  traits_type::copy(__rcs._M_local_data, _M_local_data,
274  _S_local_capacity + 1);
275  __rcs._M_length(_M_length());
276  _M_set_length(0);
277  return;
278  }
279  }
280  else
281  {
282  const size_type __tmp_capacity = __rcs._M_allocated_capacity;
283  traits_type::copy(__rcs._M_local_data, _M_local_data,
284  _S_local_capacity + 1);
285  _M_data(__rcs._M_data());
286  __rcs._M_data(__rcs._M_local_data);
287  _M_capacity(__tmp_capacity);
288  }
289  else
290  {
291  const size_type __tmp_capacity = _M_allocated_capacity;
292  if (__rcs._M_is_local())
293  {
294  traits_type::copy(_M_local_data, __rcs._M_local_data,
295  _S_local_capacity + 1);
296  __rcs._M_data(_M_data());
297  _M_data(_M_local_data);
298  }
299  else
300  {
301  _CharT* __tmp_ptr = _M_data();
302  _M_data(__rcs._M_data());
303  __rcs._M_data(__tmp_ptr);
304  _M_capacity(__rcs._M_allocated_capacity);
305  }
306  __rcs._M_capacity(__tmp_capacity);
307  }
308 
309  const size_type __tmp_length = _M_length();
310  _M_length(__rcs._M_length());
311  __rcs._M_length(__tmp_length);
312  }
313 
314  template<typename _CharT, typename _Traits, typename _Alloc>
315  _CharT*
316  __sso_string_base<_CharT, _Traits, _Alloc>::
317  _M_create(size_type& __capacity, size_type __old_capacity)
318  {
319  // _GLIBCXX_RESOLVE_LIB_DEFECTS
320  // 83. String::npos vs. string::max_size()
321  if (__capacity > _M_max_size())
322  std::__throw_length_error(__N("__sso_string_base::_M_create"));
323 
324  // The below implements an exponential growth policy, necessary to
325  // meet amortized linear time requirements of the library: see
326  // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
327  if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
328  {
329  __capacity = 2 * __old_capacity;
330  // Never allocate a string bigger than max_size.
331  if (__capacity > _M_max_size())
332  __capacity = _M_max_size();
333  }
334 
335  // NB: Need an array of char_type[__capacity], plus a terminating
336  // null char_type() element.
337  return _M_get_allocator().allocate(__capacity + 1);
338  }
339 
340  template<typename _CharT, typename _Traits, typename _Alloc>
341  __sso_string_base<_CharT, _Traits, _Alloc>::
342  __sso_string_base(const _Alloc& __a)
343  : _M_dataplus(__a, _M_local_data)
344  { _M_set_length(0); }
345 
346  template<typename _CharT, typename _Traits, typename _Alloc>
347  __sso_string_base<_CharT, _Traits, _Alloc>::
348  __sso_string_base(const __sso_string_base& __rcs)
349  : _M_dataplus(__rcs._M_get_allocator(), _M_local_data)
350  { _M_construct(__rcs._M_data(), __rcs._M_data() + __rcs._M_length()); }
351 
352 #if __cplusplus >= 201103L
353  template<typename _CharT, typename _Traits, typename _Alloc>
354  __sso_string_base<_CharT, _Traits, _Alloc>::
355  __sso_string_base(__sso_string_base&& __rcs)
356  : _M_dataplus(__rcs._M_get_allocator(), _M_local_data)
357  {
358  if (__rcs._M_is_local())
359  {
360  if (__rcs._M_length())
361  traits_type::copy(_M_local_data, __rcs._M_local_data,
362  _S_local_capacity + 1);
363  }
364  else
365  {
366  _M_data(__rcs._M_data());
367  _M_capacity(__rcs._M_allocated_capacity);
368  }
369 
370  _M_set_length(__rcs._M_length());
371  __rcs._M_data(__rcs._M_local_data);
372  __rcs._M_set_length(0);
373  }
374 #endif
375 
376  template<typename _CharT, typename _Traits, typename _Alloc>
377  __sso_string_base<_CharT, _Traits, _Alloc>::
378  __sso_string_base(size_type __n, _CharT __c, const _Alloc& __a)
379  : _M_dataplus(__a, _M_local_data)
380  { _M_construct(__n, __c); }
381 
382  template<typename _CharT, typename _Traits, typename _Alloc>
383  template<typename _InputIterator>
384  __sso_string_base<_CharT, _Traits, _Alloc>::
385  __sso_string_base(_InputIterator __beg, _InputIterator __end,
386  const _Alloc& __a)
387  : _M_dataplus(__a, _M_local_data)
388  { _M_construct(__beg, __end); }
389 
390  // NB: This is the special case for Input Iterators, used in
391  // istreambuf_iterators, etc.
392  // Input Iterators have a cost structure very different from
393  // pointers, calling for a different coding style.
394  template<typename _CharT, typename _Traits, typename _Alloc>
395  template<typename _InIterator>
396  void
397  __sso_string_base<_CharT, _Traits, _Alloc>::
398  _M_construct(_InIterator __beg, _InIterator __end,
400  {
401  size_type __len = 0;
402  size_type __capacity = size_type(_S_local_capacity);
403 
404  while (__beg != __end && __len < __capacity)
405  {
406  _M_data()[__len++] = *__beg;
407  ++__beg;
408  }
409 
410  __try
411  {
412  while (__beg != __end)
413  {
414  if (__len == __capacity)
415  {
416  // Allocate more space.
417  __capacity = __len + 1;
418  _CharT* __another = _M_create(__capacity, __len);
419  this->_S_copy(__another, _M_data(), __len);
420  _M_dispose();
421  _M_data(__another);
422  _M_capacity(__capacity);
423  }
424  _M_data()[__len++] = *__beg;
425  ++__beg;
426  }
427  }
428  __catch(...)
429  {
430  _M_dispose();
431  __throw_exception_again;
432  }
433 
434  _M_set_length(__len);
435  }
436 
437  template<typename _CharT, typename _Traits, typename _Alloc>
438  template<typename _InIterator>
439  void
440  __sso_string_base<_CharT, _Traits, _Alloc>::
441  _M_construct(_InIterator __beg, _InIterator __end,
443  {
444  // NB: Not required, but considered best practice.
445  if (__is_null_pointer(__beg) && __beg != __end)
446  std::__throw_logic_error(__N("__sso_string_base::"
447  "_M_construct null not valid"));
448 
449  size_type __dnew = static_cast<size_type>(std::distance(__beg, __end));
450 
451  if (__dnew > size_type(_S_local_capacity))
452  {
453  _M_data(_M_create(__dnew, size_type(0)));
454  _M_capacity(__dnew);
455  }
456 
457  // Check for out_of_range and length_error exceptions.
458  __try
459  { this->_S_copy_chars(_M_data(), __beg, __end); }
460  __catch(...)
461  {
462  _M_dispose();
463  __throw_exception_again;
464  }
465 
466  _M_set_length(__dnew);
467  }
468 
469  template<typename _CharT, typename _Traits, typename _Alloc>
470  void
471  __sso_string_base<_CharT, _Traits, _Alloc>::
472  _M_construct(size_type __n, _CharT __c)
473  {
474  if (__n > size_type(_S_local_capacity))
475  {
476  _M_data(_M_create(__n, size_type(0)));
477  _M_capacity(__n);
478  }
479 
480  if (__n)
481  this->_S_assign(_M_data(), __n, __c);
482 
483  _M_set_length(__n);
484  }
485 
486  template<typename _CharT, typename _Traits, typename _Alloc>
487  void
488  __sso_string_base<_CharT, _Traits, _Alloc>::
489  _M_assign(const __sso_string_base& __rcs)
490  {
491  if (this != &__rcs)
492  {
493  const size_type __rsize = __rcs._M_length();
494  const size_type __capacity = _M_capacity();
495 
496  if (__rsize > __capacity)
497  {
498  size_type __new_capacity = __rsize;
499  _CharT* __tmp = _M_create(__new_capacity, __capacity);
500  _M_dispose();
501  _M_data(__tmp);
502  _M_capacity(__new_capacity);
503  }
504 
505  if (__rsize)
506  this->_S_copy(_M_data(), __rcs._M_data(), __rsize);
507 
508  _M_set_length(__rsize);
509  }
510  }
511 
512  template<typename _CharT, typename _Traits, typename _Alloc>
513  void
514  __sso_string_base<_CharT, _Traits, _Alloc>::
515  _M_reserve(size_type __res)
516  {
517  // Make sure we don't shrink below the current size.
518  if (__res < _M_length())
519  __res = _M_length();
520 
521  const size_type __capacity = _M_capacity();
522  if (__res != __capacity)
523  {
524  if (__res > __capacity
525  || __res > size_type(_S_local_capacity))
526  {
527  _CharT* __tmp = _M_create(__res, __capacity);
528  this->_S_copy(__tmp, _M_data(), _M_length() + 1);
529  _M_dispose();
530  _M_data(__tmp);
531  _M_capacity(__res);
532  }
533  else if (!_M_is_local())
534  {
535  this->_S_copy(_M_local_data, _M_data(), _M_length() + 1);
536  _M_destroy(__capacity);
537  _M_data(_M_local_data);
538  }
539  }
540  }
541 
542  template<typename _CharT, typename _Traits, typename _Alloc>
543  void
544  __sso_string_base<_CharT, _Traits, _Alloc>::
545  _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
546  size_type __len2)
547  {
548  const size_type __how_much = _M_length() - __pos - __len1;
549 
550  size_type __new_capacity = _M_length() + __len2 - __len1;
551  _CharT* __r = _M_create(__new_capacity, _M_capacity());
552 
553  if (__pos)
554  this->_S_copy(__r, _M_data(), __pos);
555  if (__s && __len2)
556  this->_S_copy(__r + __pos, __s, __len2);
557  if (__how_much)
558  this->_S_copy(__r + __pos + __len2,
559  _M_data() + __pos + __len1, __how_much);
560 
561  _M_dispose();
562  _M_data(__r);
563  _M_capacity(__new_capacity);
564  }
565 
566  template<typename _CharT, typename _Traits, typename _Alloc>
567  void
568  __sso_string_base<_CharT, _Traits, _Alloc>::
569  _M_erase(size_type __pos, size_type __n)
570  {
571  const size_type __how_much = _M_length() - __pos - __n;
572 
573  if (__how_much && __n)
574  this->_S_move(_M_data() + __pos, _M_data() + __pos + __n, __how_much);
575 
576  _M_set_length(_M_length() - __n);
577  }
578 
579 _GLIBCXX_END_NAMESPACE_VERSION
580 } // namespace
581 
582 #endif /* _SSO_STRING_BASE_H */
constexpr iterator_traits< _InputIterator >::difference_type distance(_InputIterator __first, _InputIterator __last)
A generalization of pointer arithmetic.
GNU extensions for public use.
Marking input iterators.
Forward iterators support a superset of input iterator operations.
Traits class for iterators.