libstdc++
rc_string_base.h
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1// Reference-counted versatile string base -*- C++ -*-
2
3// Copyright (C) 2005-2022 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/rc_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 _RC_STRING_BASE_H
31#define _RC_STRING_BASE_H 1
32
33#include <ext/atomicity.h>
34#include <ext/alloc_traits.h>
36
37namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
38{
39_GLIBCXX_BEGIN_NAMESPACE_VERSION
40
41 /**
42 * Documentation? What's that?
43 * Nathan Myers <[email protected]>.
44 *
45 * A string looks like this:
46 *
47 * @code
48 * [_Rep]
49 * _M_length
50 * [__rc_string_base<char_type>] _M_capacity
51 * _M_dataplus _M_refcount
52 * _M_p ----------------> unnamed array of char_type
53 * @endcode
54 *
55 * Where the _M_p points to the first character in the string, and
56 * you cast it to a pointer-to-_Rep and subtract 1 to get a
57 * pointer to the header.
58 *
59 * This approach has the enormous advantage that a string object
60 * requires only one allocation. All the ugliness is confined
61 * within a single pair of inline functions, which each compile to
62 * a single @a add instruction: _Rep::_M_refdata(), and
63 * __rc_string_base::_M_rep(); and the allocation function which gets a
64 * block of raw bytes and with room enough and constructs a _Rep
65 * object at the front.
66 *
67 * The reason you want _M_data pointing to the character array and
68 * not the _Rep is so that the debugger can see the string
69 * contents. (Probably we should add a non-inline member to get
70 * the _Rep for the debugger to use, so users can check the actual
71 * string length.)
72 *
73 * Note that the _Rep object is a POD so that you can have a
74 * static <em>empty string</em> _Rep object already @a constructed before
75 * static constructors have run. The reference-count encoding is
76 * chosen so that a 0 indicates one reference, so you never try to
77 * destroy the empty-string _Rep object.
78 *
79 * All but the last paragraph is considered pretty conventional
80 * for a C++ string implementation.
81 */
82 template<typename _CharT, typename _Traits, typename _Alloc>
84 : protected __vstring_utility<_CharT, _Traits, _Alloc>
85 {
86 public:
87 typedef _Traits traits_type;
88 typedef typename _Traits::char_type value_type;
89 typedef _Alloc allocator_type;
90
91 typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base;
92 typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type;
93 typedef typename _CharT_alloc_type::size_type size_type;
94
95 private:
96 // _Rep: string representation
97 // Invariants:
98 // 1. String really contains _M_length + 1 characters: due to 21.3.4
99 // must be kept null-terminated.
100 // 2. _M_capacity >= _M_length
101 // Allocated memory is always (_M_capacity + 1) * sizeof(_CharT).
102 // 3. _M_refcount has three states:
103 // -1: leaked, one reference, no ref-copies allowed, non-const.
104 // 0: one reference, non-const.
105 // n>0: n + 1 references, operations require a lock, const.
106 // 4. All fields == 0 is an empty string, given the extra storage
107 // beyond-the-end for a null terminator; thus, the shared
108 // empty string representation needs no constructor.
109 struct _Rep
110 {
111 union
112 {
113 struct
114 {
115 size_type _M_length;
116 size_type _M_capacity;
117 _Atomic_word _M_refcount;
118 } _M_info;
119
120 // Only for alignment purposes.
121 _CharT _M_align;
122 };
123
124 typedef typename __alloc_traits<_Alloc>::template rebind<_Rep>::other
125 _Rep_alloc_type;
126
127 _CharT*
128 _M_refdata() throw()
129 { return reinterpret_cast<_CharT*>(this + 1); }
130
131 _CharT*
132 _M_refcopy() throw()
133 {
134 __atomic_add_dispatch(&_M_info._M_refcount, 1);
135 return _M_refdata();
136 } // XXX MT
137
138 void
139 _M_set_length(size_type __n)
140 {
141 _M_info._M_refcount = 0; // One reference.
142 _M_info._M_length = __n;
143 // grrr. (per 21.3.4)
144 // You cannot leave those LWG people alone for a second.
145 traits_type::assign(_M_refdata()[__n], _CharT());
146 }
147
148 // Create & Destroy
149 static _Rep*
150 _S_create(size_type, size_type, const _Alloc&);
151
152 void
153 _M_destroy(const _Alloc&) throw();
154
155 _CharT*
156 _M_clone(const _Alloc&, size_type __res = 0);
157 };
158
159 struct _Rep_empty
160 : public _Rep
161 {
162 _CharT _M_terminal;
163 };
164
165 static _Rep_empty _S_empty_rep;
166
167 // The maximum number of individual char_type elements of an
168 // individual string is determined by _S_max_size. This is the
169 // value that will be returned by max_size(). (Whereas npos
170 // is the maximum number of bytes the allocator can allocate.)
171 // If one was to divvy up the theoretical largest size string,
172 // with a terminating character and m _CharT elements, it'd
173 // look like this:
174 // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT)
175 // + sizeof(_Rep) - 1
176 // (NB: last two terms for rounding reasons, see _M_create below)
177 // Solving for m:
178 // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1
179 // In addition, this implementation halves this amount.
180 enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep)
181 + 1) / sizeof(_CharT)) - 1) / 2 };
182
183 // Data Member (private):
184 mutable typename _Util_Base::template _Alloc_hider<_Alloc> _M_dataplus;
185
186 void
187 _M_data(_CharT* __p)
188 { _M_dataplus._M_p = __p; }
189
190 _Rep*
191 _M_rep() const
192 { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); }
193
194 _CharT*
195 _M_grab(const _Alloc& __alloc) const
196 {
197 return (!_M_is_leaked() && _M_get_allocator() == __alloc)
198 ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc);
199 }
200
201 void
202 _M_dispose()
203 {
204 // Be race-detector-friendly. For more info see bits/c++config.
205 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_rep()->_M_info.
206 _M_refcount);
207 if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount,
208 -1) <= 0)
209 {
210 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_rep()->_M_info.
211 _M_refcount);
212 _M_rep()->_M_destroy(_M_get_allocator());
213 }
214 } // XXX MT
215
216 bool
217 _M_is_leaked() const
218 { return _M_rep()->_M_info._M_refcount < 0; }
219
220 void
221 _M_set_sharable()
222 { _M_rep()->_M_info._M_refcount = 0; }
223
224 void
225 _M_leak_hard();
226
227 // _S_construct_aux is used to implement the 21.3.1 para 15 which
228 // requires special behaviour if _InIterator is an integral type
229 template<typename _InIterator>
230 static _CharT*
231 _S_construct_aux(_InIterator __beg, _InIterator __end,
232 const _Alloc& __a, std::__false_type)
233 {
235 _Tag;
236 return _S_construct(__beg, __end, __a, _Tag());
237 }
238
239 // _GLIBCXX_RESOLVE_LIB_DEFECTS
240 // 438. Ambiguity in the "do the right thing" clause
241 template<typename _Integer>
242 static _CharT*
243 _S_construct_aux(_Integer __beg, _Integer __end,
244 const _Alloc& __a, std::__true_type)
245 { return _S_construct_aux_2(static_cast<size_type>(__beg),
246 __end, __a); }
247
248 static _CharT*
249 _S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a)
250 { return _S_construct(__req, __c, __a); }
251
252 template<typename _InIterator>
253 static _CharT*
254 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a)
255 {
256 typedef typename std::__is_integer<_InIterator>::__type _Integral;
257 return _S_construct_aux(__beg, __end, __a, _Integral());
258 }
259
260 // For Input Iterators, used in istreambuf_iterators, etc.
261 template<typename _InIterator>
262 static _CharT*
263 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
265
266 // For forward_iterators up to random_access_iterators, used for
267 // string::iterator, _CharT*, etc.
268 template<typename _FwdIterator>
269 static _CharT*
270 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a,
272
273 static _CharT*
274 _S_construct(size_type __req, _CharT __c, const _Alloc& __a);
275
276 public:
277 size_type
278 _M_max_size() const
279 { return size_type(_S_max_size); }
280
281 _CharT*
282 _M_data() const
283 { return _M_dataplus._M_p; }
284
285 size_type
286 _M_length() const
287 { return _M_rep()->_M_info._M_length; }
288
289 size_type
290 _M_capacity() const
291 { return _M_rep()->_M_info._M_capacity; }
292
293 bool
294 _M_is_shared() const
295 { return _M_rep()->_M_info._M_refcount > 0; }
296
297 void
298 _M_set_leaked()
299 { _M_rep()->_M_info._M_refcount = -1; }
300
301 void
302 _M_leak() // for use in begin() & non-const op[]
303 {
304 if (!_M_is_leaked())
305 _M_leak_hard();
306 }
307
308 void
309 _M_set_length(size_type __n)
310 { _M_rep()->_M_set_length(__n); }
311
313 : _M_dataplus(_S_empty_rep._M_refcopy()) { }
314
315 __rc_string_base(const _Alloc& __a);
316
318
319#if __cplusplus >= 201103L
321 : _M_dataplus(__rcs._M_dataplus)
322 { __rcs._M_data(_S_empty_rep._M_refcopy()); }
323#endif
324
325 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a);
326
327 template<typename _InputIterator>
328 __rc_string_base(_InputIterator __beg, _InputIterator __end,
329 const _Alloc& __a);
330
332 { _M_dispose(); }
333
334 allocator_type&
335 _M_get_allocator()
336 { return _M_dataplus; }
337
338 const allocator_type&
339 _M_get_allocator() const
340 { return _M_dataplus; }
341
342 void
343 _M_swap(__rc_string_base& __rcs);
344
345 void
346 _M_assign(const __rc_string_base& __rcs);
347
348 void
349 _M_reserve(size_type __res);
350
351 void
352 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
353 size_type __len2);
354
355 void
356 _M_erase(size_type __pos, size_type __n);
357
358 void
359 _M_clear()
360 {
361 _M_dispose();
362 _M_data(_S_empty_rep._M_refcopy());
363 }
364
365 bool
366 _M_compare(const __rc_string_base&) const
367 { return false; }
368 };
369
370 template<typename _CharT, typename _Traits, typename _Alloc>
373
374 template<typename _CharT, typename _Traits, typename _Alloc>
377 _S_create(size_type __capacity, size_type __old_capacity,
378 const _Alloc& __alloc)
379 {
380 // _GLIBCXX_RESOLVE_LIB_DEFECTS
381 // 83. String::npos vs. string::max_size()
382 if (__capacity > size_type(_S_max_size))
383 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create"));
384
385 // The standard places no restriction on allocating more memory
386 // than is strictly needed within this layer at the moment or as
387 // requested by an explicit application call to reserve().
388
389 // Many malloc implementations perform quite poorly when an
390 // application attempts to allocate memory in a stepwise fashion
391 // growing each allocation size by only 1 char. Additionally,
392 // it makes little sense to allocate less linear memory than the
393 // natural blocking size of the malloc implementation.
394 // Unfortunately, we would need a somewhat low-level calculation
395 // with tuned parameters to get this perfect for any particular
396 // malloc implementation. Fortunately, generalizations about
397 // common features seen among implementations seems to suffice.
398
399 // __pagesize need not match the actual VM page size for good
400 // results in practice, thus we pick a common value on the low
401 // side. __malloc_header_size is an estimate of the amount of
402 // overhead per memory allocation (in practice seen N * sizeof
403 // (void*) where N is 0, 2 or 4). According to folklore,
404 // picking this value on the high side is better than
405 // low-balling it (especially when this algorithm is used with
406 // malloc implementations that allocate memory blocks rounded up
407 // to a size which is a power of 2).
408 const size_type __pagesize = 4096;
409 const size_type __malloc_header_size = 4 * sizeof(void*);
410
411 // The below implements an exponential growth policy, necessary to
412 // meet amortized linear time requirements of the library: see
413 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
414 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
415 {
416 __capacity = 2 * __old_capacity;
417 // Never allocate a string bigger than _S_max_size.
418 if (__capacity > size_type(_S_max_size))
419 __capacity = size_type(_S_max_size);
420 }
421
422 // NB: Need an array of char_type[__capacity], plus a terminating
423 // null char_type() element, plus enough for the _Rep data structure,
424 // plus sizeof(_Rep) - 1 to upper round to a size multiple of
425 // sizeof(_Rep).
426 // Whew. Seemingly so needy, yet so elemental.
427 size_type __size = ((__capacity + 1) * sizeof(_CharT)
428 + 2 * sizeof(_Rep) - 1);
429
430 const size_type __adj_size = __size + __malloc_header_size;
431 if (__adj_size > __pagesize && __capacity > __old_capacity)
432 {
433 const size_type __extra = __pagesize - __adj_size % __pagesize;
434 __capacity += __extra / sizeof(_CharT);
435 if (__capacity > size_type(_S_max_size))
436 __capacity = size_type(_S_max_size);
437 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1;
438 }
439
440 // NB: Might throw, but no worries about a leak, mate: _Rep()
441 // does not throw.
442 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep));
443 _Rep* __p = new (__place) _Rep;
444 __p->_M_info._M_capacity = __capacity;
445 return __p;
446 }
447
448 template<typename _CharT, typename _Traits, typename _Alloc>
449 void
450 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
451 _M_destroy(const _Alloc& __a) throw ()
452 {
453 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT)
454 + 2 * sizeof(_Rep) - 1);
455 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep));
456 }
457
458 template<typename _CharT, typename _Traits, typename _Alloc>
459 _CharT*
460 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
461 _M_clone(const _Alloc& __alloc, size_type __res)
462 {
463 // Requested capacity of the clone.
464 const size_type __requested_cap = _M_info._M_length + __res;
465 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity,
466 __alloc);
467
468 if (_M_info._M_length)
469 __rc_string_base::_S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length);
470
471 __r->_M_set_length(_M_info._M_length);
472 return __r->_M_refdata();
473 }
474
475 template<typename _CharT, typename _Traits, typename _Alloc>
476 __rc_string_base<_CharT, _Traits, _Alloc>::
477 __rc_string_base(const _Alloc& __a)
478 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { }
479
480 template<typename _CharT, typename _Traits, typename _Alloc>
481 __rc_string_base<_CharT, _Traits, _Alloc>::
482 __rc_string_base(const __rc_string_base& __rcs)
483 : _M_dataplus(__rcs._M_get_allocator(),
484 __rcs._M_grab(__rcs._M_get_allocator())) { }
485
486 template<typename _CharT, typename _Traits, typename _Alloc>
487 __rc_string_base<_CharT, _Traits, _Alloc>::
488 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a)
489 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { }
490
491 template<typename _CharT, typename _Traits, typename _Alloc>
492 template<typename _InputIterator>
493 __rc_string_base<_CharT, _Traits, _Alloc>::
494 __rc_string_base(_InputIterator __beg, _InputIterator __end,
495 const _Alloc& __a)
496 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { }
497
498 template<typename _CharT, typename _Traits, typename _Alloc>
499 void
500 __rc_string_base<_CharT, _Traits, _Alloc>::
501 _M_leak_hard()
502 {
503 if (_M_is_shared())
504 _M_erase(0, 0);
505 _M_set_leaked();
506 }
507
508 // NB: This is the special case for Input Iterators, used in
509 // istreambuf_iterators, etc.
510 // Input Iterators have a cost structure very different from
511 // pointers, calling for a different coding style.
512 template<typename _CharT, typename _Traits, typename _Alloc>
513 template<typename _InIterator>
514 _CharT*
515 __rc_string_base<_CharT, _Traits, _Alloc>::
516 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
518 {
519 if (__beg == __end && __a == _Alloc())
520 return _S_empty_rep._M_refcopy();
521
522 // Avoid reallocation for common case.
523 _CharT __buf[128];
524 size_type __len = 0;
525 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
526 {
527 __buf[__len++] = *__beg;
528 ++__beg;
529 }
530 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
531 _S_copy(__r->_M_refdata(), __buf, __len);
532 __try
533 {
534 while (__beg != __end)
535 {
536 if (__len == __r->_M_info._M_capacity)
537 {
538 // Allocate more space.
539 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
540 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
541 __r->_M_destroy(__a);
542 __r = __another;
543 }
544 __r->_M_refdata()[__len++] = *__beg;
545 ++__beg;
546 }
547 }
548 __catch(...)
549 {
550 __r->_M_destroy(__a);
551 __throw_exception_again;
552 }
553 __r->_M_set_length(__len);
554 return __r->_M_refdata();
555 }
556
557 template<typename _CharT, typename _Traits, typename _Alloc>
558 template<typename _InIterator>
559 _CharT*
560 __rc_string_base<_CharT, _Traits, _Alloc>::
561 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
563 {
564 if (__beg == __end && __a == _Alloc())
565 return _S_empty_rep._M_refcopy();
566
567 // NB: Not required, but considered best practice.
568 if (__is_null_pointer(__beg) && __beg != __end)
569 std::__throw_logic_error(__N("__rc_string_base::"
570 "_S_construct null not valid"));
571
572 const size_type __dnew = static_cast<size_type>(std::distance(__beg,
573 __end));
574 // Check for out_of_range and length_error exceptions.
575 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
576 __try
577 { __rc_string_base::_S_copy_chars(__r->_M_refdata(), __beg, __end); }
578 __catch(...)
579 {
580 __r->_M_destroy(__a);
581 __throw_exception_again;
582 }
583 __r->_M_set_length(__dnew);
584 return __r->_M_refdata();
585 }
586
587 template<typename _CharT, typename _Traits, typename _Alloc>
588 _CharT*
589 __rc_string_base<_CharT, _Traits, _Alloc>::
590 _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
591 {
592 if (__n == 0 && __a == _Alloc())
593 return _S_empty_rep._M_refcopy();
594
595 // Check for out_of_range and length_error exceptions.
596 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
597 if (__n)
598 __rc_string_base::_S_assign(__r->_M_refdata(), __n, __c);
599
600 __r->_M_set_length(__n);
601 return __r->_M_refdata();
602 }
603
604 template<typename _CharT, typename _Traits, typename _Alloc>
605 void
606 __rc_string_base<_CharT, _Traits, _Alloc>::
607 _M_swap(__rc_string_base& __rcs)
608 {
609 if (_M_is_leaked())
610 _M_set_sharable();
611 if (__rcs._M_is_leaked())
612 __rcs._M_set_sharable();
613
614 _CharT* __tmp = _M_data();
615 _M_data(__rcs._M_data());
616 __rcs._M_data(__tmp);
617
618 // _GLIBCXX_RESOLVE_LIB_DEFECTS
619 // 431. Swapping containers with unequal allocators.
620 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(),
621 __rcs._M_get_allocator());
622 }
623
624 template<typename _CharT, typename _Traits, typename _Alloc>
625 void
626 __rc_string_base<_CharT, _Traits, _Alloc>::
627 _M_assign(const __rc_string_base& __rcs)
628 {
629 if (_M_rep() != __rcs._M_rep())
630 {
631 _CharT* __tmp = __rcs._M_grab(_M_get_allocator());
632 _M_dispose();
633 _M_data(__tmp);
634 }
635 }
636
637 template<typename _CharT, typename _Traits, typename _Alloc>
638 void
639 __rc_string_base<_CharT, _Traits, _Alloc>::
640 _M_reserve(size_type __res)
641 {
642 // Make sure we don't shrink below the current size.
643 if (__res < _M_length())
644 __res = _M_length();
645
646 if (__res != _M_capacity() || _M_is_shared())
647 {
648 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(),
649 __res - _M_length());
650 _M_dispose();
651 _M_data(__tmp);
652 }
653 }
654
655 template<typename _CharT, typename _Traits, typename _Alloc>
656 void
657 __rc_string_base<_CharT, _Traits, _Alloc>::
658 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
659 size_type __len2)
660 {
661 const size_type __how_much = _M_length() - __pos - __len1;
662
663 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1,
664 _M_capacity(), _M_get_allocator());
665
666 if (__pos)
667 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
668 if (__s && __len2)
669 this->_S_copy(__r->_M_refdata() + __pos, __s, __len2);
670 if (__how_much)
671 this->_S_copy(__r->_M_refdata() + __pos + __len2,
672 _M_data() + __pos + __len1, __how_much);
673
674 _M_dispose();
675 _M_data(__r->_M_refdata());
676 }
677
678 template<typename _CharT, typename _Traits, typename _Alloc>
679 void
680 __rc_string_base<_CharT, _Traits, _Alloc>::
681 _M_erase(size_type __pos, size_type __n)
682 {
683 const size_type __new_size = _M_length() - __n;
684 const size_type __how_much = _M_length() - __pos - __n;
685
686 if (_M_is_shared())
687 {
688 // Must reallocate.
689 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(),
690 _M_get_allocator());
691
692 if (__pos)
693 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
694 if (__how_much)
695 this->_S_copy(__r->_M_refdata() + __pos,
696 _M_data() + __pos + __n, __how_much);
697
698 _M_dispose();
699 _M_data(__r->_M_refdata());
700 }
701 else if (__how_much && __n)
702 {
703 // Work in-place.
704 this->_S_move(_M_data() + __pos,
705 _M_data() + __pos + __n, __how_much);
706 }
707
708 _M_rep()->_M_set_length(__new_size);
709 }
710
711 template<>
712 inline bool
713 __rc_string_base<char, std::char_traits<char>,
715 _M_compare(const __rc_string_base& __rcs) const
716 {
717 if (_M_rep() == __rcs._M_rep())
718 return true;
719 return false;
720 }
721
722 template<>
723 inline bool
724 __rc_string_base<wchar_t, std::char_traits<wchar_t>,
726 _M_compare(const __rc_string_base& __rcs) const
727 {
728 if (_M_rep() == __rcs._M_rep())
729 return true;
730 return false;
731 }
732
733_GLIBCXX_END_NAMESPACE_VERSION
734} // namespace
735
736#endif /* _RC_STRING_BASE_H */
constexpr iterator_traits< _InputIterator >::difference_type distance(_InputIterator __first, _InputIterator __last)
A generalization of pointer arithmetic.
GNU extensions for public use.
The standard allocator, as per C++03 [20.4.1].
Definition: allocator.h:125
Traits class for iterators.
Marking input iterators.
Forward iterators support a superset of input iterator operations.
Uniform interface to C++98 and C++11 allocators.