1 // Reference-counted versatile string base -*- C++ -*-
2
3 // Copyright (C) 2005-2023 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 <bits/requires_hosted.h> // GNU extensions are currently omitted
34
35 #include <ext/atomicity.h>
36 #include <ext/alloc_traits.h>
37 #include <bits/stl_iterator_base_funcs.h>
38
39 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
40 {
41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
42
43 /**
44 * Documentation? What's that?
45 * Nathan Myers <ncm@cantrip.org>.
46 *
47 * A string looks like this:
48 *
49 * @code
50 * [_Rep]
51 * _M_length
52 * [__rc_string_base<char_type>] _M_capacity
53 * _M_dataplus _M_refcount
54 * _M_p ----------------> unnamed array of char_type
55 * @endcode
56 *
57 * Where the _M_p points to the first character in the string, and
58 * you cast it to a pointer-to-_Rep and subtract 1 to get a
59 * pointer to the header.
60 *
61 * This approach has the enormous advantage that a string object
62 * requires only one allocation. All the ugliness is confined
63 * within a single pair of inline functions, which each compile to
64 * a single @a add instruction: _Rep::_M_refdata(), and
65 * __rc_string_base::_M_rep(); and the allocation function which gets a
66 * block of raw bytes and with room enough and constructs a _Rep
67 * object at the front.
68 *
69 * The reason you want _M_data pointing to the character array and
70 * not the _Rep is so that the debugger can see the string
71 * contents. (Probably we should add a non-inline member to get
72 * the _Rep for the debugger to use, so users can check the actual
73 * string length.)
74 *
75 * Note that the _Rep object is a POD so that you can have a
76 * static <em>empty string</em> _Rep object already @a constructed before
77 * static constructors have run. The reference-count encoding is
78 * chosen so that a 0 indicates one reference, so you never try to
79 * destroy the empty-string _Rep object.
80 *
81 * All but the last paragraph is considered pretty conventional
82 * for a C++ string implementation.
83 */
84 template<typename _CharT, typename _Traits, typename _Alloc>
85 class __rc_string_base
86 : protected __vstring_utility<_CharT, _Traits, _Alloc>
87 {
88 public:
89 typedef _Traits traits_type;
90 typedef typename _Traits::char_type value_type;
91 typedef _Alloc allocator_type;
92
93 typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base;
94 typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type;
95 typedef typename _CharT_alloc_type::size_type size_type;
96
97 private:
98 // _Rep: string representation
99 // Invariants:
100 // 1. String really contains _M_length + 1 characters: due to 21.3.4
101 // must be kept null-terminated.
102 // 2. _M_capacity >= _M_length
103 // Allocated memory is always (_M_capacity + 1) * sizeof(_CharT).
104 // 3. _M_refcount has three states:
105 // -1: leaked, one reference, no ref-copies allowed, non-const.
106 // 0: one reference, non-const.
107 // n>0: n + 1 references, operations require a lock, const.
108 // 4. All fields == 0 is an empty string, given the extra storage
109 // beyond-the-end for a null terminator; thus, the shared
110 // empty string representation needs no constructor.
111 struct _Rep
112 {
113 union
114 {
115 struct
116 {
117 size_type _M_length;
118 size_type _M_capacity;
119 _Atomic_word _M_refcount;
120 } _M_info;
121
122 // Only for alignment purposes.
123 _CharT _M_align;
124 };
125
126 typedef typename __alloc_traits<_Alloc>::template rebind<_Rep>::other
127 _Rep_alloc_type;
128
129 _CharT*
130 _M_refdata() throw()
131 { return reinterpret_cast<_CharT*>(this + 1); }
132
133 _CharT*
134 _M_refcopy() throw()
135 {
136 __atomic_add_dispatch(&_M_info._M_refcount, 1);
137 return _M_refdata();
138 } // XXX MT
139
140 void
141 _M_set_length(size_type __n)
142 {
143 _M_info._M_refcount = 0; // One reference.
144 _M_info._M_length = __n;
145 // grrr. (per 21.3.4)
146 // You cannot leave those LWG people alone for a second.
147 traits_type::assign(_M_refdata()[__n], _CharT());
148 }
149
150 // Create & Destroy
151 static _Rep*
152 _S_create(size_type, size_type, const _Alloc&);
153
154 void
155 _M_destroy(const _Alloc&) throw();
156
157 _CharT*
158 _M_clone(const _Alloc&, size_type __res = 0);
159 };
160
161 struct _Rep_empty
162 : public _Rep
163 {
164 _CharT _M_terminal;
165 };
166
167 static _Rep_empty _S_empty_rep;
168
169 // The maximum number of individual char_type elements of an
170 // individual string is determined by _S_max_size. This is the
171 // value that will be returned by max_size(). (Whereas npos
172 // is the maximum number of bytes the allocator can allocate.)
173 // If one was to divvy up the theoretical largest size string,
174 // with a terminating character and m _CharT elements, it'd
175 // look like this:
176 // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT)
177 // + sizeof(_Rep) - 1
178 // (NB: last two terms for rounding reasons, see _M_create below)
179 // Solving for m:
180 // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1
181 // In addition, this implementation halves this amount.
182 enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep)
183 + 1) / sizeof(_CharT)) - 1) / 2 };
184
185 // Data Member (private):
186 mutable typename _Util_Base::template _Alloc_hider<_Alloc> _M_dataplus;
187
188 void
189 _M_data(_CharT* __p)
190 { _M_dataplus._M_p = __p; }
191
192 _Rep*
193 _M_rep() const
194 { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); }
195
196 _CharT*
197 _M_grab(const _Alloc& __alloc) const
198 {
199 return (!_M_is_leaked() && _M_get_allocator() == __alloc)
200 ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc);
201 }
202
203 void
204 _M_dispose()
205 {
206 // Be race-detector-friendly. For more info see bits/c++config.
207 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_rep()->_M_info.
208 _M_refcount);
209 if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount,
210 -1) <= 0)
211 {
212 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_rep()->_M_info.
213 _M_refcount);
214 _M_rep()->_M_destroy(_M_get_allocator());
215 }
216 } // XXX MT
217
218 bool
219 _M_is_leaked() const
220 { return _M_rep()->_M_info._M_refcount < 0; }
221
222 void
223 _M_set_sharable()
224 { _M_rep()->_M_info._M_refcount = 0; }
225
226 void
227 _M_leak_hard();
228
229 // _S_construct_aux is used to implement the 21.3.1 para 15 which
230 // requires special behaviour if _InIterator is an integral type
231 template<typename _InIterator>
232 static _CharT*
233 _S_construct_aux(_InIterator __beg, _InIterator __end,
234 const _Alloc& __a, std::__false_type)
235 {
236 typedef typename std::iterator_traits<_InIterator>::iterator_category
237 _Tag;
238 return _S_construct(__beg, __end, __a, _Tag());
239 }
240
241 // _GLIBCXX_RESOLVE_LIB_DEFECTS
242 // 438. Ambiguity in the "do the right thing" clause
243 template<typename _Integer>
244 static _CharT*
245 _S_construct_aux(_Integer __beg, _Integer __end,
246 const _Alloc& __a, std::__true_type)
247 { return _S_construct_aux_2(static_cast<size_type>(__beg),
248 __end, __a); }
249
250 static _CharT*
251 _S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a)
252 { return _S_construct(__req, __c, __a); }
253
254 template<typename _InIterator>
255 static _CharT*
256 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a)
257 {
258 typedef typename std::__is_integer<_InIterator>::__type _Integral;
259 return _S_construct_aux(__beg, __end, __a, _Integral());
260 }
261
262 // For Input Iterators, used in istreambuf_iterators, etc.
263 template<typename _InIterator>
264 static _CharT*
265 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
266 std::input_iterator_tag);
267
268 // For forward_iterators up to random_access_iterators, used for
269 // string::iterator, _CharT*, etc.
270 template<typename _FwdIterator>
271 static _CharT*
272 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a,
273 std::forward_iterator_tag);
274
275 static _CharT*
276 _S_construct(size_type __req, _CharT __c, const _Alloc& __a);
277
278 public:
279 size_type
280 _M_max_size() const
281 { return size_type(_S_max_size); }
282
283 _CharT*
284 _M_data() const
285 { return _M_dataplus._M_p; }
286
287 size_type
288 _M_length() const
289 { return _M_rep()->_M_info._M_length; }
290
291 size_type
292 _M_capacity() const
293 { return _M_rep()->_M_info._M_capacity; }
294
295 bool
296 _M_is_shared() const
297 { return _M_rep()->_M_info._M_refcount > 0; }
298
299 void
300 _M_set_leaked()
301 { _M_rep()->_M_info._M_refcount = -1; }
302
303 void
304 _M_leak() // for use in begin() & non-const op[]
305 {
306 if (!_M_is_leaked())
307 _M_leak_hard();
308 }
309
310 void
311 _M_set_length(size_type __n)
312 { _M_rep()->_M_set_length(__n); }
313
314 __rc_string_base()
315 : _M_dataplus(_S_empty_rep._M_refcopy()) { }
316
317 __rc_string_base(const _Alloc& __a);
318
319 __rc_string_base(const __rc_string_base& __rcs);
320
321 #if __cplusplus >= 201103L
322 __rc_string_base(__rc_string_base&& __rcs)
323 : _M_dataplus(__rcs._M_dataplus)
324 { __rcs._M_data(_S_empty_rep._M_refcopy()); }
325 #endif
326
327 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a);
328
329 template<typename _InputIterator>
330 __rc_string_base(_InputIterator __beg, _InputIterator __end,
331 const _Alloc& __a);
332
333 ~__rc_string_base()
334 { _M_dispose(); }
335
336 allocator_type&
337 _M_get_allocator()
338 { return _M_dataplus; }
339
340 const allocator_type&
341 _M_get_allocator() const
342 { return _M_dataplus; }
343
344 void
345 _M_swap(__rc_string_base& __rcs);
346
347 void
348 _M_assign(const __rc_string_base& __rcs);
349
350 void
351 _M_reserve(size_type __res);
352
353 void
354 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
355 size_type __len2);
356
357 void
358 _M_erase(size_type __pos, size_type __n);
359
360 void
361 _M_clear()
362 {
363 _M_dispose();
364 _M_data(_S_empty_rep._M_refcopy());
365 }
366
367 bool
368 _M_compare(const __rc_string_base&) const
369 { return false; }
370 };
371
372 template<typename _CharT, typename _Traits, typename _Alloc>
373 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty
374 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep;
375
376 template<typename _CharT, typename _Traits, typename _Alloc>
377 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep*
378 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
379 _S_create(size_type __capacity, size_type __old_capacity,
380 const _Alloc& __alloc)
381 {
382 // _GLIBCXX_RESOLVE_LIB_DEFECTS
383 // 83. String::npos vs. string::max_size()
384 if (__capacity > size_type(_S_max_size))
385 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create"));
386
387 // The standard places no restriction on allocating more memory
388 // than is strictly needed within this layer at the moment or as
389 // requested by an explicit application call to reserve().
390
391 // Many malloc implementations perform quite poorly when an
392 // application attempts to allocate memory in a stepwise fashion
393 // growing each allocation size by only 1 char. Additionally,
394 // it makes little sense to allocate less linear memory than the
395 // natural blocking size of the malloc implementation.
396 // Unfortunately, we would need a somewhat low-level calculation
397 // with tuned parameters to get this perfect for any particular
398 // malloc implementation. Fortunately, generalizations about
399 // common features seen among implementations seems to suffice.
400
401 // __pagesize need not match the actual VM page size for good
402 // results in practice, thus we pick a common value on the low
403 // side. __malloc_header_size is an estimate of the amount of
404 // overhead per memory allocation (in practice seen N * sizeof
405 // (void*) where N is 0, 2 or 4). According to folklore,
406 // picking this value on the high side is better than
407 // low-balling it (especially when this algorithm is used with
408 // malloc implementations that allocate memory blocks rounded up
409 // to a size which is a power of 2).
410 const size_type __pagesize = 4096;
411 const size_type __malloc_header_size = 4 * sizeof(void*);
412
413 // The below implements an exponential growth policy, necessary to
414 // meet amortized linear time requirements of the library: see
415 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
416 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
417 {
418 __capacity = 2 * __old_capacity;
419 // Never allocate a string bigger than _S_max_size.
420 if (__capacity > size_type(_S_max_size))
421 __capacity = size_type(_S_max_size);
422 }
423
424 // NB: Need an array of char_type[__capacity], plus a terminating
425 // null char_type() element, plus enough for the _Rep data structure,
426 // plus sizeof(_Rep) - 1 to upper round to a size multiple of
427 // sizeof(_Rep).
428 // Whew. Seemingly so needy, yet so elemental.
429 size_type __size = ((__capacity + 1) * sizeof(_CharT)
430 + 2 * sizeof(_Rep) - 1);
431
432 const size_type __adj_size = __size + __malloc_header_size;
433 if (__adj_size > __pagesize && __capacity > __old_capacity)
434 {
435 const size_type __extra = __pagesize - __adj_size % __pagesize;
436 __capacity += __extra / sizeof(_CharT);
437 if (__capacity > size_type(_S_max_size))
438 __capacity = size_type(_S_max_size);
439 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1;
440 }
441
442 // NB: Might throw, but no worries about a leak, mate: _Rep()
443 // does not throw.
444 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep));
445 _Rep* __p = new (__place) _Rep;
446 __p->_M_info._M_capacity = __capacity;
447 return __p;
448 }
449
450 template<typename _CharT, typename _Traits, typename _Alloc>
451 void
452 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
453 _M_destroy(const _Alloc& __a) throw ()
454 {
455 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT)
456 + 2 * sizeof(_Rep) - 1);
457 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep));
458 }
459
460 template<typename _CharT, typename _Traits, typename _Alloc>
461 _CharT*
462 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
463 _M_clone(const _Alloc& __alloc, size_type __res)
464 {
465 // Requested capacity of the clone.
466 const size_type __requested_cap = _M_info._M_length + __res;
467 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity,
468 __alloc);
469
470 if (_M_info._M_length)
471 __rc_string_base::_S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length);
472
473 __r->_M_set_length(_M_info._M_length);
474 return __r->_M_refdata();
475 }
476
477 template<typename _CharT, typename _Traits, typename _Alloc>
478 __rc_string_base<_CharT, _Traits, _Alloc>::
479 __rc_string_base(const _Alloc& __a)
480 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { }
481
482 template<typename _CharT, typename _Traits, typename _Alloc>
483 __rc_string_base<_CharT, _Traits, _Alloc>::
484 __rc_string_base(const __rc_string_base& __rcs)
485 : _M_dataplus(__rcs._M_get_allocator(),
486 __rcs._M_grab(__rcs._M_get_allocator())) { }
487
488 template<typename _CharT, typename _Traits, typename _Alloc>
489 __rc_string_base<_CharT, _Traits, _Alloc>::
490 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a)
491 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { }
492
493 template<typename _CharT, typename _Traits, typename _Alloc>
494 template<typename _InputIterator>
495 __rc_string_base<_CharT, _Traits, _Alloc>::
496 __rc_string_base(_InputIterator __beg, _InputIterator __end,
497 const _Alloc& __a)
498 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { }
499
500 template<typename _CharT, typename _Traits, typename _Alloc>
501 void
502 __rc_string_base<_CharT, _Traits, _Alloc>::
503 _M_leak_hard()
504 {
505 if (_M_is_shared())
506 _M_erase(0, 0);
507 _M_set_leaked();
508 }
509
510 // NB: This is the special case for Input Iterators, used in
511 // istreambuf_iterators, etc.
512 // Input Iterators have a cost structure very different from
513 // pointers, calling for a different coding style.
514 template<typename _CharT, typename _Traits, typename _Alloc>
515 template<typename _InIterator>
516 _CharT*
517 __rc_string_base<_CharT, _Traits, _Alloc>::
518 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
519 std::input_iterator_tag)
520 {
521 if (__beg == __end && __a == _Alloc())
522 return _S_empty_rep._M_refcopy();
523
524 // Avoid reallocation for common case.
525 _CharT __buf[128];
526 size_type __len = 0;
527 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
528 {
529 __buf[__len++] = *__beg;
530 ++__beg;
531 }
532 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
533 _S_copy(__r->_M_refdata(), __buf, __len);
534 __try
535 {
536 while (__beg != __end)
537 {
538 if (__len == __r->_M_info._M_capacity)
539 {
540 // Allocate more space.
541 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
542 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
543 __r->_M_destroy(__a);
544 __r = __another;
545 }
546 __r->_M_refdata()[__len++] = *__beg;
547 ++__beg;
548 }
549 }
550 __catch(...)
551 {
552 __r->_M_destroy(__a);
553 __throw_exception_again;
554 }
555 __r->_M_set_length(__len);
556 return __r->_M_refdata();
557 }
558
559 template<typename _CharT, typename _Traits, typename _Alloc>
560 template<typename _InIterator>
561 _CharT*
562 __rc_string_base<_CharT, _Traits, _Alloc>::
563 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
564 std::forward_iterator_tag)
565 {
566 if (__beg == __end && __a == _Alloc())
567 return _S_empty_rep._M_refcopy();
568
569 // NB: Not required, but considered best practice.
570 if (__is_null_pointer(__beg) && __beg != __end)
571 std::__throw_logic_error(__N("__rc_string_base::"
572 "_S_construct null not valid"));
573
574 const size_type __dnew = static_cast<size_type>(std::distance(__beg,
575 __end));
576 // Check for out_of_range and length_error exceptions.
577 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
578 __try
579 { __rc_string_base::_S_copy_chars(__r->_M_refdata(), __beg, __end); }
580 __catch(...)
581 {
582 __r->_M_destroy(__a);
583 __throw_exception_again;
584 }
585 __r->_M_set_length(__dnew);
586 return __r->_M_refdata();
587 }
588
589 template<typename _CharT, typename _Traits, typename _Alloc>
590 _CharT*
591 __rc_string_base<_CharT, _Traits, _Alloc>::
592 _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
593 {
594 if (__n == 0 && __a == _Alloc())
595 return _S_empty_rep._M_refcopy();
596
597 // Check for out_of_range and length_error exceptions.
598 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
599 if (__n)
600 __rc_string_base::_S_assign(__r->_M_refdata(), __n, __c);
601
602 __r->_M_set_length(__n);
603 return __r->_M_refdata();
604 }
605
606 template<typename _CharT, typename _Traits, typename _Alloc>
607 void
608 __rc_string_base<_CharT, _Traits, _Alloc>::
609 _M_swap(__rc_string_base& __rcs)
610 {
611 if (_M_is_leaked())
612 _M_set_sharable();
613 if (__rcs._M_is_leaked())
614 __rcs._M_set_sharable();
615
616 _CharT* __tmp = _M_data();
617 _M_data(__rcs._M_data());
618 __rcs._M_data(__tmp);
619
620 // _GLIBCXX_RESOLVE_LIB_DEFECTS
621 // 431. Swapping containers with unequal allocators.
622 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(),
623 __rcs._M_get_allocator());
624 }
625
626 template<typename _CharT, typename _Traits, typename _Alloc>
627 void
628 __rc_string_base<_CharT, _Traits, _Alloc>::
629 _M_assign(const __rc_string_base& __rcs)
630 {
631 if (_M_rep() != __rcs._M_rep())
632 {
633 _CharT* __tmp = __rcs._M_grab(_M_get_allocator());
634 _M_dispose();
635 _M_data(__tmp);
636 }
637 }
638
639 template<typename _CharT, typename _Traits, typename _Alloc>
640 void
641 __rc_string_base<_CharT, _Traits, _Alloc>::
642 _M_reserve(size_type __res)
643 {
644 // Make sure we don't shrink below the current size.
645 if (__res < _M_length())
646 __res = _M_length();
647
648 if (__res != _M_capacity() || _M_is_shared())
649 {
650 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(),
651 __res - _M_length());
652 _M_dispose();
653 _M_data(__tmp);
654 }
655 }
656
657 template<typename _CharT, typename _Traits, typename _Alloc>
658 void
659 __rc_string_base<_CharT, _Traits, _Alloc>::
660 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
661 size_type __len2)
662 {
663 const size_type __how_much = _M_length() - __pos - __len1;
664
665 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1,
666 _M_capacity(), _M_get_allocator());
667
668 if (__pos)
669 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
670 if (__s && __len2)
671 this->_S_copy(__r->_M_refdata() + __pos, __s, __len2);
672 if (__how_much)
673 this->_S_copy(__r->_M_refdata() + __pos + __len2,
674 _M_data() + __pos + __len1, __how_much);
675
676 _M_dispose();
677 _M_data(__r->_M_refdata());
678 }
679
680 template<typename _CharT, typename _Traits, typename _Alloc>
681 void
682 __rc_string_base<_CharT, _Traits, _Alloc>::
683 _M_erase(size_type __pos, size_type __n)
684 {
685 const size_type __new_size = _M_length() - __n;
686 const size_type __how_much = _M_length() - __pos - __n;
687
688 if (_M_is_shared())
689 {
690 // Must reallocate.
691 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(),
692 _M_get_allocator());
693
694 if (__pos)
695 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
696 if (__how_much)
697 this->_S_copy(__r->_M_refdata() + __pos,
698 _M_data() + __pos + __n, __how_much);
699
700 _M_dispose();
701 _M_data(__r->_M_refdata());
702 }
703 else if (__how_much && __n)
704 {
705 // Work in-place.
706 this->_S_move(_M_data() + __pos,
707 _M_data() + __pos + __n, __how_much);
708 }
709
710 _M_rep()->_M_set_length(__new_size);
711 }
712
713 template<>
714 inline bool
715 __rc_string_base<char, std::char_traits<char>,
716 std::allocator<char> >::
717 _M_compare(const __rc_string_base& __rcs) const
718 {
719 if (_M_rep() == __rcs._M_rep())
720 return true;
721 return false;
722 }
723
724 template<>
725 inline bool
726 __rc_string_base<wchar_t, std::char_traits<wchar_t>,
727 std::allocator<wchar_t> >::
728 _M_compare(const __rc_string_base& __rcs) const
729 {
730 if (_M_rep() == __rcs._M_rep())
731 return true;
732 return false;
733 }
734
735 _GLIBCXX_END_NAMESPACE_VERSION
736 } // namespace
737
738 #endif /* _RC_STRING_BASE_H */