libstdc++

rc_string_base.h
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1 // Reference-counted versatile string base -*- C++ -*-
2
3 // Copyright (C) 2005-2013 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 <bits/stl_iterator_base_funcs.h>
35
36 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
37 {
38 _GLIBCXX_BEGIN_NAMESPACE_VERSION
39
40 /**
41 * Documentation? What's that?
42 * Nathan Myers <ncm@cantrip.org>.
43 *
44 * A string looks like this:
45 *
46 * @code
47 * [_Rep]
48 * _M_length
49 * [__rc_string_base<char_type>] _M_capacity
50 * _M_dataplus _M_refcount
51 * _M_p ----------------> unnamed array of char_type
52 * @endcode
53 *
54 * Where the _M_p points to the first character in the string, and
55 * you cast it to a pointer-to-_Rep and subtract 1 to get a
56 * pointer to the header.
57 *
58 * This approach has the enormous advantage that a string object
59 * requires only one allocation. All the ugliness is confined
60 * within a single pair of inline functions, which each compile to
61 * a single @a add instruction: _Rep::_M_refdata(), and
62 * __rc_string_base::_M_rep(); and the allocation function which gets a
63 * block of raw bytes and with room enough and constructs a _Rep
64 * object at the front.
65 *
66 * The reason you want _M_data pointing to the character array and
67 * not the _Rep is so that the debugger can see the string
68 * contents. (Probably we should add a non-inline member to get
69 * the _Rep for the debugger to use, so users can check the actual
70 * string length.)
71 *
72 * Note that the _Rep object is a POD so that you can have a
73 * static <em>empty string</em> _Rep object already @a constructed before
74 * static constructors have run. The reference-count encoding is
75 * chosen so that a 0 indicates one reference, so you never try to
76 * destroy the empty-string _Rep object.
77 *
78 * All but the last paragraph is considered pretty conventional
79 * for a C++ string implementation.
80 */
81 template<typename _CharT, typename _Traits, typename _Alloc>
82 class __rc_string_base
83 : protected __vstring_utility<_CharT, _Traits, _Alloc>
84 {
85 public:
86 typedef _Traits traits_type;
87 typedef typename _Traits::char_type value_type;
88 typedef _Alloc allocator_type;
89
90 typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base;
91 typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type;
92 typedef typename _CharT_alloc_type::size_type size_type;
93
94 private:
95 // _Rep: string representation
96 // Invariants:
97 // 1. String really contains _M_length + 1 characters: due to 21.3.4
98 // must be kept null-terminated.
99 // 2. _M_capacity >= _M_length
100 // Allocated memory is always (_M_capacity + 1) * sizeof(_CharT).
101 // 3. _M_refcount has three states:
102 // -1: leaked, one reference, no ref-copies allowed, non-const.
103 // 0: one reference, non-const.
104 // n>0: n + 1 references, operations require a lock, const.
105 // 4. All fields == 0 is an empty string, given the extra storage
106 // beyond-the-end for a null terminator; thus, the shared
107 // empty string representation needs no constructor.
108 struct _Rep
109 {
110 union
111 {
112 struct
113 {
114 size_type _M_length;
115 size_type _M_capacity;
116 _Atomic_word _M_refcount;
117 } _M_info;
118
119 // Only for alignment purposes.
120 _CharT _M_align;
121 };
122
123 typedef typename _Alloc::template rebind<_Rep>::other _Rep_alloc_type;
124
125 _CharT*
126 _M_refdata() throw()
127 { return reinterpret_cast<_CharT*>(this + 1); }
128
129 _CharT*
130 _M_refcopy() throw()
131 {
132 __atomic_add_dispatch(&_M_info._M_refcount, 1);
133 return _M_refdata();
134 } // XXX MT
135
136 void
137 _M_set_length(size_type __n)
138 {
139 _M_info._M_refcount = 0; // One reference.
140 _M_info._M_length = __n;
141 // grrr. (per 21.3.4)
142 // You cannot leave those LWG people alone for a second.
143 traits_type::assign(_M_refdata()[__n], _CharT());
144 }
145
146 // Create & Destroy
147 static _Rep*
148 _S_create(size_type, size_type, const _Alloc&);
149
150 void
151 _M_destroy(const _Alloc&) throw();
152
153 _CharT*
154 _M_clone(const _Alloc&, size_type __res = 0);
155 };
156
157 struct _Rep_empty
158 : public _Rep
159 {
160 _CharT _M_terminal;
161 };
162
163 static _Rep_empty _S_empty_rep;
164
165 // The maximum number of individual char_type elements of an
166 // individual string is determined by _S_max_size. This is the
167 // value that will be returned by max_size(). (Whereas npos
168 // is the maximum number of bytes the allocator can allocate.)
169 // If one was to divvy up the theoretical largest size string,
170 // with a terminating character and m _CharT elements, it'd
171 // look like this:
172 // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT)
173 // + sizeof(_Rep) - 1
174 // (NB: last two terms for rounding reasons, see _M_create below)
175 // Solving for m:
176 // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1
177 // In addition, this implementation halves this amount.
178 enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep)
179 + 1) / sizeof(_CharT)) - 1) / 2 };
180
181 // Data Member (private):
182 mutable typename _Util_Base::template _Alloc_hider<_Alloc> _M_dataplus;
183
184 void
185 _M_data(_CharT* __p)
186 { _M_dataplus._M_p = __p; }
187
188 _Rep*
189 _M_rep() const
190 { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); }
191
192 _CharT*
193 _M_grab(const _Alloc& __alloc) const
194 {
195 return (!_M_is_leaked() && _M_get_allocator() == __alloc)
196 ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc);
197 }
198
199 void
200 _M_dispose()
201 {
202 // Be race-detector-friendly. For more info see bits/c++config.
203 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_rep()->_M_info.
204 _M_refcount);
205 if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount,
206 -1) <= 0)
207 {
208 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_rep()->_M_info.
209 _M_refcount);
210 _M_rep()->_M_destroy(_M_get_allocator());
211 }
212 } // XXX MT
213
214 bool
215 _M_is_leaked() const
216 { return _M_rep()->_M_info._M_refcount < 0; }
217
218 void
219 _M_set_sharable()
220 { _M_rep()->_M_info._M_refcount = 0; }
221
222 void
223 _M_leak_hard();
224
225 // _S_construct_aux is used to implement the 21.3.1 para 15 which
226 // requires special behaviour if _InIterator is an integral type
227 template<typename _InIterator>
228 static _CharT*
229 _S_construct_aux(_InIterator __beg, _InIterator __end,
230 const _Alloc& __a, std::__false_type)
231 {
232 typedef typename iterator_traits<_InIterator>::iterator_category _Tag;
233 return _S_construct(__beg, __end, __a, _Tag());
234 }
235
236 // _GLIBCXX_RESOLVE_LIB_DEFECTS
237 // 438. Ambiguity in the "do the right thing" clause
238 template<typename _Integer>
239 static _CharT*
240 _S_construct_aux(_Integer __beg, _Integer __end,
241 const _Alloc& __a, std::__true_type)
242 { return _S_construct_aux_2(static_cast<size_type>(__beg),
243 __end, __a); }
244
245 static _CharT*
246 _S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a)
247 { return _S_construct(__req, __c, __a); }
248
249 template<typename _InIterator>
250 static _CharT*
251 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a)
252 {
253 typedef typename std::__is_integer<_InIterator>::__type _Integral;
254 return _S_construct_aux(__beg, __end, __a, _Integral());
255 }
256
257 // For Input Iterators, used in istreambuf_iterators, etc.
258 template<typename _InIterator>
259 static _CharT*
260 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
261 std::input_iterator_tag);
262
263 // For forward_iterators up to random_access_iterators, used for
264 // string::iterator, _CharT*, etc.
265 template<typename _FwdIterator>
266 static _CharT*
267 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a,
268 std::forward_iterator_tag);
269
270 static _CharT*
271 _S_construct(size_type __req, _CharT __c, const _Alloc& __a);
272
273 public:
274 size_type
275 _M_max_size() const
276 { return size_type(_S_max_size); }
277
278 _CharT*
279 _M_data() const
280 { return _M_dataplus._M_p; }
281
282 size_type
283 _M_length() const
284 { return _M_rep()->_M_info._M_length; }
285
286 size_type
287 _M_capacity() const
288 { return _M_rep()->_M_info._M_capacity; }
289
290 bool
291 _M_is_shared() const
292 { return _M_rep()->_M_info._M_refcount > 0; }
293
294 void
295 _M_set_leaked()
296 { _M_rep()->_M_info._M_refcount = -1; }
297
298 void
299 _M_leak() // for use in begin() & non-const op[]
300 {
301 if (!_M_is_leaked())
302 _M_leak_hard();
303 }
304
305 void
306 _M_set_length(size_type __n)
307 { _M_rep()->_M_set_length(__n); }
308
309 __rc_string_base()
310 : _M_dataplus(_S_empty_rep._M_refcopy()) { }
311
312 __rc_string_base(const _Alloc& __a);
313
314 __rc_string_base(const __rc_string_base& __rcs);
315
316 #if __cplusplus >= 201103L
317 __rc_string_base(__rc_string_base&& __rcs)
318 : _M_dataplus(__rcs._M_dataplus)
319 { __rcs._M_data(_S_empty_rep._M_refcopy()); }
320 #endif
321
322 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a);
323
324 template<typename _InputIterator>
325 __rc_string_base(_InputIterator __beg, _InputIterator __end,
326 const _Alloc& __a);
327
328 ~__rc_string_base()
329 { _M_dispose(); }
330
331 allocator_type&
332 _M_get_allocator()
333 { return _M_dataplus; }
334
335 const allocator_type&
336 _M_get_allocator() const
337 { return _M_dataplus; }
338
339 void
340 _M_swap(__rc_string_base& __rcs);
341
342 void
343 _M_assign(const __rc_string_base& __rcs);
344
345 void
346 _M_reserve(size_type __res);
347
348 void
349 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
350 size_type __len2);
351
352 void
353 _M_erase(size_type __pos, size_type __n);
354
355 void
356 _M_clear()
357 { _M_erase(size_type(0), _M_length()); }
358
359 bool
360 _M_compare(const __rc_string_base&) const
361 { return false; }
362 };
363
364 template<typename _CharT, typename _Traits, typename _Alloc>
365 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty
366 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep;
367
368 template<typename _CharT, typename _Traits, typename _Alloc>
369 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep*
370 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
371 _S_create(size_type __capacity, size_type __old_capacity,
372 const _Alloc& __alloc)
373 {
374 // _GLIBCXX_RESOLVE_LIB_DEFECTS
375 // 83. String::npos vs. string::max_size()
376 if (__capacity > size_type(_S_max_size))
377 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create"));
378
379 // The standard places no restriction on allocating more memory
380 // than is strictly needed within this layer at the moment or as
381 // requested by an explicit application call to reserve().
382
383 // Many malloc implementations perform quite poorly when an
384 // application attempts to allocate memory in a stepwise fashion
385 // growing each allocation size by only 1 char. Additionally,
386 // it makes little sense to allocate less linear memory than the
387 // natural blocking size of the malloc implementation.
388 // Unfortunately, we would need a somewhat low-level calculation
389 // with tuned parameters to get this perfect for any particular
390 // malloc implementation. Fortunately, generalizations about
391 // common features seen among implementations seems to suffice.
392
393 // __pagesize need not match the actual VM page size for good
394 // results in practice, thus we pick a common value on the low
395 // side. __malloc_header_size is an estimate of the amount of
396 // overhead per memory allocation (in practice seen N * sizeof
397 // (void*) where N is 0, 2 or 4). According to folklore,
398 // picking this value on the high side is better than
399 // low-balling it (especially when this algorithm is used with
400 // malloc implementations that allocate memory blocks rounded up
401 // to a size which is a power of 2).
402 const size_type __pagesize = 4096;
403 const size_type __malloc_header_size = 4 * sizeof(void*);
404
405 // The below implements an exponential growth policy, necessary to
406 // meet amortized linear time requirements of the library: see
407 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
408 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
409 {
410 __capacity = 2 * __old_capacity;
411 // Never allocate a string bigger than _S_max_size.
412 if (__capacity > size_type(_S_max_size))
413 __capacity = size_type(_S_max_size);
414 }
415
416 // NB: Need an array of char_type[__capacity], plus a terminating
417 // null char_type() element, plus enough for the _Rep data structure,
418 // plus sizeof(_Rep) - 1 to upper round to a size multiple of
419 // sizeof(_Rep).
420 // Whew. Seemingly so needy, yet so elemental.
421 size_type __size = ((__capacity + 1) * sizeof(_CharT)
422 + 2 * sizeof(_Rep) - 1);
423
424 const size_type __adj_size = __size + __malloc_header_size;
425 if (__adj_size > __pagesize && __capacity > __old_capacity)
426 {
427 const size_type __extra = __pagesize - __adj_size % __pagesize;
428 __capacity += __extra / sizeof(_CharT);
429 if (__capacity > size_type(_S_max_size))
430 __capacity = size_type(_S_max_size);
431 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1;
432 }
433
434 // NB: Might throw, but no worries about a leak, mate: _Rep()
435 // does not throw.
436 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep));
437 _Rep* __p = new (__place) _Rep;
438 __p->_M_info._M_capacity = __capacity;
439 return __p;
440 }
441
442 template<typename _CharT, typename _Traits, typename _Alloc>
443 void
444 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
445 _M_destroy(const _Alloc& __a) throw ()
446 {
447 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT)
448 + 2 * sizeof(_Rep) - 1);
449 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep));
450 }
451
452 template<typename _CharT, typename _Traits, typename _Alloc>
453 _CharT*
454 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
455 _M_clone(const _Alloc& __alloc, size_type __res)
456 {
457 // Requested capacity of the clone.
458 const size_type __requested_cap = _M_info._M_length + __res;
459 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity,
460 __alloc);
461
462 if (_M_info._M_length)
463 __rc_string_base::_S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length);
464
465 __r->_M_set_length(_M_info._M_length);
466 return __r->_M_refdata();
467 }
468
469 template<typename _CharT, typename _Traits, typename _Alloc>
470 __rc_string_base<_CharT, _Traits, _Alloc>::
471 __rc_string_base(const _Alloc& __a)
472 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { }
473
474 template<typename _CharT, typename _Traits, typename _Alloc>
475 __rc_string_base<_CharT, _Traits, _Alloc>::
476 __rc_string_base(const __rc_string_base& __rcs)
477 : _M_dataplus(__rcs._M_get_allocator(),
478 __rcs._M_grab(__rcs._M_get_allocator())) { }
479
480 template<typename _CharT, typename _Traits, typename _Alloc>
481 __rc_string_base<_CharT, _Traits, _Alloc>::
482 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a)
483 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { }
484
485 template<typename _CharT, typename _Traits, typename _Alloc>
486 template<typename _InputIterator>
487 __rc_string_base<_CharT, _Traits, _Alloc>::
488 __rc_string_base(_InputIterator __beg, _InputIterator __end,
489 const _Alloc& __a)
490 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { }
491
492 template<typename _CharT, typename _Traits, typename _Alloc>
493 void
494 __rc_string_base<_CharT, _Traits, _Alloc>::
495 _M_leak_hard()
496 {
497 if (_M_is_shared())
498 _M_erase(0, 0);
499 _M_set_leaked();
500 }
501
502 // NB: This is the special case for Input Iterators, used in
503 // istreambuf_iterators, etc.
504 // Input Iterators have a cost structure very different from
505 // pointers, calling for a different coding style.
506 template<typename _CharT, typename _Traits, typename _Alloc>
507 template<typename _InIterator>
508 _CharT*
509 __rc_string_base<_CharT, _Traits, _Alloc>::
510 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
511 std::input_iterator_tag)
512 {
513 if (__beg == __end && __a == _Alloc())
514 return _S_empty_rep._M_refcopy();
515
516 // Avoid reallocation for common case.
517 _CharT __buf[128];
518 size_type __len = 0;
519 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
520 {
521 __buf[__len++] = *__beg;
522 ++__beg;
523 }
524 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
525 _S_copy(__r->_M_refdata(), __buf, __len);
526 __try
527 {
528 while (__beg != __end)
529 {
530 if (__len == __r->_M_info._M_capacity)
531 {
532 // Allocate more space.
533 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
534 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
535 __r->_M_destroy(__a);
536 __r = __another;
537 }
538 __r->_M_refdata()[__len++] = *__beg;
539 ++__beg;
540 }
541 }
542 __catch(...)
543 {
544 __r->_M_destroy(__a);
545 __throw_exception_again;
546 }
547 __r->_M_set_length(__len);
548 return __r->_M_refdata();
549 }
550
551 template<typename _CharT, typename _Traits, typename _Alloc>
552 template<typename _InIterator>
553 _CharT*
554 __rc_string_base<_CharT, _Traits, _Alloc>::
555 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
556 std::forward_iterator_tag)
557 {
558 if (__beg == __end && __a == _Alloc())
559 return _S_empty_rep._M_refcopy();
560
561 // NB: Not required, but considered best practice.
562 if (__is_null_pointer(__beg) && __beg != __end)
563 std::__throw_logic_error(__N("__rc_string_base::"
564 "_S_construct null not valid"));
565
566 const size_type __dnew = static_cast<size_type>(std::distance(__beg,
567 __end));
568 // Check for out_of_range and length_error exceptions.
569 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
570 __try
571 { __rc_string_base::_S_copy_chars(__r->_M_refdata(), __beg, __end); }
572 __catch(...)
573 {
574 __r->_M_destroy(__a);
575 __throw_exception_again;
576 }
577 __r->_M_set_length(__dnew);
578 return __r->_M_refdata();
579 }
580
581 template<typename _CharT, typename _Traits, typename _Alloc>
582 _CharT*
583 __rc_string_base<_CharT, _Traits, _Alloc>::
584 _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
585 {
586 if (__n == 0 && __a == _Alloc())
587 return _S_empty_rep._M_refcopy();
588
589 // Check for out_of_range and length_error exceptions.
590 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
591 if (__n)
592 __rc_string_base::_S_assign(__r->_M_refdata(), __n, __c);
593
594 __r->_M_set_length(__n);
595 return __r->_M_refdata();
596 }
597
598 template<typename _CharT, typename _Traits, typename _Alloc>
599 void
600 __rc_string_base<_CharT, _Traits, _Alloc>::
601 _M_swap(__rc_string_base& __rcs)
602 {
603 if (_M_is_leaked())
604 _M_set_sharable();
605 if (__rcs._M_is_leaked())
606 __rcs._M_set_sharable();
607
608 _CharT* __tmp = _M_data();
609 _M_data(__rcs._M_data());
610 __rcs._M_data(__tmp);
611
612 // _GLIBCXX_RESOLVE_LIB_DEFECTS
613 // 431. Swapping containers with unequal allocators.
614 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(),
615 __rcs._M_get_allocator());
616 }
617
618 template<typename _CharT, typename _Traits, typename _Alloc>
619 void
620 __rc_string_base<_CharT, _Traits, _Alloc>::
621 _M_assign(const __rc_string_base& __rcs)
622 {
623 if (_M_rep() != __rcs._M_rep())
624 {
625 _CharT* __tmp = __rcs._M_grab(_M_get_allocator());
626 _M_dispose();
627 _M_data(__tmp);
628 }
629 }
630
631 template<typename _CharT, typename _Traits, typename _Alloc>
632 void
633 __rc_string_base<_CharT, _Traits, _Alloc>::
634 _M_reserve(size_type __res)
635 {
636 // Make sure we don't shrink below the current size.
637 if (__res < _M_length())
638 __res = _M_length();
639
640 if (__res != _M_capacity() || _M_is_shared())
641 {
642 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(),
643 __res - _M_length());
644 _M_dispose();
645 _M_data(__tmp);
646 }
647 }
648
649 template<typename _CharT, typename _Traits, typename _Alloc>
650 void
651 __rc_string_base<_CharT, _Traits, _Alloc>::
652 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
653 size_type __len2)
654 {
655 const size_type __how_much = _M_length() - __pos - __len1;
656
657 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1,
658 _M_capacity(), _M_get_allocator());
659
660 if (__pos)
661 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
662 if (__s && __len2)
663 this->_S_copy(__r->_M_refdata() + __pos, __s, __len2);
664 if (__how_much)
665 this->_S_copy(__r->_M_refdata() + __pos + __len2,
666 _M_data() + __pos + __len1, __how_much);
667
668 _M_dispose();
669 _M_data(__r->_M_refdata());
670 }
671
672 template<typename _CharT, typename _Traits, typename _Alloc>
673 void
674 __rc_string_base<_CharT, _Traits, _Alloc>::
675 _M_erase(size_type __pos, size_type __n)
676 {
677 const size_type __new_size = _M_length() - __n;
678 const size_type __how_much = _M_length() - __pos - __n;
679
680 if (_M_is_shared())
681 {
682 // Must reallocate.
683 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(),
684 _M_get_allocator());
685
686 if (__pos)
687 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
688 if (__how_much)
689 this->_S_copy(__r->_M_refdata() + __pos,
690 _M_data() + __pos + __n, __how_much);
691
692 _M_dispose();
693 _M_data(__r->_M_refdata());
694 }
695 else if (__how_much && __n)
696 {
697 // Work in-place.
698 this->_S_move(_M_data() + __pos,
699 _M_data() + __pos + __n, __how_much);
700 }
701
702 _M_rep()->_M_set_length(__new_size);
703 }
704
705 template<>
706 inline bool
707 __rc_string_base<char, std::char_traits<char>,
708 std::allocator<char> >::
709 _M_compare(const __rc_string_base& __rcs) const
710 {
711 if (_M_rep() == __rcs._M_rep())
712 return true;
713 return false;
714 }
715
716 #ifdef _GLIBCXX_USE_WCHAR_T
717 template<>
718 inline bool
719 __rc_string_base<wchar_t, std::char_traits<wchar_t>,
720 std::allocator<wchar_t> >::
721 _M_compare(const __rc_string_base& __rcs) const
722 {
723 if (_M_rep() == __rcs._M_rep())
724 return true;
725 return false;
726 }
727 #endif
728
729 _GLIBCXX_END_NAMESPACE_VERSION
730 } // namespace
731
732 #endif /* _RC_STRING_BASE_H */