1 // Reference-counted versatile string base -*- C++ -*-
2
3 // Copyright (C) 2005-2018 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
_GLIBCXX_VISIBILITY(default)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 {
358 _M_dispose();
359 _M_data(_S_empty_rep._M_refcopy());
360 }
361
362 bool
363 _M_compare(const __rc_string_base&) const
364 { return false; }
365 };
366
367 template<typename _CharT, typename _Traits, typename _Alloc>
368 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty
369 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep;
370
371 template<typename _CharT, typename _Traits, typename _Alloc>
372 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep*
373 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
374 _S_create(size_type __capacity, size_type __old_capacity,
375 const _Alloc& __alloc)
376 {
377 // _GLIBCXX_RESOLVE_LIB_DEFECTS
378 // 83. String::npos vs. string::max_size()
379 if (__capacity > size_type(_S_max_size))
380 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create"));
381
382 // The standard places no restriction on allocating more memory
383 // than is strictly needed within this layer at the moment or as
384 // requested by an explicit application call to reserve().
385
386 // Many malloc implementations perform quite poorly when an
387 // application attempts to allocate memory in a stepwise fashion
388 // growing each allocation size by only 1 char. Additionally,
389 // it makes little sense to allocate less linear memory than the
390 // natural blocking size of the malloc implementation.
391 // Unfortunately, we would need a somewhat low-level calculation
392 // with tuned parameters to get this perfect for any particular
393 // malloc implementation. Fortunately, generalizations about
394 // common features seen among implementations seems to suffice.
395
396 // __pagesize need not match the actual VM page size for good
397 // results in practice, thus we pick a common value on the low
398 // side. __malloc_header_size is an estimate of the amount of
399 // overhead per memory allocation (in practice seen N * sizeof
400 // (void*) where N is 0, 2 or 4). According to folklore,
401 // picking this value on the high side is better than
402 // low-balling it (especially when this algorithm is used with
403 // malloc implementations that allocate memory blocks rounded up
404 // to a size which is a power of 2).
405 const size_type __pagesize = 4096;
406 const size_type __malloc_header_size = 4 * sizeof(void*);
407
408 // The below implements an exponential growth policy, necessary to
409 // meet amortized linear time requirements of the library: see
410 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
411 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
412 {
413 __capacity = 2 * __old_capacity;
414 // Never allocate a string bigger than _S_max_size.
415 if (__capacity > size_type(_S_max_size))
416 __capacity = size_type(_S_max_size);
417 }
418
419 // NB: Need an array of char_type[__capacity], plus a terminating
420 // null char_type() element, plus enough for the _Rep data structure,
421 // plus sizeof(_Rep) - 1 to upper round to a size multiple of
422 // sizeof(_Rep).
423 // Whew. Seemingly so needy, yet so elemental.
424 size_type __size = ((__capacity + 1) * sizeof(_CharT)
425 + 2 * sizeof(_Rep) - 1);
426
427 const size_type __adj_size = __size + __malloc_header_size;
428 if (__adj_size > __pagesize && __capacity > __old_capacity)
429 {
430 const size_type __extra = __pagesize - __adj_size % __pagesize;
431 __capacity += __extra / sizeof(_CharT);
432 if (__capacity > size_type(_S_max_size))
433 __capacity = size_type(_S_max_size);
434 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1;
435 }
436
437 // NB: Might throw, but no worries about a leak, mate: _Rep()
438 // does not throw.
439 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep));
440 _Rep* __p = new (__place) _Rep;
441 __p->_M_info._M_capacity = __capacity;
442 return __p;
443 }
444
445 template<typename _CharT, typename _Traits, typename _Alloc>
446 void
447 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
448 _M_destroy(const _Alloc& __a) throw ()
449 {
450 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT)
451 + 2 * sizeof(_Rep) - 1);
452 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep));
453 }
454
455 template<typename _CharT, typename _Traits, typename _Alloc>
456 _CharT*
457 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
458 _M_clone(const _Alloc& __alloc, size_type __res)
459 {
460 // Requested capacity of the clone.
461 const size_type __requested_cap = _M_info._M_length + __res;
462 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity,
463 __alloc);
464
465 if (_M_info._M_length)
466 __rc_string_base::_S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length);
467
468 __r->_M_set_length(_M_info._M_length);
469 return __r->_M_refdata();
470 }
471
472 template<typename _CharT, typename _Traits, typename _Alloc>
473 __rc_string_base<_CharT, _Traits, _Alloc>::
474 __rc_string_base(const _Alloc& __a)
475 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { }
476
477 template<typename _CharT, typename _Traits, typename _Alloc>
478 __rc_string_base<_CharT, _Traits, _Alloc>::
479 __rc_string_base(const __rc_string_base& __rcs)
480 : _M_dataplus(__rcs._M_get_allocator(),
481 __rcs._M_grab(__rcs._M_get_allocator())) { }
482
483 template<typename _CharT, typename _Traits, typename _Alloc>
484 __rc_string_base<_CharT, _Traits, _Alloc>::
485 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a)
486 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { }
487
488 template<typename _CharT, typename _Traits, typename _Alloc>
489 template<typename _InputIterator>
490 __rc_string_base<_CharT, _Traits, _Alloc>::
491 __rc_string_base(_InputIterator __beg, _InputIterator __end,
492 const _Alloc& __a)
493 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { }
494
495 template<typename _CharT, typename _Traits, typename _Alloc>
496 void
497 __rc_string_base<_CharT, _Traits, _Alloc>::
498 _M_leak_hard()
499 {
500 if (_M_is_shared())
501 _M_erase(0, 0);
502 _M_set_leaked();
503 }
504
505 // NB: This is the special case for Input Iterators, used in
506 // istreambuf_iterators, etc.
507 // Input Iterators have a cost structure very different from
508 // pointers, calling for a different coding style.
509 template<typename _CharT, typename _Traits, typename _Alloc>
510 template<typename _InIterator>
511 _CharT*
512 __rc_string_base<_CharT, _Traits, _Alloc>::
513 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
514 std::input_iterator_tag)
515 {
516 if (__beg == __end && __a == _Alloc())
517 return _S_empty_rep._M_refcopy();
518
519 // Avoid reallocation for common case.
520 _CharT __buf[128];
521 size_type __len = 0;
522 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
523 {
524 __buf[__len++] = *__beg;
525 ++__beg;
526 }
527 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
528 _S_copy(__r->_M_refdata(), __buf, __len);
529 __try
530 {
531 while (__beg != __end)
532 {
533 if (__len == __r->_M_info._M_capacity)
534 {
535 // Allocate more space.
536 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
537 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
538 __r->_M_destroy(__a);
539 __r = __another;
540 }
541 __r->_M_refdata()[__len++] = *__beg;
542 ++__beg;
543 }
544 }
545 __catch(...)
546 {
547 __r->_M_destroy(__a);
548 __throw_exception_again;
549 }
550 __r->_M_set_length(__len);
551 return __r->_M_refdata();
552 }
553
554 template<typename _CharT, typename _Traits, typename _Alloc>
555 template<typename _InIterator>
556 _CharT*
557 __rc_string_base<_CharT, _Traits, _Alloc>::
558 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
559 std::forward_iterator_tag)
560 {
561 if (__beg == __end && __a == _Alloc())
562 return _S_empty_rep._M_refcopy();
563
564 // NB: Not required, but considered best practice.
565 if (__is_null_pointer(__beg) && __beg != __end)
566 std::__throw_logic_error(__N("__rc_string_base::"
567 "_S_construct null not valid"));
568
569 const size_type __dnew = static_cast<size_type>(std::distance(__beg,
570 __end));
571 // Check for out_of_range and length_error exceptions.
572 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
573 __try
574 { __rc_string_base::_S_copy_chars(__r->_M_refdata(), __beg, __end); }
575 __catch(...)
576 {
577 __r->_M_destroy(__a);
578 __throw_exception_again;
579 }
580 __r->_M_set_length(__dnew);
581 return __r->_M_refdata();
582 }
583
584 template<typename _CharT, typename _Traits, typename _Alloc>
585 _CharT*
586 __rc_string_base<_CharT, _Traits, _Alloc>::
587 _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
588 {
589 if (__n == 0 && __a == _Alloc())
590 return _S_empty_rep._M_refcopy();
591
592 // Check for out_of_range and length_error exceptions.
593 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
594 if (__n)
595 __rc_string_base::_S_assign(__r->_M_refdata(), __n, __c);
596
597 __r->_M_set_length(__n);
598 return __r->_M_refdata();
599 }
600
601 template<typename _CharT, typename _Traits, typename _Alloc>
602 void
603 __rc_string_base<_CharT, _Traits, _Alloc>::
604 _M_swap(__rc_string_base& __rcs)
605 {
606 if (_M_is_leaked())
607 _M_set_sharable();
608 if (__rcs._M_is_leaked())
609 __rcs._M_set_sharable();
610
611 _CharT* __tmp = _M_data();
612 _M_data(__rcs._M_data());
613 __rcs._M_data(__tmp);
614
615 // _GLIBCXX_RESOLVE_LIB_DEFECTS
616 // 431. Swapping containers with unequal allocators.
617 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(),
618 __rcs._M_get_allocator());
619 }
620
621 template<typename _CharT, typename _Traits, typename _Alloc>
622 void
623 __rc_string_base<_CharT, _Traits, _Alloc>::
624 _M_assign(const __rc_string_base& __rcs)
625 {
626 if (_M_rep() != __rcs._M_rep())
627 {
628 _CharT* __tmp = __rcs._M_grab(_M_get_allocator());
629 _M_dispose();
630 _M_data(__tmp);
631 }
632 }
633
634 template<typename _CharT, typename _Traits, typename _Alloc>
635 void
636 __rc_string_base<_CharT, _Traits, _Alloc>::
637 _M_reserve(size_type __res)
638 {
639 // Make sure we don't shrink below the current size.
640 if (__res < _M_length())
641 __res = _M_length();
642
643 if (__res != _M_capacity() || _M_is_shared())
644 {
645 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(),
646 __res - _M_length());
647 _M_dispose();
648 _M_data(__tmp);
649 }
650 }
651
652 template<typename _CharT, typename _Traits, typename _Alloc>
653 void
654 __rc_string_base<_CharT, _Traits, _Alloc>::
655 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
656 size_type __len2)
657 {
658 const size_type __how_much = _M_length() - __pos - __len1;
659
660 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1,
661 _M_capacity(), _M_get_allocator());
662
663 if (__pos)
664 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
665 if (__s && __len2)
666 this->_S_copy(__r->_M_refdata() + __pos, __s, __len2);
667 if (__how_much)
668 this->_S_copy(__r->_M_refdata() + __pos + __len2,
669 _M_data() + __pos + __len1, __how_much);
670
671 _M_dispose();
672 _M_data(__r->_M_refdata());
673 }
674
675 template<typename _CharT, typename _Traits, typename _Alloc>
676 void
677 __rc_string_base<_CharT, _Traits, _Alloc>::
678 _M_erase(size_type __pos, size_type __n)
679 {
680 const size_type __new_size = _M_length() - __n;
681 const size_type __how_much = _M_length() - __pos - __n;
682
683 if (_M_is_shared())
684 {
685 // Must reallocate.
686 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(),
687 _M_get_allocator());
688
689 if (__pos)
690 this->_S_copy(__r->_M_refdata(), _M_data(), __pos);
691 if (__how_much)
692 this->_S_copy(__r->_M_refdata() + __pos,
693 _M_data() + __pos + __n, __how_much);
694
695 _M_dispose();
696 _M_data(__r->_M_refdata());
697 }
698 else if (__how_much && __n)
699 {
700 // Work in-place.
701 this->_S_move(_M_data() + __pos,
702 _M_data() + __pos + __n, __how_much);
703 }
704
705 _M_rep()->_M_set_length(__new_size);
706 }
707
708 template<>
709 inline bool
710 __rc_string_base<char, std::char_traits<char>,
711 std::allocator<char> >::
712 _M_compare(const __rc_string_base& __rcs) const
713 {
714 if (_M_rep() == __rcs._M_rep())
715 return true;
716 return false;
717 }
718
719 #ifdef _GLIBCXX_USE_WCHAR_T
720 template<>
721 inline bool
722 __rc_string_base<wchar_t, std::char_traits<wchar_t>,
723 std::allocator<wchar_t> >::
724 _M_compare(const __rc_string_base& __rcs) const
725 {
726 if (_M_rep() == __rcs._M_rep())
727 return true;
728 return false;
729 }
730 #endif
731
732 _GLIBCXX_END_NAMESPACE_VERSION
733 } // namespace
734
735 #endif /* _RC_STRING_BASE_H */
736