1// Reference-counted versatile string base -*- C++ -*- 2 3// Copyright (C) 2005, 2006 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 2, 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// You should have received a copy of the GNU General Public License along 17// with this library; see the file COPYING. If not, write to the Free 18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 19// USA. 20 21// As a special exception, you may use this file as part of a free software 22// library without restriction. Specifically, if other files instantiate 23// templates or use macros or inline functions from this file, or you compile 24// this file and link it with other files to produce an executable, this 25// file does not by itself cause the resulting executable to be covered by 26// the GNU General Public License. This exception does not however 27// invalidate any other reasons why the executable file might be covered by 28// the GNU General Public License. 29 30/** @file ext/rc_string_base.h 31 * This file is a GNU extension to the Standard C++ Library. 32 * This is an internal header file, included by other library headers. 33 * You should not attempt to use it directly. 34 */ 35 36#ifndef _RC_STRING_BASE_H 37#define _RC_STRING_BASE_H 1 38 39#include <bits/atomicity.h> 40 41namespace __gnu_cxx 42{ 43 /** 44 * @if maint 45 * Documentation? What's that? 46 * Nathan Myers <ncm@cantrip.org>. 47 * 48 * A string looks like this: 49 * 50 * @code 51 * [_Rep] 52 * _M_length 53 * [__rc_string_base<char_type>] _M_capacity 54 * _M_dataplus _M_refcount 55 * _M_p ----------------> unnamed array of char_type 56 * @endcode 57 * 58 * Where the _M_p points to the first character in the string, and 59 * you cast it to a pointer-to-_Rep and subtract 1 to get a 60 * pointer to the header. 61 * 62 * This approach has the enormous advantage that a string object 63 * requires only one allocation. All the ugliness is confined 64 * within a single pair of inline functions, which each compile to 65 * a single "add" instruction: _Rep::_M_refdata(), and 66 * __rc_string_base::_M_rep(); and the allocation function which gets a 67 * block of raw bytes and with room enough and constructs a _Rep 68 * object at the front. 69 * 70 * The reason you want _M_data pointing to the character array and 71 * not the _Rep is so that the debugger can see the string 72 * contents. (Probably we should add a non-inline member to get 73 * the _Rep for the debugger to use, so users can check the actual 74 * string length.) 75 * 76 * Note that the _Rep object is a POD so that you can have a 77 * static "empty string" _Rep object already "constructed" before 78 * static constructors have run. The reference-count encoding is 79 * chosen so that a 0 indicates one reference, so you never try to 80 * destroy the empty-string _Rep object. 81 * 82 * All but the last paragraph is considered pretty conventional 83 * for a C++ string implementation. 84 * @endif 85 */ 86 template<typename _CharT, typename _Traits, typename _Alloc> 87 class __rc_string_base 88 : protected __vstring_utility<_CharT, _Traits, _Alloc> 89 { 90 public: 91 typedef _Traits traits_type; 92 typedef typename _Traits::char_type value_type; 93 typedef _Alloc allocator_type; 94 95 typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base; 96 typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type; 97 typedef typename _CharT_alloc_type::size_type size_type; 98 99 private: 100 // _Rep: string representation 101 // Invariants: 102 // 1. String really contains _M_length + 1 characters: due to 21.3.4 103 // must be kept null-terminated. 104 // 2. _M_capacity >= _M_length 105 // Allocated memory is always (_M_capacity + 1) * sizeof(_CharT). 106 // 3. _M_refcount has three states: 107 // -1: leaked, one reference, no ref-copies allowed, non-const. 108 // 0: one reference, non-const. 109 // n>0: n + 1 references, operations require a lock, const. 110 // 4. All fields == 0 is an empty string, given the extra storage 111 // beyond-the-end for a null terminator; thus, the shared 112 // empty string representation needs no constructor. 113 struct _Rep 114 { 115 union 116 { 117 struct 118 { 119 size_type _M_length; 120 size_type _M_capacity; 121 _Atomic_word _M_refcount; 122 } _M_info; 123 124 // Only for alignment purposes. 125 _CharT _M_align; 126 }; 127 128 typedef typename _Alloc::template rebind<_Rep>::other _Rep_alloc_type; 129 130 _CharT* 131 _M_refdata() throw() 132 { return reinterpret_cast<_CharT*>(this + 1); } 133 134 _CharT* 135 _M_refcopy() throw() 136 { 137 __atomic_add(&_M_info._M_refcount, 1); 138 return _M_refdata(); 139 } // XXX MT 140 141 void 142 _M_set_length(size_type __n) 143 { 144 _M_info._M_refcount = 0; // One reference. 145 _M_info._M_length = __n; 146 // grrr. (per 21.3.4) 147 // You cannot leave those LWG people alone for a second. 148 traits_type::assign(_M_refdata()[__n], _CharT()); 149 } 150 151 // Create & Destroy 152 static _Rep* 153 _S_create(size_type, size_type, const _Alloc&); 154 155 void 156 _M_destroy(const _Alloc&) throw(); 157 158 _CharT* 159 _M_clone(const _Alloc&, size_type __res = 0); 160 }; 161 162 struct _Rep_empty 163 : public _Rep 164 { 165 _CharT _M_terminal; 166 }; 167 168 static _Rep_empty _S_empty_rep; 169 170 // The maximum number of individual char_type elements of an 171 // individual string is determined by _S_max_size. This is the 172 // value that will be returned by max_size(). (Whereas npos 173 // is the maximum number of bytes the allocator can allocate.) 174 // If one was to divvy up the theoretical largest size string, 175 // with a terminating character and m _CharT elements, it'd 176 // look like this: 177 // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT) 178 // + sizeof(_Rep) - 1 179 // (NB: last two terms for rounding reasons, see _M_create below) 180 // Solving for m: 181 // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1 182 // In addition, this implementation halfs this amount. 183 enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep) 184 + 1) / sizeof(_CharT)) - 1) / 2 }; 185 186 // Data Member (private): 187 mutable typename _Util_Base::template _Alloc_hider<_Alloc> _M_dataplus; 188 189 void 190 _M_data(_CharT* __p) 191 { _M_dataplus._M_p = __p; } 192 193 _Rep* 194 _M_rep() const 195 { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); } 196 197 _CharT* 198 _M_grab(const _Alloc& __alloc) const 199 { 200 return (!_M_is_leaked() && _M_get_allocator() == __alloc) 201 ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc); 202 } 203 204 void 205 _M_dispose() 206 { 207 if (__exchange_and_add(&_M_rep()->_M_info._M_refcount, -1) <= 0) 208 _M_rep()->_M_destroy(_M_get_allocator()); 209 } // XXX MT 210 211 bool 212 _M_is_leaked() const 213 { return _M_rep()->_M_info._M_refcount < 0; } 214 215 void 216 _M_set_sharable() 217 { _M_rep()->_M_info._M_refcount = 0; } 218 219 void 220 _M_leak_hard(); 221 222 // _S_construct_aux is used to implement the 21.3.1 para 15 which 223 // requires special behaviour if _InIterator is an integral type 224 template<typename _InIterator> 225 static _CharT* 226 _S_construct_aux(_InIterator __beg, _InIterator __end, 227 const _Alloc& __a, __false_type) 228 { 229 typedef typename iterator_traits<_InIterator>::iterator_category _Tag; 230 return _S_construct(__beg, __end, __a, _Tag()); 231 } 232 233 template<typename _InIterator> 234 static _CharT* 235 _S_construct_aux(_InIterator __beg, _InIterator __end, 236 const _Alloc& __a, __true_type) 237 { return _S_construct(static_cast<size_type>(__beg), 238 static_cast<value_type>(__end), __a); } 239 240 template<typename _InIterator> 241 static _CharT* 242 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a) 243 { 244 typedef typename std::__is_integer<_InIterator>::__type _Integral; 245 return _S_construct_aux(__beg, __end, __a, _Integral()); 246 } 247 248 // For Input Iterators, used in istreambuf_iterators, etc. 249 template<typename _InIterator> 250 static _CharT* 251 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 252 std::input_iterator_tag); 253 254 // For forward_iterators up to random_access_iterators, used for 255 // string::iterator, _CharT*, etc. 256 template<typename _FwdIterator> 257 static _CharT* 258 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a, 259 std::forward_iterator_tag); 260 261 static _CharT* 262 _S_construct(size_type __req, _CharT __c, const _Alloc& __a); 263 264 public: 265 size_type 266 _M_max_size() const 267 { return size_type(_S_max_size); } 268 269 _CharT* 270 _M_data() const 271 { return _M_dataplus._M_p; } 272 273 size_type 274 _M_length() const 275 { return _M_rep()->_M_info._M_length; } 276 277 size_type 278 _M_capacity() const 279 { return _M_rep()->_M_info._M_capacity; } 280 281 bool 282 _M_is_shared() const 283 { return _M_rep()->_M_info._M_refcount > 0; } 284 285 void 286 _M_set_leaked() 287 { _M_rep()->_M_info._M_refcount = -1; } 288 289 void 290 _M_leak() // for use in begin() & non-const op[] 291 { 292 if (!_M_is_leaked()) 293 _M_leak_hard(); 294 } 295 296 void 297 _M_set_length(size_type __n) 298 { _M_rep()->_M_set_length(__n); } 299 300 __rc_string_base() 301 : _M_dataplus(_Alloc(), _S_empty_rep._M_refcopy()) { } 302 303 __rc_string_base(const _Alloc& __a); 304 305 __rc_string_base(const __rc_string_base& __rcs); 306 307 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a); 308 309 template<typename _InputIterator> 310 __rc_string_base(_InputIterator __beg, _InputIterator __end, 311 const _Alloc& __a); 312 313 ~__rc_string_base() 314 { _M_dispose(); } 315 316 allocator_type& 317 _M_get_allocator() 318 { return _M_dataplus; } 319 320 const allocator_type& 321 _M_get_allocator() const 322 { return _M_dataplus; } 323 324 void 325 _M_swap(__rc_string_base& __rcs); 326 327 void 328 _M_assign(const __rc_string_base& __rcs); 329 330 void 331 _M_reserve(size_type __res); 332 333 void 334 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 335 size_type __len2); 336 337 void 338 _M_erase(size_type __pos, size_type __n); 339 340 void 341 _M_clear() 342 { _M_erase(size_type(0), _M_length()); } 343 344 bool 345 _M_compare(const __rc_string_base&) const 346 { return false; } 347 }; 348 349 template<typename _CharT, typename _Traits, typename _Alloc> 350 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty 351 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep; 352 353 template<typename _CharT, typename _Traits, typename _Alloc> 354 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep* 355 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 356 _S_create(size_type __capacity, size_type __old_capacity, 357 const _Alloc& __alloc) 358 { 359 // _GLIBCXX_RESOLVE_LIB_DEFECTS 360 // 83. String::npos vs. string::max_size() 361 if (__capacity > size_type(_S_max_size)) 362 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create")); 363 364 // The standard places no restriction on allocating more memory 365 // than is strictly needed within this layer at the moment or as 366 // requested by an explicit application call to reserve(). 367 368 // Many malloc implementations perform quite poorly when an 369 // application attempts to allocate memory in a stepwise fashion 370 // growing each allocation size by only 1 char. Additionally, 371 // it makes little sense to allocate less linear memory than the 372 // natural blocking size of the malloc implementation. 373 // Unfortunately, we would need a somewhat low-level calculation 374 // with tuned parameters to get this perfect for any particular 375 // malloc implementation. Fortunately, generalizations about 376 // common features seen among implementations seems to suffice. 377 378 // __pagesize need not match the actual VM page size for good 379 // results in practice, thus we pick a common value on the low 380 // side. __malloc_header_size is an estimate of the amount of 381 // overhead per memory allocation (in practice seen N * sizeof 382 // (void*) where N is 0, 2 or 4). According to folklore, 383 // picking this value on the high side is better than 384 // low-balling it (especially when this algorithm is used with 385 // malloc implementations that allocate memory blocks rounded up 386 // to a size which is a power of 2). 387 const size_type __pagesize = 4096; 388 const size_type __malloc_header_size = 4 * sizeof(void*); 389 390 // The below implements an exponential growth policy, necessary to 391 // meet amortized linear time requirements of the library: see 392 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html. 393 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity) 394 { 395 __capacity = 2 * __old_capacity; 396 // Never allocate a string bigger than _S_max_size. 397 if (__capacity > size_type(_S_max_size)) 398 __capacity = size_type(_S_max_size); 399 } 400 401 // NB: Need an array of char_type[__capacity], plus a terminating 402 // null char_type() element, plus enough for the _Rep data structure, 403 // plus sizeof(_Rep) - 1 to upper round to a size multiple of 404 // sizeof(_Rep). 405 // Whew. Seemingly so needy, yet so elemental. 406 size_type __size = ((__capacity + 1) * sizeof(_CharT) 407 + 2 * sizeof(_Rep) - 1); 408 409 const size_type __adj_size = __size + __malloc_header_size; 410 if (__adj_size > __pagesize && __capacity > __old_capacity) 411 { 412 const size_type __extra = __pagesize - __adj_size % __pagesize; 413 __capacity += __extra / sizeof(_CharT); 414 if (__capacity > size_type(_S_max_size)) 415 __capacity = size_type(_S_max_size); 416 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1; 417 } 418 419 // NB: Might throw, but no worries about a leak, mate: _Rep() 420 // does not throw. 421 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep)); 422 _Rep* __p = new (__place) _Rep; 423 __p->_M_info._M_capacity = __capacity; 424 return __p; 425 } 426 427 template<typename _CharT, typename _Traits, typename _Alloc> 428 void 429 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 430 _M_destroy(const _Alloc& __a) throw () 431 { 432 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT) 433 + 2 * sizeof(_Rep) - 1); 434 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep)); 435 } 436 437 template<typename _CharT, typename _Traits, typename _Alloc> 438 _CharT* 439 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 440 _M_clone(const _Alloc& __alloc, size_type __res) 441 { 442 // Requested capacity of the clone. 443 const size_type __requested_cap = _M_info._M_length + __res; 444 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity, 445 __alloc); 446 447 if (_M_info._M_length) 448 _S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length); 449 450 __r->_M_set_length(_M_info._M_length); 451 return __r->_M_refdata(); 452 } 453 454 template<typename _CharT, typename _Traits, typename _Alloc> 455 __rc_string_base<_CharT, _Traits, _Alloc>:: 456 __rc_string_base(const _Alloc& __a) 457 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { } 458 459 template<typename _CharT, typename _Traits, typename _Alloc> 460 __rc_string_base<_CharT, _Traits, _Alloc>:: 461 __rc_string_base(const __rc_string_base& __rcs) 462 : _M_dataplus(__rcs._M_get_allocator(), 463 __rcs._M_grab(__rcs._M_get_allocator())) { } 464 465 template<typename _CharT, typename _Traits, typename _Alloc> 466 __rc_string_base<_CharT, _Traits, _Alloc>:: 467 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a) 468 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { } 469 470 template<typename _CharT, typename _Traits, typename _Alloc> 471 template<typename _InputIterator> 472 __rc_string_base<_CharT, _Traits, _Alloc>:: 473 __rc_string_base(_InputIterator __beg, _InputIterator __end, 474 const _Alloc& __a) 475 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { } 476 477 template<typename _CharT, typename _Traits, typename _Alloc> 478 void 479 __rc_string_base<_CharT, _Traits, _Alloc>:: 480 _M_leak_hard() 481 { 482 if (_M_is_shared()) 483 _M_erase(0, 0); 484 _M_set_leaked(); 485 } 486 487 // NB: This is the special case for Input Iterators, used in 488 // istreambuf_iterators, etc. 489 // Input Iterators have a cost structure very different from 490 // pointers, calling for a different coding style. 491 template<typename _CharT, typename _Traits, typename _Alloc> 492 template<typename _InIterator> 493 _CharT* 494 __rc_string_base<_CharT, _Traits, _Alloc>:: 495 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 496 std::input_iterator_tag) 497 { 498 if (__beg == __end && __a == _Alloc()) 499 return _S_empty_rep._M_refcopy(); 500 501 // Avoid reallocation for common case. 502 _CharT __buf[128]; 503 size_type __len = 0; 504 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT)) 505 { 506 __buf[__len++] = *__beg; 507 ++__beg; 508 } 509 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a); 510 _S_copy(__r->_M_refdata(), __buf, __len); 511 try 512 { 513 while (__beg != __end) 514 { 515 if (__len == __r->_M_info._M_capacity) 516 { 517 // Allocate more space. 518 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a); 519 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len); 520 __r->_M_destroy(__a); 521 __r = __another; 522 } 523 __r->_M_refdata()[__len++] = *__beg; 524 ++__beg; 525 } 526 } 527 catch(...) 528 { 529 __r->_M_destroy(__a); 530 __throw_exception_again; 531 } 532 __r->_M_set_length(__len); 533 return __r->_M_refdata(); 534 } 535 536 template<typename _CharT, typename _Traits, typename _Alloc> 537 template<typename _InIterator> 538 _CharT* 539 __rc_string_base<_CharT, _Traits, _Alloc>:: 540 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 541 std::forward_iterator_tag) 542 { 543 if (__beg == __end && __a == _Alloc()) 544 return _S_empty_rep._M_refcopy(); 545 546 // NB: Not required, but considered best practice. 547 if (__builtin_expect(_S_is_null_pointer(__beg) && __beg != __end, 0)) 548 std::__throw_logic_error(__N("__rc_string_base::" 549 "_S_construct NULL not valid")); 550 551 const size_type __dnew = static_cast<size_type>(std::distance(__beg, 552 __end)); 553 // Check for out_of_range and length_error exceptions. 554 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a); 555 try 556 { _S_copy_chars(__r->_M_refdata(), __beg, __end); } 557 catch(...) 558 { 559 __r->_M_destroy(__a); 560 __throw_exception_again; 561 } 562 __r->_M_set_length(__dnew); 563 return __r->_M_refdata(); 564 } 565 566 template<typename _CharT, typename _Traits, typename _Alloc> 567 _CharT* 568 __rc_string_base<_CharT, _Traits, _Alloc>:: 569 _S_construct(size_type __n, _CharT __c, const _Alloc& __a) 570 { 571 if (__n == 0 && __a == _Alloc()) 572 return _S_empty_rep._M_refcopy(); 573 574 // Check for out_of_range and length_error exceptions. 575 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a); 576 if (__n) 577 _S_assign(__r->_M_refdata(), __n, __c); 578 579 __r->_M_set_length(__n); 580 return __r->_M_refdata(); 581 } 582 583 template<typename _CharT, typename _Traits, typename _Alloc> 584 void 585 __rc_string_base<_CharT, _Traits, _Alloc>:: 586 _M_swap(__rc_string_base& __rcs) 587 { 588 if (_M_is_leaked()) 589 _M_set_sharable(); 590 if (__rcs._M_is_leaked()) 591 __rcs._M_set_sharable(); 592 593 _CharT* __tmp = _M_data(); 594 _M_data(__rcs._M_data()); 595 __rcs._M_data(__tmp); 596 597 // NB: Implement Option 3 of DR 431 (see N1599). 598 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(), 599 __rcs._M_get_allocator()); 600 } 601 602 template<typename _CharT, typename _Traits, typename _Alloc> 603 void 604 __rc_string_base<_CharT, _Traits, _Alloc>:: 605 _M_assign(const __rc_string_base& __rcs) 606 { 607 if (_M_rep() != __rcs._M_rep()) 608 { 609 _CharT* __tmp = __rcs._M_grab(_M_get_allocator()); 610 _M_dispose(); 611 _M_data(__tmp); 612 } 613 } 614 615 template<typename _CharT, typename _Traits, typename _Alloc> 616 void 617 __rc_string_base<_CharT, _Traits, _Alloc>:: 618 _M_reserve(size_type __res) 619 { 620 // Make sure we don't shrink below the current size. 621 if (__res < _M_length()) 622 __res = _M_length(); 623 624 if (__res != _M_capacity() || _M_is_shared()) 625 { 626 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(), 627 __res - _M_length()); 628 _M_dispose(); 629 _M_data(__tmp); 630 } 631 } 632 633 template<typename _CharT, typename _Traits, typename _Alloc> 634 void 635 __rc_string_base<_CharT, _Traits, _Alloc>:: 636 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 637 size_type __len2) 638 { 639 const size_type __how_much = _M_length() - __pos - __len1; 640 641 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1, 642 _M_capacity(), _M_get_allocator()); 643 644 if (__pos) 645 _S_copy(__r->_M_refdata(), _M_data(), __pos); 646 if (__s && __len2) 647 _S_copy(__r->_M_refdata() + __pos, __s, __len2); 648 if (__how_much) 649 _S_copy(__r->_M_refdata() + __pos + __len2, 650 _M_data() + __pos + __len1, __how_much); 651 652 _M_dispose(); 653 _M_data(__r->_M_refdata()); 654 } 655 656 template<typename _CharT, typename _Traits, typename _Alloc> 657 void 658 __rc_string_base<_CharT, _Traits, _Alloc>:: 659 _M_erase(size_type __pos, size_type __n) 660 { 661 const size_type __new_size = _M_length() - __n; 662 const size_type __how_much = _M_length() - __pos - __n; 663 664 if (_M_is_shared()) 665 { 666 // Must reallocate. 667 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(), 668 _M_get_allocator()); 669 670 if (__pos) 671 _S_copy(__r->_M_refdata(), _M_data(), __pos); 672 if (__how_much) 673 _S_copy(__r->_M_refdata() + __pos, 674 _M_data() + __pos + __n, __how_much); 675 676 _M_dispose(); 677 _M_data(__r->_M_refdata()); 678 } 679 else if (__how_much && __n) 680 { 681 // Work in-place. 682 _S_move(_M_data() + __pos, 683 _M_data() + __pos + __n, __how_much); 684 } 685 686 _M_rep()->_M_set_length(__new_size); 687 } 688 689 template<> 690 inline bool 691 __rc_string_base<char, std::char_traits<char>, 692 std::allocator<char> >:: 693 _M_compare(const __rc_string_base& __rcs) const 694 { 695 if (_M_rep() == __rcs._M_rep()) 696 return true; 697 return false; 698 } 699 700 template<> 701 inline bool 702 __rc_string_base<wchar_t, std::char_traits<wchar_t>, 703 std::allocator<wchar_t> >:: 704 _M_compare(const __rc_string_base& __rcs) const 705 { 706 if (_M_rep() == __rcs._M_rep()) 707 return true; 708 return false; 709 } 710} // namespace __gnu_cxx 711 712#endif /* _RC_STRING_BASE_H */ 713