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 <ext/atomicity.h> 40 41_GLIBCXX_BEGIN_NAMESPACE(__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_dispatch(&_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_dispatch(&_M_rep()->_M_info._M_refcount, 208 -1) <= 0) 209 _M_rep()->_M_destroy(_M_get_allocator()); 210 } // XXX MT 211 212 bool 213 _M_is_leaked() const 214 { return _M_rep()->_M_info._M_refcount < 0; } 215 216 void 217 _M_set_sharable() 218 { _M_rep()->_M_info._M_refcount = 0; } 219 220 void 221 _M_leak_hard(); 222 223 // _S_construct_aux is used to implement the 21.3.1 para 15 which 224 // requires special behaviour if _InIterator is an integral type 225 template<typename _InIterator> 226 static _CharT* 227 _S_construct_aux(_InIterator __beg, _InIterator __end, 228 const _Alloc& __a, std::__false_type) 229 { 230 typedef typename iterator_traits<_InIterator>::iterator_category _Tag; 231 return _S_construct(__beg, __end, __a, _Tag()); 232 } 233 234 template<typename _InIterator> 235 static _CharT* 236 _S_construct_aux(_InIterator __beg, _InIterator __end, 237 const _Alloc& __a, std::__true_type) 238 { return _S_construct(static_cast<size_type>(__beg), 239 static_cast<value_type>(__end), __a); } 240 241 template<typename _InIterator> 242 static _CharT* 243 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a) 244 { 245 typedef typename std::__is_integer<_InIterator>::__type _Integral; 246 return _S_construct_aux(__beg, __end, __a, _Integral()); 247 } 248 249 // For Input Iterators, used in istreambuf_iterators, etc. 250 template<typename _InIterator> 251 static _CharT* 252 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 253 std::input_iterator_tag); 254 255 // For forward_iterators up to random_access_iterators, used for 256 // string::iterator, _CharT*, etc. 257 template<typename _FwdIterator> 258 static _CharT* 259 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a, 260 std::forward_iterator_tag); 261 262 static _CharT* 263 _S_construct(size_type __req, _CharT __c, const _Alloc& __a); 264 265 public: 266 size_type 267 _M_max_size() const 268 { return size_type(_S_max_size); } 269 270 _CharT* 271 _M_data() const 272 { return _M_dataplus._M_p; } 273 274 size_type 275 _M_length() const 276 { return _M_rep()->_M_info._M_length; } 277 278 size_type 279 _M_capacity() const 280 { return _M_rep()->_M_info._M_capacity; } 281 282 bool 283 _M_is_shared() const 284 { return _M_rep()->_M_info._M_refcount > 0; } 285 286 void 287 _M_set_leaked() 288 { _M_rep()->_M_info._M_refcount = -1; } 289 290 void 291 _M_leak() // for use in begin() & non-const op[] 292 { 293 if (!_M_is_leaked()) 294 _M_leak_hard(); 295 } 296 297 void 298 _M_set_length(size_type __n) 299 { _M_rep()->_M_set_length(__n); } 300 301 __rc_string_base() 302 : _M_dataplus(_Alloc(), _S_empty_rep._M_refcopy()) { } 303 304 __rc_string_base(const _Alloc& __a); 305 306 __rc_string_base(const __rc_string_base& __rcs); 307 308 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a); 309 310 template<typename _InputIterator> 311 __rc_string_base(_InputIterator __beg, _InputIterator __end, 312 const _Alloc& __a); 313 314 ~__rc_string_base() 315 { _M_dispose(); } 316 317 allocator_type& 318 _M_get_allocator() 319 { return _M_dataplus; } 320 321 const allocator_type& 322 _M_get_allocator() const 323 { return _M_dataplus; } 324 325 void 326 _M_swap(__rc_string_base& __rcs); 327 328 void 329 _M_assign(const __rc_string_base& __rcs); 330 331 void 332 _M_reserve(size_type __res); 333 334 void 335 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 336 size_type __len2); 337 338 void 339 _M_erase(size_type __pos, size_type __n); 340 341 void 342 _M_clear() 343 { _M_erase(size_type(0), _M_length()); } 344 345 bool 346 _M_compare(const __rc_string_base&) const 347 { return false; } 348 }; 349 350 template<typename _CharT, typename _Traits, typename _Alloc> 351 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty 352 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep; 353 354 template<typename _CharT, typename _Traits, typename _Alloc> 355 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep* 356 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 357 _S_create(size_type __capacity, size_type __old_capacity, 358 const _Alloc& __alloc) 359 { 360 // _GLIBCXX_RESOLVE_LIB_DEFECTS 361 // 83. String::npos vs. string::max_size() 362 if (__capacity > size_type(_S_max_size)) 363 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create")); 364 365 // The standard places no restriction on allocating more memory 366 // than is strictly needed within this layer at the moment or as 367 // requested by an explicit application call to reserve(). 368 369 // Many malloc implementations perform quite poorly when an 370 // application attempts to allocate memory in a stepwise fashion 371 // growing each allocation size by only 1 char. Additionally, 372 // it makes little sense to allocate less linear memory than the 373 // natural blocking size of the malloc implementation. 374 // Unfortunately, we would need a somewhat low-level calculation 375 // with tuned parameters to get this perfect for any particular 376 // malloc implementation. Fortunately, generalizations about 377 // common features seen among implementations seems to suffice. 378 379 // __pagesize need not match the actual VM page size for good 380 // results in practice, thus we pick a common value on the low 381 // side. __malloc_header_size is an estimate of the amount of 382 // overhead per memory allocation (in practice seen N * sizeof 383 // (void*) where N is 0, 2 or 4). According to folklore, 384 // picking this value on the high side is better than 385 // low-balling it (especially when this algorithm is used with 386 // malloc implementations that allocate memory blocks rounded up 387 // to a size which is a power of 2). 388 const size_type __pagesize = 4096; 389 const size_type __malloc_header_size = 4 * sizeof(void*); 390 391 // The below implements an exponential growth policy, necessary to 392 // meet amortized linear time requirements of the library: see 393 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html. 394 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity) 395 { 396 __capacity = 2 * __old_capacity; 397 // Never allocate a string bigger than _S_max_size. 398 if (__capacity > size_type(_S_max_size)) 399 __capacity = size_type(_S_max_size); 400 } 401 402 // NB: Need an array of char_type[__capacity], plus a terminating 403 // null char_type() element, plus enough for the _Rep data structure, 404 // plus sizeof(_Rep) - 1 to upper round to a size multiple of 405 // sizeof(_Rep). 406 // Whew. Seemingly so needy, yet so elemental. 407 size_type __size = ((__capacity + 1) * sizeof(_CharT) 408 + 2 * sizeof(_Rep) - 1); 409 410 const size_type __adj_size = __size + __malloc_header_size; 411 if (__adj_size > __pagesize && __capacity > __old_capacity) 412 { 413 const size_type __extra = __pagesize - __adj_size % __pagesize; 414 __capacity += __extra / sizeof(_CharT); 415 if (__capacity > size_type(_S_max_size)) 416 __capacity = size_type(_S_max_size); 417 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1; 418 } 419 420 // NB: Might throw, but no worries about a leak, mate: _Rep() 421 // does not throw. 422 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep)); 423 _Rep* __p = new (__place) _Rep; 424 __p->_M_info._M_capacity = __capacity; 425 return __p; 426 } 427 428 template<typename _CharT, typename _Traits, typename _Alloc> 429 void 430 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 431 _M_destroy(const _Alloc& __a) throw () 432 { 433 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT) 434 + 2 * sizeof(_Rep) - 1); 435 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep)); 436 } 437 438 template<typename _CharT, typename _Traits, typename _Alloc> 439 _CharT* 440 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 441 _M_clone(const _Alloc& __alloc, size_type __res) 442 { 443 // Requested capacity of the clone. 444 const size_type __requested_cap = _M_info._M_length + __res; 445 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity, 446 __alloc); 447 448 if (_M_info._M_length) 449 _S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length); 450 451 __r->_M_set_length(_M_info._M_length); 452 return __r->_M_refdata(); 453 } 454 455 template<typename _CharT, typename _Traits, typename _Alloc> 456 __rc_string_base<_CharT, _Traits, _Alloc>:: 457 __rc_string_base(const _Alloc& __a) 458 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { } 459 460 template<typename _CharT, typename _Traits, typename _Alloc> 461 __rc_string_base<_CharT, _Traits, _Alloc>:: 462 __rc_string_base(const __rc_string_base& __rcs) 463 : _M_dataplus(__rcs._M_get_allocator(), 464 __rcs._M_grab(__rcs._M_get_allocator())) { } 465 466 template<typename _CharT, typename _Traits, typename _Alloc> 467 __rc_string_base<_CharT, _Traits, _Alloc>:: 468 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a) 469 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { } 470 471 template<typename _CharT, typename _Traits, typename _Alloc> 472 template<typename _InputIterator> 473 __rc_string_base<_CharT, _Traits, _Alloc>:: 474 __rc_string_base(_InputIterator __beg, _InputIterator __end, 475 const _Alloc& __a) 476 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { } 477 478 template<typename _CharT, typename _Traits, typename _Alloc> 479 void 480 __rc_string_base<_CharT, _Traits, _Alloc>:: 481 _M_leak_hard() 482 { 483 if (_M_is_shared()) 484 _M_erase(0, 0); 485 _M_set_leaked(); 486 } 487 488 // NB: This is the special case for Input Iterators, used in 489 // istreambuf_iterators, etc. 490 // Input Iterators have a cost structure very different from 491 // pointers, calling for a different coding style. 492 template<typename _CharT, typename _Traits, typename _Alloc> 493 template<typename _InIterator> 494 _CharT* 495 __rc_string_base<_CharT, _Traits, _Alloc>:: 496 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 497 std::input_iterator_tag) 498 { 499 if (__beg == __end && __a == _Alloc()) 500 return _S_empty_rep._M_refcopy(); 501 502 // Avoid reallocation for common case. 503 _CharT __buf[128]; 504 size_type __len = 0; 505 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT)) 506 { 507 __buf[__len++] = *__beg; 508 ++__beg; 509 } 510 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a); 511 _S_copy(__r->_M_refdata(), __buf, __len); 512 try 513 { 514 while (__beg != __end) 515 { 516 if (__len == __r->_M_info._M_capacity) 517 { 518 // Allocate more space. 519 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a); 520 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len); 521 __r->_M_destroy(__a); 522 __r = __another; 523 } 524 __r->_M_refdata()[__len++] = *__beg; 525 ++__beg; 526 } 527 } 528 catch(...) 529 { 530 __r->_M_destroy(__a); 531 __throw_exception_again; 532 } 533 __r->_M_set_length(__len); 534 return __r->_M_refdata(); 535 } 536 537 template<typename _CharT, typename _Traits, typename _Alloc> 538 template<typename _InIterator> 539 _CharT* 540 __rc_string_base<_CharT, _Traits, _Alloc>:: 541 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 542 std::forward_iterator_tag) 543 { 544 if (__beg == __end && __a == _Alloc()) 545 return _S_empty_rep._M_refcopy(); 546 547 // NB: Not required, but considered best practice. 548 if (__builtin_expect(_S_is_null_pointer(__beg) && __beg != __end, 0)) 549 std::__throw_logic_error(__N("__rc_string_base::" 550 "_S_construct NULL not valid")); 551 552 const size_type __dnew = static_cast<size_type>(std::distance(__beg, 553 __end)); 554 // Check for out_of_range and length_error exceptions. 555 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a); 556 try 557 { _S_copy_chars(__r->_M_refdata(), __beg, __end); } 558 catch(...) 559 { 560 __r->_M_destroy(__a); 561 __throw_exception_again; 562 } 563 __r->_M_set_length(__dnew); 564 return __r->_M_refdata(); 565 } 566 567 template<typename _CharT, typename _Traits, typename _Alloc> 568 _CharT* 569 __rc_string_base<_CharT, _Traits, _Alloc>:: 570 _S_construct(size_type __n, _CharT __c, const _Alloc& __a) 571 { 572 if (__n == 0 && __a == _Alloc()) 573 return _S_empty_rep._M_refcopy(); 574 575 // Check for out_of_range and length_error exceptions. 576 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a); 577 if (__n) 578 _S_assign(__r->_M_refdata(), __n, __c); 579 580 __r->_M_set_length(__n); 581 return __r->_M_refdata(); 582 } 583 584 template<typename _CharT, typename _Traits, typename _Alloc> 585 void 586 __rc_string_base<_CharT, _Traits, _Alloc>:: 587 _M_swap(__rc_string_base& __rcs) 588 { 589 if (_M_is_leaked()) 590 _M_set_sharable(); 591 if (__rcs._M_is_leaked()) 592 __rcs._M_set_sharable(); 593 594 _CharT* __tmp = _M_data(); 595 _M_data(__rcs._M_data()); 596 __rcs._M_data(__tmp); 597 598 // _GLIBCXX_RESOLVE_LIB_DEFECTS 599 // 431. Swapping containers with unequal allocators. 600 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(), 601 __rcs._M_get_allocator()); 602 } 603 604 template<typename _CharT, typename _Traits, typename _Alloc> 605 void 606 __rc_string_base<_CharT, _Traits, _Alloc>:: 607 _M_assign(const __rc_string_base& __rcs) 608 { 609 if (_M_rep() != __rcs._M_rep()) 610 { 611 _CharT* __tmp = __rcs._M_grab(_M_get_allocator()); 612 _M_dispose(); 613 _M_data(__tmp); 614 } 615 } 616 617 template<typename _CharT, typename _Traits, typename _Alloc> 618 void 619 __rc_string_base<_CharT, _Traits, _Alloc>:: 620 _M_reserve(size_type __res) 621 { 622 // Make sure we don't shrink below the current size. 623 if (__res < _M_length()) 624 __res = _M_length(); 625 626 if (__res != _M_capacity() || _M_is_shared()) 627 { 628 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(), 629 __res - _M_length()); 630 _M_dispose(); 631 _M_data(__tmp); 632 } 633 } 634 635 template<typename _CharT, typename _Traits, typename _Alloc> 636 void 637 __rc_string_base<_CharT, _Traits, _Alloc>:: 638 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 639 size_type __len2) 640 { 641 const size_type __how_much = _M_length() - __pos - __len1; 642 643 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1, 644 _M_capacity(), _M_get_allocator()); 645 646 if (__pos) 647 _S_copy(__r->_M_refdata(), _M_data(), __pos); 648 if (__s && __len2) 649 _S_copy(__r->_M_refdata() + __pos, __s, __len2); 650 if (__how_much) 651 _S_copy(__r->_M_refdata() + __pos + __len2, 652 _M_data() + __pos + __len1, __how_much); 653 654 _M_dispose(); 655 _M_data(__r->_M_refdata()); 656 } 657 658 template<typename _CharT, typename _Traits, typename _Alloc> 659 void 660 __rc_string_base<_CharT, _Traits, _Alloc>:: 661 _M_erase(size_type __pos, size_type __n) 662 { 663 const size_type __new_size = _M_length() - __n; 664 const size_type __how_much = _M_length() - __pos - __n; 665 666 if (_M_is_shared()) 667 { 668 // Must reallocate. 669 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(), 670 _M_get_allocator()); 671 672 if (__pos) 673 _S_copy(__r->_M_refdata(), _M_data(), __pos); 674 if (__how_much) 675 _S_copy(__r->_M_refdata() + __pos, 676 _M_data() + __pos + __n, __how_much); 677 678 _M_dispose(); 679 _M_data(__r->_M_refdata()); 680 } 681 else if (__how_much && __n) 682 { 683 // Work in-place. 684 _S_move(_M_data() + __pos, 685 _M_data() + __pos + __n, __how_much); 686 } 687 688 _M_rep()->_M_set_length(__new_size); 689 } 690 691 template<> 692 inline bool 693 __rc_string_base<char, std::char_traits<char>, 694 std::allocator<char> >:: 695 _M_compare(const __rc_string_base& __rcs) const 696 { 697 if (_M_rep() == __rcs._M_rep()) 698 return true; 699 return false; 700 } 701 702#ifdef _GLIBCXX_USE_WCHAR_T 703 template<> 704 inline bool 705 __rc_string_base<wchar_t, std::char_traits<wchar_t>, 706 std::allocator<wchar_t> >:: 707 _M_compare(const __rc_string_base& __rcs) const 708 { 709 if (_M_rep() == __rcs._M_rep()) 710 return true; 711 return false; 712 } 713#endif 714 715_GLIBCXX_END_NAMESPACE 716 717#endif /* _RC_STRING_BASE_H */ 718