1// Reference-counted versatile string base -*- C++ -*- 2 3// Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 4// Free Software Foundation, Inc. 5// 6// This file is part of the GNU ISO C++ Library. This library is free 7// software; you can redistribute it and/or modify it under the 8// terms of the GNU General Public License as published by the 9// Free Software Foundation; either version 3, or (at your option) 10// any later version. 11 12// This library is distributed in the hope that it will be useful, 13// but WITHOUT ANY WARRANTY; without even the implied warranty of 14// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15// GNU General Public License for more details. 16 17// Under Section 7 of GPL version 3, you are granted additional 18// permissions described in the GCC Runtime Library Exception, version 19// 3.1, as published by the Free Software Foundation. 20 21// You should have received a copy of the GNU General Public License and 22// a copy of the GCC Runtime Library Exception along with this program; 23// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 24// <http://www.gnu.org/licenses/>. 25 26/** @file ext/rc_string_base.h 27 * This is an internal header file, included by other library headers. 28 * Do not attempt to use it directly. @headername{ext/vstring.h} 29 */ 30 31#ifndef _RC_STRING_BASE_H 32#define _RC_STRING_BASE_H 1 33 34#include <ext/atomicity.h> 35#include <bits/stl_iterator_base_funcs.h> 36 37namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 38{ 39_GLIBCXX_BEGIN_NAMESPACE_VERSION 40 41 /** 42 * Documentation? What's that? 43 * Nathan Myers <ncm@cantrip.org>. 44 * 45 * A string looks like this: 46 * 47 * @code 48 * [_Rep] 49 * _M_length 50 * [__rc_string_base<char_type>] _M_capacity 51 * _M_dataplus _M_refcount 52 * _M_p ----------------> unnamed array of char_type 53 * @endcode 54 * 55 * Where the _M_p points to the first character in the string, and 56 * you cast it to a pointer-to-_Rep and subtract 1 to get a 57 * pointer to the header. 58 * 59 * This approach has the enormous advantage that a string object 60 * requires only one allocation. All the ugliness is confined 61 * within a single pair of inline functions, which each compile to 62 * a single @a add instruction: _Rep::_M_refdata(), and 63 * __rc_string_base::_M_rep(); and the allocation function which gets a 64 * block of raw bytes and with room enough and constructs a _Rep 65 * object at the front. 66 * 67 * The reason you want _M_data pointing to the character array and 68 * not the _Rep is so that the debugger can see the string 69 * contents. (Probably we should add a non-inline member to get 70 * the _Rep for the debugger to use, so users can check the actual 71 * string length.) 72 * 73 * Note that the _Rep object is a POD so that you can have a 74 * static <em>empty string</em> _Rep object already @a constructed before 75 * static constructors have run. The reference-count encoding is 76 * chosen so that a 0 indicates one reference, so you never try to 77 * destroy the empty-string _Rep object. 78 * 79 * All but the last paragraph is considered pretty conventional 80 * for a C++ string implementation. 81 */ 82 template<typename _CharT, typename _Traits, typename _Alloc> 83 class __rc_string_base 84 : protected __vstring_utility<_CharT, _Traits, _Alloc> 85 { 86 public: 87 typedef _Traits traits_type; 88 typedef typename _Traits::char_type value_type; 89 typedef _Alloc allocator_type; 90 91 typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base; 92 typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type; 93 typedef typename _CharT_alloc_type::size_type size_type; 94 95 private: 96 // _Rep: string representation 97 // Invariants: 98 // 1. String really contains _M_length + 1 characters: due to 21.3.4 99 // must be kept null-terminated. 100 // 2. _M_capacity >= _M_length 101 // Allocated memory is always (_M_capacity + 1) * sizeof(_CharT). 102 // 3. _M_refcount has three states: 103 // -1: leaked, one reference, no ref-copies allowed, non-const. 104 // 0: one reference, non-const. 105 // n>0: n + 1 references, operations require a lock, const. 106 // 4. All fields == 0 is an empty string, given the extra storage 107 // beyond-the-end for a null terminator; thus, the shared 108 // empty string representation needs no constructor. 109 struct _Rep 110 { 111 union 112 { 113 struct 114 { 115 size_type _M_length; 116 size_type _M_capacity; 117 _Atomic_word _M_refcount; 118 } _M_info; 119 120 // Only for alignment purposes. 121 _CharT _M_align; 122 }; 123 124 typedef typename _Alloc::template rebind<_Rep>::other _Rep_alloc_type; 125 126 _CharT* 127 _M_refdata() throw() 128 { return reinterpret_cast<_CharT*>(this + 1); } 129 130 _CharT* 131 _M_refcopy() throw() 132 { 133 __atomic_add_dispatch(&_M_info._M_refcount, 1); 134 return _M_refdata(); 135 } // XXX MT 136 137 void 138 _M_set_length(size_type __n) 139 { 140 _M_info._M_refcount = 0; // One reference. 141 _M_info._M_length = __n; 142 // grrr. (per 21.3.4) 143 // You cannot leave those LWG people alone for a second. 144 traits_type::assign(_M_refdata()[__n], _CharT()); 145 } 146 147 // Create & Destroy 148 static _Rep* 149 _S_create(size_type, size_type, const _Alloc&); 150 151 void 152 _M_destroy(const _Alloc&) throw(); 153 154 _CharT* 155 _M_clone(const _Alloc&, size_type __res = 0); 156 }; 157 158 struct _Rep_empty 159 : public _Rep 160 { 161 _CharT _M_terminal; 162 }; 163 164 static _Rep_empty _S_empty_rep; 165 166 // The maximum number of individual char_type elements of an 167 // individual string is determined by _S_max_size. This is the 168 // value that will be returned by max_size(). (Whereas npos 169 // is the maximum number of bytes the allocator can allocate.) 170 // If one was to divvy up the theoretical largest size string, 171 // with a terminating character and m _CharT elements, it'd 172 // look like this: 173 // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT) 174 // + sizeof(_Rep) - 1 175 // (NB: last two terms for rounding reasons, see _M_create below) 176 // Solving for m: 177 // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1 178 // In addition, this implementation halves this amount. 179 enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep) 180 + 1) / sizeof(_CharT)) - 1) / 2 }; 181 182 // Data Member (private): 183 mutable typename _Util_Base::template _Alloc_hider<_Alloc> _M_dataplus; 184 185 void 186 _M_data(_CharT* __p) 187 { _M_dataplus._M_p = __p; } 188 189 _Rep* 190 _M_rep() const 191 { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); } 192 193 _CharT* 194 _M_grab(const _Alloc& __alloc) const 195 { 196 return (!_M_is_leaked() && _M_get_allocator() == __alloc) 197 ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc); 198 } 199 200 void 201 _M_dispose() 202 { 203 // Be race-detector-friendly. For more info see bits/c++config. 204 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_rep()->_M_info. 205 _M_refcount); 206 if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount, 207 -1) <= 0) 208 { 209 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_rep()->_M_info. 210 _M_refcount); 211 _M_rep()->_M_destroy(_M_get_allocator()); 212 } 213 } // XXX MT 214 215 bool 216 _M_is_leaked() const 217 { return _M_rep()->_M_info._M_refcount < 0; } 218 219 void 220 _M_set_sharable() 221 { _M_rep()->_M_info._M_refcount = 0; } 222 223 void 224 _M_leak_hard(); 225 226 // _S_construct_aux is used to implement the 21.3.1 para 15 which 227 // requires special behaviour if _InIterator is an integral type 228 template<typename _InIterator> 229 static _CharT* 230 _S_construct_aux(_InIterator __beg, _InIterator __end, 231 const _Alloc& __a, std::__false_type) 232 { 233 typedef typename iterator_traits<_InIterator>::iterator_category _Tag; 234 return _S_construct(__beg, __end, __a, _Tag()); 235 } 236 237 // _GLIBCXX_RESOLVE_LIB_DEFECTS 238 // 438. Ambiguity in the "do the right thing" clause 239 template<typename _Integer> 240 static _CharT* 241 _S_construct_aux(_Integer __beg, _Integer __end, 242 const _Alloc& __a, std::__true_type) 243 { return _S_construct_aux_2(static_cast<size_type>(__beg), 244 __end, __a); } 245 246 static _CharT* 247 _S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a) 248 { return _S_construct(__req, __c, __a); } 249 250 template<typename _InIterator> 251 static _CharT* 252 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a) 253 { 254 typedef typename std::__is_integer<_InIterator>::__type _Integral; 255 return _S_construct_aux(__beg, __end, __a, _Integral()); 256 } 257 258 // For Input Iterators, used in istreambuf_iterators, etc. 259 template<typename _InIterator> 260 static _CharT* 261 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 262 std::input_iterator_tag); 263 264 // For forward_iterators up to random_access_iterators, used for 265 // string::iterator, _CharT*, etc. 266 template<typename _FwdIterator> 267 static _CharT* 268 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a, 269 std::forward_iterator_tag); 270 271 static _CharT* 272 _S_construct(size_type __req, _CharT __c, const _Alloc& __a); 273 274 public: 275 size_type 276 _M_max_size() const 277 { return size_type(_S_max_size); } 278 279 _CharT* 280 _M_data() const 281 { return _M_dataplus._M_p; } 282 283 size_type 284 _M_length() const 285 { return _M_rep()->_M_info._M_length; } 286 287 size_type 288 _M_capacity() const 289 { return _M_rep()->_M_info._M_capacity; } 290 291 bool 292 _M_is_shared() const 293 { return _M_rep()->_M_info._M_refcount > 0; } 294 295 void 296 _M_set_leaked() 297 { _M_rep()->_M_info._M_refcount = -1; } 298 299 void 300 _M_leak() // for use in begin() & non-const op[] 301 { 302 if (!_M_is_leaked()) 303 _M_leak_hard(); 304 } 305 306 void 307 _M_set_length(size_type __n) 308 { _M_rep()->_M_set_length(__n); } 309 310 __rc_string_base() 311 : _M_dataplus(_S_empty_rep._M_refcopy()) { } 312 313 __rc_string_base(const _Alloc& __a); 314 315 __rc_string_base(const __rc_string_base& __rcs); 316 317#ifdef __GXX_EXPERIMENTAL_CXX0X__ 318 __rc_string_base(__rc_string_base&& __rcs) 319 : _M_dataplus(__rcs._M_dataplus) 320 { __rcs._M_data(_S_empty_rep._M_refcopy()); } 321#endif 322 323 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a); 324 325 template<typename _InputIterator> 326 __rc_string_base(_InputIterator __beg, _InputIterator __end, 327 const _Alloc& __a); 328 329 ~__rc_string_base() 330 { _M_dispose(); } 331 332 allocator_type& 333 _M_get_allocator() 334 { return _M_dataplus; } 335 336 const allocator_type& 337 _M_get_allocator() const 338 { return _M_dataplus; } 339 340 void 341 _M_swap(__rc_string_base& __rcs); 342 343 void 344 _M_assign(const __rc_string_base& __rcs); 345 346 void 347 _M_reserve(size_type __res); 348 349 void 350 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 351 size_type __len2); 352 353 void 354 _M_erase(size_type __pos, size_type __n); 355 356 void 357 _M_clear() 358 { _M_erase(size_type(0), _M_length()); } 359 360 bool 361 _M_compare(const __rc_string_base&) const 362 { return false; } 363 }; 364 365 template<typename _CharT, typename _Traits, typename _Alloc> 366 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty 367 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep; 368 369 template<typename _CharT, typename _Traits, typename _Alloc> 370 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep* 371 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 372 _S_create(size_type __capacity, size_type __old_capacity, 373 const _Alloc& __alloc) 374 { 375 // _GLIBCXX_RESOLVE_LIB_DEFECTS 376 // 83. String::npos vs. string::max_size() 377 if (__capacity > size_type(_S_max_size)) 378 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create")); 379 380 // The standard places no restriction on allocating more memory 381 // than is strictly needed within this layer at the moment or as 382 // requested by an explicit application call to reserve(). 383 384 // Many malloc implementations perform quite poorly when an 385 // application attempts to allocate memory in a stepwise fashion 386 // growing each allocation size by only 1 char. Additionally, 387 // it makes little sense to allocate less linear memory than the 388 // natural blocking size of the malloc implementation. 389 // Unfortunately, we would need a somewhat low-level calculation 390 // with tuned parameters to get this perfect for any particular 391 // malloc implementation. Fortunately, generalizations about 392 // common features seen among implementations seems to suffice. 393 394 // __pagesize need not match the actual VM page size for good 395 // results in practice, thus we pick a common value on the low 396 // side. __malloc_header_size is an estimate of the amount of 397 // overhead per memory allocation (in practice seen N * sizeof 398 // (void*) where N is 0, 2 or 4). According to folklore, 399 // picking this value on the high side is better than 400 // low-balling it (especially when this algorithm is used with 401 // malloc implementations that allocate memory blocks rounded up 402 // to a size which is a power of 2). 403 const size_type __pagesize = 4096; 404 const size_type __malloc_header_size = 4 * sizeof(void*); 405 406 // The below implements an exponential growth policy, necessary to 407 // meet amortized linear time requirements of the library: see 408 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html. 409 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity) 410 { 411 __capacity = 2 * __old_capacity; 412 // Never allocate a string bigger than _S_max_size. 413 if (__capacity > size_type(_S_max_size)) 414 __capacity = size_type(_S_max_size); 415 } 416 417 // NB: Need an array of char_type[__capacity], plus a terminating 418 // null char_type() element, plus enough for the _Rep data structure, 419 // plus sizeof(_Rep) - 1 to upper round to a size multiple of 420 // sizeof(_Rep). 421 // Whew. Seemingly so needy, yet so elemental. 422 size_type __size = ((__capacity + 1) * sizeof(_CharT) 423 + 2 * sizeof(_Rep) - 1); 424 425 const size_type __adj_size = __size + __malloc_header_size; 426 if (__adj_size > __pagesize && __capacity > __old_capacity) 427 { 428 const size_type __extra = __pagesize - __adj_size % __pagesize; 429 __capacity += __extra / sizeof(_CharT); 430 if (__capacity > size_type(_S_max_size)) 431 __capacity = size_type(_S_max_size); 432 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1; 433 } 434 435 // NB: Might throw, but no worries about a leak, mate: _Rep() 436 // does not throw. 437 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep)); 438 _Rep* __p = new (__place) _Rep; 439 __p->_M_info._M_capacity = __capacity; 440 return __p; 441 } 442 443 template<typename _CharT, typename _Traits, typename _Alloc> 444 void 445 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 446 _M_destroy(const _Alloc& __a) throw () 447 { 448 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT) 449 + 2 * sizeof(_Rep) - 1); 450 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep)); 451 } 452 453 template<typename _CharT, typename _Traits, typename _Alloc> 454 _CharT* 455 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 456 _M_clone(const _Alloc& __alloc, size_type __res) 457 { 458 // Requested capacity of the clone. 459 const size_type __requested_cap = _M_info._M_length + __res; 460 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity, 461 __alloc); 462 463 if (_M_info._M_length) 464 _S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length); 465 466 __r->_M_set_length(_M_info._M_length); 467 return __r->_M_refdata(); 468 } 469 470 template<typename _CharT, typename _Traits, typename _Alloc> 471 __rc_string_base<_CharT, _Traits, _Alloc>:: 472 __rc_string_base(const _Alloc& __a) 473 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { } 474 475 template<typename _CharT, typename _Traits, typename _Alloc> 476 __rc_string_base<_CharT, _Traits, _Alloc>:: 477 __rc_string_base(const __rc_string_base& __rcs) 478 : _M_dataplus(__rcs._M_get_allocator(), 479 __rcs._M_grab(__rcs._M_get_allocator())) { } 480 481 template<typename _CharT, typename _Traits, typename _Alloc> 482 __rc_string_base<_CharT, _Traits, _Alloc>:: 483 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a) 484 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { } 485 486 template<typename _CharT, typename _Traits, typename _Alloc> 487 template<typename _InputIterator> 488 __rc_string_base<_CharT, _Traits, _Alloc>:: 489 __rc_string_base(_InputIterator __beg, _InputIterator __end, 490 const _Alloc& __a) 491 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { } 492 493 template<typename _CharT, typename _Traits, typename _Alloc> 494 void 495 __rc_string_base<_CharT, _Traits, _Alloc>:: 496 _M_leak_hard() 497 { 498 if (_M_is_shared()) 499 _M_erase(0, 0); 500 _M_set_leaked(); 501 } 502 503 // NB: This is the special case for Input Iterators, used in 504 // istreambuf_iterators, etc. 505 // Input Iterators have a cost structure very different from 506 // pointers, calling for a different coding style. 507 template<typename _CharT, typename _Traits, typename _Alloc> 508 template<typename _InIterator> 509 _CharT* 510 __rc_string_base<_CharT, _Traits, _Alloc>:: 511 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 512 std::input_iterator_tag) 513 { 514 if (__beg == __end && __a == _Alloc()) 515 return _S_empty_rep._M_refcopy(); 516 517 // Avoid reallocation for common case. 518 _CharT __buf[128]; 519 size_type __len = 0; 520 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT)) 521 { 522 __buf[__len++] = *__beg; 523 ++__beg; 524 } 525 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a); 526 _S_copy(__r->_M_refdata(), __buf, __len); 527 __try 528 { 529 while (__beg != __end) 530 { 531 if (__len == __r->_M_info._M_capacity) 532 { 533 // Allocate more space. 534 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a); 535 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len); 536 __r->_M_destroy(__a); 537 __r = __another; 538 } 539 __r->_M_refdata()[__len++] = *__beg; 540 ++__beg; 541 } 542 } 543 __catch(...) 544 { 545 __r->_M_destroy(__a); 546 __throw_exception_again; 547 } 548 __r->_M_set_length(__len); 549 return __r->_M_refdata(); 550 } 551 552 template<typename _CharT, typename _Traits, typename _Alloc> 553 template<typename _InIterator> 554 _CharT* 555 __rc_string_base<_CharT, _Traits, _Alloc>:: 556 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 557 std::forward_iterator_tag) 558 { 559 if (__beg == __end && __a == _Alloc()) 560 return _S_empty_rep._M_refcopy(); 561 562 // NB: Not required, but considered best practice. 563 if (__is_null_pointer(__beg) && __beg != __end) 564 std::__throw_logic_error(__N("__rc_string_base::" 565 "_S_construct null not valid")); 566 567 const size_type __dnew = static_cast<size_type>(std::distance(__beg, 568 __end)); 569 // Check for out_of_range and length_error exceptions. 570 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a); 571 __try 572 { _S_copy_chars(__r->_M_refdata(), __beg, __end); } 573 __catch(...) 574 { 575 __r->_M_destroy(__a); 576 __throw_exception_again; 577 } 578 __r->_M_set_length(__dnew); 579 return __r->_M_refdata(); 580 } 581 582 template<typename _CharT, typename _Traits, typename _Alloc> 583 _CharT* 584 __rc_string_base<_CharT, _Traits, _Alloc>:: 585 _S_construct(size_type __n, _CharT __c, const _Alloc& __a) 586 { 587 if (__n == 0 && __a == _Alloc()) 588 return _S_empty_rep._M_refcopy(); 589 590 // Check for out_of_range and length_error exceptions. 591 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a); 592 if (__n) 593 _S_assign(__r->_M_refdata(), __n, __c); 594 595 __r->_M_set_length(__n); 596 return __r->_M_refdata(); 597 } 598 599 template<typename _CharT, typename _Traits, typename _Alloc> 600 void 601 __rc_string_base<_CharT, _Traits, _Alloc>:: 602 _M_swap(__rc_string_base& __rcs) 603 { 604 if (_M_is_leaked()) 605 _M_set_sharable(); 606 if (__rcs._M_is_leaked()) 607 __rcs._M_set_sharable(); 608 609 _CharT* __tmp = _M_data(); 610 _M_data(__rcs._M_data()); 611 __rcs._M_data(__tmp); 612 613 // _GLIBCXX_RESOLVE_LIB_DEFECTS 614 // 431. Swapping containers with unequal allocators. 615 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(), 616 __rcs._M_get_allocator()); 617 } 618 619 template<typename _CharT, typename _Traits, typename _Alloc> 620 void 621 __rc_string_base<_CharT, _Traits, _Alloc>:: 622 _M_assign(const __rc_string_base& __rcs) 623 { 624 if (_M_rep() != __rcs._M_rep()) 625 { 626 _CharT* __tmp = __rcs._M_grab(_M_get_allocator()); 627 _M_dispose(); 628 _M_data(__tmp); 629 } 630 } 631 632 template<typename _CharT, typename _Traits, typename _Alloc> 633 void 634 __rc_string_base<_CharT, _Traits, _Alloc>:: 635 _M_reserve(size_type __res) 636 { 637 // Make sure we don't shrink below the current size. 638 if (__res < _M_length()) 639 __res = _M_length(); 640 641 if (__res != _M_capacity() || _M_is_shared()) 642 { 643 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(), 644 __res - _M_length()); 645 _M_dispose(); 646 _M_data(__tmp); 647 } 648 } 649 650 template<typename _CharT, typename _Traits, typename _Alloc> 651 void 652 __rc_string_base<_CharT, _Traits, _Alloc>:: 653 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 654 size_type __len2) 655 { 656 const size_type __how_much = _M_length() - __pos - __len1; 657 658 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1, 659 _M_capacity(), _M_get_allocator()); 660 661 if (__pos) 662 _S_copy(__r->_M_refdata(), _M_data(), __pos); 663 if (__s && __len2) 664 _S_copy(__r->_M_refdata() + __pos, __s, __len2); 665 if (__how_much) 666 _S_copy(__r->_M_refdata() + __pos + __len2, 667 _M_data() + __pos + __len1, __how_much); 668 669 _M_dispose(); 670 _M_data(__r->_M_refdata()); 671 } 672 673 template<typename _CharT, typename _Traits, typename _Alloc> 674 void 675 __rc_string_base<_CharT, _Traits, _Alloc>:: 676 _M_erase(size_type __pos, size_type __n) 677 { 678 const size_type __new_size = _M_length() - __n; 679 const size_type __how_much = _M_length() - __pos - __n; 680 681 if (_M_is_shared()) 682 { 683 // Must reallocate. 684 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(), 685 _M_get_allocator()); 686 687 if (__pos) 688 _S_copy(__r->_M_refdata(), _M_data(), __pos); 689 if (__how_much) 690 _S_copy(__r->_M_refdata() + __pos, 691 _M_data() + __pos + __n, __how_much); 692 693 _M_dispose(); 694 _M_data(__r->_M_refdata()); 695 } 696 else if (__how_much && __n) 697 { 698 // Work in-place. 699 _S_move(_M_data() + __pos, 700 _M_data() + __pos + __n, __how_much); 701 } 702 703 _M_rep()->_M_set_length(__new_size); 704 } 705 706 template<> 707 inline bool 708 __rc_string_base<char, std::char_traits<char>, 709 std::allocator<char> >:: 710 _M_compare(const __rc_string_base& __rcs) const 711 { 712 if (_M_rep() == __rcs._M_rep()) 713 return true; 714 return false; 715 } 716 717#ifdef _GLIBCXX_USE_WCHAR_T 718 template<> 719 inline bool 720 __rc_string_base<wchar_t, std::char_traits<wchar_t>, 721 std::allocator<wchar_t> >:: 722 _M_compare(const __rc_string_base& __rcs) const 723 { 724 if (_M_rep() == __rcs._M_rep()) 725 return true; 726 return false; 727 } 728#endif 729 730_GLIBCXX_END_NAMESPACE_VERSION 731} // namespace 732 733#endif /* _RC_STRING_BASE_H */ 734