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 file is a GNU extension to the Standard C++ Library. 28 * This is an internal header file, included by other library headers. 29 * You should not attempt to use it directly. 30 */ 31 32 #ifndef _RC_STRING_BASE_H 33 #define _RC_STRING_BASE_H 1 34 35 #include <ext/atomicity.h> 36 #include <bits/stl_iterator_base_funcs.h> 37 38 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 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 if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount, 203 -1) <= 0) 204 _M_rep()->_M_destroy(_M_get_allocator()); 205 } // XXX MT 206 207 bool 208 _M_is_leaked() const 209 { return _M_rep()->_M_info._M_refcount < 0; } 210 211 void 212 _M_set_sharable() 213 { _M_rep()->_M_info._M_refcount = 0; } 214 215 void 216 _M_leak_hard(); 217 218 // _S_construct_aux is used to implement the 21.3.1 para 15 which 219 // requires special behaviour if _InIterator is an integral type 220 template<typename _InIterator> 221 static _CharT* 222 _S_construct_aux(_InIterator __beg, _InIterator __end, 223 const _Alloc& __a, std::__false_type) 224 { 225 typedef typename iterator_traits<_InIterator>::iterator_category _Tag; 226 return _S_construct(__beg, __end, __a, _Tag()); 227 } 228 229 // _GLIBCXX_RESOLVE_LIB_DEFECTS 230 // 438. Ambiguity in the "do the right thing" clause 231 template<typename _Integer> 232 static _CharT* 233 _S_construct_aux(_Integer __beg, _Integer __end, 234 const _Alloc& __a, std::__true_type) 235 { return _S_construct_aux_2(static_cast<size_type>(__beg), 236 __end, __a); } 237 238 static _CharT* 239 _S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a) 240 { return _S_construct(__req, __c, __a); } 241 242 template<typename _InIterator> 243 static _CharT* 244 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a) 245 { 246 typedef typename std::__is_integer<_InIterator>::__type _Integral; 247 return _S_construct_aux(__beg, __end, __a, _Integral()); 248 } 249 250 // For Input Iterators, used in istreambuf_iterators, etc. 251 template<typename _InIterator> 252 static _CharT* 253 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 254 std::input_iterator_tag); 255 256 // For forward_iterators up to random_access_iterators, used for 257 // string::iterator, _CharT*, etc. 258 template<typename _FwdIterator> 259 static _CharT* 260 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a, 261 std::forward_iterator_tag); 262 263 static _CharT* 264 _S_construct(size_type __req, _CharT __c, const _Alloc& __a); 265 266 public: 267 size_type 268 _M_max_size() const 269 { return size_type(_S_max_size); } 270 271 _CharT* 272 _M_data() const 273 { return _M_dataplus._M_p; } 274 275 size_type 276 _M_length() const 277 { return _M_rep()->_M_info._M_length; } 278 279 size_type 280 _M_capacity() const 281 { return _M_rep()->_M_info._M_capacity; } 282 283 bool 284 _M_is_shared() const 285 { return _M_rep()->_M_info._M_refcount > 0; } 286 287 void 288 _M_set_leaked() 289 { _M_rep()->_M_info._M_refcount = -1; } 290 291 void 292 _M_leak() // for use in begin() & non-const op[] 293 { 294 if (!_M_is_leaked()) 295 _M_leak_hard(); 296 } 297 298 void 299 _M_set_length(size_type __n) 300 { _M_rep()->_M_set_length(__n); } 301 302 __rc_string_base() 303 : _M_dataplus(_S_empty_rep._M_refcopy()) { } 304 305 __rc_string_base(const _Alloc& __a); 306 307 __rc_string_base(const __rc_string_base& __rcs); 308 309 #ifdef __GXX_EXPERIMENTAL_CXX0X__ 310 __rc_string_base(__rc_string_base&& __rcs) 311 : _M_dataplus(__rcs._M_dataplus) 312 { __rcs._M_data(_S_empty_rep._M_refcopy()); } 313 #endif 314 315 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a); 316 317 template<typename _InputIterator> 318 __rc_string_base(_InputIterator __beg, _InputIterator __end, 319 const _Alloc& __a); 320 321 ~__rc_string_base() 322 { _M_dispose(); } 323 324 allocator_type& 325 _M_get_allocator() 326 { return _M_dataplus; } 327 328 const allocator_type& 329 _M_get_allocator() const 330 { return _M_dataplus; } 331 332 void 333 _M_swap(__rc_string_base& __rcs); 334 335 void 336 _M_assign(const __rc_string_base& __rcs); 337 338 void 339 _M_reserve(size_type __res); 340 341 void 342 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 343 size_type __len2); 344 345 void 346 _M_erase(size_type __pos, size_type __n); 347 348 void 349 _M_clear() 350 { _M_erase(size_type(0), _M_length()); } 351 352 bool 353 _M_compare(const __rc_string_base&) const 354 { return false; } 355 }; 356 357 template<typename _CharT, typename _Traits, typename _Alloc> 358 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty 359 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep; 360 361 template<typename _CharT, typename _Traits, typename _Alloc> 362 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep* 363 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 364 _S_create(size_type __capacity, size_type __old_capacity, 365 const _Alloc& __alloc) 366 { 367 // _GLIBCXX_RESOLVE_LIB_DEFECTS 368 // 83. String::npos vs. string::max_size() 369 if (__capacity > size_type(_S_max_size)) 370 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create")); 371 372 // The standard places no restriction on allocating more memory 373 // than is strictly needed within this layer at the moment or as 374 // requested by an explicit application call to reserve(). 375 376 // Many malloc implementations perform quite poorly when an 377 // application attempts to allocate memory in a stepwise fashion 378 // growing each allocation size by only 1 char. Additionally, 379 // it makes little sense to allocate less linear memory than the 380 // natural blocking size of the malloc implementation. 381 // Unfortunately, we would need a somewhat low-level calculation 382 // with tuned parameters to get this perfect for any particular 383 // malloc implementation. Fortunately, generalizations about 384 // common features seen among implementations seems to suffice. 385 386 // __pagesize need not match the actual VM page size for good 387 // results in practice, thus we pick a common value on the low 388 // side. __malloc_header_size is an estimate of the amount of 389 // overhead per memory allocation (in practice seen N * sizeof 390 // (void*) where N is 0, 2 or 4). According to folklore, 391 // picking this value on the high side is better than 392 // low-balling it (especially when this algorithm is used with 393 // malloc implementations that allocate memory blocks rounded up 394 // to a size which is a power of 2). 395 const size_type __pagesize = 4096; 396 const size_type __malloc_header_size = 4 * sizeof(void*); 397 398 // The below implements an exponential growth policy, necessary to 399 // meet amortized linear time requirements of the library: see 400 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html. 401 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity) 402 { 403 __capacity = 2 * __old_capacity; 404 // Never allocate a string bigger than _S_max_size. 405 if (__capacity > size_type(_S_max_size)) 406 __capacity = size_type(_S_max_size); 407 } 408 409 // NB: Need an array of char_type[__capacity], plus a terminating 410 // null char_type() element, plus enough for the _Rep data structure, 411 // plus sizeof(_Rep) - 1 to upper round to a size multiple of 412 // sizeof(_Rep). 413 // Whew. Seemingly so needy, yet so elemental. 414 size_type __size = ((__capacity + 1) * sizeof(_CharT) 415 + 2 * sizeof(_Rep) - 1); 416 417 const size_type __adj_size = __size + __malloc_header_size; 418 if (__adj_size > __pagesize && __capacity > __old_capacity) 419 { 420 const size_type __extra = __pagesize - __adj_size % __pagesize; 421 __capacity += __extra / sizeof(_CharT); 422 if (__capacity > size_type(_S_max_size)) 423 __capacity = size_type(_S_max_size); 424 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1; 425 } 426 427 // NB: Might throw, but no worries about a leak, mate: _Rep() 428 // does not throw. 429 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep)); 430 _Rep* __p = new (__place) _Rep; 431 __p->_M_info._M_capacity = __capacity; 432 return __p; 433 } 434 435 template<typename _CharT, typename _Traits, typename _Alloc> 436 void 437 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 438 _M_destroy(const _Alloc& __a) throw () 439 { 440 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT) 441 + 2 * sizeof(_Rep) - 1); 442 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep)); 443 } 444 445 template<typename _CharT, typename _Traits, typename _Alloc> 446 _CharT* 447 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 448 _M_clone(const _Alloc& __alloc, size_type __res) 449 { 450 // Requested capacity of the clone. 451 const size_type __requested_cap = _M_info._M_length + __res; 452 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity, 453 __alloc); 454 455 if (_M_info._M_length) 456 _S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length); 457 458 __r->_M_set_length(_M_info._M_length); 459 return __r->_M_refdata(); 460 } 461 462 template<typename _CharT, typename _Traits, typename _Alloc> 463 __rc_string_base<_CharT, _Traits, _Alloc>:: 464 __rc_string_base(const _Alloc& __a) 465 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { } 466 467 template<typename _CharT, typename _Traits, typename _Alloc> 468 __rc_string_base<_CharT, _Traits, _Alloc>:: 469 __rc_string_base(const __rc_string_base& __rcs) 470 : _M_dataplus(__rcs._M_get_allocator(), 471 __rcs._M_grab(__rcs._M_get_allocator())) { } 472 473 template<typename _CharT, typename _Traits, typename _Alloc> 474 __rc_string_base<_CharT, _Traits, _Alloc>:: 475 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a) 476 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { } 477 478 template<typename _CharT, typename _Traits, typename _Alloc> 479 template<typename _InputIterator> 480 __rc_string_base<_CharT, _Traits, _Alloc>:: 481 __rc_string_base(_InputIterator __beg, _InputIterator __end, 482 const _Alloc& __a) 483 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { } 484 485 template<typename _CharT, typename _Traits, typename _Alloc> 486 void 487 __rc_string_base<_CharT, _Traits, _Alloc>:: 488 _M_leak_hard() 489 { 490 if (_M_is_shared()) 491 _M_erase(0, 0); 492 _M_set_leaked(); 493 } 494 495 // NB: This is the special case for Input Iterators, used in 496 // istreambuf_iterators, etc. 497 // Input Iterators have a cost structure very different from 498 // pointers, calling for a different coding style. 499 template<typename _CharT, typename _Traits, typename _Alloc> 500 template<typename _InIterator> 501 _CharT* 502 __rc_string_base<_CharT, _Traits, _Alloc>:: 503 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 504 std::input_iterator_tag) 505 { 506 if (__beg == __end && __a == _Alloc()) 507 return _S_empty_rep._M_refcopy(); 508 509 // Avoid reallocation for common case. 510 _CharT __buf[128]; 511 size_type __len = 0; 512 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT)) 513 { 514 __buf[__len++] = *__beg; 515 ++__beg; 516 } 517 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a); 518 _S_copy(__r->_M_refdata(), __buf, __len); 519 __try 520 { 521 while (__beg != __end) 522 { 523 if (__len == __r->_M_info._M_capacity) 524 { 525 // Allocate more space. 526 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a); 527 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len); 528 __r->_M_destroy(__a); 529 __r = __another; 530 } 531 __r->_M_refdata()[__len++] = *__beg; 532 ++__beg; 533 } 534 } 535 __catch(...) 536 { 537 __r->_M_destroy(__a); 538 __throw_exception_again; 539 } 540 __r->_M_set_length(__len); 541 return __r->_M_refdata(); 542 } 543 544 template<typename _CharT, typename _Traits, typename _Alloc> 545 template<typename _InIterator> 546 _CharT* 547 __rc_string_base<_CharT, _Traits, _Alloc>:: 548 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 549 std::forward_iterator_tag) 550 { 551 if (__beg == __end && __a == _Alloc()) 552 return _S_empty_rep._M_refcopy(); 553 554 // NB: Not required, but considered best practice. 555 if (__is_null_pointer(__beg) && __beg != __end) 556 std::__throw_logic_error(__N("__rc_string_base::" 557 "_S_construct NULL not valid")); 558 559 const size_type __dnew = static_cast<size_type>(std::distance(__beg, 560 __end)); 561 // Check for out_of_range and length_error exceptions. 562 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a); 563 __try 564 { _S_copy_chars(__r->_M_refdata(), __beg, __end); } 565 __catch(...) 566 { 567 __r->_M_destroy(__a); 568 __throw_exception_again; 569 } 570 __r->_M_set_length(__dnew); 571 return __r->_M_refdata(); 572 } 573 574 template<typename _CharT, typename _Traits, typename _Alloc> 575 _CharT* 576 __rc_string_base<_CharT, _Traits, _Alloc>:: 577 _S_construct(size_type __n, _CharT __c, const _Alloc& __a) 578 { 579 if (__n == 0 && __a == _Alloc()) 580 return _S_empty_rep._M_refcopy(); 581 582 // Check for out_of_range and length_error exceptions. 583 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a); 584 if (__n) 585 _S_assign(__r->_M_refdata(), __n, __c); 586 587 __r->_M_set_length(__n); 588 return __r->_M_refdata(); 589 } 590 591 template<typename _CharT, typename _Traits, typename _Alloc> 592 void 593 __rc_string_base<_CharT, _Traits, _Alloc>:: 594 _M_swap(__rc_string_base& __rcs) 595 { 596 if (_M_is_leaked()) 597 _M_set_sharable(); 598 if (__rcs._M_is_leaked()) 599 __rcs._M_set_sharable(); 600 601 _CharT* __tmp = _M_data(); 602 _M_data(__rcs._M_data()); 603 __rcs._M_data(__tmp); 604 605 // _GLIBCXX_RESOLVE_LIB_DEFECTS 606 // 431. Swapping containers with unequal allocators. 607 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(), 608 __rcs._M_get_allocator()); 609 } 610 611 template<typename _CharT, typename _Traits, typename _Alloc> 612 void 613 __rc_string_base<_CharT, _Traits, _Alloc>:: 614 _M_assign(const __rc_string_base& __rcs) 615 { 616 if (_M_rep() != __rcs._M_rep()) 617 { 618 _CharT* __tmp = __rcs._M_grab(_M_get_allocator()); 619 _M_dispose(); 620 _M_data(__tmp); 621 } 622 } 623 624 template<typename _CharT, typename _Traits, typename _Alloc> 625 void 626 __rc_string_base<_CharT, _Traits, _Alloc>:: 627 _M_reserve(size_type __res) 628 { 629 // Make sure we don't shrink below the current size. 630 if (__res < _M_length()) 631 __res = _M_length(); 632 633 if (__res != _M_capacity() || _M_is_shared()) 634 { 635 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(), 636 __res - _M_length()); 637 _M_dispose(); 638 _M_data(__tmp); 639 } 640 } 641 642 template<typename _CharT, typename _Traits, typename _Alloc> 643 void 644 __rc_string_base<_CharT, _Traits, _Alloc>:: 645 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 646 size_type __len2) 647 { 648 const size_type __how_much = _M_length() - __pos - __len1; 649 650 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1, 651 _M_capacity(), _M_get_allocator()); 652 653 if (__pos) 654 _S_copy(__r->_M_refdata(), _M_data(), __pos); 655 if (__s && __len2) 656 _S_copy(__r->_M_refdata() + __pos, __s, __len2); 657 if (__how_much) 658 _S_copy(__r->_M_refdata() + __pos + __len2, 659 _M_data() + __pos + __len1, __how_much); 660 661 _M_dispose(); 662 _M_data(__r->_M_refdata()); 663 } 664 665 template<typename _CharT, typename _Traits, typename _Alloc> 666 void 667 __rc_string_base<_CharT, _Traits, _Alloc>:: 668 _M_erase(size_type __pos, size_type __n) 669 { 670 const size_type __new_size = _M_length() - __n; 671 const size_type __how_much = _M_length() - __pos - __n; 672 673 if (_M_is_shared()) 674 { 675 // Must reallocate. 676 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(), 677 _M_get_allocator()); 678 679 if (__pos) 680 _S_copy(__r->_M_refdata(), _M_data(), __pos); 681 if (__how_much) 682 _S_copy(__r->_M_refdata() + __pos, 683 _M_data() + __pos + __n, __how_much); 684 685 _M_dispose(); 686 _M_data(__r->_M_refdata()); 687 } 688 else if (__how_much && __n) 689 { 690 // Work in-place. 691 _S_move(_M_data() + __pos, 692 _M_data() + __pos + __n, __how_much); 693 } 694 695 _M_rep()->_M_set_length(__new_size); 696 } 697 698 template<> 699 inline bool 700 __rc_string_base<char, std::char_traits<char>, 701 std::allocator<char> >:: 702 _M_compare(const __rc_string_base& __rcs) const 703 { 704 if (_M_rep() == __rcs._M_rep()) 705 return true; 706 return false; 707 } 708 709 #ifdef _GLIBCXX_USE_WCHAR_T 710 template<> 711 inline bool 712 __rc_string_base<wchar_t, std::char_traits<wchar_t>, 713 std::allocator<wchar_t> >:: 714 _M_compare(const __rc_string_base& __rcs) const 715 { 716 if (_M_rep() == __rcs._M_rep()) 717 return true; 718 return false; 719 } 720 #endif 721 722 _GLIBCXX_END_NAMESPACE 723 724 #endif /* _RC_STRING_BASE_H */ 725