1// Reference-counted versatile string base -*- C++ -*- 2 3// Copyright (C) 2005-2013 Free Software Foundation, Inc. 4// 5// This file is part of the GNU ISO C++ Library. This library is free 6// software; you can redistribute it and/or modify it under the 7// terms of the GNU General Public License as published by the 8// Free Software Foundation; either version 3, or (at your option) 9// any later version. 10 11// This library is distributed in the hope that it will be useful, 12// but WITHOUT ANY WARRANTY; without even the implied warranty of 13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14// GNU General Public License for more details. 15 16// Under Section 7 of GPL version 3, you are granted additional 17// permissions described in the GCC Runtime Library Exception, version 18// 3.1, as published by the Free Software Foundation. 19 20// You should have received a copy of the GNU General Public License and 21// a copy of the GCC Runtime Library Exception along with this program; 22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23// <http://www.gnu.org/licenses/>. 24 25/** @file ext/rc_string_base.h 26 * This is an internal header file, included by other library headers. 27 * Do not attempt to use it directly. @headername{ext/vstring.h} 28 */ 29 30#ifndef _RC_STRING_BASE_H 31#define _RC_STRING_BASE_H 1 32 33#include <ext/atomicity.h> 34#include <bits/stl_iterator_base_funcs.h> 35 36namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 37{ 38_GLIBCXX_BEGIN_NAMESPACE_VERSION 39 40 /** 41 * Documentation? What's that? 42 * Nathan Myers <ncm@cantrip.org>. 43 * 44 * A string looks like this: 45 * 46 * @code 47 * [_Rep] 48 * _M_length 49 * [__rc_string_base<char_type>] _M_capacity 50 * _M_dataplus _M_refcount 51 * _M_p ----------------> unnamed array of char_type 52 * @endcode 53 * 54 * Where the _M_p points to the first character in the string, and 55 * you cast it to a pointer-to-_Rep and subtract 1 to get a 56 * pointer to the header. 57 * 58 * This approach has the enormous advantage that a string object 59 * requires only one allocation. All the ugliness is confined 60 * within a single pair of inline functions, which each compile to 61 * a single @a add instruction: _Rep::_M_refdata(), and 62 * __rc_string_base::_M_rep(); and the allocation function which gets a 63 * block of raw bytes and with room enough and constructs a _Rep 64 * object at the front. 65 * 66 * The reason you want _M_data pointing to the character array and 67 * not the _Rep is so that the debugger can see the string 68 * contents. (Probably we should add a non-inline member to get 69 * the _Rep for the debugger to use, so users can check the actual 70 * string length.) 71 * 72 * Note that the _Rep object is a POD so that you can have a 73 * static <em>empty string</em> _Rep object already @a constructed before 74 * static constructors have run. The reference-count encoding is 75 * chosen so that a 0 indicates one reference, so you never try to 76 * destroy the empty-string _Rep object. 77 * 78 * All but the last paragraph is considered pretty conventional 79 * for a C++ string implementation. 80 */ 81 template<typename _CharT, typename _Traits, typename _Alloc> 82 class __rc_string_base 83 : protected __vstring_utility<_CharT, _Traits, _Alloc> 84 { 85 public: 86 typedef _Traits traits_type; 87 typedef typename _Traits::char_type value_type; 88 typedef _Alloc allocator_type; 89 90 typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base; 91 typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type; 92 typedef typename _CharT_alloc_type::size_type size_type; 93 94 private: 95 // _Rep: string representation 96 // Invariants: 97 // 1. String really contains _M_length + 1 characters: due to 21.3.4 98 // must be kept null-terminated. 99 // 2. _M_capacity >= _M_length 100 // Allocated memory is always (_M_capacity + 1) * sizeof(_CharT). 101 // 3. _M_refcount has three states: 102 // -1: leaked, one reference, no ref-copies allowed, non-const. 103 // 0: one reference, non-const. 104 // n>0: n + 1 references, operations require a lock, const. 105 // 4. All fields == 0 is an empty string, given the extra storage 106 // beyond-the-end for a null terminator; thus, the shared 107 // empty string representation needs no constructor. 108 struct _Rep 109 { 110 union 111 { 112 struct 113 { 114 size_type _M_length; 115 size_type _M_capacity; 116 _Atomic_word _M_refcount; 117 } _M_info; 118 119 // Only for alignment purposes. 120 _CharT _M_align; 121 }; 122 123 typedef typename _Alloc::template rebind<_Rep>::other _Rep_alloc_type; 124 125 _CharT* 126 _M_refdata() throw() 127 { return reinterpret_cast<_CharT*>(this + 1); } 128 129 _CharT* 130 _M_refcopy() throw() 131 { 132 __atomic_add_dispatch(&_M_info._M_refcount, 1); 133 return _M_refdata(); 134 } // XXX MT 135 136 void 137 _M_set_length(size_type __n) 138 { 139 _M_info._M_refcount = 0; // One reference. 140 _M_info._M_length = __n; 141 // grrr. (per 21.3.4) 142 // You cannot leave those LWG people alone for a second. 143 traits_type::assign(_M_refdata()[__n], _CharT()); 144 } 145 146 // Create & Destroy 147 static _Rep* 148 _S_create(size_type, size_type, const _Alloc&); 149 150 void 151 _M_destroy(const _Alloc&) throw(); 152 153 _CharT* 154 _M_clone(const _Alloc&, size_type __res = 0); 155 }; 156 157 struct _Rep_empty 158 : public _Rep 159 { 160 _CharT _M_terminal; 161 }; 162 163 static _Rep_empty _S_empty_rep; 164 165 // The maximum number of individual char_type elements of an 166 // individual string is determined by _S_max_size. This is the 167 // value that will be returned by max_size(). (Whereas npos 168 // is the maximum number of bytes the allocator can allocate.) 169 // If one was to divvy up the theoretical largest size string, 170 // with a terminating character and m _CharT elements, it'd 171 // look like this: 172 // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT) 173 // + sizeof(_Rep) - 1 174 // (NB: last two terms for rounding reasons, see _M_create below) 175 // Solving for m: 176 // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1 177 // In addition, this implementation halves this amount. 178 enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep) 179 + 1) / sizeof(_CharT)) - 1) / 2 }; 180 181 // Data Member (private): 182 mutable typename _Util_Base::template _Alloc_hider<_Alloc> _M_dataplus; 183 184 void 185 _M_data(_CharT* __p) 186 { _M_dataplus._M_p = __p; } 187 188 _Rep* 189 _M_rep() const 190 { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); } 191 192 _CharT* 193 _M_grab(const _Alloc& __alloc) const 194 { 195 return (!_M_is_leaked() && _M_get_allocator() == __alloc) 196 ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc); 197 } 198 199 void 200 _M_dispose() 201 { 202 // Be race-detector-friendly. For more info see bits/c++config. 203 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_rep()->_M_info. 204 _M_refcount); 205 if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount, 206 -1) <= 0) 207 { 208 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_rep()->_M_info. 209 _M_refcount); 210 _M_rep()->_M_destroy(_M_get_allocator()); 211 } 212 } // XXX MT 213 214 bool 215 _M_is_leaked() const 216 { return _M_rep()->_M_info._M_refcount < 0; } 217 218 void 219 _M_set_sharable() 220 { _M_rep()->_M_info._M_refcount = 0; } 221 222 void 223 _M_leak_hard(); 224 225 // _S_construct_aux is used to implement the 21.3.1 para 15 which 226 // requires special behaviour if _InIterator is an integral type 227 template<typename _InIterator> 228 static _CharT* 229 _S_construct_aux(_InIterator __beg, _InIterator __end, 230 const _Alloc& __a, std::__false_type) 231 { 232 typedef typename iterator_traits<_InIterator>::iterator_category _Tag; 233 return _S_construct(__beg, __end, __a, _Tag()); 234 } 235 236 // _GLIBCXX_RESOLVE_LIB_DEFECTS 237 // 438. Ambiguity in the "do the right thing" clause 238 template<typename _Integer> 239 static _CharT* 240 _S_construct_aux(_Integer __beg, _Integer __end, 241 const _Alloc& __a, std::__true_type) 242 { return _S_construct_aux_2(static_cast<size_type>(__beg), 243 __end, __a); } 244 245 static _CharT* 246 _S_construct_aux_2(size_type __req, _CharT __c, const _Alloc& __a) 247 { return _S_construct(__req, __c, __a); } 248 249 template<typename _InIterator> 250 static _CharT* 251 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a) 252 { 253 typedef typename std::__is_integer<_InIterator>::__type _Integral; 254 return _S_construct_aux(__beg, __end, __a, _Integral()); 255 } 256 257 // For Input Iterators, used in istreambuf_iterators, etc. 258 template<typename _InIterator> 259 static _CharT* 260 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 261 std::input_iterator_tag); 262 263 // For forward_iterators up to random_access_iterators, used for 264 // string::iterator, _CharT*, etc. 265 template<typename _FwdIterator> 266 static _CharT* 267 _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a, 268 std::forward_iterator_tag); 269 270 static _CharT* 271 _S_construct(size_type __req, _CharT __c, const _Alloc& __a); 272 273 public: 274 size_type 275 _M_max_size() const 276 { return size_type(_S_max_size); } 277 278 _CharT* 279 _M_data() const 280 { return _M_dataplus._M_p; } 281 282 size_type 283 _M_length() const 284 { return _M_rep()->_M_info._M_length; } 285 286 size_type 287 _M_capacity() const 288 { return _M_rep()->_M_info._M_capacity; } 289 290 bool 291 _M_is_shared() const 292 { return _M_rep()->_M_info._M_refcount > 0; } 293 294 void 295 _M_set_leaked() 296 { _M_rep()->_M_info._M_refcount = -1; } 297 298 void 299 _M_leak() // for use in begin() & non-const op[] 300 { 301 if (!_M_is_leaked()) 302 _M_leak_hard(); 303 } 304 305 void 306 _M_set_length(size_type __n) 307 { _M_rep()->_M_set_length(__n); } 308 309 __rc_string_base() 310 : _M_dataplus(_S_empty_rep._M_refcopy()) { } 311 312 __rc_string_base(const _Alloc& __a); 313 314 __rc_string_base(const __rc_string_base& __rcs); 315 316#if __cplusplus >= 201103L 317 __rc_string_base(__rc_string_base&& __rcs) 318 : _M_dataplus(__rcs._M_dataplus) 319 { __rcs._M_data(_S_empty_rep._M_refcopy()); } 320#endif 321 322 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a); 323 324 template<typename _InputIterator> 325 __rc_string_base(_InputIterator __beg, _InputIterator __end, 326 const _Alloc& __a); 327 328 ~__rc_string_base() 329 { _M_dispose(); } 330 331 allocator_type& 332 _M_get_allocator() 333 { return _M_dataplus; } 334 335 const allocator_type& 336 _M_get_allocator() const 337 { return _M_dataplus; } 338 339 void 340 _M_swap(__rc_string_base& __rcs); 341 342 void 343 _M_assign(const __rc_string_base& __rcs); 344 345 void 346 _M_reserve(size_type __res); 347 348 void 349 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 350 size_type __len2); 351 352 void 353 _M_erase(size_type __pos, size_type __n); 354 355 void 356 _M_clear() 357 { _M_erase(size_type(0), _M_length()); } 358 359 bool 360 _M_compare(const __rc_string_base&) const 361 { return false; } 362 }; 363 364 template<typename _CharT, typename _Traits, typename _Alloc> 365 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty 366 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep; 367 368 template<typename _CharT, typename _Traits, typename _Alloc> 369 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep* 370 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 371 _S_create(size_type __capacity, size_type __old_capacity, 372 const _Alloc& __alloc) 373 { 374 // _GLIBCXX_RESOLVE_LIB_DEFECTS 375 // 83. String::npos vs. string::max_size() 376 if (__capacity > size_type(_S_max_size)) 377 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create")); 378 379 // The standard places no restriction on allocating more memory 380 // than is strictly needed within this layer at the moment or as 381 // requested by an explicit application call to reserve(). 382 383 // Many malloc implementations perform quite poorly when an 384 // application attempts to allocate memory in a stepwise fashion 385 // growing each allocation size by only 1 char. Additionally, 386 // it makes little sense to allocate less linear memory than the 387 // natural blocking size of the malloc implementation. 388 // Unfortunately, we would need a somewhat low-level calculation 389 // with tuned parameters to get this perfect for any particular 390 // malloc implementation. Fortunately, generalizations about 391 // common features seen among implementations seems to suffice. 392 393 // __pagesize need not match the actual VM page size for good 394 // results in practice, thus we pick a common value on the low 395 // side. __malloc_header_size is an estimate of the amount of 396 // overhead per memory allocation (in practice seen N * sizeof 397 // (void*) where N is 0, 2 or 4). According to folklore, 398 // picking this value on the high side is better than 399 // low-balling it (especially when this algorithm is used with 400 // malloc implementations that allocate memory blocks rounded up 401 // to a size which is a power of 2). 402 const size_type __pagesize = 4096; 403 const size_type __malloc_header_size = 4 * sizeof(void*); 404 405 // The below implements an exponential growth policy, necessary to 406 // meet amortized linear time requirements of the library: see 407 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html. 408 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity) 409 { 410 __capacity = 2 * __old_capacity; 411 // Never allocate a string bigger than _S_max_size. 412 if (__capacity > size_type(_S_max_size)) 413 __capacity = size_type(_S_max_size); 414 } 415 416 // NB: Need an array of char_type[__capacity], plus a terminating 417 // null char_type() element, plus enough for the _Rep data structure, 418 // plus sizeof(_Rep) - 1 to upper round to a size multiple of 419 // sizeof(_Rep). 420 // Whew. Seemingly so needy, yet so elemental. 421 size_type __size = ((__capacity + 1) * sizeof(_CharT) 422 + 2 * sizeof(_Rep) - 1); 423 424 const size_type __adj_size = __size + __malloc_header_size; 425 if (__adj_size > __pagesize && __capacity > __old_capacity) 426 { 427 const size_type __extra = __pagesize - __adj_size % __pagesize; 428 __capacity += __extra / sizeof(_CharT); 429 if (__capacity > size_type(_S_max_size)) 430 __capacity = size_type(_S_max_size); 431 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1; 432 } 433 434 // NB: Might throw, but no worries about a leak, mate: _Rep() 435 // does not throw. 436 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep)); 437 _Rep* __p = new (__place) _Rep; 438 __p->_M_info._M_capacity = __capacity; 439 return __p; 440 } 441 442 template<typename _CharT, typename _Traits, typename _Alloc> 443 void 444 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 445 _M_destroy(const _Alloc& __a) throw () 446 { 447 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT) 448 + 2 * sizeof(_Rep) - 1); 449 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep)); 450 } 451 452 template<typename _CharT, typename _Traits, typename _Alloc> 453 _CharT* 454 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 455 _M_clone(const _Alloc& __alloc, size_type __res) 456 { 457 // Requested capacity of the clone. 458 const size_type __requested_cap = _M_info._M_length + __res; 459 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity, 460 __alloc); 461 462 if (_M_info._M_length) 463 __rc_string_base::_S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length); 464 465 __r->_M_set_length(_M_info._M_length); 466 return __r->_M_refdata(); 467 } 468 469 template<typename _CharT, typename _Traits, typename _Alloc> 470 __rc_string_base<_CharT, _Traits, _Alloc>:: 471 __rc_string_base(const _Alloc& __a) 472 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { } 473 474 template<typename _CharT, typename _Traits, typename _Alloc> 475 __rc_string_base<_CharT, _Traits, _Alloc>:: 476 __rc_string_base(const __rc_string_base& __rcs) 477 : _M_dataplus(__rcs._M_get_allocator(), 478 __rcs._M_grab(__rcs._M_get_allocator())) { } 479 480 template<typename _CharT, typename _Traits, typename _Alloc> 481 __rc_string_base<_CharT, _Traits, _Alloc>:: 482 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a) 483 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { } 484 485 template<typename _CharT, typename _Traits, typename _Alloc> 486 template<typename _InputIterator> 487 __rc_string_base<_CharT, _Traits, _Alloc>:: 488 __rc_string_base(_InputIterator __beg, _InputIterator __end, 489 const _Alloc& __a) 490 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { } 491 492 template<typename _CharT, typename _Traits, typename _Alloc> 493 void 494 __rc_string_base<_CharT, _Traits, _Alloc>:: 495 _M_leak_hard() 496 { 497 if (_M_is_shared()) 498 _M_erase(0, 0); 499 _M_set_leaked(); 500 } 501 502 // NB: This is the special case for Input Iterators, used in 503 // istreambuf_iterators, etc. 504 // Input Iterators have a cost structure very different from 505 // pointers, calling for a different coding style. 506 template<typename _CharT, typename _Traits, typename _Alloc> 507 template<typename _InIterator> 508 _CharT* 509 __rc_string_base<_CharT, _Traits, _Alloc>:: 510 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 511 std::input_iterator_tag) 512 { 513 if (__beg == __end && __a == _Alloc()) 514 return _S_empty_rep._M_refcopy(); 515 516 // Avoid reallocation for common case. 517 _CharT __buf[128]; 518 size_type __len = 0; 519 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT)) 520 { 521 __buf[__len++] = *__beg; 522 ++__beg; 523 } 524 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a); 525 _S_copy(__r->_M_refdata(), __buf, __len); 526 __try 527 { 528 while (__beg != __end) 529 { 530 if (__len == __r->_M_info._M_capacity) 531 { 532 // Allocate more space. 533 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a); 534 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len); 535 __r->_M_destroy(__a); 536 __r = __another; 537 } 538 __r->_M_refdata()[__len++] = *__beg; 539 ++__beg; 540 } 541 } 542 __catch(...) 543 { 544 __r->_M_destroy(__a); 545 __throw_exception_again; 546 } 547 __r->_M_set_length(__len); 548 return __r->_M_refdata(); 549 } 550 551 template<typename _CharT, typename _Traits, typename _Alloc> 552 template<typename _InIterator> 553 _CharT* 554 __rc_string_base<_CharT, _Traits, _Alloc>:: 555 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 556 std::forward_iterator_tag) 557 { 558 if (__beg == __end && __a == _Alloc()) 559 return _S_empty_rep._M_refcopy(); 560 561 // NB: Not required, but considered best practice. 562 if (__is_null_pointer(__beg) && __beg != __end) 563 std::__throw_logic_error(__N("__rc_string_base::" 564 "_S_construct null not valid")); 565 566 const size_type __dnew = static_cast<size_type>(std::distance(__beg, 567 __end)); 568 // Check for out_of_range and length_error exceptions. 569 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a); 570 __try 571 { __rc_string_base::_S_copy_chars(__r->_M_refdata(), __beg, __end); } 572 __catch(...) 573 { 574 __r->_M_destroy(__a); 575 __throw_exception_again; 576 } 577 __r->_M_set_length(__dnew); 578 return __r->_M_refdata(); 579 } 580 581 template<typename _CharT, typename _Traits, typename _Alloc> 582 _CharT* 583 __rc_string_base<_CharT, _Traits, _Alloc>:: 584 _S_construct(size_type __n, _CharT __c, const _Alloc& __a) 585 { 586 if (__n == 0 && __a == _Alloc()) 587 return _S_empty_rep._M_refcopy(); 588 589 // Check for out_of_range and length_error exceptions. 590 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a); 591 if (__n) 592 __rc_string_base::_S_assign(__r->_M_refdata(), __n, __c); 593 594 __r->_M_set_length(__n); 595 return __r->_M_refdata(); 596 } 597 598 template<typename _CharT, typename _Traits, typename _Alloc> 599 void 600 __rc_string_base<_CharT, _Traits, _Alloc>:: 601 _M_swap(__rc_string_base& __rcs) 602 { 603 if (_M_is_leaked()) 604 _M_set_sharable(); 605 if (__rcs._M_is_leaked()) 606 __rcs._M_set_sharable(); 607 608 _CharT* __tmp = _M_data(); 609 _M_data(__rcs._M_data()); 610 __rcs._M_data(__tmp); 611 612 // _GLIBCXX_RESOLVE_LIB_DEFECTS 613 // 431. Swapping containers with unequal allocators. 614 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(), 615 __rcs._M_get_allocator()); 616 } 617 618 template<typename _CharT, typename _Traits, typename _Alloc> 619 void 620 __rc_string_base<_CharT, _Traits, _Alloc>:: 621 _M_assign(const __rc_string_base& __rcs) 622 { 623 if (_M_rep() != __rcs._M_rep()) 624 { 625 _CharT* __tmp = __rcs._M_grab(_M_get_allocator()); 626 _M_dispose(); 627 _M_data(__tmp); 628 } 629 } 630 631 template<typename _CharT, typename _Traits, typename _Alloc> 632 void 633 __rc_string_base<_CharT, _Traits, _Alloc>:: 634 _M_reserve(size_type __res) 635 { 636 // Make sure we don't shrink below the current size. 637 if (__res < _M_length()) 638 __res = _M_length(); 639 640 if (__res != _M_capacity() || _M_is_shared()) 641 { 642 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(), 643 __res - _M_length()); 644 _M_dispose(); 645 _M_data(__tmp); 646 } 647 } 648 649 template<typename _CharT, typename _Traits, typename _Alloc> 650 void 651 __rc_string_base<_CharT, _Traits, _Alloc>:: 652 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 653 size_type __len2) 654 { 655 const size_type __how_much = _M_length() - __pos - __len1; 656 657 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1, 658 _M_capacity(), _M_get_allocator()); 659 660 if (__pos) 661 this->_S_copy(__r->_M_refdata(), _M_data(), __pos); 662 if (__s && __len2) 663 this->_S_copy(__r->_M_refdata() + __pos, __s, __len2); 664 if (__how_much) 665 this->_S_copy(__r->_M_refdata() + __pos + __len2, 666 _M_data() + __pos + __len1, __how_much); 667 668 _M_dispose(); 669 _M_data(__r->_M_refdata()); 670 } 671 672 template<typename _CharT, typename _Traits, typename _Alloc> 673 void 674 __rc_string_base<_CharT, _Traits, _Alloc>:: 675 _M_erase(size_type __pos, size_type __n) 676 { 677 const size_type __new_size = _M_length() - __n; 678 const size_type __how_much = _M_length() - __pos - __n; 679 680 if (_M_is_shared()) 681 { 682 // Must reallocate. 683 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(), 684 _M_get_allocator()); 685 686 if (__pos) 687 this->_S_copy(__r->_M_refdata(), _M_data(), __pos); 688 if (__how_much) 689 this->_S_copy(__r->_M_refdata() + __pos, 690 _M_data() + __pos + __n, __how_much); 691 692 _M_dispose(); 693 _M_data(__r->_M_refdata()); 694 } 695 else if (__how_much && __n) 696 { 697 // Work in-place. 698 this->_S_move(_M_data() + __pos, 699 _M_data() + __pos + __n, __how_much); 700 } 701 702 _M_rep()->_M_set_length(__new_size); 703 } 704 705 template<> 706 inline bool 707 __rc_string_base<char, std::char_traits<char>, 708 std::allocator<char> >:: 709 _M_compare(const __rc_string_base& __rcs) const 710 { 711 if (_M_rep() == __rcs._M_rep()) 712 return true; 713 return false; 714 } 715 716#ifdef _GLIBCXX_USE_WCHAR_T 717 template<> 718 inline bool 719 __rc_string_base<wchar_t, std::char_traits<wchar_t>, 720 std::allocator<wchar_t> >:: 721 _M_compare(const __rc_string_base& __rcs) const 722 { 723 if (_M_rep() == __rcs._M_rep()) 724 return true; 725 return false; 726 } 727#endif 728 729_GLIBCXX_END_NAMESPACE_VERSION 730} // namespace 731 732#endif /* _RC_STRING_BASE_H */ 733