1 // Reference-counted versatile string base -*- C++ -*- 2 3 // Copyright (C) 2005-2018 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 36 namespace __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 { 358 _M_dispose(); 359 _M_data(_S_empty_rep._M_refcopy()); 360 } 361 362 bool 363 _M_compare(const __rc_string_base&) const 364 { return false; } 365 }; 366 367 template<typename _CharT, typename _Traits, typename _Alloc> 368 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty 369 __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep; 370 371 template<typename _CharT, typename _Traits, typename _Alloc> 372 typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep* 373 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 374 _S_create(size_type __capacity, size_type __old_capacity, 375 const _Alloc& __alloc) 376 { 377 // _GLIBCXX_RESOLVE_LIB_DEFECTS 378 // 83. String::npos vs. string::max_size() 379 if (__capacity > size_type(_S_max_size)) 380 std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create")); 381 382 // The standard places no restriction on allocating more memory 383 // than is strictly needed within this layer at the moment or as 384 // requested by an explicit application call to reserve(). 385 386 // Many malloc implementations perform quite poorly when an 387 // application attempts to allocate memory in a stepwise fashion 388 // growing each allocation size by only 1 char. Additionally, 389 // it makes little sense to allocate less linear memory than the 390 // natural blocking size of the malloc implementation. 391 // Unfortunately, we would need a somewhat low-level calculation 392 // with tuned parameters to get this perfect for any particular 393 // malloc implementation. Fortunately, generalizations about 394 // common features seen among implementations seems to suffice. 395 396 // __pagesize need not match the actual VM page size for good 397 // results in practice, thus we pick a common value on the low 398 // side. __malloc_header_size is an estimate of the amount of 399 // overhead per memory allocation (in practice seen N * sizeof 400 // (void*) where N is 0, 2 or 4). According to folklore, 401 // picking this value on the high side is better than 402 // low-balling it (especially when this algorithm is used with 403 // malloc implementations that allocate memory blocks rounded up 404 // to a size which is a power of 2). 405 const size_type __pagesize = 4096; 406 const size_type __malloc_header_size = 4 * sizeof(void*); 407 408 // The below implements an exponential growth policy, necessary to 409 // meet amortized linear time requirements of the library: see 410 // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html. 411 if (__capacity > __old_capacity && __capacity < 2 * __old_capacity) 412 { 413 __capacity = 2 * __old_capacity; 414 // Never allocate a string bigger than _S_max_size. 415 if (__capacity > size_type(_S_max_size)) 416 __capacity = size_type(_S_max_size); 417 } 418 419 // NB: Need an array of char_type[__capacity], plus a terminating 420 // null char_type() element, plus enough for the _Rep data structure, 421 // plus sizeof(_Rep) - 1 to upper round to a size multiple of 422 // sizeof(_Rep). 423 // Whew. Seemingly so needy, yet so elemental. 424 size_type __size = ((__capacity + 1) * sizeof(_CharT) 425 + 2 * sizeof(_Rep) - 1); 426 427 const size_type __adj_size = __size + __malloc_header_size; 428 if (__adj_size > __pagesize && __capacity > __old_capacity) 429 { 430 const size_type __extra = __pagesize - __adj_size % __pagesize; 431 __capacity += __extra / sizeof(_CharT); 432 if (__capacity > size_type(_S_max_size)) 433 __capacity = size_type(_S_max_size); 434 __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1; 435 } 436 437 // NB: Might throw, but no worries about a leak, mate: _Rep() 438 // does not throw. 439 _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep)); 440 _Rep* __p = new (__place) _Rep; 441 __p->_M_info._M_capacity = __capacity; 442 return __p; 443 } 444 445 template<typename _CharT, typename _Traits, typename _Alloc> 446 void 447 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 448 _M_destroy(const _Alloc& __a) throw () 449 { 450 const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT) 451 + 2 * sizeof(_Rep) - 1); 452 _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep)); 453 } 454 455 template<typename _CharT, typename _Traits, typename _Alloc> 456 _CharT* 457 __rc_string_base<_CharT, _Traits, _Alloc>::_Rep:: 458 _M_clone(const _Alloc& __alloc, size_type __res) 459 { 460 // Requested capacity of the clone. 461 const size_type __requested_cap = _M_info._M_length + __res; 462 _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity, 463 __alloc); 464 465 if (_M_info._M_length) 466 __rc_string_base::_S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length); 467 468 __r->_M_set_length(_M_info._M_length); 469 return __r->_M_refdata(); 470 } 471 472 template<typename _CharT, typename _Traits, typename _Alloc> 473 __rc_string_base<_CharT, _Traits, _Alloc>:: 474 __rc_string_base(const _Alloc& __a) 475 : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { } 476 477 template<typename _CharT, typename _Traits, typename _Alloc> 478 __rc_string_base<_CharT, _Traits, _Alloc>:: 479 __rc_string_base(const __rc_string_base& __rcs) 480 : _M_dataplus(__rcs._M_get_allocator(), 481 __rcs._M_grab(__rcs._M_get_allocator())) { } 482 483 template<typename _CharT, typename _Traits, typename _Alloc> 484 __rc_string_base<_CharT, _Traits, _Alloc>:: 485 __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a) 486 : _M_dataplus(__a, _S_construct(__n, __c, __a)) { } 487 488 template<typename _CharT, typename _Traits, typename _Alloc> 489 template<typename _InputIterator> 490 __rc_string_base<_CharT, _Traits, _Alloc>:: 491 __rc_string_base(_InputIterator __beg, _InputIterator __end, 492 const _Alloc& __a) 493 : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { } 494 495 template<typename _CharT, typename _Traits, typename _Alloc> 496 void 497 __rc_string_base<_CharT, _Traits, _Alloc>:: 498 _M_leak_hard() 499 { 500 if (_M_is_shared()) 501 _M_erase(0, 0); 502 _M_set_leaked(); 503 } 504 505 // NB: This is the special case for Input Iterators, used in 506 // istreambuf_iterators, etc. 507 // Input Iterators have a cost structure very different from 508 // pointers, calling for a different coding style. 509 template<typename _CharT, typename _Traits, typename _Alloc> 510 template<typename _InIterator> 511 _CharT* 512 __rc_string_base<_CharT, _Traits, _Alloc>:: 513 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 514 std::input_iterator_tag) 515 { 516 if (__beg == __end && __a == _Alloc()) 517 return _S_empty_rep._M_refcopy(); 518 519 // Avoid reallocation for common case. 520 _CharT __buf[128]; 521 size_type __len = 0; 522 while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT)) 523 { 524 __buf[__len++] = *__beg; 525 ++__beg; 526 } 527 _Rep* __r = _Rep::_S_create(__len, size_type(0), __a); 528 _S_copy(__r->_M_refdata(), __buf, __len); 529 __try 530 { 531 while (__beg != __end) 532 { 533 if (__len == __r->_M_info._M_capacity) 534 { 535 // Allocate more space. 536 _Rep* __another = _Rep::_S_create(__len + 1, __len, __a); 537 _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len); 538 __r->_M_destroy(__a); 539 __r = __another; 540 } 541 __r->_M_refdata()[__len++] = *__beg; 542 ++__beg; 543 } 544 } 545 __catch(...) 546 { 547 __r->_M_destroy(__a); 548 __throw_exception_again; 549 } 550 __r->_M_set_length(__len); 551 return __r->_M_refdata(); 552 } 553 554 template<typename _CharT, typename _Traits, typename _Alloc> 555 template<typename _InIterator> 556 _CharT* 557 __rc_string_base<_CharT, _Traits, _Alloc>:: 558 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a, 559 std::forward_iterator_tag) 560 { 561 if (__beg == __end && __a == _Alloc()) 562 return _S_empty_rep._M_refcopy(); 563 564 // NB: Not required, but considered best practice. 565 if (__is_null_pointer(__beg) && __beg != __end) 566 std::__throw_logic_error(__N("__rc_string_base::" 567 "_S_construct null not valid")); 568 569 const size_type __dnew = static_cast<size_type>(std::distance(__beg, 570 __end)); 571 // Check for out_of_range and length_error exceptions. 572 _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a); 573 __try 574 { __rc_string_base::_S_copy_chars(__r->_M_refdata(), __beg, __end); } 575 __catch(...) 576 { 577 __r->_M_destroy(__a); 578 __throw_exception_again; 579 } 580 __r->_M_set_length(__dnew); 581 return __r->_M_refdata(); 582 } 583 584 template<typename _CharT, typename _Traits, typename _Alloc> 585 _CharT* 586 __rc_string_base<_CharT, _Traits, _Alloc>:: 587 _S_construct(size_type __n, _CharT __c, const _Alloc& __a) 588 { 589 if (__n == 0 && __a == _Alloc()) 590 return _S_empty_rep._M_refcopy(); 591 592 // Check for out_of_range and length_error exceptions. 593 _Rep* __r = _Rep::_S_create(__n, size_type(0), __a); 594 if (__n) 595 __rc_string_base::_S_assign(__r->_M_refdata(), __n, __c); 596 597 __r->_M_set_length(__n); 598 return __r->_M_refdata(); 599 } 600 601 template<typename _CharT, typename _Traits, typename _Alloc> 602 void 603 __rc_string_base<_CharT, _Traits, _Alloc>:: 604 _M_swap(__rc_string_base& __rcs) 605 { 606 if (_M_is_leaked()) 607 _M_set_sharable(); 608 if (__rcs._M_is_leaked()) 609 __rcs._M_set_sharable(); 610 611 _CharT* __tmp = _M_data(); 612 _M_data(__rcs._M_data()); 613 __rcs._M_data(__tmp); 614 615 // _GLIBCXX_RESOLVE_LIB_DEFECTS 616 // 431. Swapping containers with unequal allocators. 617 std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(), 618 __rcs._M_get_allocator()); 619 } 620 621 template<typename _CharT, typename _Traits, typename _Alloc> 622 void 623 __rc_string_base<_CharT, _Traits, _Alloc>:: 624 _M_assign(const __rc_string_base& __rcs) 625 { 626 if (_M_rep() != __rcs._M_rep()) 627 { 628 _CharT* __tmp = __rcs._M_grab(_M_get_allocator()); 629 _M_dispose(); 630 _M_data(__tmp); 631 } 632 } 633 634 template<typename _CharT, typename _Traits, typename _Alloc> 635 void 636 __rc_string_base<_CharT, _Traits, _Alloc>:: 637 _M_reserve(size_type __res) 638 { 639 // Make sure we don't shrink below the current size. 640 if (__res < _M_length()) 641 __res = _M_length(); 642 643 if (__res != _M_capacity() || _M_is_shared()) 644 { 645 _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(), 646 __res - _M_length()); 647 _M_dispose(); 648 _M_data(__tmp); 649 } 650 } 651 652 template<typename _CharT, typename _Traits, typename _Alloc> 653 void 654 __rc_string_base<_CharT, _Traits, _Alloc>:: 655 _M_mutate(size_type __pos, size_type __len1, const _CharT* __s, 656 size_type __len2) 657 { 658 const size_type __how_much = _M_length() - __pos - __len1; 659 660 _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1, 661 _M_capacity(), _M_get_allocator()); 662 663 if (__pos) 664 this->_S_copy(__r->_M_refdata(), _M_data(), __pos); 665 if (__s && __len2) 666 this->_S_copy(__r->_M_refdata() + __pos, __s, __len2); 667 if (__how_much) 668 this->_S_copy(__r->_M_refdata() + __pos + __len2, 669 _M_data() + __pos + __len1, __how_much); 670 671 _M_dispose(); 672 _M_data(__r->_M_refdata()); 673 } 674 675 template<typename _CharT, typename _Traits, typename _Alloc> 676 void 677 __rc_string_base<_CharT, _Traits, _Alloc>:: 678 _M_erase(size_type __pos, size_type __n) 679 { 680 const size_type __new_size = _M_length() - __n; 681 const size_type __how_much = _M_length() - __pos - __n; 682 683 if (_M_is_shared()) 684 { 685 // Must reallocate. 686 _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(), 687 _M_get_allocator()); 688 689 if (__pos) 690 this->_S_copy(__r->_M_refdata(), _M_data(), __pos); 691 if (__how_much) 692 this->_S_copy(__r->_M_refdata() + __pos, 693 _M_data() + __pos + __n, __how_much); 694 695 _M_dispose(); 696 _M_data(__r->_M_refdata()); 697 } 698 else if (__how_much && __n) 699 { 700 // Work in-place. 701 this->_S_move(_M_data() + __pos, 702 _M_data() + __pos + __n, __how_much); 703 } 704 705 _M_rep()->_M_set_length(__new_size); 706 } 707 708 template<> 709 inline bool 710 __rc_string_base<char, std::char_traits<char>, 711 std::allocator<char> >:: 712 _M_compare(const __rc_string_base& __rcs) const 713 { 714 if (_M_rep() == __rcs._M_rep()) 715 return true; 716 return false; 717 } 718 719 #ifdef _GLIBCXX_USE_WCHAR_T 720 template<> 721 inline bool 722 __rc_string_base<wchar_t, std::char_traits<wchar_t>, 723 std::allocator<wchar_t> >:: 724 _M_compare(const __rc_string_base& __rcs) const 725 { 726 if (_M_rep() == __rcs._M_rep()) 727 return true; 728 return false; 729 } 730 #endif 731 732 _GLIBCXX_END_NAMESPACE_VERSION 733 } // namespace 734 735 #endif /* _RC_STRING_BASE_H */ 736