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