libstdc++-v3/include/bits/basic_string.tcc

   1 // Components for manipulating sequences of characters -*- C++ -*-
   2
   3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   4 // 2006, 2007, 2008, 2009
   5 // Free Software Foundation, Inc.
   6 //
   7 // This file is part of the GNU ISO C++ Library.  This library is free
   8 // software; you can redistribute it and/or modify it under the
   9 // terms of the GNU General Public License as published by the
  10 // Free Software Foundation; either version 3, or (at your option)
  11 // any later version.
  12
  13 // This library is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // Under Section 7 of GPL version 3, you are granted additional
  19 // permissions described in the GCC Runtime Library Exception, version
  20 // 3.1, as published by the Free Software Foundation.
  21
  22 // You should have received a copy of the GNU General Public License and
  23 // a copy of the GCC Runtime Library Exception along with this program;
  24 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 // <http://www.gnu.org/licenses/>.
  26
  27 /** @file basic_string.tcc
  28  *  This is an internal header file, included by other library headers.
  29  *  You should not attempt to use it directly.
  30  */
  31
  32 //
  33 // ISO C++ 14882: 21  Strings library
  34 //
  35
  36 // Written by Jason Merrill based upon the specification by Takanori Adachi
  37 // in ANSI X3J16/94-0013R2.  Rewritten by Nathan Myers to ISO-14882.
  38
  39 #ifndef _BASIC_STRING_TCC
  40 #define _BASIC_STRING_TCC 1
  41
  42 #pragma GCC system_header
  43
  44 #include <cxxabi-forced.h>
  45
  46 _GLIBCXX_BEGIN_NAMESPACE(std)
  47
  48   template<typename _CharT, typename _Traits, typename _Alloc>
  49     const typename basic_string<_CharT, _Traits, _Alloc>::size_type
  50     basic_string<_CharT, _Traits, _Alloc>::
  51     _Rep::_S_max_size = (((npos - sizeof(_Rep_base))/sizeof(_CharT)) - 1) / 4;
  52
  53   template<typename _CharT, typename _Traits, typename _Alloc>
  54     const _CharT
  55     basic_string<_CharT, _Traits, _Alloc>::
  56     _Rep::_S_terminal = _CharT();
  57
  58   template<typename _CharT, typename _Traits, typename _Alloc>
  59     const typename basic_string<_CharT, _Traits, _Alloc>::size_type
  60     basic_string<_CharT, _Traits, _Alloc>::npos;
  61
  62   // Linker sets _S_empty_rep_storage to all 0s (one reference, empty string)
  63   // at static init time (before static ctors are run).
  64   template<typename _CharT, typename _Traits, typename _Alloc>
  65     typename basic_string<_CharT, _Traits, _Alloc>::size_type
  66     basic_string<_CharT, _Traits, _Alloc>::_Rep::_S_empty_rep_storage[
  67     (sizeof(_Rep_base) + sizeof(_CharT) + sizeof(size_type) - 1) /
  68       sizeof(size_type)];
  69
  70   // NB: This is the special case for Input Iterators, used in
  71   // istreambuf_iterators, etc.
  72   // Input Iterators have a cost structure very different from
  73   // pointers, calling for a different coding style.
  74   template<typename _CharT, typename _Traits, typename _Alloc>
  75     template<typename _InIterator>
  76       _CharT*
  77       basic_string<_CharT, _Traits, _Alloc>::
  78       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
  79                    input_iterator_tag)
  80       {
  81 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
  82         if (__beg == __end && __a == _Alloc())
  83           return _S_empty_rep()._M_refdata();
  84 #endif
  85         // Avoid reallocation for common case.
  86         _CharT __buf[128];
  87         size_type __len = 0;
  88         while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
  89           {
  90             __buf[__len++] = *__beg;
  91             ++__beg;
  92           }
  93         _Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
  94         _M_copy(__r->_M_refdata(), __buf, __len);
  95         __try
  96           {
  97             while (__beg != __end)
  98               {
  99                 if (__len == __r->_M_capacity)
 100                   {
 101                     // Allocate more space.
 102                     _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
 103                     _M_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
 104                     __r->_M_destroy(__a);
 105                     __r = __another;
 106                   }
 107                 __r->_M_refdata()[__len++] = *__beg;
 108                 ++__beg;
 109               }
 110           }
 111         __catch(...)
 112           {
 113             __r->_M_destroy(__a);
 114             __throw_exception_again;
 115           }
 116         __r->_M_set_length_and_sharable(__len);
 117         return __r->_M_refdata();
 118       }
 119
 120   template<typename _CharT, typename _Traits, typename _Alloc>
 121     template <typename _InIterator>
 122       _CharT*
 123       basic_string<_CharT, _Traits, _Alloc>::
 124       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
 125                    forward_iterator_tag)
 126       {
 127 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
 128         if (__beg == __end && __a == _Alloc())
 129           return _S_empty_rep()._M_refdata();
 130 #endif
 131         // NB: Not required, but considered best practice.
 132         if (__builtin_expect(__gnu_cxx::__is_null_pointer(__beg)
 133                              && __beg != __end, 0))
 134           __throw_logic_error(__N("basic_string::_S_construct NULL not valid"));
 135
 136         const size_type __dnew = static_cast<size_type>(std::distance(__beg,
 137                                                                       __end));
 138         // Check for out_of_range and length_error exceptions.
 139         _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
 140         __try
 141           { _S_copy_chars(__r->_M_refdata(), __beg, __end); }
 142         __catch(...)
 143           {
 144             __r->_M_destroy(__a);
 145             __throw_exception_again;
 146           }
 147         __r->_M_set_length_and_sharable(__dnew);
 148         return __r->_M_refdata();
 149       }
 150
 151   template<typename _CharT, typename _Traits, typename _Alloc>
 152     _CharT*
 153     basic_string<_CharT, _Traits, _Alloc>::
 154     _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
 155     {
 156 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
 157       if (__n == 0 && __a == _Alloc())
 158         return _S_empty_rep()._M_refdata();
 159 #endif
 160       // Check for out_of_range and length_error exceptions.
 161       _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
 162       if (__n)
 163         _M_assign(__r->_M_refdata(), __n, __c);
 164
 165       __r->_M_set_length_and_sharable(__n);
 166       return __r->_M_refdata();
 167     }
 168
 169   template<typename _CharT, typename _Traits, typename _Alloc>
 170     basic_string<_CharT, _Traits, _Alloc>::
 171     basic_string(const basic_string& __str)
 172     : _M_dataplus(__str._M_rep()->_M_grab(_Alloc(__str.get_allocator()),
 173                                           __str.get_allocator()),
 174                   __str.get_allocator())
 175     { }
 176
 177   template<typename _CharT, typename _Traits, typename _Alloc>
 178     basic_string<_CharT, _Traits, _Alloc>::
 179     basic_string(const _Alloc& __a)
 180     : _M_dataplus(_S_construct(size_type(), _CharT(), __a), __a)
 181     { }
 182
 183   template<typename _CharT, typename _Traits, typename _Alloc>
 184     basic_string<_CharT, _Traits, _Alloc>::
 185     basic_string(const basic_string& __str, size_type __pos, size_type __n)
 186     : _M_dataplus(_S_construct(__str._M_data()
 187                                + __str._M_check(__pos,
 188                                                 "basic_string::basic_string"),
 189                                __str._M_data() + __str._M_limit(__pos, __n)
 190                                + __pos, _Alloc()), _Alloc())
 191     { }
 192
 193   template<typename _CharT, typename _Traits, typename _Alloc>
 194     basic_string<_CharT, _Traits, _Alloc>::
 195     basic_string(const basic_string& __str, size_type __pos,
 196                  size_type __n, const _Alloc& __a)
 197     : _M_dataplus(_S_construct(__str._M_data()
 198                                + __str._M_check(__pos,
 199                                                 "basic_string::basic_string"),
 200                                __str._M_data() + __str._M_limit(__pos, __n)
 201                                + __pos, __a), __a)
 202     { }
 203
 204   // TBD: DPG annotate
 205   template<typename _CharT, typename _Traits, typename _Alloc>
 206     basic_string<_CharT, _Traits, _Alloc>::
 207     basic_string(const _CharT* __s, size_type __n, const _Alloc& __a)
 208     : _M_dataplus(_S_construct(__s, __s + __n, __a), __a)
 209     { }
 210
 211   // TBD: DPG annotate
 212   template<typename _CharT, typename _Traits, typename _Alloc>
 213     basic_string<_CharT, _Traits, _Alloc>::
 214     basic_string(const _CharT* __s, const _Alloc& __a)
 215     : _M_dataplus(_S_construct(__s, __s ? __s + traits_type::length(__s) :
 216                                __s + npos, __a), __a)
 217     { }
 218
 219   template<typename _CharT, typename _Traits, typename _Alloc>
 220     basic_string<_CharT, _Traits, _Alloc>::
 221     basic_string(size_type __n, _CharT __c, const _Alloc& __a)
 222     : _M_dataplus(_S_construct(__n, __c, __a), __a)
 223     { }
 224
 225   // TBD: DPG annotate
 226   template<typename _CharT, typename _Traits, typename _Alloc>
 227     template<typename _InputIterator>
 228     basic_string<_CharT, _Traits, _Alloc>::
 229     basic_string(_InputIterator __beg, _InputIterator __end, const _Alloc& __a)
 230     : _M_dataplus(_S_construct(__beg, __end, __a), __a)
 231     { }
 232
 233 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 234   template<typename _CharT, typename _Traits, typename _Alloc>
 235     basic_string<_CharT, _Traits, _Alloc>::
 236     basic_string(initializer_list<_CharT> __l, const _Alloc& __a)
 237     : _M_dataplus(_S_construct(__l.begin(), __l.end(), __a), __a)
 238     { }
 239 #endif
 240
 241   template<typename _CharT, typename _Traits, typename _Alloc>
 242     basic_string<_CharT, _Traits, _Alloc>&
 243     basic_string<_CharT, _Traits, _Alloc>::
 244     assign(const basic_string& __str)
 245     {
 246       if (_M_rep() != __str._M_rep())
 247         {
 248           // XXX MT
 249           const allocator_type __a = this->get_allocator();
 250           _CharT* __tmp = __str._M_rep()->_M_grab(__a, __str.get_allocator());
 251           _M_rep()->_M_dispose(__a);
 252           _M_data(__tmp);
 253         }
 254       return *this;
 255     }
 256
 257   template<typename _CharT, typename _Traits, typename _Alloc>
 258     basic_string<_CharT, _Traits, _Alloc>&
 259     basic_string<_CharT, _Traits, _Alloc>::
 260     assign(const _CharT* __s, size_type __n)
 261     {
 262       __glibcxx_requires_string_len(__s, __n);
 263       _M_check_length(this->size(), __n, "basic_string::assign");
 264       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
 265         return _M_replace_safe(size_type(0), this->size(), __s, __n);
 266       else
 267         {
 268           // Work in-place.
 269           const size_type __pos = __s - _M_data();
 270           if (__pos >= __n)
 271             _M_copy(_M_data(), __s, __n);
 272           else if (__pos)
 273             _M_move(_M_data(), __s, __n);
 274           _M_rep()->_M_set_length_and_sharable(__n);
 275           return *this;
 276         }
 277      }
 278
 279   template<typename _CharT, typename _Traits, typename _Alloc>
 280     basic_string<_CharT, _Traits, _Alloc>&
 281     basic_string<_CharT, _Traits, _Alloc>::
 282     append(size_type __n, _CharT __c)
 283     {
 284       if (__n)
 285         {
 286           _M_check_length(size_type(0), __n, "basic_string::append");
 287           const size_type __len = __n + this->size();
 288           if (__len > this->capacity() || _M_rep()->_M_is_shared())
 289             this->reserve(__len);
 290           _M_assign(_M_data() + this->size(), __n, __c);
 291           _M_rep()->_M_set_length_and_sharable(__len);
 292         }
 293       return *this;
 294     }
 295
 296   template<typename _CharT, typename _Traits, typename _Alloc>
 297     basic_string<_CharT, _Traits, _Alloc>&
 298     basic_string<_CharT, _Traits, _Alloc>::
 299     append(const _CharT* __s, size_type __n)
 300     {
 301       __glibcxx_requires_string_len(__s, __n);
 302       if (__n)
 303         {
 304           _M_check_length(size_type(0), __n, "basic_string::append");
 305           const size_type __len = __n + this->size();
 306           if (__len > this->capacity() || _M_rep()->_M_is_shared())
 307             {
 308               if (_M_disjunct(__s))
 309                 this->reserve(__len);
 310               else
 311                 {
 312                   const size_type __off = __s - _M_data();
 313                   this->reserve(__len);
 314                   __s = _M_data() + __off;
 315                 }
 316             }
 317           _M_copy(_M_data() + this->size(), __s, __n);
 318           _M_rep()->_M_set_length_and_sharable(__len);
 319         }
 320       return *this;
 321     }
 322
 323   template<typename _CharT, typename _Traits, typename _Alloc>
 324     basic_string<_CharT, _Traits, _Alloc>&
 325     basic_string<_CharT, _Traits, _Alloc>::
 326     append(const basic_string& __str)
 327     {
 328       const size_type __size = __str.size();
 329       if (__size)
 330         {
 331           const size_type __len = __size + this->size();
 332           if (__len > this->capacity() || _M_rep()->_M_is_shared())
 333             this->reserve(__len);
 334           _M_copy(_M_data() + this->size(), __str._M_data(), __size);
 335           _M_rep()->_M_set_length_and_sharable(__len);
 336         }
 337       return *this;
 338     }
 339
 340   template<typename _CharT, typename _Traits, typename _Alloc>
 341     basic_string<_CharT, _Traits, _Alloc>&
 342     basic_string<_CharT, _Traits, _Alloc>::
 343     append(const basic_string& __str, size_type __pos, size_type __n)
 344     {
 345       __str._M_check(__pos, "basic_string::append");
 346       __n = __str._M_limit(__pos, __n);
 347       if (__n)
 348         {
 349           const size_type __len = __n + this->size();
 350           if (__len > this->capacity() || _M_rep()->_M_is_shared())
 351             this->reserve(__len);
 352           _M_copy(_M_data() + this->size(), __str._M_data() + __pos, __n);
 353           _M_rep()->_M_set_length_and_sharable(__len);
 354         }
 355       return *this;
 356     }
 357
 358    template<typename _CharT, typename _Traits, typename _Alloc>
 359      basic_string<_CharT, _Traits, _Alloc>&
 360      basic_string<_CharT, _Traits, _Alloc>::
 361      insert(size_type __pos, const _CharT* __s, size_type __n)
 362      {
 363        __glibcxx_requires_string_len(__s, __n);
 364        _M_check(__pos, "basic_string::insert");
 365        _M_check_length(size_type(0), __n, "basic_string::insert");
 366        if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
 367          return _M_replace_safe(__pos, size_type(0), __s, __n);
 368        else
 369          {
 370            // Work in-place.
 371            const size_type __off = __s - _M_data();
 372            _M_mutate(__pos, 0, __n);
 373            __s = _M_data() + __off;
 374            _CharT* __p = _M_data() + __pos;
 375            if (__s  + __n <= __p)
 376              _M_copy(__p, __s, __n);
 377            else if (__s >= __p)
 378              _M_copy(__p, __s + __n, __n);
 379            else
 380              {
 381                const size_type __nleft = __p - __s;
 382                _M_copy(__p, __s, __nleft);
 383                _M_copy(__p + __nleft, __p + __n, __n - __nleft);
 384              }
 385            return *this;
 386          }
 387      }
 388
 389    template<typename _CharT, typename _Traits, typename _Alloc>
 390      basic_string<_CharT, _Traits, _Alloc>&
 391      basic_string<_CharT, _Traits, _Alloc>::
 392      replace(size_type __pos, size_type __n1, const _CharT* __s,
 393              size_type __n2)
 394      {
 395        __glibcxx_requires_string_len(__s, __n2);
 396        _M_check(__pos, "basic_string::replace");
 397        __n1 = _M_limit(__pos, __n1);
 398        _M_check_length(__n1, __n2, "basic_string::replace");
 399        bool __left;
 400        if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
 401          return _M_replace_safe(__pos, __n1, __s, __n2);
 402        else if ((__left = __s + __n2 <= _M_data() + __pos)
 403                 || _M_data() + __pos + __n1 <= __s)
 404          {
 405            // Work in-place: non-overlapping case.
 406            size_type __off = __s - _M_data();
 407            __left ? __off : (__off += __n2 - __n1);
 408            _M_mutate(__pos, __n1, __n2);
 409            _M_copy(_M_data() + __pos, _M_data() + __off, __n2);
 410            return *this;
 411          }
 412        else
 413          {
 414            // Todo: overlapping case.
 415            const basic_string __tmp(__s, __n2);
 416            return _M_replace_safe(__pos, __n1, __tmp._M_data(), __n2);
 417          }
 418      }
 419
 420   template<typename _CharT, typename _Traits, typename _Alloc>
 421     void
 422     basic_string<_CharT, _Traits, _Alloc>::_Rep::
 423     _M_destroy(const _Alloc& __a) throw ()
 424     {
 425       const size_type __size = sizeof(_Rep_base) +
 426                                (this->_M_capacity + 1) * sizeof(_CharT);
 427       _Raw_bytes_alloc(__a).deallocate(reinterpret_cast<char*>(this), __size);
 428     }
 429
 430   template<typename _CharT, typename _Traits, typename _Alloc>
 431     void
 432     basic_string<_CharT, _Traits, _Alloc>::
 433     _M_leak_hard()
 434     {
 435 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
 436       if (_M_rep() == &_S_empty_rep())
 437         return;
 438 #endif
 439       if (_M_rep()->_M_is_shared())
 440         _M_mutate(0, 0, 0);
 441       _M_rep()->_M_set_leaked();
 442     }
 443
 444   template<typename _CharT, typename _Traits, typename _Alloc>
 445     void
 446     basic_string<_CharT, _Traits, _Alloc>::
 447     _M_mutate(size_type __pos, size_type __len1, size_type __len2)
 448     {
 449       const size_type __old_size = this->size();
 450       const size_type __new_size = __old_size + __len2 - __len1;
 451       const size_type __how_much = __old_size - __pos - __len1;
 452
 453       if (__new_size > this->capacity() || _M_rep()->_M_is_shared())
 454         {
 455           // Must reallocate.
 456           const allocator_type __a = get_allocator();
 457           _Rep* __r = _Rep::_S_create(__new_size, this->capacity(), __a);
 458
 459           if (__pos)
 460             _M_copy(__r->_M_refdata(), _M_data(), __pos);
 461           if (__how_much)
 462             _M_copy(__r->_M_refdata() + __pos + __len2,
 463                     _M_data() + __pos + __len1, __how_much);
 464
 465           _M_rep()->_M_dispose(__a);
 466           _M_data(__r->_M_refdata());
 467         }
 468       else if (__how_much && __len1 != __len2)
 469         {
 470           // Work in-place.
 471           _M_move(_M_data() + __pos + __len2,
 472                   _M_data() + __pos + __len1, __how_much);
 473         }
 474       _M_rep()->_M_set_length_and_sharable(__new_size);
 475     }
 476
 477   template<typename _CharT, typename _Traits, typename _Alloc>
 478     void
 479     basic_string<_CharT, _Traits, _Alloc>::
 480     reserve(size_type __res)
 481     {
 482       if (__res != this->capacity() || _M_rep()->_M_is_shared())
 483         {
 484           // Make sure we don't shrink below the current size
 485           if (__res < this->size())
 486             __res = this->size();
 487           const allocator_type __a = get_allocator();
 488           _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
 489           _M_rep()->_M_dispose(__a);
 490           _M_data(__tmp);
 491         }
 492     }
 493
 494   template<typename _CharT, typename _Traits, typename _Alloc>
 495     void
 496     basic_string<_CharT, _Traits, _Alloc>::
 497     swap(basic_string& __s)
 498     {
 499       if (_M_rep()->_M_is_leaked())
 500         _M_rep()->_M_set_sharable();
 501       if (__s._M_rep()->_M_is_leaked())
 502         __s._M_rep()->_M_set_sharable();
 503       if (this->get_allocator() == __s.get_allocator())
 504         {
 505           _CharT* __tmp = _M_data();
 506           _M_data(__s._M_data());
 507           __s._M_data(__tmp);
 508         }
 509       // The code below can usually be optimized away.
 510       else
 511         {
 512           const basic_string __tmp1(_M_ibegin(), _M_iend(),
 513                                     __s.get_allocator());
 514           const basic_string __tmp2(__s._M_ibegin(), __s._M_iend(),
 515                                     this->get_allocator());
 516           *this = __tmp2;
 517           __s = __tmp1;
 518         }
 519     }
 520
 521   template<typename _CharT, typename _Traits, typename _Alloc>
 522     typename basic_string<_CharT, _Traits, _Alloc>::_Rep*
 523     basic_string<_CharT, _Traits, _Alloc>::_Rep::
 524     _S_create(size_type __capacity, size_type __old_capacity,
 525               const _Alloc& __alloc)
 526     {
 527       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 528       // 83.  String::npos vs. string::max_size()
 529       if (__capacity > _S_max_size)
 530         __throw_length_error(__N("basic_string::_S_create"));
 531
 532       // The standard places no restriction on allocating more memory
 533       // than is strictly needed within this layer at the moment or as
 534       // requested by an explicit application call to reserve().
 535
 536       // Many malloc implementations perform quite poorly when an
 537       // application attempts to allocate memory in a stepwise fashion
 538       // growing each allocation size by only 1 char.  Additionally,
 539       // it makes little sense to allocate less linear memory than the
 540       // natural blocking size of the malloc implementation.
 541       // Unfortunately, we would need a somewhat low-level calculation
 542       // with tuned parameters to get this perfect for any particular
 543       // malloc implementation.  Fortunately, generalizations about
 544       // common features seen among implementations seems to suffice.
 545
 546       // __pagesize need not match the actual VM page size for good
 547       // results in practice, thus we pick a common value on the low
 548       // side.  __malloc_header_size is an estimate of the amount of
 549       // overhead per memory allocation (in practice seen N * sizeof
 550       // (void*) where N is 0, 2 or 4).  According to folklore,
 551       // picking this value on the high side is better than
 552       // low-balling it (especially when this algorithm is used with
 553       // malloc implementations that allocate memory blocks rounded up
 554       // to a size which is a power of 2).
 555       const size_type __pagesize = 4096;
 556       const size_type __malloc_header_size = 4 * sizeof(void*);
 557
 558       // The below implements an exponential growth policy, necessary to
 559       // meet amortized linear time requirements of the library: see
 560       // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
 561       // It's active for allocations requiring an amount of memory above
 562       // system pagesize. This is consistent with the requirements of the
 563       // standard: http://gcc.gnu.org/ml/libstdc++/2001-07/msg00130.html
 564       if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
 565         __capacity = 2 * __old_capacity;
 566
 567       // NB: Need an array of char_type[__capacity], plus a terminating
 568       // null char_type() element, plus enough for the _Rep data structure.
 569       // Whew. Seemingly so needy, yet so elemental.
 570       size_type __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
 571
 572       const size_type __adj_size = __size + __malloc_header_size;
 573       if (__adj_size > __pagesize && __capacity > __old_capacity)
 574         {
 575           const size_type __extra = __pagesize - __adj_size % __pagesize;
 576           __capacity += __extra / sizeof(_CharT);
 577           // Never allocate a string bigger than _S_max_size.
 578           if (__capacity > _S_max_size)
 579             __capacity = _S_max_size;
 580           __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
 581         }
 582
 583       // NB: Might throw, but no worries about a leak, mate: _Rep()
 584       // does not throw.
 585       void* __place = _Raw_bytes_alloc(__alloc).allocate(__size);
 586       _Rep *__p = new (__place) _Rep;
 587       __p->_M_capacity = __capacity;
 588       // ABI compatibility - 3.4.x set in _S_create both
 589       // _M_refcount and _M_length.  All callers of _S_create
 590       // in basic_string.tcc then set just _M_length.
 591       // In 4.0.x and later both _M_refcount and _M_length
 592       // are initialized in the callers, unfortunately we can
 593       // have 3.4.x compiled code with _S_create callers inlined
 594       // calling 4.0.x+ _S_create.
 595       __p->_M_set_sharable();
 596       return __p;
 597     }
 598
 599   template<typename _CharT, typename _Traits, typename _Alloc>
 600     _CharT*
 601     basic_string<_CharT, _Traits, _Alloc>::_Rep::
 602     _M_clone(const _Alloc& __alloc, size_type __res)
 603     {
 604       // Requested capacity of the clone.
 605       const size_type __requested_cap = this->_M_length + __res;
 606       _Rep* __r = _Rep::_S_create(__requested_cap, this->_M_capacity,
 607                                   __alloc);
 608       if (this->_M_length)
 609         _M_copy(__r->_M_refdata(), _M_refdata(), this->_M_length);
 610
 611       __r->_M_set_length_and_sharable(this->_M_length);
 612       return __r->_M_refdata();
 613     }
 614
 615   template<typename _CharT, typename _Traits, typename _Alloc>
 616     void
 617     basic_string<_CharT, _Traits, _Alloc>::
 618     resize(size_type __n, _CharT __c)
 619     {
 620       const size_type __size = this->size();
 621       _M_check_length(__size, __n, "basic_string::resize");
 622       if (__size < __n)
 623         this->append(__n - __size, __c);
 624       else if (__n < __size)
 625         this->erase(__n);
 626       // else nothing (in particular, avoid calling _M_mutate() unnecessarily.)
 627     }
 628
 629   template<typename _CharT, typename _Traits, typename _Alloc>
 630     template<typename _InputIterator>
 631       basic_string<_CharT, _Traits, _Alloc>&
 632       basic_string<_CharT, _Traits, _Alloc>::
 633       _M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator __k1,
 634                           _InputIterator __k2, __false_type)
 635       {
 636         const basic_string __s(__k1, __k2);
 637         const size_type __n1 = __i2 - __i1;
 638         _M_check_length(__n1, __s.size(), "basic_string::_M_replace_dispatch");
 639         return _M_replace_safe(__i1 - _M_ibegin(), __n1, __s._M_data(),
 640                                __s.size());
 641       }
 642
 643   template<typename _CharT, typename _Traits, typename _Alloc>
 644     basic_string<_CharT, _Traits, _Alloc>&
 645     basic_string<_CharT, _Traits, _Alloc>::
 646     _M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
 647                    _CharT __c)
 648     {
 649       _M_check_length(__n1, __n2, "basic_string::_M_replace_aux");
 650       _M_mutate(__pos1, __n1, __n2);
 651       if (__n2)
 652         _M_assign(_M_data() + __pos1, __n2, __c);
 653       return *this;
 654     }
 655
 656   template<typename _CharT, typename _Traits, typename _Alloc>
 657     basic_string<_CharT, _Traits, _Alloc>&
 658     basic_string<_CharT, _Traits, _Alloc>::
 659     _M_replace_safe(size_type __pos1, size_type __n1, const _CharT* __s,
 660                     size_type __n2)
 661     {
 662       _M_mutate(__pos1, __n1, __n2);
 663       if (__n2)
 664         _M_copy(_M_data() + __pos1, __s, __n2);
 665       return *this;
 666     }
 667
 668   template<typename _CharT, typename _Traits, typename _Alloc>
 669     basic_string<_CharT, _Traits, _Alloc>
 670     operator+(const _CharT* __lhs,
 671               const basic_string<_CharT, _Traits, _Alloc>& __rhs)
 672     {
 673       __glibcxx_requires_string(__lhs);
 674       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
 675       typedef typename __string_type::size_type   __size_type;
 676       const __size_type __len = _Traits::length(__lhs);
 677       __string_type __str;
 678       __str.reserve(__len + __rhs.size());
 679       __str.append(__lhs, __len);
 680       __str.append(__rhs);
 681       return __str;
 682     }
 683
 684   template<typename _CharT, typename _Traits, typename _Alloc>
 685     basic_string<_CharT, _Traits, _Alloc>
 686     operator+(_CharT __lhs, const basic_string<_CharT, _Traits, _Alloc>& __rhs)
 687     {
 688       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
 689       typedef typename __string_type::size_type   __size_type;
 690       __string_type __str;
 691       const __size_type __len = __rhs.size();
 692       __str.reserve(__len + 1);
 693       __str.append(__size_type(1), __lhs);
 694       __str.append(__rhs);
 695       return __str;
 696     }
 697
 698   template<typename _CharT, typename _Traits, typename _Alloc>
 699     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 700     basic_string<_CharT, _Traits, _Alloc>::
 701     copy(_CharT* __s, size_type __n, size_type __pos) const
 702     {
 703       _M_check(__pos, "basic_string::copy");
 704       __n = _M_limit(__pos, __n);
 705       __glibcxx_requires_string_len(__s, __n);
 706       if (__n)
 707         _M_copy(__s, _M_data() + __pos, __n);
 708       // 21.3.5.7 par 3: do not append null.  (good.)
 709       return __n;
 710     }
 711
 712   template<typename _CharT, typename _Traits, typename _Alloc>
 713     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 714     basic_string<_CharT, _Traits, _Alloc>::
 715     find(const _CharT* __s, size_type __pos, size_type __n) const
 716     {
 717       __glibcxx_requires_string_len(__s, __n);
 718       const size_type __size = this->size();
 719       const _CharT* __data = _M_data();
 720
 721       if (__n == 0)
 722         return __pos <= __size ? __pos : npos;
 723
 724       if (__n <= __size)
 725         {
 726           for (; __pos <= __size - __n; ++__pos)
 727             if (traits_type::eq(__data[__pos], __s[0])
 728                 && traits_type::compare(__data + __pos + 1,
 729                                         __s + 1, __n - 1) == 0)
 730               return __pos;
 731         }
 732       return npos;
 733     }
 734
 735   template<typename _CharT, typename _Traits, typename _Alloc>
 736     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 737     basic_string<_CharT, _Traits, _Alloc>::
 738     find(_CharT __c, size_type __pos) const
 739     {
 740       size_type __ret = npos;
 741       const size_type __size = this->size();
 742       if (__pos < __size)
 743         {
 744           const _CharT* __data = _M_data();
 745           const size_type __n = __size - __pos;
 746           const _CharT* __p = traits_type::find(__data + __pos, __n, __c);
 747           if (__p)
 748             __ret = __p - __data;
 749         }
 750       return __ret;
 751     }
 752
 753   template<typename _CharT, typename _Traits, typename _Alloc>
 754     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 755     basic_string<_CharT, _Traits, _Alloc>::
 756     rfind(const _CharT* __s, size_type __pos, size_type __n) const
 757     {
 758       __glibcxx_requires_string_len(__s, __n);
 759       const size_type __size = this->size();
 760       if (__n <= __size)
 761         {
 762           __pos = std::min(size_type(__size - __n), __pos);
 763           const _CharT* __data = _M_data();
 764           do
 765             {
 766               if (traits_type::compare(__data + __pos, __s, __n) == 0)
 767                 return __pos;
 768             }
 769           while (__pos-- > 0);
 770         }
 771       return npos;
 772     }
 773
 774   template<typename _CharT, typename _Traits, typename _Alloc>
 775     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 776     basic_string<_CharT, _Traits, _Alloc>::
 777     rfind(_CharT __c, size_type __pos) const
 778     {
 779       size_type __size = this->size();
 780       if (__size)
 781         {
 782           if (--__size > __pos)
 783             __size = __pos;
 784           for (++__size; __size-- > 0; )
 785             if (traits_type::eq(_M_data()[__size], __c))
 786               return __size;
 787         }
 788       return npos;
 789     }
 790
 791   template<typename _CharT, typename _Traits, typename _Alloc>
 792     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 793     basic_string<_CharT, _Traits, _Alloc>::
 794     find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
 795     {
 796       __glibcxx_requires_string_len(__s, __n);
 797       for (; __n && __pos < this->size(); ++__pos)
 798         {
 799           const _CharT* __p = traits_type::find(__s, __n, _M_data()[__pos]);
 800           if (__p)
 801             return __pos;
 802         }
 803       return npos;
 804     }
 805
 806   template<typename _CharT, typename _Traits, typename _Alloc>
 807     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 808     basic_string<_CharT, _Traits, _Alloc>::
 809     find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
 810     {
 811       __glibcxx_requires_string_len(__s, __n);
 812       size_type __size = this->size();
 813       if (__size && __n)
 814         {
 815           if (--__size > __pos)
 816             __size = __pos;
 817           do
 818             {
 819               if (traits_type::find(__s, __n, _M_data()[__size]))
 820                 return __size;
 821             }
 822           while (__size-- != 0);
 823         }
 824       return npos;
 825     }
 826
 827   template<typename _CharT, typename _Traits, typename _Alloc>
 828     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 829     basic_string<_CharT, _Traits, _Alloc>::
 830     find_first_not_of(const _CharT* __s, size_type __pos, size_type __n) const
 831     {
 832       __glibcxx_requires_string_len(__s, __n);
 833       for (; __pos < this->size(); ++__pos)
 834         if (!traits_type::find(__s, __n, _M_data()[__pos]))
 835           return __pos;
 836       return npos;
 837     }
 838
 839   template<typename _CharT, typename _Traits, typename _Alloc>
 840     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 841     basic_string<_CharT, _Traits, _Alloc>::
 842     find_first_not_of(_CharT __c, size_type __pos) const
 843     {
 844       for (; __pos < this->size(); ++__pos)
 845         if (!traits_type::eq(_M_data()[__pos], __c))
 846           return __pos;
 847       return npos;
 848     }
 849
 850   template<typename _CharT, typename _Traits, typename _Alloc>
 851     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 852     basic_string<_CharT, _Traits, _Alloc>::
 853     find_last_not_of(const _CharT* __s, size_type __pos, size_type __n) const
 854     {
 855       __glibcxx_requires_string_len(__s, __n);
 856       size_type __size = this->size();
 857       if (__size)
 858         {
 859           if (--__size > __pos)
 860             __size = __pos;
 861           do
 862             {
 863               if (!traits_type::find(__s, __n, _M_data()[__size]))
 864                 return __size;
 865             }
 866           while (__size--);
 867         }
 868       return npos;
 869     }
 870
 871   template<typename _CharT, typename _Traits, typename _Alloc>
 872     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 873     basic_string<_CharT, _Traits, _Alloc>::
 874     find_last_not_of(_CharT __c, size_type __pos) const
 875     {
 876       size_type __size = this->size();
 877       if (__size)
 878         {
 879           if (--__size > __pos)
 880             __size = __pos;
 881           do
 882             {
 883               if (!traits_type::eq(_M_data()[__size], __c))
 884                 return __size;
 885             }
 886           while (__size--);
 887         }
 888       return npos;
 889     }
 890
 891   template<typename _CharT, typename _Traits, typename _Alloc>
 892     int
 893     basic_string<_CharT, _Traits, _Alloc>::
 894     compare(size_type __pos, size_type __n, const basic_string& __str) const
 895     {
 896       _M_check(__pos, "basic_string::compare");
 897       __n = _M_limit(__pos, __n);
 898       const size_type __osize = __str.size();
 899       const size_type __len = std::min(__n, __osize);
 900       int __r = traits_type::compare(_M_data() + __pos, __str.data(), __len);
 901       if (!__r)
 902         __r = _S_compare(__n, __osize);
 903       return __r;
 904     }
 905
 906   template<typename _CharT, typename _Traits, typename _Alloc>
 907     int
 908     basic_string<_CharT, _Traits, _Alloc>::
 909     compare(size_type __pos1, size_type __n1, const basic_string& __str,
 910             size_type __pos2, size_type __n2) const
 911     {
 912       _M_check(__pos1, "basic_string::compare");
 913       __str._M_check(__pos2, "basic_string::compare");
 914       __n1 = _M_limit(__pos1, __n1);
 915       __n2 = __str._M_limit(__pos2, __n2);
 916       const size_type __len = std::min(__n1, __n2);
 917       int __r = traits_type::compare(_M_data() + __pos1,
 918                                      __str.data() + __pos2, __len);
 919       if (!__r)
 920         __r = _S_compare(__n1, __n2);
 921       return __r;
 922     }
 923
 924   template<typename _CharT, typename _Traits, typename _Alloc>
 925     int
 926     basic_string<_CharT, _Traits, _Alloc>::
 927     compare(const _CharT* __s) const
 928     {
 929       __glibcxx_requires_string(__s);
 930       const size_type __size = this->size();
 931       const size_type __osize = traits_type::length(__s);
 932       const size_type __len = std::min(__size, __osize);
 933       int __r = traits_type::compare(_M_data(), __s, __len);
 934       if (!__r)
 935         __r = _S_compare(__size, __osize);
 936       return __r;
 937     }
 938
 939   template<typename _CharT, typename _Traits, typename _Alloc>
 940     int
 941     basic_string <_CharT, _Traits, _Alloc>::
 942     compare(size_type __pos, size_type __n1, const _CharT* __s) const
 943     {
 944       __glibcxx_requires_string(__s);
 945       _M_check(__pos, "basic_string::compare");
 946       __n1 = _M_limit(__pos, __n1);
 947       const size_type __osize = traits_type::length(__s);
 948       const size_type __len = std::min(__n1, __osize);
 949       int __r = traits_type::compare(_M_data() + __pos, __s, __len);
 950       if (!__r)
 951         __r = _S_compare(__n1, __osize);
 952       return __r;
 953     }
 954
 955   template<typename _CharT, typename _Traits, typename _Alloc>
 956     int
 957     basic_string <_CharT, _Traits, _Alloc>::
 958     compare(size_type __pos, size_type __n1, const _CharT* __s,
 959             size_type __n2) const
 960     {
 961       __glibcxx_requires_string_len(__s, __n2);
 962       _M_check(__pos, "basic_string::compare");
 963       __n1 = _M_limit(__pos, __n1);
 964       const size_type __len = std::min(__n1, __n2);
 965       int __r = traits_type::compare(_M_data() + __pos, __s, __len);
 966       if (!__r)
 967         __r = _S_compare(__n1, __n2);
 968       return __r;
 969     }
 970
 971   // 21.3.7.9 basic_string::getline and operators
 972   template<typename _CharT, typename _Traits, typename _Alloc>
 973     basic_istream<_CharT, _Traits>&
 974     operator>>(basic_istream<_CharT, _Traits>& __in,
 975                basic_string<_CharT, _Traits, _Alloc>& __str)
 976     {
 977       typedef basic_istream<_CharT, _Traits>            __istream_type;
 978       typedef basic_string<_CharT, _Traits, _Alloc>     __string_type;
 979       typedef typename __istream_type::ios_base         __ios_base;
 980       typedef typename __istream_type::int_type         __int_type;
 981       typedef typename __string_type::size_type         __size_type;
 982       typedef ctype<_CharT>                             __ctype_type;
 983       typedef typename __ctype_type::ctype_base         __ctype_base;
 984
 985       __size_type __extracted = 0;
 986       typename __ios_base::iostate __err = __ios_base::goodbit;
 987       typename __istream_type::sentry __cerb(__in, false);
 988       if (__cerb)
 989         {
 990           __try
 991             {
 992               // Avoid reallocation for common case.
 993               __str.erase();
 994               _CharT __buf[128];
 995               __size_type __len = 0;
 996               const streamsize __w = __in.width();
 997               const __size_type __n = __w > 0 ? static_cast<__size_type>(__w)
 998                                               : __str.max_size();
 999               const __ctype_type& __ct = use_facet<__ctype_type>(__in.getloc());
1000               const __int_type __eof = _Traits::eof();
1001               __int_type __c = __in.rdbuf()->sgetc();
1002
1003               while (__extracted < __n
1004                      && !_Traits::eq_int_type(__c, __eof)
1005                      && !__ct.is(__ctype_base::space,
1006                                  _Traits::to_char_type(__c)))
1007                 {
1008                   if (__len == sizeof(__buf) / sizeof(_CharT))
1009                     {
1010                       __str.append(__buf, sizeof(__buf) / sizeof(_CharT));
1011                       __len = 0;
1012                     }
1013                   __buf[__len++] = _Traits::to_char_type(__c);
1014                   ++__extracted;
1015                   __c = __in.rdbuf()->snextc();
1016                 }
1017               __str.append(__buf, __len);
1018
1019               if (_Traits::eq_int_type(__c, __eof))
1020                 __err |= __ios_base::eofbit;
1021               __in.width(0);
1022             }
1023           __catch(__cxxabiv1::__forced_unwind&)
1024             {
1025               __in._M_setstate(__ios_base::badbit);
1026               __throw_exception_again;
1027             }
1028           __catch(...)
1029             {
1030               // _GLIBCXX_RESOLVE_LIB_DEFECTS
1031               // 91. Description of operator>> and getline() for string<>
1032               // might cause endless loop
1033               __in._M_setstate(__ios_base::badbit);
1034             }
1035         }
1036       // 211.  operator>>(istream&, string&) doesn't set failbit
1037       if (!__extracted)
1038         __err |= __ios_base::failbit;
1039       if (__err)
1040         __in.setstate(__err);
1041       return __in;
1042     }
1043
1044   template<typename _CharT, typename _Traits, typename _Alloc>
1045     basic_istream<_CharT, _Traits>&
1046     getline(basic_istream<_CharT, _Traits>& __in,
1047             basic_string<_CharT, _Traits, _Alloc>& __str, _CharT __delim)
1048     {
1049       typedef basic_istream<_CharT, _Traits>            __istream_type;
1050       typedef basic_string<_CharT, _Traits, _Alloc>     __string_type;
1051       typedef typename __istream_type::ios_base         __ios_base;
1052       typedef typename __istream_type::int_type         __int_type;
1053       typedef typename __string_type::size_type         __size_type;
1054
1055       __size_type __extracted = 0;
1056       const __size_type __n = __str.max_size();
1057       typename __ios_base::iostate __err = __ios_base::goodbit;
1058       typename __istream_type::sentry __cerb(__in, true);
1059       if (__cerb)
1060         {
1061           __try
1062             {
1063               __str.erase();
1064               const __int_type __idelim = _Traits::to_int_type(__delim);
1065               const __int_type __eof = _Traits::eof();
1066               __int_type __c = __in.rdbuf()->sgetc();
1067
1068               while (__extracted < __n
1069                      && !_Traits::eq_int_type(__c, __eof)
1070                      && !_Traits::eq_int_type(__c, __idelim))
1071                 {
1072                   __str += _Traits::to_char_type(__c);
1073                   ++__extracted;
1074                   __c = __in.rdbuf()->snextc();
1075                 }
1076
1077               if (_Traits::eq_int_type(__c, __eof))
1078                 __err |= __ios_base::eofbit;
1079               else if (_Traits::eq_int_type(__c, __idelim))
1080                 {
1081                   ++__extracted;
1082                   __in.rdbuf()->sbumpc();
1083                 }
1084               else
1085                 __err |= __ios_base::failbit;
1086             }
1087           __catch(__cxxabiv1::__forced_unwind&)
1088             {
1089               __in._M_setstate(__ios_base::badbit);
1090               __throw_exception_again;
1091             }
1092           __catch(...)
1093             {
1094               // _GLIBCXX_RESOLVE_LIB_DEFECTS
1095               // 91. Description of operator>> and getline() for string<>
1096               // might cause endless loop
1097               __in._M_setstate(__ios_base::badbit);
1098             }
1099         }
1100       if (!__extracted)
1101         __err |= __ios_base::failbit;
1102       if (__err)
1103         __in.setstate(__err);
1104       return __in;
1105     }
1106
1107   // Inhibit implicit instantiations for required instantiations,
1108   // which are defined via explicit instantiations elsewhere.
1109   // NB: This syntax is a GNU extension.
1110 #if _GLIBCXX_EXTERN_TEMPLATE > 0
1111   extern template class basic_string<char>;
1112   extern template
1113     basic_istream<char>&
1114     operator>>(basic_istream<char>&, string&);
1115   extern template
1116     basic_ostream<char>&
1117     operator<<(basic_ostream<char>&, const string&);
1118   extern template
1119     basic_istream<char>&
1120     getline(basic_istream<char>&, string&, char);
1121   extern template
1122     basic_istream<char>&
1123     getline(basic_istream<char>&, string&);
1124
1125 #ifdef _GLIBCXX_USE_WCHAR_T
1126   extern template class basic_string<wchar_t>;
1127   extern template
1128     basic_istream<wchar_t>&
1129     operator>>(basic_istream<wchar_t>&, wstring&);
1130   extern template
1131     basic_ostream<wchar_t>&
1132     operator<<(basic_ostream<wchar_t>&, const wstring&);
1133   extern template
1134     basic_istream<wchar_t>&
1135     getline(basic_istream<wchar_t>&, wstring&, wchar_t);
1136   extern template
1137     basic_istream<wchar_t>&
1138     getline(basic_istream<wchar_t>&, wstring&);
1139 #endif
1140 #endif
1141
1142 _GLIBCXX_END_NAMESPACE
1143
1144 #endif