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
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 2, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 //
  32 // ISO C++ 14882: 21  Strings library
  33 //
  34
  35 // This file is included by <string>.  It is not meant to be included
  36 // separately.
  37
  38 // Written by Jason Merrill based upon the specification by Takanori Adachi
  39 // in ANSI X3J16/94-0013R2.  Rewritten by Nathan Myers to ISO-14882.
  40
  41 #ifndef _BASIC_STRING_TCC
  42 #define _BASIC_STRING_TCC 1
  43
  44 #pragma GCC system_header
  45
  46 namespace std
  47 {
  48   template<typename _Type>
  49     inline bool
  50     __is_null_pointer(_Type* __ptr)
  51     { return __ptr == 0; }
  52
  53   template<typename _Type>
  54     inline bool
  55     __is_null_pointer(_Type)
  56     { return false; }
  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>::
  61     _Rep::_S_max_size = (((npos - sizeof(_Rep_base))/sizeof(_CharT)) - 1) / 4;
  62
  63   template<typename _CharT, typename _Traits, typename _Alloc>
  64     const _CharT
  65     basic_string<_CharT, _Traits, _Alloc>::
  66     _Rep::_S_terminal = _CharT();
  67
  68   template<typename _CharT, typename _Traits, typename _Alloc>
  69     const typename basic_string<_CharT, _Traits, _Alloc>::size_type
  70     basic_string<_CharT, _Traits, _Alloc>::npos;
  71
  72   // Linker sets _S_empty_rep_storage to all 0s (one reference, empty string)
  73   // at static init time (before static ctors are run).
  74   template<typename _CharT, typename _Traits, typename _Alloc>
  75     typename basic_string<_CharT, _Traits, _Alloc>::size_type
  76     basic_string<_CharT, _Traits, _Alloc>::_Rep::_S_empty_rep_storage[
  77     (sizeof(_Rep_base) + sizeof(_CharT) + sizeof(size_type) - 1) /
  78       sizeof(size_type)];
  79
  80   // NB: This is the special case for Input Iterators, used in
  81   // istreambuf_iterators, etc.
  82   // Input Iterators have a cost structure very different from
  83   // pointers, calling for a different coding style.
  84   template<typename _CharT, typename _Traits, typename _Alloc>
  85     template<typename _InIterator>
  86       _CharT*
  87       basic_string<_CharT, _Traits, _Alloc>::
  88       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
  89                    input_iterator_tag)
  90       {
  91         if (__beg == __end && __a == _Alloc())
  92           return _S_empty_rep()._M_refdata();
  93         // Avoid reallocation for common case.
  94         _CharT __buf[100];
  95         size_type __i = 0;
  96         while (__beg != __end && __i < sizeof(__buf) / sizeof(_CharT))
  97           {
  98             __buf[__i++] = *__beg;
  99             ++__beg;
 100           }
 101         _Rep* __r = _Rep::_S_create(__i, __a);
 102         traits_type::copy(__r->_M_refdata(), __buf, __i);
 103         __r->_M_length = __i;
 104         try
 105           {
 106             // NB: this loop looks precisely this way because
 107             // it avoids comparing __beg != __end any more
 108             // than strictly necessary; != might be expensive!
 109             for (;;)
 110               {
 111                 _CharT* __p = __r->_M_refdata() + __r->_M_length;
 112                 _CharT* __last = __r->_M_refdata() + __r->_M_capacity;
 113                 for (;;)
 114                   {
 115                     if (__beg == __end)
 116                       {
 117                         __r->_M_length = __p - __r->_M_refdata();
 118                         *__p = _Rep::_S_terminal;       // grrr.
 119                         return __r->_M_refdata();
 120                       }
 121                     if (__p == __last)
 122                       break;
 123                     *__p++ = *__beg;
 124                     ++__beg;
 125                   }
 126                 // Allocate more space.
 127                 const size_type __len = __p - __r->_M_refdata();
 128                 _Rep* __another = _Rep::_S_create(__len + 1, __a);
 129                 traits_type::copy(__another->_M_refdata(),
 130                                   __r->_M_refdata(), __len);
 131                 __r->_M_destroy(__a);
 132                 __r = __another;
 133                 __r->_M_length = __len;
 134               }
 135           }
 136         catch(...)
 137           {
 138             __r->_M_destroy(__a);
 139             __throw_exception_again;
 140           }
 141         return 0;
 142       }
 143
 144   template<typename _CharT, typename _Traits, typename _Alloc>
 145     template <class _InIterator>
 146       _CharT*
 147       basic_string<_CharT, _Traits, _Alloc>::
 148       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
 149                    forward_iterator_tag)
 150       {
 151         if (__beg == __end && __a == _Alloc())
 152           return _S_empty_rep()._M_refdata();
 153
 154         // NB: Not required, but considered best practice.
 155         if (__builtin_expect(__is_null_pointer(__beg), 0))
 156           __throw_logic_error("basic_string::_S_construct NULL not valid");
 157
 158         const size_type __dnew = static_cast<size_type>(std::distance(__beg, __end));
 159
 160         // Check for out_of_range and length_error exceptions.
 161         _Rep* __r = _Rep::_S_create(__dnew, __a);
 162         try
 163           { _S_copy_chars(__r->_M_refdata(), __beg, __end); }
 164         catch(...)
 165           {
 166             __r->_M_destroy(__a);
 167             __throw_exception_again;
 168           }
 169         __r->_M_length = __dnew;
 170
 171         __r->_M_refdata()[__dnew] = _Rep::_S_terminal;  // grrr.
 172         return __r->_M_refdata();
 173       }
 174
 175   template<typename _CharT, typename _Traits, typename _Alloc>
 176     _CharT*
 177     basic_string<_CharT, _Traits, _Alloc>::
 178     _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
 179     {
 180       if (__n == 0 && __a == _Alloc())
 181         return _S_empty_rep()._M_refdata();
 182
 183       // Check for out_of_range and length_error exceptions.
 184       _Rep* __r = _Rep::_S_create(__n, __a);
 185       if (__n)
 186         traits_type::assign(__r->_M_refdata(), __n, __c);
 187
 188       __r->_M_length = __n;
 189       __r->_M_refdata()[__n] = _Rep::_S_terminal;  // grrr
 190       return __r->_M_refdata();
 191     }
 192
 193   template<typename _CharT, typename _Traits, typename _Alloc>
 194     basic_string<_CharT, _Traits, _Alloc>::
 195     basic_string(const basic_string& __str)
 196     : _M_dataplus(__str._M_rep()->_M_grab(_Alloc(), __str.get_allocator()),
 197                  __str.get_allocator())
 198     { }
 199
 200   template<typename _CharT, typename _Traits, typename _Alloc>
 201     basic_string<_CharT, _Traits, _Alloc>::
 202     basic_string(const _Alloc& __a)
 203     : _M_dataplus(_S_construct(size_type(), _CharT(), __a), __a)
 204     { }
 205
 206   template<typename _CharT, typename _Traits, typename _Alloc>
 207     basic_string<_CharT, _Traits, _Alloc>::
 208     basic_string(const basic_string& __str, size_type __pos, size_type __n)
 209     : _M_dataplus(_S_construct(__str._M_ibegin()
 210                                + __str._M_check(__pos, "basic_string::basic_string"),
 211                                __str._M_ibegin() + __pos + __str._M_limit(__pos, __n),
 212                                _Alloc()), _Alloc())
 213     { }
 214
 215   template<typename _CharT, typename _Traits, typename _Alloc>
 216     basic_string<_CharT, _Traits, _Alloc>::
 217     basic_string(const basic_string& __str, size_type __pos,
 218                  size_type __n, const _Alloc& __a)
 219     : _M_dataplus(_S_construct(__str._M_ibegin()
 220                                + __str._M_check(__pos, "basic_string::basic_string"),
 221                                __str._M_ibegin() + __pos + __str._M_limit(__pos, __n),
 222                                __a), __a)
 223     { }
 224
 225   // TBD: DPG annotate
 226   template<typename _CharT, typename _Traits, typename _Alloc>
 227     basic_string<_CharT, _Traits, _Alloc>::
 228     basic_string(const _CharT* __s, size_type __n, const _Alloc& __a)
 229     : _M_dataplus(_S_construct(__s, __s + __n, __a), __a)
 230     { }
 231
 232   // TBD: DPG annotate
 233   template<typename _CharT, typename _Traits, typename _Alloc>
 234     basic_string<_CharT, _Traits, _Alloc>::
 235     basic_string(const _CharT* __s, const _Alloc& __a)
 236     : _M_dataplus(_S_construct(__s, __s ? __s + traits_type::length(__s) :
 237                                __s + npos, __a), __a)
 238     { }
 239
 240   template<typename _CharT, typename _Traits, typename _Alloc>
 241     basic_string<_CharT, _Traits, _Alloc>::
 242     basic_string(size_type __n, _CharT __c, const _Alloc& __a)
 243     : _M_dataplus(_S_construct(__n, __c, __a), __a)
 244     { }
 245
 246   // TBD: DPG annotate
 247   template<typename _CharT, typename _Traits, typename _Alloc>
 248     template<typename _InputIterator>
 249     basic_string<_CharT, _Traits, _Alloc>::
 250     basic_string(_InputIterator __beg, _InputIterator __end, const _Alloc& __a)
 251     : _M_dataplus(_S_construct(__beg, __end, __a), __a)
 252     { }
 253
 254   template<typename _CharT, typename _Traits, typename _Alloc>
 255     basic_string<_CharT, _Traits, _Alloc>&
 256     basic_string<_CharT, _Traits, _Alloc>::
 257     assign(const basic_string& __str)
 258     {
 259       if (_M_rep() != __str._M_rep())
 260         {
 261           // XXX MT
 262           allocator_type __a = this->get_allocator();
 263           _CharT* __tmp = __str._M_rep()->_M_grab(__a, __str.get_allocator());
 264           _M_rep()->_M_dispose(__a);
 265           _M_data(__tmp);
 266         }
 267       return *this;
 268     }
 269
 270    template<typename _CharT, typename _Traits, typename _Alloc>
 271      basic_string<_CharT, _Traits, _Alloc>&
 272      basic_string<_CharT, _Traits, _Alloc>::
 273      assign(const _CharT* __s, size_type __n)
 274      {
 275        __glibcxx_requires_string_len(__s, __n);
 276        if (__n > this->max_size())
 277          __throw_length_error("basic_string::assign");
 278        if (_M_rep()->_M_is_shared() || less<const _CharT*>()(__s, _M_data())
 279            || less<const _CharT*>()(_M_data() + this->size(), __s))
 280          return _M_replace_safe(size_type(0), this->size(), __s, __n);
 281        else
 282          {
 283            // Work in-place
 284            const size_type __pos = __s - _M_data();
 285            if (__pos >= __n)
 286              traits_type::copy(_M_data(), __s, __n);
 287            else if (__pos)
 288              traits_type::move(_M_data(), __s, __n);
 289            _M_rep()->_M_length = __n;
 290            _M_data()[__n] = _Rep::_S_terminal;  // grr.
 291            return *this;
 292          }
 293      }
 294
 295    template<typename _CharT, typename _Traits, typename _Alloc>
 296      basic_string<_CharT, _Traits, _Alloc>&
 297      basic_string<_CharT, _Traits, _Alloc>::
 298      insert(size_type __pos1, const basic_string& __str,
 299             size_type __pos2, size_type __n)
 300      {
 301        return this->insert(__pos1, __str._M_data()
 302                            + __str._M_check(__pos2, "basic_string::insert"),
 303                            __str._M_limit(__pos2, __n));
 304      }
 305
 306    template<typename _CharT, typename _Traits, typename _Alloc>
 307      basic_string<_CharT, _Traits, _Alloc>&
 308      basic_string<_CharT, _Traits, _Alloc>::
 309      insert(size_type __pos, const _CharT* __s, size_type __n)
 310      {
 311        __glibcxx_requires_string_len(__s, __n);
 312        __pos = _M_check(__pos, "basic_string::insert");
 313        if (this->max_size() - this->size() < __n)
 314          __throw_length_error("basic_string::insert");
 315        if (_M_rep()->_M_is_shared() || less<const _CharT*>()(__s, _M_data())
 316            || less<const _CharT*>()(_M_data() + this->size(), __s))
 317          return _M_replace_safe(__pos, size_type(0), __s, __n);
 318        else
 319          {
 320            // Work in-place. If _M_mutate reallocates the string, __s
 321            // does not point anymore to valid data, therefore we save its
 322            // offset, then we restore it.
 323            const size_type __off = __s - _M_data();
 324            _M_mutate(__pos, 0, __n);
 325            __s = _M_data() + __off;
 326            _CharT* __p = _M_data() + __pos;
 327            if (__s  + __n <= __p)
 328              traits_type::copy(__p, __s, __n);
 329            else if (__s >= __p)
 330              traits_type::copy(__p, __s + __n, __n);
 331            else
 332              {
 333                traits_type::copy(__p, __s, __p - __s);
 334                traits_type::copy(__p + (__p-__s), __p + __n, __n - (__p-__s));
 335              }
 336            return *this;
 337          }
 338      }
 339
 340    template<typename _CharT, typename _Traits, typename _Alloc>
 341      basic_string<_CharT, _Traits, _Alloc>&
 342      basic_string<_CharT, _Traits, _Alloc>::
 343      replace(size_type __pos, size_type __n1, const _CharT* __s,
 344              size_type __n2)
 345      {
 346        __glibcxx_requires_string_len(__s, __n2);
 347        __pos = _M_check(__pos, "basic_string::replace");
 348        __n1 = _M_limit(__pos, __n1);
 349        if (this->max_size() - (this->size() - __n1) < __n2)
 350          __throw_length_error("basic_string::replace");
 351        if (_M_rep()->_M_is_shared() || less<const _CharT*>()(__s, _M_data())
 352            || less<const _CharT*>()(_M_data() + this->size(), __s))
 353          return _M_replace_safe(__pos, __n1, __s, __n2);
 354        else
 355          {
 356            // Todo: optimized in-place replace.
 357            const basic_string __tmp(__s, __n2);
 358            return _M_replace_safe(__pos, __n1, __tmp._M_data(), __n2);
 359          }
 360      }
 361
 362   template<typename _CharT, typename _Traits, typename _Alloc>
 363     void
 364     basic_string<_CharT, _Traits, _Alloc>::_Rep::
 365     _M_destroy(const _Alloc& __a) throw ()
 366     {
 367       if (this == &_S_empty_rep())
 368         return;
 369       const size_type __size = sizeof(_Rep_base) +
 370                                (this->_M_capacity + 1) * sizeof(_CharT);
 371       _Raw_bytes_alloc(__a).deallocate(reinterpret_cast<char*>(this), __size);
 372     }
 373
 374   template<typename _CharT, typename _Traits, typename _Alloc>
 375     void
 376     basic_string<_CharT, _Traits, _Alloc>::_M_leak_hard()
 377     {
 378       if (_M_rep() == &_S_empty_rep())
 379         return;
 380       if (_M_rep()->_M_is_shared())
 381         _M_mutate(0, 0, 0);
 382       _M_rep()->_M_set_leaked();
 383     }
 384
 385   // _M_mutate and, below, _M_clone, include, in the same form, an exponential
 386   // growth policy, necessary to meet amortized linear time requirements of
 387   // the library: see http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
 388   // The policy is active for allocations requiring an amount of memory above
 389   // system pagesize. This is consistent with the requirements of the standard:
 390   // see, f.i., http://gcc.gnu.org/ml/libstdc++/2001-07/msg00130.html
 391   template<typename _CharT, typename _Traits, typename _Alloc>
 392     void
 393     basic_string<_CharT, _Traits, _Alloc>::
 394     _M_mutate(size_type __pos, size_type __len1, size_type __len2)
 395     {
 396       const size_type __old_size = this->size();
 397       const size_type __new_size = __old_size + __len2 - __len1;
 398       const _CharT*        __src = _M_data()  + __pos + __len1;
 399       const size_type __how_much = __old_size - __pos - __len1;
 400
 401       if (_M_rep() == &_S_empty_rep()
 402           || _M_rep()->_M_is_shared() || __new_size > capacity())
 403         {
 404           // Must reallocate.
 405           allocator_type __a = get_allocator();
 406           // See below (_S_create) for the meaning and value of these
 407           // constants.
 408           const size_type __pagesize = 4096;
 409           const size_type __malloc_header_size = 4 * sizeof (void*);
 410           // The biggest string which fits in a memory page
 411           const size_type __page_capacity = (__pagesize - __malloc_header_size
 412                                              - sizeof(_Rep) - sizeof(_CharT))
 413                                              / sizeof(_CharT);
 414           _Rep* __r;
 415           if (__new_size > capacity() && __new_size > __page_capacity)
 416             // Growing exponentially.
 417             __r = _Rep::_S_create(__new_size > 2*capacity() ?
 418                                   __new_size : 2*capacity(), __a);
 419           else
 420             __r = _Rep::_S_create(__new_size, __a);
 421
 422           if (__pos)
 423             traits_type::copy(__r->_M_refdata(), _M_data(), __pos);
 424           if (__how_much)
 425             traits_type::copy(__r->_M_refdata() + __pos + __len2,
 426                               __src, __how_much);
 427
 428           _M_rep()->_M_dispose(__a);
 429           _M_data(__r->_M_refdata());
 430         }
 431       else if (__how_much && __len1 != __len2)
 432         {
 433           // Work in-place
 434           traits_type::move(_M_data() + __pos + __len2, __src, __how_much);
 435         }
 436       _M_rep()->_M_set_sharable();
 437       _M_rep()->_M_length = __new_size;
 438       _M_data()[__new_size] = _Rep::_S_terminal; // grrr. (per 21.3.4)
 439       // You cannot leave those LWG people alone for a second.
 440     }
 441
 442   template<typename _CharT, typename _Traits, typename _Alloc>
 443     void
 444     basic_string<_CharT, _Traits, _Alloc>::reserve(size_type __res)
 445     {
 446       if (__res != this->capacity() || _M_rep()->_M_is_shared())
 447         {
 448           if (__res > this->max_size())
 449             __throw_length_error("basic_string::reserve");
 450           // Make sure we don't shrink below the current size
 451           if (__res < this->size())
 452             __res = this->size();
 453           allocator_type __a = get_allocator();
 454           _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
 455           _M_rep()->_M_dispose(__a);
 456           _M_data(__tmp);
 457         }
 458     }
 459
 460   template<typename _CharT, typename _Traits, typename _Alloc>
 461     void basic_string<_CharT, _Traits, _Alloc>::swap(basic_string& __s)
 462     {
 463       if (_M_rep()->_M_is_leaked())
 464         _M_rep()->_M_set_sharable();
 465       if (__s._M_rep()->_M_is_leaked())
 466         __s._M_rep()->_M_set_sharable();
 467       if (this->get_allocator() == __s.get_allocator())
 468         {
 469           _CharT* __tmp = _M_data();
 470           _M_data(__s._M_data());
 471           __s._M_data(__tmp);
 472         }
 473       // The code below can usually be optimized away.
 474       else
 475         {
 476           basic_string __tmp1(_M_ibegin(), _M_iend(), __s.get_allocator());
 477           basic_string __tmp2(__s._M_ibegin(), __s._M_iend(),
 478                               this->get_allocator());
 479           *this = __tmp2;
 480           __s = __tmp1;
 481         }
 482     }
 483
 484   template<typename _CharT, typename _Traits, typename _Alloc>
 485     typename basic_string<_CharT, _Traits, _Alloc>::_Rep*
 486     basic_string<_CharT, _Traits, _Alloc>::_Rep::
 487     _S_create(size_t __capacity, const _Alloc& __alloc)
 488     {
 489       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
 490       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 491       // 83.  String::npos vs. string::max_size()
 492       if (__capacity > _S_max_size)
 493         __throw_length_error("basic_string::_S_create");
 494
 495       // NB: Need an array of char_type[__capacity], plus a
 496       // terminating null char_type() element, plus enough for the
 497       // _Rep data structure. Whew. Seemingly so needy, yet so elemental.
 498       size_t __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep_base);
 499
 500       // The standard places no restriction on allocating more memory
 501       // than is strictly needed within this layer at the moment or as
 502       // requested by an explicit application call to reserve().  Many
 503       // malloc implementations perform quite poorly when an
 504       // application attempts to allocate memory in a stepwise fashion
 505       // growing each allocation size by only 1 char.  Additionally,
 506       // it makes little sense to allocate less linear memory than the
 507       // natural blocking size of the malloc implementation.
 508       // Unfortunately, we would need a somewhat low-level calculation
 509       // with tuned parameters to get this perfect for any particular
 510       // malloc implementation.  Fortunately, generalizations about
 511       // common features seen among implementations seems to suffice.
 512
 513       // __pagesize need not match the actual VM page size for good
 514       // results in practice, thus we pick a common value on the low
 515       // side.  __malloc_header_size is an estimate of the amount of
 516       // overhead per memory allocation (in practice seen N * sizeof
 517       // (void*) where N is 0, 2 or 4).  According to folklore,
 518       // picking this value on the high side is better than
 519       // low-balling it (especially when this algorithm is used with
 520       // malloc implementations that allocate memory blocks rounded up
 521       // to a size which is a power of 2).
 522       const size_t __pagesize = 4096; // must be 2^i * __subpagesize
 523       const size_t __subpagesize = 128; // should be >> __malloc_header_size
 524       const size_t __malloc_header_size = 4 * sizeof (void*);
 525       if ((__size + __malloc_header_size) > __pagesize)
 526         {
 527           const size_t __extra =
 528             (__pagesize - ((__size + __malloc_header_size) % __pagesize))
 529             % __pagesize;
 530           __capacity += __extra / sizeof(_CharT);
 531           __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep_base);
 532         }
 533       else if (__size > __subpagesize)
 534         {
 535           const size_t __extra =
 536             (__subpagesize - ((__size + __malloc_header_size) % __subpagesize))
 537             % __subpagesize;
 538           __capacity += __extra / sizeof(_CharT);
 539           __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep_base);
 540         }
 541
 542       // NB: Might throw, but no worries about a leak, mate: _Rep()
 543       // does not throw.
 544       void* __place = _Raw_bytes_alloc(__alloc).allocate(__size);
 545       _Rep *__p = new (__place) _Rep;
 546       __p->_M_capacity = __capacity;
 547       __p->_M_set_sharable();  // One reference.
 548       __p->_M_length = 0;
 549       return __p;
 550     }
 551
 552   template<typename _CharT, typename _Traits, typename _Alloc>
 553     _CharT*
 554     basic_string<_CharT, _Traits, _Alloc>::_Rep::
 555     _M_clone(const _Alloc& __alloc, size_type __res)
 556     {
 557       // Requested capacity of the clone.
 558       const size_type __requested_cap = this->_M_length + __res;
 559       // See above (_S_create) for the meaning and value of these constants.
 560       const size_type __pagesize = 4096;
 561       const size_type __malloc_header_size = 4 * sizeof (void*);
 562       // The biggest string which fits in a memory page.
 563       const size_type __page_capacity =
 564         (__pagesize - __malloc_header_size - sizeof(_Rep_base) - sizeof(_CharT))
 565         / sizeof(_CharT);
 566       _Rep* __r;
 567       if (__requested_cap > this->_M_capacity
 568           && __requested_cap > __page_capacity)
 569         // Growing exponentially.
 570         __r = _Rep::_S_create(__requested_cap > 2*this->_M_capacity ?
 571                               __requested_cap : 2*this->_M_capacity, __alloc);
 572       else
 573         __r = _Rep::_S_create(__requested_cap, __alloc);
 574
 575       if (this->_M_length)
 576         traits_type::copy(__r->_M_refdata(), _M_refdata(),
 577                           this->_M_length);
 578
 579       __r->_M_length = this->_M_length;
 580       __r->_M_refdata()[this->_M_length] = _Rep::_S_terminal;
 581       return __r->_M_refdata();
 582     }
 583
 584   template<typename _CharT, typename _Traits, typename _Alloc>
 585     void
 586     basic_string<_CharT, _Traits, _Alloc>::resize(size_type __n, _CharT __c)
 587     {
 588       if (__n > max_size())
 589         __throw_length_error("basic_string::resize");
 590       const size_type __size = this->size();
 591       if (__size < __n)
 592         this->append(__n - __size, __c);
 593       else if (__n < __size)
 594         this->erase(__n);
 595       // else nothing (in particular, avoid calling _M_mutate() unnecessarily.)
 596     }
 597
 598   template<typename _CharT, typename _Traits, typename _Alloc>
 599     template<typename _InputIterator>
 600       basic_string<_CharT, _Traits, _Alloc>&
 601       basic_string<_CharT, _Traits, _Alloc>::
 602       _M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator __k1,
 603                           _InputIterator __k2, __false_type)
 604       {
 605         const basic_string __s(__k1, __k2);
 606         const size_type __n1 = __i2 - __i1;
 607         if (this->max_size() - (this->size() - __n1) < __s.size())
 608           __throw_length_error("basic_string::_M_replace_dispatch");
 609         return _M_replace_safe(__i1 - _M_ibegin(), __n1, __s._M_data(),
 610                                __s.size());
 611       }
 612
 613   // This helper doesn't buffer internally and can be used in "safe" situations,
 614   // i.e., when source and destination ranges are known to not overlap.
 615   template<typename _CharT, typename _Traits, typename _Alloc>
 616     basic_string<_CharT, _Traits, _Alloc>&
 617     basic_string<_CharT, _Traits, _Alloc>::
 618     _M_replace_safe(size_type __pos1, size_type __n1, const _CharT* __s,
 619                     size_type __n2)
 620     {
 621       _M_mutate(__pos1, __n1, __n2);
 622       if (__n2)
 623         traits_type::copy(_M_data() + __pos1, __s, __n2);
 624       return *this;
 625     }
 626
 627   template<typename _CharT, typename _Traits, typename _Alloc>
 628     basic_string<_CharT, _Traits, _Alloc>&
 629     basic_string<_CharT, _Traits, _Alloc>::
 630     _M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
 631                    _CharT __c)
 632     {
 633       if (this->max_size() - (this->size() - __n1) < __n2)
 634         __throw_length_error("basic_string::_M_replace_aux");
 635       _M_mutate(__pos1, __n1, __n2);
 636       if (__n2)
 637         traits_type::assign(_M_data() + __pos1, __n2, __c);
 638       return *this;
 639     }
 640
 641   template<typename _CharT, typename _Traits, typename _Alloc>
 642     basic_string<_CharT, _Traits, _Alloc>&
 643     basic_string<_CharT, _Traits, _Alloc>::
 644     append(const basic_string& __str)
 645     {
 646       // Iff appending itself, string needs to pre-reserve the
 647       // correct size so that _M_mutate does not clobber the
 648       // pointer __str._M_data() formed here.
 649       const size_type __size = __str.size();
 650       const size_type __len = __size + this->size();
 651       if (__len > this->capacity())
 652         this->reserve(__len);
 653       return _M_replace_safe(this->size(), size_type(0), __str._M_data(),
 654                              __str.size());
 655     }
 656
 657   template<typename _CharT, typename _Traits, typename _Alloc>
 658     basic_string<_CharT, _Traits, _Alloc>&
 659     basic_string<_CharT, _Traits, _Alloc>::
 660     append(const basic_string& __str, size_type __pos, size_type __n)
 661     {
 662       // Iff appending itself, string needs to pre-reserve the
 663       // correct size so that _M_mutate does not clobber the
 664       // pointer __str._M_data() formed here.
 665       __pos = __str._M_check(__pos, "basic_string::append");
 666       __n = __str._M_limit(__pos, __n);
 667       const size_type __len = __n + this->size();
 668       if (__len > this->capacity())
 669         this->reserve(__len);
 670       return _M_replace_safe(this->size(), size_type(0), __str._M_data()
 671                              + __pos, __n);
 672     }
 673
 674   template<typename _CharT, typename _Traits, typename _Alloc>
 675     basic_string<_CharT, _Traits, _Alloc>&
 676     basic_string<_CharT, _Traits, _Alloc>::
 677     append(const _CharT* __s, size_type __n)
 678     {
 679       __glibcxx_requires_string_len(__s, __n);
 680       const size_type __len = __n + this->size();
 681       if (__len > this->capacity())
 682         this->reserve(__len);
 683       return _M_replace_safe(this->size(), size_type(0), __s, __n);
 684     }
 685
 686   template<typename _CharT, typename _Traits, typename _Alloc>
 687     basic_string<_CharT, _Traits, _Alloc>
 688     operator+(const _CharT* __lhs,
 689               const basic_string<_CharT, _Traits, _Alloc>& __rhs)
 690     {
 691       __glibcxx_requires_string(__lhs);
 692       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
 693       typedef typename __string_type::size_type   __size_type;
 694       const __size_type __len = _Traits::length(__lhs);
 695       __string_type __str;
 696       __str.reserve(__len + __rhs.size());
 697       __str.append(__lhs, __lhs + __len);
 698       __str.append(__rhs);
 699       return __str;
 700     }
 701
 702   template<typename _CharT, typename _Traits, typename _Alloc>
 703     basic_string<_CharT, _Traits, _Alloc>
 704     operator+(_CharT __lhs, const basic_string<_CharT, _Traits, _Alloc>& __rhs)
 705     {
 706       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
 707       typedef typename __string_type::size_type   __size_type;
 708       __string_type __str;
 709       const __size_type __len = __rhs.size();
 710       __str.reserve(__len + 1);
 711       __str.append(__size_type(1), __lhs);
 712       __str.append(__rhs);
 713       return __str;
 714     }
 715
 716   template<typename _CharT, typename _Traits, typename _Alloc>
 717     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 718     basic_string<_CharT, _Traits, _Alloc>::
 719     copy(_CharT* __s, size_type __n, size_type __pos) const
 720     {
 721       __pos = _M_check(__pos, "basic_string::copy");
 722       __n = _M_limit(__pos, __n);
 723       __glibcxx_requires_string_len(__s, __n);
 724       if (__n)
 725         traits_type::copy(__s, _M_data() + __pos, __n);
 726       // 21.3.5.7 par 3: do not append null.  (good.)
 727       return __n;
 728     }
 729
 730   template<typename _CharT, typename _Traits, typename _Alloc>
 731     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 732     basic_string<_CharT, _Traits, _Alloc>::
 733     find(const _CharT* __s, size_type __pos, size_type __n) const
 734     {
 735       __glibcxx_requires_string_len(__s, __n);
 736       const size_type __size = this->size();
 737       const _CharT* __data = _M_data();
 738       for (; __pos + __n <= __size; ++__pos)
 739         if (traits_type::compare(__data + __pos, __s, __n) == 0)
 740           return __pos;
 741       return npos;
 742     }
 743
 744   template<typename _CharT, typename _Traits, typename _Alloc>
 745     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 746     basic_string<_CharT, _Traits, _Alloc>::
 747     find(_CharT __c, size_type __pos) const
 748     {
 749       const size_type __size = this->size();
 750       size_type __ret = npos;
 751       if (__pos < __size)
 752         {
 753           const _CharT* __data = _M_data();
 754           const size_type __n = __size - __pos;
 755           const _CharT* __p = traits_type::find(__data + __pos, __n, __c);
 756           if (__p)
 757             __ret = __p - __data;
 758         }
 759       return __ret;
 760     }
 761
 762   template<typename _CharT, typename _Traits, typename _Alloc>
 763     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 764     basic_string<_CharT, _Traits, _Alloc>::
 765     rfind(const _CharT* __s, size_type __pos, size_type __n) const
 766     {
 767       __glibcxx_requires_string_len(__s, __n);
 768       const size_type __size = this->size();
 769       if (__n <= __size)
 770         {
 771           __pos = std::min(size_type(__size - __n), __pos);
 772           const _CharT* __data = _M_data();
 773           do
 774             {
 775               if (traits_type::compare(__data + __pos, __s, __n) == 0)
 776                 return __pos;
 777             }
 778           while (__pos-- > 0);
 779         }
 780       return npos;
 781     }
 782
 783   template<typename _CharT, typename _Traits, typename _Alloc>
 784     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 785     basic_string<_CharT, _Traits, _Alloc>::
 786     rfind(_CharT __c, size_type __pos) const
 787     {
 788       const size_type __size = this->size();
 789       if (__size)
 790         {
 791           __pos = std::min(size_type(__size - 1), __pos);
 792           for (++__pos; __pos-- > 0; )
 793             if (traits_type::eq(_M_data()[__pos], __c))
 794               return __pos;
 795         }
 796       return npos;
 797     }
 798
 799   template<typename _CharT, typename _Traits, typename _Alloc>
 800     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 801     basic_string<_CharT, _Traits, _Alloc>::
 802     find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
 803     {
 804       __glibcxx_requires_string_len(__s, __n);
 805       for (; __n && __pos < this->size(); ++__pos)
 806         {
 807           const _CharT* __p = traits_type::find(__s, __n, _M_data()[__pos]);
 808           if (__p)
 809             return __pos;
 810         }
 811       return npos;
 812     }
 813
 814   template<typename _CharT, typename _Traits, typename _Alloc>
 815     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 816     basic_string<_CharT, _Traits, _Alloc>::
 817     find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
 818     {
 819       __glibcxx_requires_string_len(__s, __n);
 820       size_type __size = this->size();
 821       if (__size && __n)
 822         {
 823           if (--__size > __pos)
 824             __size = __pos;
 825           do
 826             {
 827               if (traits_type::find(__s, __n, _M_data()[__size]))
 828                 return __size;
 829             }
 830           while (__size-- != 0);
 831         }
 832       return npos;
 833     }
 834
 835   template<typename _CharT, typename _Traits, typename _Alloc>
 836     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 837     basic_string<_CharT, _Traits, _Alloc>::
 838     find_first_not_of(const _CharT* __s, size_type __pos, size_type __n) const
 839     {
 840       __glibcxx_requires_string_len(__s, __n);
 841       for (; __pos < this->size(); ++__pos)
 842         if (!traits_type::find(__s, __n, _M_data()[__pos]))
 843           return __pos;
 844       return npos;
 845     }
 846
 847   template<typename _CharT, typename _Traits, typename _Alloc>
 848     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 849     basic_string<_CharT, _Traits, _Alloc>::
 850     find_first_not_of(_CharT __c, size_type __pos) const
 851     {
 852       for (; __pos < this->size(); ++__pos)
 853         if (!traits_type::eq(_M_data()[__pos], __c))
 854           return __pos;
 855       return npos;
 856     }
 857
 858   template<typename _CharT, typename _Traits, typename _Alloc>
 859     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 860     basic_string<_CharT, _Traits, _Alloc>::
 861     find_last_not_of(const _CharT* __s, size_type __pos, size_type __n) const
 862     {
 863       __glibcxx_requires_string_len(__s, __n);
 864       const size_type __size = this->size();
 865       if (__size)
 866         {
 867           __pos = std::min(size_type(__size - 1), __pos);
 868           do
 869             {
 870               if (!traits_type::find(__s, __n, _M_data()[__pos]))
 871                 return __pos;
 872             }
 873           while (__pos--);
 874         }
 875       return npos;
 876     }
 877
 878   template<typename _CharT, typename _Traits, typename _Alloc>
 879     typename basic_string<_CharT, _Traits, _Alloc>::size_type
 880     basic_string<_CharT, _Traits, _Alloc>::
 881     find_last_not_of(_CharT __c, size_type __pos) const
 882     {
 883       const size_type __size = this->size();
 884       if (__size)
 885         {
 886           __pos = std::min(size_type(__size - 1), __pos);
 887           do
 888             {
 889               if (!traits_type::eq(_M_data()[__pos], __c))
 890                 return __pos;
 891             }
 892           while (__pos--);
 893         }
 894       return npos;
 895     }
 896
 897   template<typename _CharT, typename _Traits, typename _Alloc>
 898     int
 899     basic_string<_CharT, _Traits, _Alloc>::
 900     compare(size_type __pos, size_type __n, const basic_string& __str) const
 901     {
 902       __pos = _M_check(__pos, "basic_string::compare");
 903       __n = _M_limit(__pos, __n);
 904       const size_type __osize = __str.size();
 905       const size_type __len = std::min(__n, __osize);
 906       int __r = traits_type::compare(_M_data() + __pos, __str.data(), __len);
 907       if (!__r)
 908         __r = __n - __osize;
 909       return __r;
 910     }
 911
 912   template<typename _CharT, typename _Traits, typename _Alloc>
 913     int
 914     basic_string<_CharT, _Traits, _Alloc>::
 915     compare(size_type __pos1, size_type __n1, const basic_string& __str,
 916             size_type __pos2, size_type __n2) const
 917     {
 918       __pos1 = _M_check(__pos1, "basic_string::compare");
 919       __pos2 = __str._M_check(__pos2, "basic_string::compare");
 920       __n1 = _M_limit(__pos1, __n1);
 921       __n2 = __str._M_limit(__pos2, __n2);
 922       const size_type __len = std::min(__n1, __n2);
 923       int __r = traits_type::compare(_M_data() + __pos1,
 924                                      __str.data() + __pos2, __len);
 925       if (!__r)
 926         __r = __n1 - __n2;
 927       return __r;
 928     }
 929
 930   template<typename _CharT, typename _Traits, typename _Alloc>
 931     int
 932     basic_string<_CharT, _Traits, _Alloc>::
 933     compare(const _CharT* __s) const
 934     {
 935       __glibcxx_requires_string(__s);
 936       const size_type __size = this->size();
 937       const size_type __osize = traits_type::length(__s);
 938       const size_type __len = std::min(__size, __osize);
 939       int __r = traits_type::compare(_M_data(), __s, __len);
 940       if (!__r)
 941         __r = __size - __osize;
 942       return __r;
 943     }
 944
 945   template<typename _CharT, typename _Traits, typename _Alloc>
 946     int
 947     basic_string <_CharT, _Traits, _Alloc>::
 948     compare(size_type __pos, size_type __n1, const _CharT* __s) const
 949     {
 950       __glibcxx_requires_string(__s);
 951       __pos = _M_check(__pos, "basic_string::compare");
 952       __n1 = _M_limit(__pos, __n1);
 953       const size_type __osize = traits_type::length(__s);
 954       const size_type __len = std::min(__n1, __osize);
 955       int __r = traits_type::compare(_M_data() + __pos, __s, __len);
 956       if (!__r)
 957         __r = __n1 - __osize;
 958       return __r;
 959     }
 960
 961   template<typename _CharT, typename _Traits, typename _Alloc>
 962     int
 963     basic_string <_CharT, _Traits, _Alloc>::
 964     compare(size_type __pos, size_type __n1, const _CharT* __s,
 965             size_type __n2) const
 966     {
 967       __glibcxx_requires_string_len(__s, __n2);
 968       __pos = _M_check(__pos, "basic_string::compare");
 969       __n1 = _M_limit(__pos, __n1);
 970       const size_type __len = std::min(__n1, __n2);
 971       int __r = traits_type::compare(_M_data() + __pos, __s, __len);
 972       if (!__r)
 973         __r = __n1 - __n2;
 974       return __r;
 975     }
 976
 977   // Inhibit implicit instantiations for required instantiations,
 978   // which are defined via explicit instantiations elsewhere.
 979   // NB: This syntax is a GNU extension.
 980 #if _GLIBCXX_EXTERN_TEMPLATE
 981   extern template class basic_string<char>;
 982   extern template
 983     basic_istream<char>&
 984     operator>>(basic_istream<char>&, string&);
 985   extern template
 986     basic_ostream<char>&
 987     operator<<(basic_ostream<char>&, const string&);
 988   extern template
 989     basic_istream<char>&
 990     getline(basic_istream<char>&, string&, char);
 991   extern template
 992     basic_istream<char>&
 993     getline(basic_istream<char>&, string&);
 994
 995 #ifdef _GLIBCXX_USE_WCHAR_T
 996   extern template class basic_string<wchar_t>;
 997   extern template
 998     basic_istream<wchar_t>&
 999     operator>>(basic_istream<wchar_t>&, wstring&);
1000   extern template
1001     basic_ostream<wchar_t>&
1002     operator<<(basic_ostream<wchar_t>&, const wstring&);
1003   extern template
1004     basic_istream<wchar_t>&
1005     getline(basic_istream<wchar_t>&, wstring&, wchar_t);
1006   extern template
1007     basic_istream<wchar_t>&
1008     getline(basic_istream<wchar_t>&, wstring&);
1009 #endif
1010 #endif
1011 } // namespace std
1012
1013 #endif