libstdc++-v3/include/ext/sso_string_base.h

   1 // Short-string-optimized versatile string base -*- C++ -*-
   2
   3 // Copyright (C) 2005-2022 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/sso_string_base.h
  26  *  This is an internal header file, included by other library headers.
  27  *  Do not attempt to use it directly. @headername{ext/vstring.h}
  28  */
  29
  30 #ifndef _SSO_STRING_BASE_H
  31 #define _SSO_STRING_BASE_H 1
  32
  33 #include <bits/requires_hosted.h> // GNU extensions are currently omitted
  34
  35 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  36 {
  37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  38
  39   template<typename _CharT, typename _Traits, typename _Alloc>
  40     class __sso_string_base
  41     : protected __vstring_utility<_CharT, _Traits, _Alloc>
  42     {
  43     public:
  44       typedef _Traits                                       traits_type;
  45       typedef typename _Traits::char_type                   value_type;
  46
  47       typedef __vstring_utility<_CharT, _Traits, _Alloc>    _Util_Base;
  48       typedef typename _Util_Base::_CharT_alloc_type        _CharT_alloc_type;
  49       typedef typename _CharT_alloc_type::size_type         size_type;
  50
  51     private:
  52       // Data Members:
  53       typename _Util_Base::template _Alloc_hider<_CharT_alloc_type>
  54                                                             _M_dataplus;
  55       size_type                                             _M_string_length;
  56
  57       enum { _S_local_capacity = 15 };
  58
  59       union
  60       {
  61         _CharT           _M_local_data[_S_local_capacity + 1];
  62         size_type        _M_allocated_capacity;
  63       };
  64
  65       void
  66       _M_data(_CharT* __p)
  67       { _M_dataplus._M_p = __p; }
  68
  69       void
  70       _M_length(size_type __length)
  71       { _M_string_length = __length; }
  72
  73       void
  74       _M_capacity(size_type __capacity)
  75       { _M_allocated_capacity = __capacity; }
  76
  77       bool
  78       _M_is_local() const
  79       { return _M_data() == _M_local_data; }
  80
  81       // Create & Destroy
  82       _CharT*
  83       _M_create(size_type&, size_type);
  84
  85       void
  86       _M_dispose()
  87       {
  88         if (!_M_is_local())
  89           _M_destroy(_M_allocated_capacity);
  90       }
  91
  92       void
  93       _M_destroy(size_type __size) throw()
  94       { _M_get_allocator().deallocate(_M_data(), __size + 1); }
  95
  96       // _M_construct_aux is used to implement the 21.3.1 para 15 which
  97       // requires special behaviour if _InIterator is an integral type
  98       template<typename _InIterator>
  99         void
 100         _M_construct_aux(_InIterator __beg, _InIterator __end,
 101                          std::__false_type)
 102         {
 103           typedef typename std::iterator_traits<_InIterator>::iterator_category
 104             _Tag;
 105           _M_construct(__beg, __end, _Tag());
 106         }
 107
 108       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 109       // 438. Ambiguity in the "do the right thing" clause
 110       template<typename _Integer>
 111         void
 112         _M_construct_aux(_Integer __beg, _Integer __end, std::__true_type)
 113         { _M_construct_aux_2(static_cast<size_type>(__beg), __end); }
 114
 115       void
 116       _M_construct_aux_2(size_type __req, _CharT __c)
 117       { _M_construct(__req, __c); }
 118
 119       template<typename _InIterator>
 120         void
 121         _M_construct(_InIterator __beg, _InIterator __end)
 122         {
 123           typedef typename std::__is_integer<_InIterator>::__type _Integral;
 124           _M_construct_aux(__beg, __end, _Integral());
 125         }
 126
 127       // For Input Iterators, used in istreambuf_iterators, etc.
 128       template<typename _InIterator>
 129         void
 130         _M_construct(_InIterator __beg, _InIterator __end,
 131                      std::input_iterator_tag);
 132
 133       // For forward_iterators up to random_access_iterators, used for
 134       // string::iterator, _CharT*, etc.
 135       template<typename _FwdIterator>
 136         void
 137         _M_construct(_FwdIterator __beg, _FwdIterator __end,
 138                      std::forward_iterator_tag);
 139
 140       void
 141       _M_construct(size_type __req, _CharT __c);
 142
 143     public:
 144       size_type
 145       _M_max_size() const
 146       {
 147         typedef __alloc_traits<_CharT_alloc_type> _ATraits;
 148         return (_ATraits::max_size(_M_get_allocator()) - 1) / 2;
 149       }
 150
 151       _CharT*
 152       _M_data() const
 153       { return _M_dataplus._M_p; }
 154
 155       size_type
 156       _M_length() const
 157       { return _M_string_length; }
 158
 159       size_type
 160       _M_capacity() const
 161       {
 162         return _M_is_local() ? size_type(_S_local_capacity)
 163                              : _M_allocated_capacity;
 164       }
 165
 166       bool
 167       _M_is_shared() const
 168       { return false; }
 169
 170       void
 171       _M_set_leaked() { }
 172
 173       void
 174       _M_leak() { }
 175
 176       void
 177       _M_set_length(size_type __n)
 178       {
 179         _M_length(__n);
 180         traits_type::assign(_M_data()[__n], _CharT());
 181       }
 182
 183       __sso_string_base()
 184       : _M_dataplus(_M_local_data)
 185       { _M_set_length(0); }
 186
 187       __sso_string_base(const _Alloc& __a);
 188
 189       __sso_string_base(const __sso_string_base& __rcs);
 190
 191 #if __cplusplus >= 201103L
 192       __sso_string_base(__sso_string_base&& __rcs);
 193 #endif
 194
 195       __sso_string_base(size_type __n, _CharT __c, const _Alloc& __a);
 196
 197       template<typename _InputIterator>
 198         __sso_string_base(_InputIterator __beg, _InputIterator __end,
 199                           const _Alloc& __a);
 200
 201       ~__sso_string_base()
 202       { _M_dispose(); }
 203
 204       _CharT_alloc_type&
 205       _M_get_allocator()
 206       { return _M_dataplus; }
 207
 208       const _CharT_alloc_type&
 209       _M_get_allocator() const
 210       { return _M_dataplus; }
 211
 212       void
 213       _M_swap(__sso_string_base& __rcs);
 214
 215       void
 216       _M_assign(const __sso_string_base& __rcs);
 217
 218       void
 219       _M_reserve(size_type __res);
 220
 221       void
 222       _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
 223                 size_type __len2);
 224
 225       void
 226       _M_erase(size_type __pos, size_type __n);
 227
 228       void
 229       _M_clear()
 230       { _M_set_length(0); }
 231
 232       bool
 233       _M_compare(const __sso_string_base&) const
 234       { return false; }
 235     };
 236
 237   template<typename _CharT, typename _Traits, typename _Alloc>
 238     void
 239     __sso_string_base<_CharT, _Traits, _Alloc>::
 240     _M_swap(__sso_string_base& __rcs)
 241     {
 242       if (this == &__rcs)
 243         return;
 244
 245       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 246       // 431. Swapping containers with unequal allocators.
 247       std::__alloc_swap<_CharT_alloc_type>::_S_do_it(_M_get_allocator(),
 248                                                      __rcs._M_get_allocator());
 249
 250       if (_M_is_local())
 251         if (__rcs._M_is_local())
 252           {
 253             if (_M_length() && __rcs._M_length())
 254               {
 255                 _CharT __tmp_data[_S_local_capacity + 1];
 256                 traits_type::copy(__tmp_data, __rcs._M_local_data,
 257                                   _S_local_capacity + 1);
 258                 traits_type::copy(__rcs._M_local_data, _M_local_data,
 259                                   _S_local_capacity + 1);
 260                 traits_type::copy(_M_local_data, __tmp_data,
 261                                   _S_local_capacity + 1);
 262               }
 263             else if (__rcs._M_length())
 264               {
 265                 traits_type::copy(_M_local_data, __rcs._M_local_data,
 266                                   _S_local_capacity + 1);
 267                 _M_length(__rcs._M_length());
 268                 __rcs._M_set_length(0);
 269                 return;
 270               }
 271             else if (_M_length())
 272               {
 273                 traits_type::copy(__rcs._M_local_data, _M_local_data,
 274                                   _S_local_capacity + 1);
 275                 __rcs._M_length(_M_length());
 276                 _M_set_length(0);
 277                 return;
 278               }
 279           }
 280         else
 281           {
 282             const size_type __tmp_capacity = __rcs._M_allocated_capacity;
 283             traits_type::copy(__rcs._M_local_data, _M_local_data,
 284                               _S_local_capacity + 1);
 285             _M_data(__rcs._M_data());
 286             __rcs._M_data(__rcs._M_local_data);
 287             _M_capacity(__tmp_capacity);
 288           }
 289       else
 290         {
 291           const size_type __tmp_capacity = _M_allocated_capacity;
 292           if (__rcs._M_is_local())
 293             {
 294               traits_type::copy(_M_local_data, __rcs._M_local_data,
 295                                 _S_local_capacity + 1);
 296               __rcs._M_data(_M_data());
 297               _M_data(_M_local_data);
 298             }
 299           else
 300             {
 301               _CharT* __tmp_ptr = _M_data();
 302               _M_data(__rcs._M_data());
 303               __rcs._M_data(__tmp_ptr);
 304               _M_capacity(__rcs._M_allocated_capacity);
 305             }
 306           __rcs._M_capacity(__tmp_capacity);
 307         }
 308
 309       const size_type __tmp_length = _M_length();
 310       _M_length(__rcs._M_length());
 311       __rcs._M_length(__tmp_length);
 312     }
 313
 314   template<typename _CharT, typename _Traits, typename _Alloc>
 315     _CharT*
 316     __sso_string_base<_CharT, _Traits, _Alloc>::
 317     _M_create(size_type& __capacity, size_type __old_capacity)
 318     {
 319       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 320       // 83.  String::npos vs. string::max_size()
 321       if (__capacity > _M_max_size())
 322         std::__throw_length_error(__N("__sso_string_base::_M_create"));
 323
 324       // The below implements an exponential growth policy, necessary to
 325       // meet amortized linear time requirements of the library: see
 326       // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
 327       if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
 328         {
 329           __capacity = 2 * __old_capacity;
 330           // Never allocate a string bigger than max_size.
 331           if (__capacity > _M_max_size())
 332             __capacity = _M_max_size();
 333         }
 334
 335       // NB: Need an array of char_type[__capacity], plus a terminating
 336       // null char_type() element.
 337       return _M_get_allocator().allocate(__capacity + 1);
 338     }
 339
 340   template<typename _CharT, typename _Traits, typename _Alloc>
 341     __sso_string_base<_CharT, _Traits, _Alloc>::
 342     __sso_string_base(const _Alloc& __a)
 343     : _M_dataplus(__a, _M_local_data)
 344     { _M_set_length(0); }
 345
 346   template<typename _CharT, typename _Traits, typename _Alloc>
 347     __sso_string_base<_CharT, _Traits, _Alloc>::
 348     __sso_string_base(const __sso_string_base& __rcs)
 349     : _M_dataplus(__rcs._M_get_allocator(), _M_local_data)
 350     { _M_construct(__rcs._M_data(), __rcs._M_data() + __rcs._M_length()); }
 351
 352 #if __cplusplus >= 201103L
 353   template<typename _CharT, typename _Traits, typename _Alloc>
 354     __sso_string_base<_CharT, _Traits, _Alloc>::
 355     __sso_string_base(__sso_string_base&& __rcs)
 356     : _M_dataplus(__rcs._M_get_allocator(), _M_local_data)
 357     {
 358       if (__rcs._M_is_local())
 359         {
 360           if (__rcs._M_length())
 361             traits_type::copy(_M_local_data, __rcs._M_local_data,
 362                               _S_local_capacity + 1);
 363         }
 364       else
 365         {
 366           _M_data(__rcs._M_data());
 367           _M_capacity(__rcs._M_allocated_capacity);
 368         }
 369
 370       _M_set_length(__rcs._M_length());
 371       __rcs._M_data(__rcs._M_local_data);
 372       __rcs._M_set_length(0);
 373     }
 374 #endif
 375
 376   template<typename _CharT, typename _Traits, typename _Alloc>
 377     __sso_string_base<_CharT, _Traits, _Alloc>::
 378     __sso_string_base(size_type __n, _CharT __c, const _Alloc& __a)
 379     : _M_dataplus(__a, _M_local_data)
 380     { _M_construct(__n, __c); }
 381
 382   template<typename _CharT, typename _Traits, typename _Alloc>
 383     template<typename _InputIterator>
 384     __sso_string_base<_CharT, _Traits, _Alloc>::
 385     __sso_string_base(_InputIterator __beg, _InputIterator __end,
 386                       const _Alloc& __a)
 387     : _M_dataplus(__a, _M_local_data)
 388     { _M_construct(__beg, __end); }
 389
 390   // NB: This is the special case for Input Iterators, used in
 391   // istreambuf_iterators, etc.
 392   // Input Iterators have a cost structure very different from
 393   // pointers, calling for a different coding style.
 394   template<typename _CharT, typename _Traits, typename _Alloc>
 395     template<typename _InIterator>
 396       void
 397       __sso_string_base<_CharT, _Traits, _Alloc>::
 398       _M_construct(_InIterator __beg, _InIterator __end,
 399                    std::input_iterator_tag)
 400       {
 401         size_type __len = 0;
 402         size_type __capacity = size_type(_S_local_capacity);
 403
 404         while (__beg != __end && __len < __capacity)
 405           {
 406             _M_data()[__len++] = *__beg;
 407             ++__beg;
 408           }
 409
 410         __try
 411           {
 412             while (__beg != __end)
 413               {
 414                 if (__len == __capacity)
 415                   {
 416                     // Allocate more space.
 417                     __capacity = __len + 1;
 418                     _CharT* __another = _M_create(__capacity, __len);
 419                     this->_S_copy(__another, _M_data(), __len);
 420                     _M_dispose();
 421                     _M_data(__another);
 422                     _M_capacity(__capacity);
 423                   }
 424                 _M_data()[__len++] = *__beg;
 425                 ++__beg;
 426               }
 427           }
 428         __catch(...)
 429           {
 430             _M_dispose();
 431             __throw_exception_again;
 432           }
 433
 434         _M_set_length(__len);
 435       }
 436
 437   template<typename _CharT, typename _Traits, typename _Alloc>
 438     template<typename _InIterator>
 439       void
 440       __sso_string_base<_CharT, _Traits, _Alloc>::
 441       _M_construct(_InIterator __beg, _InIterator __end,
 442                    std::forward_iterator_tag)
 443       {
 444         // NB: Not required, but considered best practice.
 445         if (__is_null_pointer(__beg) && __beg != __end)
 446           std::__throw_logic_error(__N("__sso_string_base::"
 447                                        "_M_construct null not valid"));
 448
 449         size_type __dnew = static_cast<size_type>(std::distance(__beg, __end));
 450
 451         if (__dnew > size_type(_S_local_capacity))
 452           {
 453             _M_data(_M_create(__dnew, size_type(0)));
 454             _M_capacity(__dnew);
 455           }
 456
 457         // Check for out_of_range and length_error exceptions.
 458         __try
 459           { this->_S_copy_chars(_M_data(), __beg, __end); }
 460         __catch(...)
 461           {
 462             _M_dispose();
 463             __throw_exception_again;
 464           }
 465
 466         _M_set_length(__dnew);
 467       }
 468
 469   template<typename _CharT, typename _Traits, typename _Alloc>
 470     void
 471     __sso_string_base<_CharT, _Traits, _Alloc>::
 472     _M_construct(size_type __n, _CharT __c)
 473     {
 474       if (__n > size_type(_S_local_capacity))
 475         {
 476           _M_data(_M_create(__n, size_type(0)));
 477           _M_capacity(__n);
 478         }
 479
 480       if (__n)
 481         this->_S_assign(_M_data(), __n, __c);
 482
 483       _M_set_length(__n);
 484     }
 485
 486   template<typename _CharT, typename _Traits, typename _Alloc>
 487     void
 488     __sso_string_base<_CharT, _Traits, _Alloc>::
 489     _M_assign(const __sso_string_base& __rcs)
 490     {
 491       if (this != &__rcs)
 492         {
 493           const size_type __rsize = __rcs._M_length();
 494           const size_type __capacity = _M_capacity();
 495
 496           if (__rsize > __capacity)
 497             {
 498               size_type __new_capacity = __rsize;
 499               _CharT* __tmp = _M_create(__new_capacity, __capacity);
 500               _M_dispose();
 501               _M_data(__tmp);
 502               _M_capacity(__new_capacity);
 503             }
 504
 505           if (__rsize)
 506             this->_S_copy(_M_data(), __rcs._M_data(), __rsize);
 507
 508           _M_set_length(__rsize);
 509         }
 510     }
 511
 512   template<typename _CharT, typename _Traits, typename _Alloc>
 513     void
 514     __sso_string_base<_CharT, _Traits, _Alloc>::
 515     _M_reserve(size_type __res)
 516     {
 517       // Make sure we don't shrink below the current size.
 518       if (__res < _M_length())
 519         __res = _M_length();
 520
 521       const size_type __capacity = _M_capacity();
 522       if (__res != __capacity)
 523         {
 524           if (__res > __capacity
 525               || __res > size_type(_S_local_capacity))
 526             {
 527               _CharT* __tmp = _M_create(__res, __capacity);
 528               this->_S_copy(__tmp, _M_data(), _M_length() + 1);
 529               _M_dispose();
 530               _M_data(__tmp);
 531               _M_capacity(__res);
 532             }
 533           else if (!_M_is_local())
 534             {
 535               this->_S_copy(_M_local_data, _M_data(), _M_length() + 1);
 536               _M_destroy(__capacity);
 537               _M_data(_M_local_data);
 538             }
 539         }
 540     }
 541
 542   template<typename _CharT, typename _Traits, typename _Alloc>
 543     void
 544     __sso_string_base<_CharT, _Traits, _Alloc>::
 545     _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
 546               size_type __len2)
 547     {
 548       const size_type __how_much = _M_length() - __pos - __len1;
 549
 550       size_type __new_capacity = _M_length() + __len2 - __len1;
 551       _CharT* __r = _M_create(__new_capacity, _M_capacity());
 552
 553       if (__pos)
 554         this->_S_copy(__r, _M_data(), __pos);
 555       if (__s && __len2)
 556         this->_S_copy(__r + __pos, __s, __len2);
 557       if (__how_much)
 558         this->_S_copy(__r + __pos + __len2,
 559                       _M_data() + __pos + __len1, __how_much);
 560
 561       _M_dispose();
 562       _M_data(__r);
 563       _M_capacity(__new_capacity);
 564     }
 565
 566   template<typename _CharT, typename _Traits, typename _Alloc>
 567     void
 568     __sso_string_base<_CharT, _Traits, _Alloc>::
 569     _M_erase(size_type __pos, size_type __n)
 570     {
 571       const size_type __how_much = _M_length() - __pos - __n;
 572
 573       if (__how_much && __n)
 574         this->_S_move(_M_data() + __pos, _M_data() + __pos + __n, __how_much);
 575
 576       _M_set_length(_M_length() - __n);
 577     }
 578
 579 _GLIBCXX_END_NAMESPACE_VERSION
 580 } // namespace
 581
 582 #endif /* _SSO_STRING_BASE_H */