# rc_string_base.h

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    00001 // Reference-counted versatile string base -*- C++ -*-
    00002
    00003 // Copyright (C) 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
    00004 //
    00005 // This file is part of the GNU ISO C++ Library.  This library is free
    00006 // software; you can redistribute it and/or modify it under the
    00007 // terms of the GNU General Public License as published by the
    00008 // Free Software Foundation; either version 2, or (at your option)
    00009 // any later version.
    00010
    00011 // This library is distributed in the hope that it will be useful,
    00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00014 // GNU General Public License for more details.
    00015
    00016 // You should have received a copy of the GNU General Public License along
    00017 // with this library; see the file COPYING.  If not, write to the Free
    00018 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
    00019 // USA.
    00020
    00021 // As a special exception, you may use this file as part of a free software
    00022 // library without restriction.  Specifically, if other files instantiate
    00023 // templates or use macros or inline functions from this file, or you compile
    00024 // this file and link it with other files to produce an executable, this
    00025 // file does not by itself cause the resulting executable to be covered by
    00026 // the GNU General Public License.  This exception does not however
    00027 // invalidate any other reasons why the executable file might be covered by
    00028 // the GNU General Public License.
    00029
    00030 /** @file ext/rc_string_base.h
    00031  *  This file is a GNU extension to the Standard C++ Library.
    00032  *  This is an internal header file, included by other library headers.
    00033  *  You should not attempt to use it directly.
    00034  */
    00035
    00036 #ifndef _RC_STRING_BASE_H
    00037 #define _RC_STRING_BASE_H 1
    00038
    00039 #include <ext/atomicity.h>
    00040 #include <bits/stl_iterator_base_funcs.h>
    00041
    00042 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
    00043
    00044   /**
    00045    *  Documentation?  What's that?
    00046    *  Nathan Myers <ncm@cantrip.org>.
    00047    *
    00048    *  A string looks like this:
    00049    *
    00050    *  @code
    00051    *                                        [_Rep]
    00052    *                                        _M_length
    00053    *   [__rc_string_base<char_type>]        _M_capacity
    00054    *   _M_dataplus                          _M_refcount
    00055    *   _M_p ---------------->               unnamed array of char_type
    00056    *  @endcode
    00057    *
    00058    *  Where the _M_p points to the first character in the string, and
    00059    *  you cast it to a pointer-to-_Rep and subtract 1 to get a
    00060    *  pointer to the header.
    00061    *
    00062    *  This approach has the enormous advantage that a string object
    00063    *  requires only one allocation.  All the ugliness is confined
    00064    *  within a single pair of inline functions, which each compile to
    00065    *  a single "add" instruction: _Rep::_M_refdata(), and
    00066    *  __rc_string_base::_M_rep(); and the allocation function which gets a
    00067    *  block of raw bytes and with room enough and constructs a _Rep
    00068    *  object at the front.
    00069    *
    00070    *  The reason you want _M_data pointing to the character array and
    00071    *  not the _Rep is so that the debugger can see the string
    00072    *  contents. (Probably we should add a non-inline member to get
    00073    *  the _Rep for the debugger to use, so users can check the actual
    00074    *  string length.)
    00075    *
    00076    *  Note that the _Rep object is a POD so that you can have a
    00077    *  static "empty string" _Rep object already "constructed" before
    00078    *  static constructors have run.  The reference-count encoding is
    00079    *  chosen so that a 0 indicates one reference, so you never try to
    00080    *  destroy the empty-string _Rep object.
    00081    *
    00082    *  All but the last paragraph is considered pretty conventional
    00083    *  for a C++ string implementation.
    00084   */
    00085  template<typename _CharT, typename _Traits, typename _Alloc>
    00086     class __rc_string_base
    00087     : protected __vstring_utility<_CharT, _Traits, _Alloc>
    00088     {
    00089     public:
    00090       typedef _Traits                       traits_type;
    00091       typedef typename _Traits::char_type           value_type;
    00092       typedef _Alloc                        allocator_type;
    00093
    00094       typedef __vstring_utility<_CharT, _Traits, _Alloc>    _Util_Base;
    00095       typedef typename _Util_Base::_CharT_alloc_type        _CharT_alloc_type;
    00096       typedef typename _CharT_alloc_type::size_type     size_type;
    00097
    00098     private:
    00099       // _Rep: string representation
    00100       //   Invariants:
    00101       //   1. String really contains _M_length + 1 characters: due to 21.3.4
    00102       //      must be kept null-terminated.
    00103       //   2. _M_capacity >= _M_length
    00104       //      Allocated memory is always (_M_capacity + 1) * sizeof(_CharT).
    00105       //   3. _M_refcount has three states:
    00106       //      -1: leaked, one reference, no ref-copies allowed, non-const.
    00107       //       0: one reference, non-const.
    00108       //     n>0: n + 1 references, operations require a lock, const.
    00109       //   4. All fields == 0 is an empty string, given the extra storage
    00110       //      beyond-the-end for a null terminator; thus, the shared
    00111       //      empty string representation needs no constructor.
    00112       struct _Rep
    00113       {
    00114     union
    00115     {
    00116       struct
    00117       {
    00118         size_type       _M_length;
    00119         size_type       _M_capacity;
    00120         _Atomic_word    _M_refcount;
    00121       }                 _M_info;
    00122
    00123       // Only for alignment purposes.
    00124       _CharT            _M_align;
    00125     };
    00126
    00127     typedef typename _Alloc::template rebind<_Rep>::other _Rep_alloc_type;
    00128
    00129     _CharT*
    00130     _M_refdata() throw()
    00131     { return reinterpret_cast<_CharT*>(this + 1); }
    00132
    00133     _CharT*
    00134     _M_refcopy() throw()
    00135     {
    00136       __atomic_add_dispatch(&_M_info._M_refcount, 1);
    00137       return _M_refdata();
    00138     }  // XXX MT
    00139
    00140     void
    00141     _M_set_length(size_type __n)
    00142     {
    00143       _M_info._M_refcount = 0;  // One reference.
    00144       _M_info._M_length = __n;
    00145       // grrr. (per 21.3.4)
    00146       // You cannot leave those LWG people alone for a second.
    00147       traits_type::assign(_M_refdata()[__n], _CharT());
    00148     }
    00149
    00150     // Create & Destroy
    00151     static _Rep*
    00152     _S_create(size_type, size_type, const _Alloc&);
    00153
    00154     void
    00155     _M_destroy(const _Alloc&) throw();
    00156
    00157     _CharT*
    00158     _M_clone(const _Alloc&, size_type __res = 0);
    00159       };
    00160
    00161       struct _Rep_empty
    00162       : public _Rep
    00163       {
    00164     _CharT              _M_terminal;
    00165       };
    00166
    00167       static _Rep_empty     _S_empty_rep;
    00168
    00169       // The maximum number of individual char_type elements of an
    00170       // individual string is determined by _S_max_size. This is the
    00171       // value that will be returned by max_size().  (Whereas npos
    00172       // is the maximum number of bytes the allocator can allocate.)
    00173       // If one was to divvy up the theoretical largest size string,
    00174       // with a terminating character and m _CharT elements, it'd
    00175       // look like this:
    00176       // npos = sizeof(_Rep) + (m * sizeof(_CharT)) + sizeof(_CharT)
    00177       //        + sizeof(_Rep) - 1
    00178       // (NB: last two terms for rounding reasons, see _M_create below)
    00179       // Solving for m:
    00180       // m = ((npos - 2 * sizeof(_Rep) + 1) / sizeof(_CharT)) - 1
    00181       // In addition, this implementation halves this amount.
    00182       enum { _S_max_size = (((static_cast<size_type>(-1) - 2 * sizeof(_Rep)
    00183                   + 1) / sizeof(_CharT)) - 1) / 2 };
    00184
    00185       // Data Member (private):
    00186       mutable typename _Util_Base::template _Alloc_hider<_Alloc>  _M_dataplus;
    00187
    00188       void
    00189       _M_data(_CharT* __p)
    00190       { _M_dataplus._M_p = __p; }
    00191
    00192       _Rep*
    00193       _M_rep() const
    00194       { return &((reinterpret_cast<_Rep*>(_M_data()))[-1]); }
    00195
    00196       _CharT*
    00197       _M_grab(const _Alloc& __alloc) const
    00198       {
    00199     return (!_M_is_leaked() && _M_get_allocator() == __alloc)
    00200             ? _M_rep()->_M_refcopy() : _M_rep()->_M_clone(__alloc);
    00201       }
    00202
    00203       void
    00204       _M_dispose()
    00205       {
    00206     if (__exchange_and_add_dispatch(&_M_rep()->_M_info._M_refcount,
    00207                     -1) <= 0)
    00208       _M_rep()->_M_destroy(_M_get_allocator());
    00209       }  // XXX MT
    00210
    00211       bool
    00212       _M_is_leaked() const
    00213       { return _M_rep()->_M_info._M_refcount < 0; }
    00214
    00215       void
    00216       _M_set_sharable()
    00217       { _M_rep()->_M_info._M_refcount = 0; }
    00218
    00219       void
    00220       _M_leak_hard();
    00221
    00222       // _S_construct_aux is used to implement the 21.3.1 para 15 which
    00223       // requires special behaviour if _InIterator is an integral type
    00224       template<typename _InIterator>
    00225         static _CharT*
    00226         _S_construct_aux(_InIterator __beg, _InIterator __end,
    00227              const _Alloc& __a, std::__false_type)
    00228     {
    00229           typedef typename iterator_traits<_InIterator>::iterator_category _Tag;
    00230           return _S_construct(__beg, __end, __a, _Tag());
    00231     }
    00232
    00233       // _GLIBCXX_RESOLVE_LIB_DEFECTS
    00234       // 438. Ambiguity in the "do the right thing" clause
    00235       template<typename _Integer>
    00236         static _CharT*
    00237         _S_construct_aux(_Integer __beg, _Integer __end,
    00238              const _Alloc& __a, std::__true_type)
    00239     { return _S_construct(static_cast<size_type>(__beg), __end, __a); }
    00240
    00241       template<typename _InIterator>
    00242         static _CharT*
    00243         _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a)
    00244     {
    00245       typedef typename std::__is_integer<_InIterator>::__type _Integral;
    00246       return _S_construct_aux(__beg, __end, __a, _Integral());
    00247         }
    00248
    00249       // For Input Iterators, used in istreambuf_iterators, etc.
    00250       template<typename _InIterator>
    00251         static _CharT*
    00252          _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
    00253               std::input_iterator_tag);
    00254
    00255       // For forward_iterators up to random_access_iterators, used for
    00256       // string::iterator, _CharT*, etc.
    00257       template<typename _FwdIterator>
    00258         static _CharT*
    00259         _S_construct(_FwdIterator __beg, _FwdIterator __end, const _Alloc& __a,
    00260              std::forward_iterator_tag);
    00261
    00262       static _CharT*
    00263       _S_construct(size_type __req, _CharT __c, const _Alloc& __a);
    00264
    00265     public:
    00266       size_type
    00267       _M_max_size() const
    00268       { return size_type(_S_max_size); }
    00269
    00270       _CharT*
    00271       _M_data() const
    00272       { return _M_dataplus._M_p; }
    00273
    00274       size_type
    00275       _M_length() const
    00276       { return _M_rep()->_M_info._M_length; }
    00277
    00278       size_type
    00279       _M_capacity() const
    00280       { return _M_rep()->_M_info._M_capacity; }
    00281
    00282       bool
    00283       _M_is_shared() const
    00284       { return _M_rep()->_M_info._M_refcount > 0; }
    00285
    00286       void
    00287       _M_set_leaked()
    00288       { _M_rep()->_M_info._M_refcount = -1; }
    00289
    00290       void
    00291       _M_leak()    // for use in begin() & non-const op[]
    00292       {
    00293     if (!_M_is_leaked())
    00294       _M_leak_hard();
    00295       }
    00296
    00297       void
    00298       _M_set_length(size_type __n)
    00299       { _M_rep()->_M_set_length(__n); }
    00300
    00301       __rc_string_base()
    00302       : _M_dataplus(_S_empty_rep._M_refcopy()) { }
    00303
    00304       __rc_string_base(const _Alloc& __a);
    00305
    00306       __rc_string_base(const __rc_string_base& __rcs);
    00307
    00308 #ifdef __GXX_EXPERIMENTAL_CXX0X__
    00309       __rc_string_base(__rc_string_base&& __rcs)
    00310       : _M_dataplus(__rcs._M_get_allocator(), __rcs._M_data())
    00311       { __rcs._M_data(_S_empty_rep._M_refcopy()); }
    00312 #endif
    00313
    00314       __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a);
    00315
    00316       template<typename _InputIterator>
    00317         __rc_string_base(_InputIterator __beg, _InputIterator __end,
    00318              const _Alloc& __a);
    00319
    00320       ~__rc_string_base()
    00321       { _M_dispose(); }
    00322
    00323       allocator_type&
    00324       _M_get_allocator()
    00325       { return _M_dataplus; }
    00326
    00327       const allocator_type&
    00328       _M_get_allocator() const
    00329       { return _M_dataplus; }
    00330
    00331       void
    00332       _M_swap(__rc_string_base& __rcs);
    00333
    00334       void
    00335       _M_assign(const __rc_string_base& __rcs);
    00336
    00337       void
    00338       _M_reserve(size_type __res);
    00339
    00340       void
    00341       _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
    00342         size_type __len2);
    00343
    00344       void
    00345       _M_erase(size_type __pos, size_type __n);
    00346
    00347       void
    00348       _M_clear()
    00349       { _M_erase(size_type(0), _M_length()); }
    00350
    00351       bool
    00352       _M_compare(const __rc_string_base&) const
    00353       { return false; }
    00354     };
    00355
    00356   template<typename _CharT, typename _Traits, typename _Alloc>
    00357     typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep_empty
    00358     __rc_string_base<_CharT, _Traits, _Alloc>::_S_empty_rep;
    00359
    00360   template<typename _CharT, typename _Traits, typename _Alloc>
    00361     typename __rc_string_base<_CharT, _Traits, _Alloc>::_Rep*
    00362     __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
    00363     _S_create(size_type __capacity, size_type __old_capacity,
    00364           const _Alloc& __alloc)
    00365     {
    00366       // _GLIBCXX_RESOLVE_LIB_DEFECTS
    00367       // 83.  String::npos vs. string::max_size()
    00368       if (__capacity > size_type(_S_max_size))
    00369     std::__throw_length_error(__N("__rc_string_base::_Rep::_S_create"));
    00370
    00371       // The standard places no restriction on allocating more memory
    00372       // than is strictly needed within this layer at the moment or as
    00373       // requested by an explicit application call to reserve().
    00374
    00375       // Many malloc implementations perform quite poorly when an
    00376       // application attempts to allocate memory in a stepwise fashion
    00377       // growing each allocation size by only 1 char.  Additionally,
    00378       // it makes little sense to allocate less linear memory than the
    00379       // natural blocking size of the malloc implementation.
    00380       // Unfortunately, we would need a somewhat low-level calculation
    00381       // with tuned parameters to get this perfect for any particular
    00382       // malloc implementation.  Fortunately, generalizations about
    00383       // common features seen among implementations seems to suffice.
    00384
    00385       // __pagesize need not match the actual VM page size for good
    00386       // results in practice, thus we pick a common value on the low
    00387       // side.  __malloc_header_size is an estimate of the amount of
    00388       // overhead per memory allocation (in practice seen N * sizeof
    00389       // (void*) where N is 0, 2 or 4).  According to folklore,
    00390       // picking this value on the high side is better than
    00391       // low-balling it (especially when this algorithm is used with
    00392       // malloc implementations that allocate memory blocks rounded up
    00393       // to a size which is a power of 2).
    00394       const size_type __pagesize = 4096;
    00395       const size_type __malloc_header_size = 4 * sizeof(void*);
    00396
    00397       // The below implements an exponential growth policy, necessary to
    00398       // meet amortized linear time requirements of the library: see
    00399       // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
    00400       if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
    00401     {
    00402       __capacity = 2 * __old_capacity;
    00403       // Never allocate a string bigger than _S_max_size.
    00404       if (__capacity > size_type(_S_max_size))
    00405         __capacity = size_type(_S_max_size);
    00406     }
    00407
    00408       // NB: Need an array of char_type[__capacity], plus a terminating
    00409       // null char_type() element, plus enough for the _Rep data structure,
    00410       // plus sizeof(_Rep) - 1 to upper round to a size multiple of
    00411       // sizeof(_Rep).
    00412       // Whew. Seemingly so needy, yet so elemental.
    00413       size_type __size = ((__capacity + 1) * sizeof(_CharT)
    00414               + 2 * sizeof(_Rep) - 1);
    00415
    00416       const size_type __adj_size = __size + __malloc_header_size;
    00417       if (__adj_size > __pagesize && __capacity > __old_capacity)
    00418     {
    00419       const size_type __extra = __pagesize - __adj_size % __pagesize;
    00420       __capacity += __extra / sizeof(_CharT);
    00421       if (__capacity > size_type(_S_max_size))
    00422         __capacity = size_type(_S_max_size);
    00423       __size = (__capacity + 1) * sizeof(_CharT) + 2 * sizeof(_Rep) - 1;
    00424     }
    00425
    00426       // NB: Might throw, but no worries about a leak, mate: _Rep()
    00427       // does not throw.
    00428       _Rep* __place = _Rep_alloc_type(__alloc).allocate(__size / sizeof(_Rep));
    00429       _Rep* __p = new (__place) _Rep;
    00430       __p->_M_info._M_capacity = __capacity;
    00431       return __p;
    00432     }
    00433
    00434   template<typename _CharT, typename _Traits, typename _Alloc>
    00435     void
    00436     __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
    00437     _M_destroy(const _Alloc& __a) throw ()
    00438     {
    00439       const size_type __size = ((_M_info._M_capacity + 1) * sizeof(_CharT)
    00440                 + 2 * sizeof(_Rep) - 1);
    00441       _Rep_alloc_type(__a).deallocate(this, __size / sizeof(_Rep));
    00442     }
    00443
    00444   template<typename _CharT, typename _Traits, typename _Alloc>
    00445     _CharT*
    00446     __rc_string_base<_CharT, _Traits, _Alloc>::_Rep::
    00447     _M_clone(const _Alloc& __alloc, size_type __res)
    00448     {
    00449       // Requested capacity of the clone.
    00450       const size_type __requested_cap = _M_info._M_length + __res;
    00451       _Rep* __r = _Rep::_S_create(__requested_cap, _M_info._M_capacity,
    00452                   __alloc);
    00453
    00454       if (_M_info._M_length)
    00455     _S_copy(__r->_M_refdata(), _M_refdata(), _M_info._M_length);
    00456
    00457       __r->_M_set_length(_M_info._M_length);
    00458       return __r->_M_refdata();
    00459     }
    00460
    00461   template<typename _CharT, typename _Traits, typename _Alloc>
    00462     __rc_string_base<_CharT, _Traits, _Alloc>::
    00463     __rc_string_base(const _Alloc& __a)
    00464     : _M_dataplus(__a, _S_construct(size_type(), _CharT(), __a)) { }
    00465
    00466   template<typename _CharT, typename _Traits, typename _Alloc>
    00467     __rc_string_base<_CharT, _Traits, _Alloc>::
    00468     __rc_string_base(const __rc_string_base& __rcs)
    00469     : _M_dataplus(__rcs._M_get_allocator(),
    00470           __rcs._M_grab(__rcs._M_get_allocator())) { }
    00471
    00472   template<typename _CharT, typename _Traits, typename _Alloc>
    00473     __rc_string_base<_CharT, _Traits, _Alloc>::
    00474     __rc_string_base(size_type __n, _CharT __c, const _Alloc& __a)
    00475     : _M_dataplus(__a, _S_construct(__n, __c, __a)) { }
    00476
    00477   template<typename _CharT, typename _Traits, typename _Alloc>
    00478     template<typename _InputIterator>
    00479     __rc_string_base<_CharT, _Traits, _Alloc>::
    00480     __rc_string_base(_InputIterator __beg, _InputIterator __end,
    00481              const _Alloc& __a)
    00482     : _M_dataplus(__a, _S_construct(__beg, __end, __a)) { }
    00483
    00484   template<typename _CharT, typename _Traits, typename _Alloc>
    00485     void
    00486     __rc_string_base<_CharT, _Traits, _Alloc>::
    00487     _M_leak_hard()
    00488     {
    00489       if (_M_is_shared())
    00490     _M_erase(0, 0);
    00491       _M_set_leaked();
    00492     }
    00493
    00494   // NB: This is the special case for Input Iterators, used in
    00495   // istreambuf_iterators, etc.
    00496   // Input Iterators have a cost structure very different from
    00497   // pointers, calling for a different coding style.
    00498   template<typename _CharT, typename _Traits, typename _Alloc>
    00499     template<typename _InIterator>
    00500       _CharT*
    00501       __rc_string_base<_CharT, _Traits, _Alloc>::
    00502       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
    00503            std::input_iterator_tag)
    00504       {
    00505     if (__beg == __end && __a == _Alloc())
    00506       return _S_empty_rep._M_refcopy();
    00507
    00508     // Avoid reallocation for common case.
    00509     _CharT __buf[128];
    00510     size_type __len = 0;
    00511     while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
    00512       {
    00513         __buf[__len++] = *__beg;
    00514         ++__beg;
    00515       }
    00516     _Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
    00517     _S_copy(__r->_M_refdata(), __buf, __len);
    00518     try
    00519       {
    00520         while (__beg != __end)
    00521           {
    00522         if (__len == __r->_M_info._M_capacity)
    00523           {
    00524             // Allocate more space.
    00525             _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
    00526             _S_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
    00527             __r->_M_destroy(__a);
    00528             __r = __another;
    00529           }
    00530         __r->_M_refdata()[__len++] = *__beg;
    00531         ++__beg;
    00532           }
    00533       }
    00534     catch(...)
    00535       {
    00536         __r->_M_destroy(__a);
    00537         __throw_exception_again;
    00538       }
    00539     __r->_M_set_length(__len);
    00540     return __r->_M_refdata();
    00541       }
    00542
    00543   template<typename _CharT, typename _Traits, typename _Alloc>
    00544     template<typename _InIterator>
    00545       _CharT*
    00546       __rc_string_base<_CharT, _Traits, _Alloc>::
    00547       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
    00548            std::forward_iterator_tag)
    00549       {
    00550     if (__beg == __end && __a == _Alloc())
    00551       return _S_empty_rep._M_refcopy();
    00552
    00553     // NB: Not required, but considered best practice.
    00554     if (__builtin_expect(__is_null_pointer(__beg) && __beg != __end, 0))
    00555       std::__throw_logic_error(__N("__rc_string_base::"
    00556                        "_S_construct NULL not valid"));
    00557
    00558     const size_type __dnew = static_cast<size_type>(std::distance(__beg,
    00559                                       __end));
    00560     // Check for out_of_range and length_error exceptions.
    00561     _Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
    00562     try
    00563       { _S_copy_chars(__r->_M_refdata(), __beg, __end); }
    00564     catch(...)
    00565       {
    00566         __r->_M_destroy(__a);
    00567         __throw_exception_again;
    00568       }
    00569     __r->_M_set_length(__dnew);
    00570     return __r->_M_refdata();
    00571       }
    00572
    00573   template<typename _CharT, typename _Traits, typename _Alloc>
    00574     _CharT*
    00575     __rc_string_base<_CharT, _Traits, _Alloc>::
    00576     _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
    00577     {
    00578       if (__n == 0 && __a == _Alloc())
    00579     return _S_empty_rep._M_refcopy();
    00580
    00581       // Check for out_of_range and length_error exceptions.
    00582       _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
    00583       if (__n)
    00584     _S_assign(__r->_M_refdata(), __n, __c);
    00585
    00586       __r->_M_set_length(__n);
    00587       return __r->_M_refdata();
    00588     }
    00589
    00590   template<typename _CharT, typename _Traits, typename _Alloc>
    00591     void
    00592     __rc_string_base<_CharT, _Traits, _Alloc>::
    00593     _M_swap(__rc_string_base& __rcs)
    00594     {
    00595       if (_M_is_leaked())
    00596     _M_set_sharable();
    00597       if (__rcs._M_is_leaked())
    00598     __rcs._M_set_sharable();
    00599
    00600       _CharT* __tmp = _M_data();
    00601       _M_data(__rcs._M_data());
    00602       __rcs._M_data(__tmp);
    00603
    00604       // _GLIBCXX_RESOLVE_LIB_DEFECTS
    00605       // 431. Swapping containers with unequal allocators.
    00606       std::__alloc_swap<allocator_type>::_S_do_it(_M_get_allocator(),
    00607                           __rcs._M_get_allocator());
    00608     }
    00609
    00610   template<typename _CharT, typename _Traits, typename _Alloc>
    00611     void
    00612     __rc_string_base<_CharT, _Traits, _Alloc>::
    00613     _M_assign(const __rc_string_base& __rcs)
    00614     {
    00615       if (_M_rep() != __rcs._M_rep())
    00616     {
    00617       _CharT* __tmp = __rcs._M_grab(_M_get_allocator());
    00618       _M_dispose();
    00619       _M_data(__tmp);
    00620     }
    00621     }
    00622
    00623   template<typename _CharT, typename _Traits, typename _Alloc>
    00624     void
    00625     __rc_string_base<_CharT, _Traits, _Alloc>::
    00626     _M_reserve(size_type __res)
    00627     {
    00628       // Make sure we don't shrink below the current size.
    00629       if (__res < _M_length())
    00630     __res = _M_length();
    00631
    00632       if (__res != _M_capacity() || _M_is_shared())
    00633     {
    00634       _CharT* __tmp = _M_rep()->_M_clone(_M_get_allocator(),
    00635                          __res - _M_length());
    00636       _M_dispose();
    00637       _M_data(__tmp);
    00638     }
    00639     }
    00640
    00641   template<typename _CharT, typename _Traits, typename _Alloc>
    00642     void
    00643     __rc_string_base<_CharT, _Traits, _Alloc>::
    00644     _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
    00645           size_type __len2)
    00646     {
    00647       const size_type __how_much = _M_length() - __pos - __len1;
    00648
    00649       _Rep* __r = _Rep::_S_create(_M_length() + __len2 - __len1,
    00650                   _M_capacity(), _M_get_allocator());
    00651
    00652       if (__pos)
    00653     _S_copy(__r->_M_refdata(), _M_data(), __pos);
    00654       if (__s && __len2)
    00655     _S_copy(__r->_M_refdata() + __pos, __s, __len2);
    00656       if (__how_much)
    00657     _S_copy(__r->_M_refdata() + __pos + __len2,
    00658         _M_data() + __pos + __len1, __how_much);
    00659
    00660       _M_dispose();
    00661       _M_data(__r->_M_refdata());
    00662     }
    00663
    00664   template<typename _CharT, typename _Traits, typename _Alloc>
    00665     void
    00666     __rc_string_base<_CharT, _Traits, _Alloc>::
    00667     _M_erase(size_type __pos, size_type __n)
    00668     {
    00669       const size_type __new_size = _M_length() - __n;
    00670       const size_type __how_much = _M_length() - __pos - __n;
    00671
    00672       if (_M_is_shared())
    00673     {
    00674       // Must reallocate.
    00675       _Rep* __r = _Rep::_S_create(__new_size, _M_capacity(),
    00676                       _M_get_allocator());
    00677
    00678       if (__pos)
    00679         _S_copy(__r->_M_refdata(), _M_data(), __pos);
    00680       if (__how_much)
    00681         _S_copy(__r->_M_refdata() + __pos,
    00682             _M_data() + __pos + __n, __how_much);
    00683
    00684       _M_dispose();
    00685       _M_data(__r->_M_refdata());
    00686     }
    00687       else if (__how_much && __n)
    00688     {
    00689       // Work in-place.
    00690       _S_move(_M_data() + __pos,
    00691           _M_data() + __pos + __n, __how_much);
    00692     }
    00693
    00694       _M_rep()->_M_set_length(__new_size);
    00695     }
    00696
    00697   template<>
    00698     inline bool
    00699     __rc_string_base<char, std::char_traits<char>,
    00700              std::allocator<char> >::
    00701     _M_compare(const __rc_string_base& __rcs) const
    00702     {
    00703       if (_M_rep() == __rcs._M_rep())
    00704     return true;
    00705       return false;
    00706     }
    00707
    00708 #ifdef _GLIBCXX_USE_WCHAR_T
    00709   template<>
    00710     inline bool
    00711     __rc_string_base<wchar_t, std::char_traits<wchar_t>,
    00712              std::allocator<wchar_t> >::
    00713     _M_compare(const __rc_string_base& __rcs) const
    00714     {
    00715       if (_M_rep() == __rcs._M_rep())
    00716     return true;
    00717       return false;
    00718     }
    00719 #endif
    00720
    00721 _GLIBCXX_END_NAMESPACE
    00722
    00723 #endif /* _RC_STRING_BASE_H */