libstdc++-v3/include/bits/stl_tempbuf.h

   1 // Temporary buffer implementation -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
   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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  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  *
  33  * Copyright (c) 1994
  34  * Hewlett-Packard Company
  35  *
  36  * Permission to use, copy, modify, distribute and sell this software
  37  * and its documentation for any purpose is hereby granted without fee,
  38  * provided that the above copyright notice appear in all copies and
  39  * that both that copyright notice and this permission notice appear
  40  * in supporting documentation.  Hewlett-Packard Company makes no
  41  * representations about the suitability of this software for any
  42  * purpose.  It is provided "as is" without express or implied warranty.
  43  *
  44  *
  45  * Copyright (c) 1996,1997
  46  * Silicon Graphics Computer Systems, Inc.
  47  *
  48  * Permission to use, copy, modify, distribute and sell this software
  49  * and its documentation for any purpose is hereby granted without fee,
  50  * provided that the above copyright notice appear in all copies and
  51  * that both that copyright notice and this permission notice appear
  52  * in supporting documentation.  Silicon Graphics makes no
  53  * representations about the suitability of this software for any
  54  * purpose.  It is provided "as is" without express or implied warranty.
  55  */
  56
  57 /** @file stl_tempbuf.h
  58  *  This is an internal header file, included by other library headers.
  59  *  You should not attempt to use it directly.
  60  */
  61
  62 #ifndef _STL_TEMPBUF_H
  63 #define _STL_TEMPBUF_H 1
  64
  65 #include <bits/stl_algobase.h>
  66 #include <bits/stl_construct.h>
  67 #include <bits/stl_uninitialized.h>
  68
  69 _GLIBCXX_BEGIN_NAMESPACE(std)
  70
  71   /**
  72    *  @if maint
  73    *  This is a helper function.  The unused second parameter exists to
  74    *  permit the real get_temporary_buffer to use template parameter deduction.
  75    *  @endif
  76    */
  77   template<typename _Tp>
  78     pair<_Tp*, ptrdiff_t>
  79     __get_temporary_buffer(ptrdiff_t __len, _Tp*)
  80     {
  81       const ptrdiff_t __max =
  82         __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
  83       if (__len > __max)
  84         __len = __max;
  85
  86       while (__len > 0)
  87         {
  88           _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp),
  89                                                         std::nothrow));
  90           if (__tmp != 0)
  91             return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
  92           __len /= 2;
  93         }
  94       return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
  95     }
  96
  97   /**
  98    *  @brief Allocates a temporary buffer.
  99    *  @param  len  The number of objects of type Tp.
 100    *  @return See full description.
 101    *
 102    *  Reinventing the wheel, but this time with prettier spokes!
 103    *
 104    *  This function tries to obtain storage for @c len adjacent Tp
 105    *  objects.  The objects themselves are not constructed, of course.
 106    *  A pair<> is returned containing "the buffer s address and
 107    *  capacity (in the units of sizeof(Tp)), or a pair of 0 values if
 108    *  no storage can be obtained."  Note that the capacity obtained
 109    *  may be less than that requested if the memory is unavailable;
 110    *  you should compare len with the .second return value.
 111    *
 112    * Provides the nothrow exception guarantee.
 113    */
 114   template<typename _Tp>
 115     inline pair<_Tp*, ptrdiff_t>
 116     get_temporary_buffer(ptrdiff_t __len)
 117     { return std::__get_temporary_buffer(__len, static_cast<_Tp*>(0)); }
 118
 119   /**
 120    *  @brief The companion to get_temporary_buffer().
 121    *  @param  p  A buffer previously allocated by get_temporary_buffer.
 122    *  @return   None.
 123    *
 124    *  Frees the memory pointed to by p.
 125    */
 126   template<typename _Tp>
 127     inline void
 128     return_temporary_buffer(_Tp* __p)
 129     { ::operator delete(__p, std::nothrow); }
 130
 131
 132   /**
 133    *  @if maint
 134    *  This class is used in two places: stl_algo.h and ext/memory,
 135    *  where it is wrapped as the temporary_buffer class.  See
 136    *  temporary_buffer docs for more notes.
 137    *  @endif
 138    */
 139   template<typename _ForwardIterator, typename _Tp>
 140     class _Temporary_buffer
 141     {
 142       // concept requirements
 143       __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
 144
 145     public:
 146       typedef _Tp         value_type;
 147       typedef value_type* pointer;
 148       typedef pointer     iterator;
 149       typedef ptrdiff_t   size_type;
 150
 151     protected:
 152       size_type  _M_original_len;
 153       size_type  _M_len;
 154       pointer    _M_buffer;
 155
 156     public:
 157       /// As per Table mumble.
 158       size_type
 159       size() const
 160       { return _M_len; }
 161
 162       /// Returns the size requested by the constructor; may be >size().
 163       size_type
 164       requested_size() const
 165       { return _M_original_len; }
 166
 167       /// As per Table mumble.
 168       iterator
 169       begin()
 170       { return _M_buffer; }
 171
 172       /// As per Table mumble.
 173       iterator
 174       end()
 175       { return _M_buffer + _M_len; }
 176
 177       /**
 178        * Constructs a temporary buffer of a size somewhere between
 179        * zero and the size of the given range.
 180        */
 181       _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last);
 182
 183       ~_Temporary_buffer()
 184       {
 185         std::_Destroy(_M_buffer, _M_buffer + _M_len);
 186         std::return_temporary_buffer(_M_buffer);
 187       }
 188
 189     private:
 190       // Disable copy constructor and assignment operator.
 191       _Temporary_buffer(const _Temporary_buffer&);
 192
 193       void
 194       operator=(const _Temporary_buffer&);
 195     };
 196
 197   template<typename _ForwardIterator, typename _Tp>
 198     _Temporary_buffer<_ForwardIterator, _Tp>::
 199     _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last)
 200     : _M_original_len(std::distance(__first, __last)),
 201       _M_len(0), _M_buffer(0)
 202     {
 203       try
 204         {
 205           std::pair<pointer, size_type> __p(std::get_temporary_buffer<
 206                                             value_type>(_M_original_len));
 207           _M_buffer = __p.first;
 208           _M_len = __p.second;
 209           if (!__is_pod(_Tp) && _M_len > 0)
 210             std::uninitialized_fill_n(_M_buffer, _M_len, *__first);
 211         }
 212       catch(...)
 213         {
 214           std::return_temporary_buffer(_M_buffer);
 215           _M_buffer = 0;
 216           _M_len = 0;
 217           __throw_exception_again;
 218         }
 219     }
 220
 221 _GLIBCXX_END_NAMESPACE
 222
 223 #endif /* _STL_TEMPBUF_H */
 224