stl_tempbuf.h

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00001 // Temporary buffer implementation -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
00004 // Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 2, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // You should have received a copy of the GNU General Public License along
00018 // with this library; see the file COPYING.  If not, write to the Free
00019 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
00020 // USA.
00021 
00022 // As a special exception, you may use this file as part of a free software
00023 // library without restriction.  Specifically, if other files instantiate
00024 // templates or use macros or inline functions from this file, or you compile
00025 // this file and link it with other files to produce an executable, this
00026 // file does not by itself cause the resulting executable to be covered by
00027 // the GNU General Public License.  This exception does not however
00028 // invalidate any other reasons why the executable file might be covered by
00029 // the GNU General Public License.
00030 
00031 /*
00032  *
00033  * Copyright (c) 1994
00034  * Hewlett-Packard Company
00035  *
00036  * Permission to use, copy, modify, distribute and sell this software
00037  * and its documentation for any purpose is hereby granted without fee,
00038  * provided that the above copyright notice appear in all copies and
00039  * that both that copyright notice and this permission notice appear
00040  * in supporting documentation.  Hewlett-Packard Company makes no
00041  * representations about the suitability of this software for any
00042  * purpose.  It is provided "as is" without express or implied warranty.
00043  *
00044  *
00045  * Copyright (c) 1996,1997
00046  * Silicon Graphics Computer Systems, Inc.
00047  *
00048  * Permission to use, copy, modify, distribute and sell this software
00049  * and its documentation for any purpose is hereby granted without fee,
00050  * provided that the above copyright notice appear in all copies and
00051  * that both that copyright notice and this permission notice appear
00052  * in supporting documentation.  Silicon Graphics makes no
00053  * representations about the suitability of this software for any
00054  * purpose.  It is provided "as is" without express or implied warranty.
00055  */
00056 
00057 /** @file stl_tempbuf.h
00058  *  This is an internal header file, included by other library headers.
00059  *  You should not attempt to use it directly.
00060  */
00061 
00062 #ifndef _STL_TEMPBUF_H
00063 #define _STL_TEMPBUF_H 1
00064 
00065 #include <bits/stl_algobase.h>
00066 #include <bits/stl_construct.h>
00067 #include <bits/stl_uninitialized.h>
00068 
00069 _GLIBCXX_BEGIN_NAMESPACE(std)
00070 
00071   /**
00072    *  @brief Allocates a temporary buffer.
00073    *  @param  len  The number of objects of type Tp.
00074    *  @return See full description.
00075    *
00076    *  Reinventing the wheel, but this time with prettier spokes!
00077    *
00078    *  This function tries to obtain storage for @c len adjacent Tp
00079    *  objects.  The objects themselves are not constructed, of course.
00080    *  A pair<> is returned containing "the buffer s address and
00081    *  capacity (in the units of sizeof(Tp)), or a pair of 0 values if
00082    *  no storage can be obtained."  Note that the capacity obtained
00083    *  may be less than that requested if the memory is unavailable;
00084    *  you should compare len with the .second return value.
00085    *
00086    * Provides the nothrow exception guarantee.
00087    */
00088   template<typename _Tp>
00089     pair<_Tp*, ptrdiff_t>
00090     get_temporary_buffer(ptrdiff_t __len)
00091     {
00092       const ptrdiff_t __max =
00093     __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
00094       if (__len > __max)
00095     __len = __max;
00096       
00097       while (__len > 0) 
00098     {
00099       _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp), 
00100                             std::nothrow));
00101       if (__tmp != 0)
00102         return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
00103       __len /= 2;
00104     }
00105       return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
00106     }
00107 
00108   /**
00109    *  @brief The companion to get_temporary_buffer().
00110    *  @param  p  A buffer previously allocated by get_temporary_buffer.
00111    *  @return   None.
00112    *
00113    *  Frees the memory pointed to by p.
00114    */
00115   template<typename _Tp>
00116     inline void
00117     return_temporary_buffer(_Tp* __p)
00118     { ::operator delete(__p, std::nothrow); }
00119 
00120 
00121   /**
00122    *  This class is used in two places: stl_algo.h and ext/memory,
00123    *  where it is wrapped as the temporary_buffer class.  See
00124    *  temporary_buffer docs for more notes.
00125    */
00126   template<typename _ForwardIterator, typename _Tp>
00127     class _Temporary_buffer
00128     {
00129       // concept requirements
00130       __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
00131 
00132     public:
00133       typedef _Tp         value_type;
00134       typedef value_type* pointer;
00135       typedef pointer     iterator;
00136       typedef ptrdiff_t   size_type;
00137 
00138     protected:
00139       size_type  _M_original_len;
00140       size_type  _M_len;
00141       pointer    _M_buffer;
00142 
00143     public:
00144       /// As per Table mumble.
00145       size_type
00146       size() const
00147       { return _M_len; }
00148 
00149       /// Returns the size requested by the constructor; may be >size().
00150       size_type
00151       requested_size() const
00152       { return _M_original_len; }
00153 
00154       /// As per Table mumble.
00155       iterator
00156       begin()
00157       { return _M_buffer; }
00158 
00159       /// As per Table mumble.
00160       iterator
00161       end()
00162       { return _M_buffer + _M_len; }
00163 
00164       /**
00165        * Constructs a temporary buffer of a size somewhere between
00166        * zero and the size of the given range.
00167        */
00168       _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last);
00169 
00170       ~_Temporary_buffer()
00171       {
00172     std::_Destroy(_M_buffer, _M_buffer + _M_len);
00173     std::return_temporary_buffer(_M_buffer);
00174       }
00175 
00176     private:
00177       // Disable copy constructor and assignment operator.
00178       _Temporary_buffer(const _Temporary_buffer&);
00179 
00180       void
00181       operator=(const _Temporary_buffer&);
00182     };
00183 
00184   template<typename _ForwardIterator, typename _Tp>
00185     _Temporary_buffer<_ForwardIterator, _Tp>::
00186     _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last)
00187     : _M_original_len(std::distance(__first, __last)),
00188       _M_len(0), _M_buffer(0)
00189     {
00190       try
00191     {
00192       std::pair<pointer, size_type> __p(std::get_temporary_buffer<
00193                         value_type>(_M_original_len));
00194       _M_buffer = __p.first;
00195       _M_len = __p.second;
00196       if (!__is_pod(_Tp) && _M_len > 0)
00197         std::uninitialized_fill_n(_M_buffer, _M_len, *__first);
00198     }
00199       catch(...)
00200     {
00201       std::return_temporary_buffer(_M_buffer);
00202       _M_buffer = 0;
00203       _M_len = 0;
00204       __throw_exception_again;
00205     }
00206     }
00207 
00208 _GLIBCXX_END_NAMESPACE
00209 
00210 #endif /* _STL_TEMPBUF_H */
00211 

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