stl_tempbuf.h

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00001 // Temporary buffer implementation -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /*
00027  *
00028  * Copyright (c) 1994
00029  * Hewlett-Packard Company
00030  *
00031  * Permission to use, copy, modify, distribute and sell this software
00032  * and its documentation for any purpose is hereby granted without fee,
00033  * provided that the above copyright notice appear in all copies and
00034  * that both that copyright notice and this permission notice appear
00035  * in supporting documentation.  Hewlett-Packard Company makes no
00036  * representations about the suitability of this software for any
00037  * purpose.  It is provided "as is" without express or implied warranty.
00038  *
00039  *
00040  * Copyright (c) 1996,1997
00041  * Silicon Graphics Computer Systems, Inc.
00042  *
00043  * Permission to use, copy, modify, distribute and sell this software
00044  * and its documentation for any purpose is hereby granted without fee,
00045  * provided that the above copyright notice appear in all copies and
00046  * that both that copyright notice and this permission notice appear
00047  * in supporting documentation.  Silicon Graphics makes no
00048  * representations about the suitability of this software for any
00049  * purpose.  It is provided "as is" without express or implied warranty.
00050  */
00051 
00052 /** @file stl_tempbuf.h
00053  *  This is an internal header file, included by other library headers.
00054  *  You should not attempt to use it directly.
00055  */
00056 
00057 #ifndef _STL_TEMPBUF_H
00058 #define _STL_TEMPBUF_H 1
00059 
00060 #include <bits/stl_algobase.h>
00061 #include <bits/stl_construct.h>
00062 #include <bits/stl_uninitialized.h>
00063 
00064 _GLIBCXX_BEGIN_NAMESPACE(std)
00065 
00066   /**
00067    *  @brief Allocates a temporary buffer.
00068    *  @param  len  The number of objects of type Tp.
00069    *  @return See full description.
00070    *
00071    *  Reinventing the wheel, but this time with prettier spokes!
00072    *
00073    *  This function tries to obtain storage for @c len adjacent Tp
00074    *  objects.  The objects themselves are not constructed, of course.
00075    *  A pair<> is returned containing "the buffer s address and
00076    *  capacity (in the units of sizeof(Tp)), or a pair of 0 values if
00077    *  no storage can be obtained."  Note that the capacity obtained
00078    *  may be less than that requested if the memory is unavailable;
00079    *  you should compare len with the .second return value.
00080    *
00081    * Provides the nothrow exception guarantee.
00082    */
00083   template<typename _Tp>
00084     pair<_Tp*, ptrdiff_t>
00085     get_temporary_buffer(ptrdiff_t __len)
00086     {
00087       const ptrdiff_t __max =
00088     __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
00089       if (__len > __max)
00090     __len = __max;
00091       
00092       while (__len > 0) 
00093     {
00094       _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp), 
00095                             std::nothrow));
00096       if (__tmp != 0)
00097         return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
00098       __len /= 2;
00099     }
00100       return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
00101     }
00102 
00103   /**
00104    *  @brief The companion to get_temporary_buffer().
00105    *  @param  p  A buffer previously allocated by get_temporary_buffer.
00106    *  @return   None.
00107    *
00108    *  Frees the memory pointed to by p.
00109    */
00110   template<typename _Tp>
00111     inline void
00112     return_temporary_buffer(_Tp* __p)
00113     { ::operator delete(__p, std::nothrow); }
00114 
00115 
00116   /**
00117    *  This class is used in two places: stl_algo.h and ext/memory,
00118    *  where it is wrapped as the temporary_buffer class.  See
00119    *  temporary_buffer docs for more notes.
00120    */
00121   template<typename _ForwardIterator, typename _Tp>
00122     class _Temporary_buffer
00123     {
00124       // concept requirements
00125       __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
00126 
00127     public:
00128       typedef _Tp         value_type;
00129       typedef value_type* pointer;
00130       typedef pointer     iterator;
00131       typedef ptrdiff_t   size_type;
00132 
00133     protected:
00134       size_type  _M_original_len;
00135       size_type  _M_len;
00136       pointer    _M_buffer;
00137 
00138     public:
00139       /// As per Table mumble.
00140       size_type
00141       size() const
00142       { return _M_len; }
00143 
00144       /// Returns the size requested by the constructor; may be >size().
00145       size_type
00146       requested_size() const
00147       { return _M_original_len; }
00148 
00149       /// As per Table mumble.
00150       iterator
00151       begin()
00152       { return _M_buffer; }
00153 
00154       /// As per Table mumble.
00155       iterator
00156       end()
00157       { return _M_buffer + _M_len; }
00158 
00159       /**
00160        * Constructs a temporary buffer of a size somewhere between
00161        * zero and the size of the given range.
00162        */
00163       _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last);
00164 
00165       ~_Temporary_buffer()
00166       {
00167     std::_Destroy(_M_buffer, _M_buffer + _M_len);
00168     std::return_temporary_buffer(_M_buffer);
00169       }
00170 
00171     private:
00172       // Disable copy constructor and assignment operator.
00173       _Temporary_buffer(const _Temporary_buffer&);
00174 
00175       void
00176       operator=(const _Temporary_buffer&);
00177     };
00178 
00179   template<typename _ForwardIterator, typename _Tp>
00180     _Temporary_buffer<_ForwardIterator, _Tp>::
00181     _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last)
00182     : _M_original_len(std::distance(__first, __last)),
00183       _M_len(0), _M_buffer(0)
00184     {
00185       __try
00186     {
00187       std::pair<pointer, size_type> __p(std::get_temporary_buffer<
00188                         value_type>(_M_original_len));
00189       _M_buffer = __p.first;
00190       _M_len = __p.second;
00191       if (!__is_pod(_Tp) && _M_len > 0)
00192         std::uninitialized_fill_n(_M_buffer, _M_len, *__first);
00193     }
00194       __catch(...)
00195     {
00196       std::return_temporary_buffer(_M_buffer);
00197       _M_buffer = 0;
00198       _M_len = 0;
00199       __throw_exception_again;
00200     }
00201     }
00202 
00203 _GLIBCXX_END_NAMESPACE
00204 
00205 #endif /* _STL_TEMPBUF_H */
00206 

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