285 lines
8.5 KiB
C++
285 lines
8.5 KiB
C++
// Temporary buffer implementation -*- C++ -*-
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// Copyright (C) 2001-2021 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/*
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*
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* Copyright (c) 1994
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* Hewlett-Packard Company
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*
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* Permission to use, copy, modify, distribute and sell this software
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* and its documentation for any purpose is hereby granted without fee,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation. Hewlett-Packard Company makes no
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* representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*
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*
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* Copyright (c) 1996,1997
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* Silicon Graphics Computer Systems, Inc.
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*
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* Permission to use, copy, modify, distribute and sell this software
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* and its documentation for any purpose is hereby granted without fee,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation. Silicon Graphics makes no
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* representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*/
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/** @file bits/stl_tempbuf.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{memory}
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*/
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#ifndef _STL_TEMPBUF_H
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#define _STL_TEMPBUF_H 1
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#include <bits/stl_algobase.h>
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#include <bits/stl_construct.h>
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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namespace __detail
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{
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template<typename _Tp>
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inline void
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__return_temporary_buffer(_Tp* __p,
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size_t __len __attribute__((__unused__)))
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{
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#if __cpp_sized_deallocation
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::operator delete(__p, __len * sizeof(_Tp));
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#else
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::operator delete(__p);
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#endif
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}
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}
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/**
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* @brief Allocates a temporary buffer.
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* @param __len The number of objects of type Tp.
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* @return See full description.
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*
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* Reinventing the wheel, but this time with prettier spokes!
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*
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* This function tries to obtain storage for @c __len adjacent Tp
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* objects. The objects themselves are not constructed, of course.
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* A pair<> is returned containing <em>the buffer s address and
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* capacity (in the units of sizeof(_Tp)), or a pair of 0 values if
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* no storage can be obtained.</em> Note that the capacity obtained
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* may be less than that requested if the memory is unavailable;
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* you should compare len with the .second return value.
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*
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* Provides the nothrow exception guarantee.
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*/
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template<typename _Tp>
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pair<_Tp*, ptrdiff_t>
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get_temporary_buffer(ptrdiff_t __len) _GLIBCXX_NOEXCEPT
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{
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const ptrdiff_t __max =
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__gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
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if (__len > __max)
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__len = __max;
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while (__len > 0)
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{
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_Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp),
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std::nothrow));
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if (__tmp != 0)
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return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
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__len = __len == 1 ? 0 : ((__len + 1) / 2);
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}
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return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
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}
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/**
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* @brief The companion to get_temporary_buffer().
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* @param __p A buffer previously allocated by get_temporary_buffer.
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* @return None.
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*
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* Frees the memory pointed to by __p.
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*/
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template<typename _Tp>
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inline void
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return_temporary_buffer(_Tp* __p)
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{ ::operator delete(__p); }
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/**
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* This class is used in two places: stl_algo.h and ext/memory,
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* where it is wrapped as the temporary_buffer class. See
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* temporary_buffer docs for more notes.
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*/
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template<typename _ForwardIterator, typename _Tp>
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class _Temporary_buffer
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{
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// concept requirements
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__glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
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public:
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typedef _Tp value_type;
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typedef value_type* pointer;
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typedef pointer iterator;
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typedef ptrdiff_t size_type;
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protected:
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size_type _M_original_len;
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size_type _M_len;
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pointer _M_buffer;
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public:
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/// As per Table mumble.
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size_type
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size() const
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{ return _M_len; }
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/// Returns the size requested by the constructor; may be >size().
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size_type
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requested_size() const
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{ return _M_original_len; }
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/// As per Table mumble.
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iterator
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begin()
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{ return _M_buffer; }
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/// As per Table mumble.
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iterator
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end()
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{ return _M_buffer + _M_len; }
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/**
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* Constructs a temporary buffer of a size somewhere between
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* zero and the given length.
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*/
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_Temporary_buffer(_ForwardIterator __seed, size_type __original_len);
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~_Temporary_buffer()
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{
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std::_Destroy(_M_buffer, _M_buffer + _M_len);
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std::__detail::__return_temporary_buffer(_M_buffer, _M_len);
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}
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private:
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// Disable copy constructor and assignment operator.
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_Temporary_buffer(const _Temporary_buffer&);
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void
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operator=(const _Temporary_buffer&);
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};
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template<bool>
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struct __uninitialized_construct_buf_dispatch
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{
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template<typename _Pointer, typename _ForwardIterator>
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static void
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__ucr(_Pointer __first, _Pointer __last,
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_ForwardIterator __seed)
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{
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if (__first == __last)
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return;
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_Pointer __cur = __first;
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__try
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{
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std::_Construct(std::__addressof(*__first),
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_GLIBCXX_MOVE(*__seed));
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_Pointer __prev = __cur;
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++__cur;
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for(; __cur != __last; ++__cur, ++__prev)
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std::_Construct(std::__addressof(*__cur),
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_GLIBCXX_MOVE(*__prev));
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*__seed = _GLIBCXX_MOVE(*__prev);
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}
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__catch(...)
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{
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std::_Destroy(__first, __cur);
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__throw_exception_again;
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}
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}
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};
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template<>
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struct __uninitialized_construct_buf_dispatch<true>
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{
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template<typename _Pointer, typename _ForwardIterator>
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static void
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__ucr(_Pointer, _Pointer, _ForwardIterator) { }
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};
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// Constructs objects in the range [first, last).
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// Note that while these new objects will take valid values,
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// their exact value is not defined. In particular they may
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// be 'moved from'.
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//
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// While *__seed may be altered during this algorithm, it will have
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// the same value when the algorithm finishes, unless one of the
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// constructions throws.
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//
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// Requirements: _Pointer::value_type(_Tp&&) is valid.
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template<typename _Pointer, typename _ForwardIterator>
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inline void
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__uninitialized_construct_buf(_Pointer __first, _Pointer __last,
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_ForwardIterator __seed)
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{
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typedef typename std::iterator_traits<_Pointer>::value_type
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_ValueType;
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std::__uninitialized_construct_buf_dispatch<
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__has_trivial_constructor(_ValueType)>::
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__ucr(__first, __last, __seed);
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}
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template<typename _ForwardIterator, typename _Tp>
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_Temporary_buffer<_ForwardIterator, _Tp>::
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_Temporary_buffer(_ForwardIterator __seed, size_type __original_len)
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: _M_original_len(__original_len), _M_len(0), _M_buffer(0)
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{
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std::pair<pointer, size_type> __p(
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std::get_temporary_buffer<value_type>(_M_original_len));
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if (__p.first)
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{
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__try
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{
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std::__uninitialized_construct_buf(__p.first, __p.first + __p.second,
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__seed);
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_M_buffer = __p.first;
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_M_len = __p.second;
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}
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__catch(...)
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{
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std::__detail::__return_temporary_buffer(__p.first, __p.second);
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__throw_exception_again;
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}
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}
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}
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif /* _STL_TEMPBUF_H */
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