1 // Temporary buffer implementation -*- C++ -*-
3 // Copyright (C) 2001-2018 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
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16 // Under Section 7 of GPL version 3, you are granted additional
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39 * Copyright (c) 1996,1997
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51 /** @file bits/stl_tempbuf.h
52 * This is an internal header file, included by other library headers.
53 * Do not attempt to use it directly. @headername{memory}
56 #ifndef _STL_TEMPBUF_H
57 #define _STL_TEMPBUF_H 1
59 #include <bits/stl_algobase.h>
60 #include <bits/stl_construct.h>
62 namespace std
_GLIBCXX_VISIBILITY(default)
64 _GLIBCXX_BEGIN_NAMESPACE_VERSION
67 * @brief Allocates a temporary buffer.
68 * @param __len The number of objects of type Tp.
69 * @return See full description.
71 * Reinventing the wheel, but this time with prettier spokes!
73 * This function tries to obtain storage for @c __len adjacent Tp
74 * objects. The objects themselves are not constructed, of course.
75 * A pair<> is returned containing <em>the buffer s address and
76 * capacity (in the units of sizeof(_Tp)), or a pair of 0 values if
77 * no storage can be obtained.</em> Note that the capacity obtained
78 * may be less than that requested if the memory is unavailable;
79 * you should compare len with the .second return value.
81 * Provides the nothrow exception guarantee.
83 template<typename _Tp
>
85 get_temporary_buffer(ptrdiff_t __len
) _GLIBCXX_NOEXCEPT
87 const ptrdiff_t __max
=
88 __gnu_cxx::__numeric_traits
<ptrdiff_t>::__max
/ sizeof(_Tp
);
94 _Tp
* __tmp
= static_cast<_Tp
*>(::operator new(__len
* sizeof(_Tp
),
97 return std::pair
<_Tp
*, ptrdiff_t>(__tmp
, __len
);
100 return std::pair
<_Tp
*, ptrdiff_t>(static_cast<_Tp
*>(0), 0);
104 * @brief The companion to get_temporary_buffer().
105 * @param __p A buffer previously allocated by get_temporary_buffer.
108 * Frees the memory pointed to by __p.
110 template<typename _Tp
>
112 return_temporary_buffer(_Tp
* __p
)
113 { ::operator delete(__p
, std::nothrow
); }
117 * This class is used in two places: stl_algo.h and ext/memory,
118 * where it is wrapped as the temporary_buffer class. See
119 * temporary_buffer docs for more notes.
121 template<typename _ForwardIterator
, typename _Tp
>
122 class _Temporary_buffer
124 // concept requirements
125 __glibcxx_class_requires(_ForwardIterator
, _ForwardIteratorConcept
)
128 typedef _Tp value_type
;
129 typedef value_type
* pointer
;
130 typedef pointer iterator
;
131 typedef ptrdiff_t size_type
;
134 size_type _M_original_len
;
139 /// As per Table mumble.
144 /// Returns the size requested by the constructor; may be >size().
146 requested_size() const
147 { return _M_original_len
; }
149 /// As per Table mumble.
152 { return _M_buffer
; }
154 /// As per Table mumble.
157 { return _M_buffer
+ _M_len
; }
160 * Constructs a temporary buffer of a size somewhere between
161 * zero and the size of the given range.
163 _Temporary_buffer(_ForwardIterator __first
, _ForwardIterator __last
);
167 std::_Destroy(_M_buffer
, _M_buffer
+ _M_len
);
168 std::return_temporary_buffer(_M_buffer
);
172 // Disable copy constructor and assignment operator.
173 _Temporary_buffer(const _Temporary_buffer
&);
176 operator=(const _Temporary_buffer
&);
181 struct __uninitialized_construct_buf_dispatch
183 template<typename _Pointer
, typename _ForwardIterator
>
185 __ucr(_Pointer __first
, _Pointer __last
,
186 _ForwardIterator __seed
)
188 if(__first
== __last
)
191 _Pointer __cur
= __first
;
194 std::_Construct(std::__addressof(*__first
),
195 _GLIBCXX_MOVE(*__seed
));
196 _Pointer __prev
= __cur
;
198 for(; __cur
!= __last
; ++__cur
, ++__prev
)
199 std::_Construct(std::__addressof(*__cur
),
200 _GLIBCXX_MOVE(*__prev
));
201 *__seed
= _GLIBCXX_MOVE(*__prev
);
205 std::_Destroy(__first
, __cur
);
206 __throw_exception_again
;
212 struct __uninitialized_construct_buf_dispatch
<true>
214 template<typename _Pointer
, typename _ForwardIterator
>
216 __ucr(_Pointer
, _Pointer
, _ForwardIterator
) { }
219 // Constructs objects in the range [first, last).
220 // Note that while these new objects will take valid values,
221 // their exact value is not defined. In particular they may
224 // While *__seed may be altered during this algorithm, it will have
225 // the same value when the algorithm finishes, unless one of the
226 // constructions throws.
228 // Requirements: _Pointer::value_type(_Tp&&) is valid.
229 template<typename _Pointer
, typename _ForwardIterator
>
231 __uninitialized_construct_buf(_Pointer __first
, _Pointer __last
,
232 _ForwardIterator __seed
)
234 typedef typename
std::iterator_traits
<_Pointer
>::value_type
237 std::__uninitialized_construct_buf_dispatch
<
238 __has_trivial_constructor(_ValueType
)>::
239 __ucr(__first
, __last
, __seed
);
242 template<typename _ForwardIterator
, typename _Tp
>
243 _Temporary_buffer
<_ForwardIterator
, _Tp
>::
244 _Temporary_buffer(_ForwardIterator __first
, _ForwardIterator __last
)
245 : _M_original_len(std::distance(__first
, __last
)),
246 _M_len(0), _M_buffer(0)
250 std::pair
<pointer
, size_type
> __p(std::get_temporary_buffer
<
251 value_type
>(_M_original_len
));
252 _M_buffer
= __p
.first
;
255 std::__uninitialized_construct_buf(_M_buffer
, _M_buffer
+ _M_len
,
260 std::return_temporary_buffer(_M_buffer
);
263 __throw_exception_again
;
267 _GLIBCXX_END_NAMESPACE_VERSION
270 #endif /* _STL_TEMPBUF_H */