1 // Temporary buffer implementation -*- C++ -*-
3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 // Free Software Foundation, Inc.
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40 * Copyright (c) 1996,1997
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52 /** @file bits/stl_tempbuf.h
53 * This is an internal header file, included by other library headers.
54 * Do not attempt to use it directly. @headername{memory}
57 #ifndef _STL_TEMPBUF_H
58 #define _STL_TEMPBUF_H 1
60 #include <bits/stl_algobase.h>
61 #include <bits/stl_construct.h>
63 namespace std _GLIBCXX_VISIBILITY(default)
65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
68 * @brief Allocates a temporary buffer.
69 * @param len The number of objects of type Tp.
70 * @return See full description.
72 * Reinventing the wheel, but this time with prettier spokes!
74 * This function tries to obtain storage for @c len adjacent Tp
75 * objects. The objects themselves are not constructed, of course.
76 * A pair<> is returned containing <em>the buffer s address and
77 * capacity (in the units of sizeof(Tp)), or a pair of 0 values if
78 * no storage can be obtained.</em> Note that the capacity obtained
79 * may be less than that requested if the memory is unavailable;
80 * you should compare len with the .second return value.
82 * Provides the nothrow exception guarantee.
84 template<typename _Tp>
86 get_temporary_buffer(ptrdiff_t __len)
88 const ptrdiff_t __max =
89 __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
95 _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp),
98 return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
101 return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
105 * @brief The companion to get_temporary_buffer().
106 * @param p A buffer previously allocated by get_temporary_buffer.
109 * Frees the memory pointed to by p.
111 template<typename _Tp>
113 return_temporary_buffer(_Tp* __p)
114 { ::operator delete(__p, std::nothrow); }
118 * This class is used in two places: stl_algo.h and ext/memory,
119 * where it is wrapped as the temporary_buffer class. See
120 * temporary_buffer docs for more notes.
122 template<typename _ForwardIterator, typename _Tp>
123 class _Temporary_buffer
125 // concept requirements
126 __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
129 typedef _Tp value_type;
130 typedef value_type* pointer;
131 typedef pointer iterator;
132 typedef ptrdiff_t size_type;
135 size_type _M_original_len;
140 /// As per Table mumble.
145 /// Returns the size requested by the constructor; may be >size().
147 requested_size() const
148 { return _M_original_len; }
150 /// As per Table mumble.
153 { return _M_buffer; }
155 /// As per Table mumble.
158 { return _M_buffer + _M_len; }
161 * Constructs a temporary buffer of a size somewhere between
162 * zero and the size of the given range.
164 _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last);
168 std::_Destroy(_M_buffer, _M_buffer + _M_len);
169 std::return_temporary_buffer(_M_buffer);
173 // Disable copy constructor and assignment operator.
174 _Temporary_buffer(const _Temporary_buffer&);
177 operator=(const _Temporary_buffer&);
182 struct __uninitialized_construct_buf_dispatch
184 template<typename _ForwardIterator, typename _Tp>
186 __ucr(_ForwardIterator __first, _ForwardIterator __last,
189 if(__first == __last)
192 _ForwardIterator __cur = __first;
195 std::_Construct(std::__addressof(*__first),
196 _GLIBCXX_MOVE(__value));
197 _ForwardIterator __prev = __cur;
199 for(; __cur != __last; ++__cur, ++__prev)
200 std::_Construct(std::__addressof(*__cur),
201 _GLIBCXX_MOVE(*__prev));
202 __value = _GLIBCXX_MOVE(*__prev);
206 std::_Destroy(__first, __cur);
207 __throw_exception_again;
213 struct __uninitialized_construct_buf_dispatch<true>
215 template<typename _ForwardIterator, typename _Tp>
217 __ucr(_ForwardIterator, _ForwardIterator, _Tp&) { }
220 // Constructs objects in the range [first, last).
221 // Note that while these new objects will take valid values,
222 // their exact value is not defined. In particular they may
225 // While __value may altered during this algorithm, it will have
226 // the same value when the algorithm finishes, unless one of the
227 // constructions throws.
229 // Requirements: _ForwardIterator::value_type(_Tp&&) is valid.
230 template<typename _ForwardIterator, typename _Tp>
232 __uninitialized_construct_buf(_ForwardIterator __first,
233 _ForwardIterator __last,
236 typedef typename std::iterator_traits<_ForwardIterator>::value_type
239 std::__uninitialized_construct_buf_dispatch<
240 __has_trivial_constructor(_ValueType)>::
241 __ucr(__first, __last, __value);
244 template<typename _ForwardIterator, typename _Tp>
245 _Temporary_buffer<_ForwardIterator, _Tp>::
246 _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last)
247 : _M_original_len(std::distance(__first, __last)),
248 _M_len(0), _M_buffer(0)
252 std::pair<pointer, size_type> __p(std::get_temporary_buffer<
253 value_type>(_M_original_len));
254 _M_buffer = __p.first;
257 std::__uninitialized_construct_buf(_M_buffer, _M_buffer + _M_len,
262 std::return_temporary_buffer(_M_buffer);
265 __throw_exception_again;
269 _GLIBCXX_END_NAMESPACE_VERSION
272 #endif /* _STL_TEMPBUF_H */