stl_tempbuf.h
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// Temporary buffer implementation -*- C++ -*-
// Copyright (C) 2001-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/*
*
* Copyright (c) 1994
* Hewlett-Packard Company
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Hewlett-Packard Company makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
*
* Copyright (c) 1996,1997
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/** @file bits/stl_tempbuf.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{memory}
*/
#ifndef _STL_TEMPBUF_H
#define _STL_TEMPBUF_H 1
#include <bits/stl_algobase.h>
#include <bits/stl_construct.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __detail
{
template<typename _Tp>
inline void
__return_temporary_buffer(_Tp* __p,
size_t __len __attribute__((__unused__)))
{
#if __cpp_sized_deallocation
::operator delete(__p, __len * sizeof(_Tp));
#else
::operator delete(__p);
#endif
}
}
/**
* @brief Allocates a temporary buffer.
* @param __len The number of objects of type Tp.
* @return See full description.
*
* Reinventing the wheel, but this time with prettier spokes!
*
* This function tries to obtain storage for @c __len adjacent Tp
* objects. The objects themselves are not constructed, of course.
* A pair<> is returned containing <em>the buffer s address and
* capacity (in the units of sizeof(_Tp)), or a pair of 0 values if
* no storage can be obtained.</em> Note that the capacity obtained
* may be less than that requested if the memory is unavailable;
* you should compare len with the .second return value.
*
* Provides the nothrow exception guarantee.
*/
template<typename _Tp>
pair<_Tp*, ptrdiff_t>
get_temporary_buffer(ptrdiff_t __len) _GLIBCXX_NOEXCEPT
{
const ptrdiff_t __max =
__gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
if (__len > __max)
__len = __max;
while (__len > 0)
{
_Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp),
std::nothrow));
if (__tmp != 0)
return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
__len = __len == 1 ? 0 : ((__len + 1) / 2);
}
return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
}
/**
* @brief The companion to get_temporary_buffer().
* @param __p A buffer previously allocated by get_temporary_buffer.
* @return None.
*
* Frees the memory pointed to by __p.
*/
template<typename _Tp>
inline void
return_temporary_buffer(_Tp* __p)
{ ::operator delete(__p); }
/**
* This class is used in two places: stl_algo.h and ext/memory,
* where it is wrapped as the temporary_buffer class. See
* temporary_buffer docs for more notes.
*/
template<typename _ForwardIterator, typename _Tp>
class _Temporary_buffer
{
// concept requirements
__glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
public:
typedef _Tp value_type;
typedef value_type* pointer;
typedef pointer iterator;
typedef ptrdiff_t size_type;
protected:
size_type _M_original_len;
size_type _M_len;
pointer _M_buffer;
public:
/// As per Table mumble.
size_type
size() const
{ return _M_len; }
/// Returns the size requested by the constructor; may be >size().
size_type
requested_size() const
{ return _M_original_len; }
/// As per Table mumble.
iterator
begin()
{ return _M_buffer; }
/// As per Table mumble.
iterator
end()
{ return _M_buffer + _M_len; }
/**
* Constructs a temporary buffer of a size somewhere between
* zero and the given length.
*/
_Temporary_buffer(_ForwardIterator __seed, size_type __original_len);
~_Temporary_buffer()
{
std::_Destroy(_M_buffer, _M_buffer + _M_len);
std::__detail::__return_temporary_buffer(_M_buffer, _M_len);
}
private:
// Disable copy constructor and assignment operator.
_Temporary_buffer(const _Temporary_buffer&);
void
operator=(const _Temporary_buffer&);
};
template<bool>
struct __uninitialized_construct_buf_dispatch
{
template<typename _Pointer, typename _ForwardIterator>
static void
__ucr(_Pointer __first, _Pointer __last,
_ForwardIterator __seed)
{
if (__first == __last)
return;
_Pointer __cur = __first;
__try
{
std::_Construct(std::__addressof(*__first),
_GLIBCXX_MOVE(*__seed));
_Pointer __prev = __cur;
++__cur;
for(; __cur != __last; ++__cur, ++__prev)
std::_Construct(std::__addressof(*__cur),
_GLIBCXX_MOVE(*__prev));
*__seed = _GLIBCXX_MOVE(*__prev);
}
__catch(...)
{
std::_Destroy(__first, __cur);
__throw_exception_again;
}
}
};
template<>
struct __uninitialized_construct_buf_dispatch<true>
{
template<typename _Pointer, typename _ForwardIterator>
static void
__ucr(_Pointer, _Pointer, _ForwardIterator) { }
};
// Constructs objects in the range [first, last).
// Note that while these new objects will take valid values,
// their exact value is not defined. In particular they may
// be 'moved from'.
//
// While *__seed may be altered during this algorithm, it will have
// the same value when the algorithm finishes, unless one of the
// constructions throws.
//
// Requirements: _Pointer::value_type(_Tp&&) is valid.
template<typename _Pointer, typename _ForwardIterator>
inline void
__uninitialized_construct_buf(_Pointer __first, _Pointer __last,
_ForwardIterator __seed)
{
typedef typename std::iterator_traits<_Pointer>::value_type
_ValueType;
std::__uninitialized_construct_buf_dispatch<
__has_trivial_constructor(_ValueType)>::
__ucr(__first, __last, __seed);
}
template<typename _ForwardIterator, typename _Tp>
_Temporary_buffer<_ForwardIterator, _Tp>::
_Temporary_buffer(_ForwardIterator __seed, size_type __original_len)
: _M_original_len(__original_len), _M_len(0), _M_buffer(0)
{
std::pair<pointer, size_type> __p(
std::get_temporary_buffer<value_type>(_M_original_len));
if (__p.first)
{
__try
{
std::__uninitialized_construct_buf(__p.first, __p.first + __p.second,
__seed);
_M_buffer = __p.first;
_M_len = __p.second;
}
__catch(...)
{
std::__detail::__return_temporary_buffer(__p.first, __p.second);
__throw_exception_again;
}
}
}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif /* _STL_TEMPBUF_H */
stl_algobase.h
stl_construct.h
std::__addressof
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
std
ISO C++ entities toplevel namespace is std.
std::return_temporary_buffer
void return_temporary_buffer(_Tp *__p)
The companion to get_temporary_buffer().
Definition: stl_tempbuf.h:127
std::_Construct
constexpr void _Construct(_Tp *__p, _Args &&... __args)
Definition: stl_construct.h:109
std::_Destroy
void _Destroy(_ForwardIterator __first, _ForwardIterator __last, _Allocator &__alloc)
Definition: bits/alloc_traits.h:837
std::get_temporary_buffer
pair< _Tp *, ptrdiff_t > get_temporary_buffer(ptrdiff_t __len) noexcept
Allocates a temporary buffer.
Definition: stl_tempbuf.h:100
std::iterator_traits
Traits class for iterators.
Definition: stl_iterator_base_types.h:178
std::iterator
Common iterator class.
Definition: stl_iterator_base_types.h:128
std::pair
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:213
std::pair::first
_T1 first
The first member.
Definition: stl_pair.h:217
std::pair::second
_T2 second
The second member.
Definition: stl_pair.h:218
std::_Temporary_buffer
Definition: stl_tempbuf.h:137
std::_Temporary_buffer::end
iterator end()
As per Table mumble.
Definition: stl_tempbuf.h:170
std::_Temporary_buffer::requested_size
size_type requested_size() const
Returns the size requested by the constructor; may be >size().
Definition: stl_tempbuf.h:160
std::_Temporary_buffer::size
size_type size() const
As per Table mumble.
Definition: stl_tempbuf.h:155
std::_Temporary_buffer::begin
iterator begin()
As per Table mumble.
Definition: stl_tempbuf.h:165
std::_Temporary_buffer::_Temporary_buffer
_Temporary_buffer(_ForwardIterator __seed, size_type __original_len)
Definition: stl_tempbuf.h:258