1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___MEMORY_TEMPORARY_BUFFER_H
11 #define _LIBCPP___MEMORY_TEMPORARY_BUFFER_H
12 
13 #include <__config>
14 #include <__type_traits/alignment_of.h>
15 #include <__utility/pair.h>
16 #include <cstddef>
17 #include <new>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #  pragma GCC system_header
21 #endif
22 
23 _LIBCPP_BEGIN_NAMESPACE_STD
24 
25 template <class _Tp>
26 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _LIBCPP_DEPRECATED_IN_CXX17
27 pair<_Tp*, ptrdiff_t>
28 get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
29 {
30     pair<_Tp*, ptrdiff_t> __r(0, 0);
31     const ptrdiff_t __m = (~ptrdiff_t(0) ^
32                            ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1)))
33                            / sizeof(_Tp);
34     if (__n > __m)
35         __n = __m;
36     while (__n > 0)
37     {
38 #if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
39     if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
40         {
41             align_val_t __al =
42                 align_val_t(alignment_of<_Tp>::value);
43             __r.first = static_cast<_Tp*>(::operator new(
44                 __n * sizeof(_Tp), __al, nothrow));
45         } else {
46             __r.first = static_cast<_Tp*>(::operator new(
47                 __n * sizeof(_Tp), nothrow));
48         }
49 #else
50     if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
51         {
52             // Since aligned operator new is unavailable, return an empty
53             // buffer rather than one with invalid alignment.
54             return __r;
55         }
56 
57         __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
58 #endif
59 
60         if (__r.first)
61         {
62             __r.second = __n;
63             break;
64         }
65         __n /= 2;
66     }
67     return __r;
68 }
69 
70 template <class _Tp>
71 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_IN_CXX17
72 void return_temporary_buffer(_Tp* __p) _NOEXCEPT
73 {
74   _VSTD::__libcpp_deallocate_unsized((void*)__p, _LIBCPP_ALIGNOF(_Tp));
75 }
76 
77 struct __return_temporary_buffer
78 {
79 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
80     template <class _Tp>
81     _LIBCPP_INLINE_VISIBILITY void operator()(_Tp* __p) const {_VSTD::return_temporary_buffer(__p);}
82 _LIBCPP_SUPPRESS_DEPRECATED_POP
83 };
84 
85 _LIBCPP_END_NAMESPACE_STD
86 
87 #endif // _LIBCPP___MEMORY_TEMPORARY_BUFFER_H
88