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 <cstddef>
15 #include <new>
16 #include <utility> // pair
17
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #pragma GCC system_header
20 #endif
21
22 _LIBCPP_PUSH_MACROS
23 #include <__undef_macros>
24
25 _LIBCPP_BEGIN_NAMESPACE_STD
26
27 template <class _Tp>
28 _LIBCPP_NODISCARD_EXT _LIBCPP_NO_CFI
29 pair<_Tp*, ptrdiff_t>
get_temporary_buffer(ptrdiff_t __n)30 get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
31 {
32 pair<_Tp*, ptrdiff_t> __r(0, 0);
33 const ptrdiff_t __m = (~ptrdiff_t(0) ^
34 ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1)))
35 / sizeof(_Tp);
36 if (__n > __m)
37 __n = __m;
38 while (__n > 0)
39 {
40 #if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
41 if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
42 {
43 align_val_t __al =
44 align_val_t(alignment_of<_Tp>::value);
45 __r.first = static_cast<_Tp*>(::operator new(
46 __n * sizeof(_Tp), __al, nothrow));
47 } else {
48 __r.first = static_cast<_Tp*>(::operator new(
49 __n * sizeof(_Tp), nothrow));
50 }
51 #else
52 if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
53 {
54 // Since aligned operator new is unavailable, return an empty
55 // buffer rather than one with invalid alignment.
56 return __r;
57 }
58
59 __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
60 #endif
61
62 if (__r.first)
63 {
64 __r.second = __n;
65 break;
66 }
67 __n /= 2;
68 }
69 return __r;
70 }
71
72 template <class _Tp>
73 inline _LIBCPP_INLINE_VISIBILITY
return_temporary_buffer(_Tp * __p)74 void return_temporary_buffer(_Tp* __p) _NOEXCEPT
75 {
76 _VSTD::__libcpp_deallocate_unsized((void*)__p, _LIBCPP_ALIGNOF(_Tp));
77 }
78
79 _LIBCPP_END_NAMESPACE_STD
80
81 _LIBCPP_POP_MACROS
82
83 #endif // _LIBCPP___MEMORY_TEMPORARY_BUFFER_H
84