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_UNIQUE_TEMPORARY_BUFFER_H
11 #define _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H
12
13 #include <__assert>
14 #include <__config>
15
16 #include <__cstddef/ptrdiff_t.h>
17 #include <__memory/allocator.h>
18 #include <__memory/unique_ptr.h>
19 #include <__new/allocate.h>
20 #include <__new/global_new_delete.h>
21 #include <__type_traits/is_constant_evaluated.h>
22
23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24 # pragma GCC system_header
25 #endif
26
27 _LIBCPP_BEGIN_NAMESPACE_STD
28
29 template <class _Tp>
30 struct __temporary_buffer_deleter {
31 ptrdiff_t __count_; // ignored in non-constant evaluation
32
__temporary_buffer_deleter__temporary_buffer_deleter33 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __temporary_buffer_deleter() _NOEXCEPT : __count_(0) {}
34 _LIBCPP_HIDE_FROM_ABI
__temporary_buffer_deleter__temporary_buffer_deleter35 _LIBCPP_CONSTEXPR explicit __temporary_buffer_deleter(ptrdiff_t __count) _NOEXCEPT : __count_(__count) {}
36
operator__temporary_buffer_deleter37 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 void operator()(_Tp* __ptr) _NOEXCEPT {
38 if (__libcpp_is_constant_evaluated()) {
39 allocator<_Tp>().deallocate(__ptr, __count_);
40 return;
41 }
42
43 std::__libcpp_deallocate_unsized<_Tp>(__ptr);
44 }
45 };
46
47 template <class _Tp>
48 using __unique_temporary_buffer _LIBCPP_NODEBUG = unique_ptr<_Tp, __temporary_buffer_deleter<_Tp> >;
49
50 template <class _Tp>
51 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _LIBCPP_CONSTEXPR_SINCE_CXX23 __unique_temporary_buffer<_Tp>
__allocate_unique_temporary_buffer(ptrdiff_t __count)52 __allocate_unique_temporary_buffer(ptrdiff_t __count) {
53 using __deleter_type = __temporary_buffer_deleter<_Tp>;
54 using __unique_buffer_type = __unique_temporary_buffer<_Tp>;
55
56 if (__libcpp_is_constant_evaluated()) {
57 return __unique_buffer_type(allocator<_Tp>().allocate(__count), __deleter_type(__count));
58 }
59
60 _Tp* __ptr = nullptr;
61 const ptrdiff_t __max_count =
62 (~ptrdiff_t(0) ^ ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1))) / sizeof(_Tp);
63 if (__count > __max_count)
64 __count = __max_count;
65 while (__count > 0) {
66 #if _LIBCPP_HAS_ALIGNED_ALLOCATION
67 if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) {
68 align_val_t __al = align_val_t(_LIBCPP_ALIGNOF(_Tp));
69 __ptr = static_cast<_Tp*>(::operator new(__count * sizeof(_Tp), __al, nothrow));
70 } else {
71 __ptr = static_cast<_Tp*>(::operator new(__count * sizeof(_Tp), nothrow));
72 }
73 #else
74 if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) {
75 // Since aligned operator new is unavailable, constructs an empty buffer rather than one with invalid alignment.
76 return __unique_buffer_type();
77 }
78
79 __ptr = static_cast<_Tp*>(::operator new(__count * sizeof(_Tp), nothrow));
80 #endif
81
82 if (__ptr) {
83 break;
84 }
85 __count /= 2;
86 }
87
88 return __unique_buffer_type(__ptr, __deleter_type(__count));
89 }
90
91 _LIBCPP_END_NAMESPACE_STD
92
93 #endif // _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H
94