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| 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 | |
| 33 | _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __temporary_buffer_deleter() _NOEXCEPT : __count_(0) {} |
| 34 | _LIBCPP_HIDE_FROM_ABI |
| 35 | _LIBCPP_CONSTEXPR explicit __temporary_buffer_deleter(ptrdiff_t __count) _NOEXCEPT : __count_(__count) {} |
| 36 | |
| 37 | _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> |
| 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 |
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