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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-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H11#define _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H12 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_header25#endif26 27_LIBCPP_BEGIN_NAMESPACE_STD28 29template <class _Tp>30struct __temporary_buffer_deleter {31 ptrdiff_t __count_; // ignored in non-constant evaluation32 33 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __temporary_buffer_deleter() _NOEXCEPT : __count_(0) {}34 _LIBCPP_HIDE_FROM_ABI35 _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 47template <class _Tp>48using __unique_temporary_buffer _LIBCPP_NODEBUG = unique_ptr<_Tp, __temporary_buffer_deleter<_Tp> >;49 50template <class _Tp>51inline _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_ALLOCATION67 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#else74 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#endif81 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_STD92 93#endif // _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H94