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