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 <__type_traits/alignment_of.h> 15 #include <__utility/pair.h> 16 #include <cstddef> 17 #include <new> 18 19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20 # pragma GCC system_header 21 #endif 22 23 _LIBCPP_BEGIN_NAMESPACE_STD 24 25 template <class _Tp> 26 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _LIBCPP_DEPRECATED_IN_CXX17 pair<_Tp*, ptrdiff_t> 27 get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT { 28 pair<_Tp*, ptrdiff_t> __r(0, 0); 29 const ptrdiff_t __m = 30 (~ptrdiff_t(0) ^ ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1))) / sizeof(_Tp); 31 if (__n > __m) 32 __n = __m; 33 while (__n > 0) { 34 #if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION) 35 if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) { 36 align_val_t __al = align_val_t(_LIBCPP_ALIGNOF(_Tp)); 37 __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al, nothrow)); 38 } else { 39 __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow)); 40 } 41 #else 42 if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) { 43 // Since aligned operator new is unavailable, return an empty 44 // buffer rather than one with invalid alignment. 45 return __r; 46 } 47 48 __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow)); 49 #endif 50 51 if (__r.first) { 52 __r.second = __n; 53 break; 54 } 55 __n /= 2; 56 } 57 return __r; 58 } 59 60 template <class _Tp> 61 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_DEPRECATED_IN_CXX17 void return_temporary_buffer(_Tp* __p) _NOEXCEPT { 62 std::__libcpp_deallocate_unsized((void*)__p, _LIBCPP_ALIGNOF(_Tp)); 63 } 64 65 struct __return_temporary_buffer { 66 _LIBCPP_SUPPRESS_DEPRECATED_PUSH 67 template <class _Tp> 68 _LIBCPP_HIDE_FROM_ABI void operator()(_Tp* __p) const { 69 std::return_temporary_buffer(__p); 70 } 71 _LIBCPP_SUPPRESS_DEPRECATED_POP 72 }; 73 74 _LIBCPP_END_NAMESPACE_STD 75 76 #endif // _LIBCPP___MEMORY_TEMPORARY_BUFFER_H 77