libcxx/include/__cxx03/__memory/temporary_buffer.h

   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 <__cxx03/__config>
  14 #include <__cxx03/__utility/pair.h>
  15 #include <__cxx03/cstddef>
  16 #include <__cxx03/new>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 template <class _Tp>
  25 _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _LIBCPP_DEPRECATED_IN_CXX17 pair<_Tp*, ptrdiff_t>
  26 get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT {
  27   pair<_Tp*, ptrdiff_t> __r(0, 0);
  28   const ptrdiff_t __m =
  29       (~ptrdiff_t(0) ^ ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1))) / sizeof(_Tp);
  30   if (__n > __m)
  31     __n = __m;
  32   while (__n > 0) {
  33 #if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
  34     if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) {
  35       align_val_t __al = align_val_t(_LIBCPP_ALIGNOF(_Tp));
  36       __r.first        = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al, nothrow));
  37     } else {
  38       __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
  39     }
  40 #else
  41     if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) {
  42       // Since aligned operator new is unavailable, return an empty
  43       // buffer rather than one with invalid alignment.
  44       return __r;
  45     }
  46
  47     __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
  48 #endif
  49
  50     if (__r.first) {
  51       __r.second = __n;
  52       break;
  53     }
  54     __n /= 2;
  55   }
  56   return __r;
  57 }
  58
  59 template <class _Tp>
  60 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_DEPRECATED_IN_CXX17 void return_temporary_buffer(_Tp* __p) _NOEXCEPT {
  61   std::__libcpp_deallocate_unsized((void*)__p, _LIBCPP_ALIGNOF(_Tp));
  62 }
  63
  64 struct __return_temporary_buffer {
  65   _LIBCPP_SUPPRESS_DEPRECATED_PUSH
  66   template <class _Tp>
  67   _LIBCPP_HIDE_FROM_ABI void operator()(_Tp* __p) const {
  68     std::return_temporary_buffer(__p);
  69   }
  70   _LIBCPP_SUPPRESS_DEPRECATED_POP
  71 };
  72
  73 _LIBCPP_END_NAMESPACE_STD
  74
  75 #endif // _LIBCPP___MEMORY_TEMPORARY_BUFFER_H