93 lines
3.0 KiB
C++
93 lines
3.0 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H
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#define _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H
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#include <__assert>
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#include <__config>
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#include <__cstddef/ptrdiff_t.h>
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#include <__memory/allocator.h>
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#include <__memory/unique_ptr.h>
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#include <__type_traits/is_constant_evaluated.h>
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#include <new>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _Tp>
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struct __temporary_buffer_deleter {
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ptrdiff_t __count_; // ignored in non-constant evaluation
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __temporary_buffer_deleter() _NOEXCEPT : __count_(0) {}
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_LIBCPP_HIDE_FROM_ABI
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_LIBCPP_CONSTEXPR explicit __temporary_buffer_deleter(ptrdiff_t __count) _NOEXCEPT : __count_(__count) {}
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 void operator()(_Tp* __ptr) _NOEXCEPT {
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if (__libcpp_is_constant_evaluated()) {
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allocator<_Tp>().deallocate(__ptr, __count_);
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return;
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}
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std::__libcpp_deallocate_unsized((void*)__ptr, _LIBCPP_ALIGNOF(_Tp));
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}
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};
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template <class _Tp>
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using __unique_temporary_buffer = unique_ptr<_Tp, __temporary_buffer_deleter<_Tp> >;
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template <class _Tp>
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _LIBCPP_CONSTEXPR_SINCE_CXX23 __unique_temporary_buffer<_Tp>
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__allocate_unique_temporary_buffer(ptrdiff_t __count) {
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using __deleter_type = __temporary_buffer_deleter<_Tp>;
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using __unique_buffer_type = __unique_temporary_buffer<_Tp>;
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if (__libcpp_is_constant_evaluated()) {
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return __unique_buffer_type(allocator<_Tp>().allocate(__count), __deleter_type(__count));
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}
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_Tp* __ptr = nullptr;
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const ptrdiff_t __max_count =
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(~ptrdiff_t(0) ^ ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1))) / sizeof(_Tp);
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if (__count > __max_count)
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__count = __max_count;
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while (__count > 0) {
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#if _LIBCPP_HAS_ALIGNED_ALLOCATION
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if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) {
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align_val_t __al = align_val_t(_LIBCPP_ALIGNOF(_Tp));
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__ptr = static_cast<_Tp*>(::operator new(__count * sizeof(_Tp), __al, nothrow));
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} else {
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__ptr = static_cast<_Tp*>(::operator new(__count * sizeof(_Tp), nothrow));
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}
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#else
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if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp))) {
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// Since aligned operator new is unavailable, constructs an empty buffer rather than one with invalid alignment.
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return __unique_buffer_type();
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}
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__ptr = static_cast<_Tp*>(::operator new(__count * sizeof(_Tp), nothrow));
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#endif
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if (__ptr) {
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break;
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}
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__count /= 2;
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}
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return __unique_buffer_type(__ptr, __deleter_type(__count));
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___MEMORY_UNIQUE_TEMPORARY_BUFFER_H
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