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80 lines
2.3 KiB
C++
80 lines
2.3 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_SSO_ALLOCATOR_H
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#define _LIBCPP_SSO_ALLOCATOR_H
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#include <__config>
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#include <cstddef>
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#include <memory>
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#include <new>
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#include <type_traits>
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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, size_t _Np>
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class _LIBCPP_HIDDEN __sso_allocator;
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template <size_t _Np>
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class _LIBCPP_HIDDEN __sso_allocator<void, _Np> {
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public:
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typedef const void* const_pointer;
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typedef void value_type;
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};
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template <class _Tp, size_t _Np>
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class _LIBCPP_HIDDEN __sso_allocator {
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alignas(_Tp) std::byte buf_[sizeof(_Tp) * _Np];
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bool __allocated_;
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public:
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typedef size_t size_type;
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typedef _Tp* pointer;
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typedef _Tp value_type;
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template <class U>
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struct rebind {
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using other = __sso_allocator<U, _Np>;
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};
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_LIBCPP_HIDE_FROM_ABI __sso_allocator() throw() : __allocated_(false) {}
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_LIBCPP_HIDE_FROM_ABI __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {}
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template <class _Up>
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_LIBCPP_HIDE_FROM_ABI __sso_allocator(const __sso_allocator<_Up, _Np>&) throw() : __allocated_(false) {}
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private:
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__sso_allocator& operator=(const __sso_allocator&);
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public:
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_LIBCPP_HIDE_FROM_ABI pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = nullptr) {
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if (!__allocated_ && __n <= _Np) {
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__allocated_ = true;
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return (pointer)&buf_;
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}
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return allocator<_Tp>().allocate(__n);
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}
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_LIBCPP_HIDE_FROM_ABI void deallocate(pointer __p, size_type __n) {
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if (__p == (pointer)&buf_)
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__allocated_ = false;
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else
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allocator<_Tp>().deallocate(__p, __n);
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}
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_LIBCPP_HIDE_FROM_ABI size_type max_size() const throw() { return size_type(~0) / sizeof(_Tp); }
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_LIBCPP_HIDE_FROM_ABI bool operator==(const __sso_allocator& __a) const { return &buf_ == &__a.buf_; }
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_LIBCPP_HIDE_FROM_ABI bool operator!=(const __sso_allocator& __a) const { return &buf_ != &__a.buf_; }
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};
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_SSO_ALLOCATOR_H
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