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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-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP_SSO_ALLOCATOR_H11#define _LIBCPP_SSO_ALLOCATOR_H12 13#include <__config>14#include <cstddef>15#include <memory>16#include <new>17#include <type_traits>18 19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)20# pragma GCC system_header21#endif22 23_LIBCPP_BEGIN_NAMESPACE_STD24 25template <class _Tp, size_t _Np>26class _LIBCPP_HIDDEN __sso_allocator;27 28template <size_t _Np>29class _LIBCPP_HIDDEN __sso_allocator<void, _Np> {30public:31 typedef const void* const_pointer;32 typedef void value_type;33};34 35template <class _Tp, size_t _Np>36class _LIBCPP_HIDDEN __sso_allocator {37 alignas(_Tp) std::byte buf_[sizeof(_Tp) * _Np];38 bool __allocated_;39 40public:41 typedef size_t size_type;42 typedef _Tp* pointer;43 typedef _Tp value_type;44 45 template <class U>46 struct rebind {47 using other = __sso_allocator<U, _Np>;48 };49 50 _LIBCPP_HIDE_FROM_ABI __sso_allocator() throw() : __allocated_(false) {}51 _LIBCPP_HIDE_FROM_ABI __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {}52 template <class _Up>53 _LIBCPP_HIDE_FROM_ABI __sso_allocator(const __sso_allocator<_Up, _Np>&) throw() : __allocated_(false) {}54 55private:56 __sso_allocator& operator=(const __sso_allocator&);57 58public:59 _LIBCPP_HIDE_FROM_ABI pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = nullptr) {60 if (!__allocated_ && __n <= _Np) {61 __allocated_ = true;62 return (pointer)&buf_;63 }64 return allocator<_Tp>().allocate(__n);65 }66 _LIBCPP_HIDE_FROM_ABI void deallocate(pointer __p, size_type __n) {67 if (__p == (pointer)&buf_)68 __allocated_ = false;69 else70 allocator<_Tp>().deallocate(__p, __n);71 }72 _LIBCPP_HIDE_FROM_ABI size_type max_size() const throw() { return size_type(~0) / sizeof(_Tp); }73 74 _LIBCPP_HIDE_FROM_ABI bool operator==(const __sso_allocator& __a) const { return &buf_ == &__a.buf_; }75 _LIBCPP_HIDE_FROM_ABI bool operator!=(const __sso_allocator& __a) const { return &buf_ != &__a.buf_; }76};77 78_LIBCPP_END_NAMESPACE_STD79 80#endif // _LIBCPP_SSO_ALLOCATOR_H81