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_SSO_ALLOCATOR_H 11 #define _LIBCPP_SSO_ALLOCATOR_H 12 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_header 21 #endif 22 23 _LIBCPP_BEGIN_NAMESPACE_STD 24 25 template <class _Tp, size_t _Np> 26 class _LIBCPP_HIDDEN __sso_allocator; 27 28 template <size_t _Np> 29 class _LIBCPP_HIDDEN __sso_allocator<void, _Np> { 30 public: 31 typedef const void* const_pointer; 32 typedef void value_type; 33 }; 34 35 template <class _Tp, size_t _Np> 36 class _LIBCPP_HIDDEN __sso_allocator { 37 alignas(_Tp) std::byte buf_[sizeof(_Tp) * _Np]; 38 bool __allocated_; 39 40 public: 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 55 private: 56 __sso_allocator& operator=(const __sso_allocator&); 57 58 public: 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 else 70 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_STD 79 80 #endif // _LIBCPP_SSO_ALLOCATOR_H 81