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 <memory> 15 #include <new> 16 #include <type_traits> 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, size_t _Np> class _LIBCPP_HIDDEN __sso_allocator; 25 26 template <size_t _Np> 27 class _LIBCPP_HIDDEN __sso_allocator<void, _Np> 28 { 29 public: 30 typedef const void* const_pointer; 31 typedef void value_type; 32 }; 33 34 template <class _Tp, size_t _Np> 35 class _LIBCPP_HIDDEN __sso_allocator 36 { 37 typename aligned_storage<sizeof(_Tp) * _Np>::type buf_; 38 bool __allocated_; 39 public: 40 typedef size_t size_type; 41 typedef _Tp* pointer; 42 typedef _Tp value_type; 43 44 template <class U> 45 struct rebind { 46 using other = __sso_allocator<U, _Np>; 47 }; 48 49 _LIBCPP_INLINE_VISIBILITY __sso_allocator() throw() : __allocated_(false) {} 50 _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {} 51 template <class _Up> _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator<_Up, _Np>&) throw() 52 : __allocated_(false) {} 53 private: 54 __sso_allocator& operator=(const __sso_allocator&); 55 public: 56 _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = nullptr) 57 { 58 if (!__allocated_ && __n <= _Np) 59 { 60 __allocated_ = true; 61 return (pointer)&buf_; 62 } 63 return allocator<_Tp>().allocate(__n); 64 } 65 _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n) 66 { 67 if (__p == (pointer)&buf_) 68 __allocated_ = false; 69 else 70 allocator<_Tp>().deallocate(__p, __n); 71 } 72 _LIBCPP_INLINE_VISIBILITY size_type max_size() const throw() {return size_type(~0) / sizeof(_Tp);} 73 74 _LIBCPP_INLINE_VISIBILITY 75 bool operator==(const __sso_allocator& __a) const {return &buf_ == &__a.buf_;} 76 _LIBCPP_INLINE_VISIBILITY 77 bool operator!=(const __sso_allocator& __a) const {return &buf_ != &__a.buf_;} 78 }; 79 80 _LIBCPP_END_NAMESPACE_STD 81 82 #endif // _LIBCPP_SSO_ALLOCATOR_H 83