/src/llvm-project-16.0.6.src/libcxx/src/include/sso_allocator.h
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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-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 | 6 | _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 | 6 | { |
58 | 6 | if (!__allocated_ && __n <= _Np) |
59 | 6 | { |
60 | 6 | __allocated_ = true; |
61 | 6 | return (pointer)&buf_; |
62 | 6 | } |
63 | 0 | return allocator<_Tp>().allocate(__n); |
64 | 6 | } |
65 | | _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n) |
66 | 0 | { |
67 | 0 | if (__p == (pointer)&buf_) |
68 | 0 | __allocated_ = false; |
69 | 0 | else |
70 | 0 | allocator<_Tp>().deallocate(__p, __n); |
71 | 0 | } |
72 | 6 | _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 |