1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
10 #define _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
11 
12 #include <__availability>
13 #include <__config>
14 #include <__memory/addressof.h>
15 #include <__memory_resource/memory_resource.h>
16 #include <cstddef>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #  pragma GCC system_header
20 #endif
21 
22 #if _LIBCPP_STD_VER >= 17
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 namespace pmr {
27 
28 // [mem.res.monotonic.buffer]
29 
30 class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resource : public memory_resource {
31   static const size_t __default_buffer_capacity  = 1024;
32   static const size_t __default_buffer_alignment = 16;
33 
34   struct __chunk_footer {
35     __chunk_footer* __next_;
36     char* __start_;
37     char* __cur_;
38     size_t __align_;
39     _LIBCPP_HIDE_FROM_ABI size_t __allocation_size() {
40       return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this);
41     }
42     void* __try_allocate_from_chunk(size_t, size_t);
43   };
44 
45   struct __initial_descriptor {
46     char* __start_;
47     char* __cur_;
48     union {
49       char* __end_;
50       size_t __size_;
51     };
52     void* __try_allocate_from_chunk(size_t, size_t);
53   };
54 
55 public:
56   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource()
57       : monotonic_buffer_resource(nullptr, __default_buffer_capacity, get_default_resource()) {}
58 
59   _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(size_t __initial_size)
60       : monotonic_buffer_resource(nullptr, __initial_size, get_default_resource()) {}
61 
62   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size)
63       : monotonic_buffer_resource(__buffer, __buffer_size, get_default_resource()) {}
64 
65   _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(memory_resource* __upstream)
66       : monotonic_buffer_resource(nullptr, __default_buffer_capacity, __upstream) {}
67 
68   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(size_t __initial_size, memory_resource* __upstream)
69       : monotonic_buffer_resource(nullptr, __initial_size, __upstream) {}
70 
71   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size, memory_resource* __upstream)
72       : __res_(__upstream) {
73     __initial_.__start_ = static_cast<char*>(__buffer);
74     if (__buffer != nullptr) {
75       __initial_.__cur_ = static_cast<char*>(__buffer) + __buffer_size;
76       __initial_.__end_ = static_cast<char*>(__buffer) + __buffer_size;
77     } else {
78       __initial_.__cur_  = nullptr;
79       __initial_.__size_ = __buffer_size;
80     }
81     __chunks_ = nullptr;
82   }
83 
84   monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
85 
86   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~monotonic_buffer_resource() override { release(); }
87 
88   monotonic_buffer_resource& operator=(const monotonic_buffer_resource&) = delete;
89 
90   _LIBCPP_HIDE_FROM_ABI void release() {
91     if (__initial_.__start_ != nullptr)
92       __initial_.__cur_ = __initial_.__end_;
93     while (__chunks_ != nullptr) {
94       __chunk_footer* __next = __chunks_->__next_;
95       __res_->deallocate(__chunks_->__start_, __chunks_->__allocation_size(), __chunks_->__align_);
96       __chunks_ = __next;
97     }
98   }
99 
100   _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
101 
102 protected:
103   void* do_allocate(size_t __bytes, size_t __alignment) override; // key function
104 
105   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void do_deallocate(void*, size_t, size_t) override {}
106 
107   _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
108     return this == std::addressof(__other);
109   }
110 
111 private:
112   __initial_descriptor __initial_;
113   __chunk_footer* __chunks_;
114   memory_resource* __res_;
115 };
116 
117 } // namespace pmr
118 
119 _LIBCPP_END_NAMESPACE_STD
120 
121 #endif // _LIBCPP_STD_VER >= 17
122 
123 #endif // _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
124