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

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source code of libcxx/include/__memory_resource/monotonic_buffer_resource.h