impl/monotonic_resource.ipp

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monotonic_resource.ipp

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1		//
2		// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
3		// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)
4		//
5		// Distributed under the Boost Software License, Version 1.0. (See accompanying
6		// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7		//
8		// Official repository: https://github.com/boostorg/json
9		//
10
11		#ifndef BOOST_JSON_IMPL_MONOTONIC_RESOURCE_IPP
12		#define BOOST_JSON_IMPL_MONOTONIC_RESOURCE_IPP
13
14		#include <boost/json/monotonic_resource.hpp>
15		#include <boost/json/detail/except.hpp>
16		#include <boost/core/max_align.hpp>
17
18		#include <memory>
19
20		namespace boost {
21		namespace json {
22
23		struct alignas(core::max_align_t)
24		monotonic_resource::block : block_base
25		{
26		};
27
28		constexpr
29		std::size_t
30	179x	monotonic_resource::
31		max_size()
32		{
33	179x	return std::size_t(-1) - sizeof(block);
34		}
35
36		// lowest power of 2 greater than or equal to n
37		std::size_t
38	42x	monotonic_resource::
39		round_pow2(
40		std::size_t n) noexcept
41		{
42	42x	if(n & (n - 1))
43	8x	return next_pow2(n);
44	34x	return n;
45		}
46
47		// lowest power of 2 greater than n
48		std::size_t
49	56x	monotonic_resource::
50		next_pow2(
51		std::size_t n) noexcept
52		{
53	56x	std::size_t result = min_size_;
54	233x	while(result <= n)
55		{
56	178x	if(result >= max_size() - result)
57		{
58		// overflow
59	1x	result = max_size();
60	1x	break;
61		}
62	177x	result *= 2;
63		}
64	56x	return result;
65		}
66
67		//----------------------------------------------------------
68
69	49x	monotonic_resource::
70	49x	~monotonic_resource()
71		{
72	49x	release();
73	49x	}
74
75	39x	monotonic_resource::
76		monotonic_resource(
77		std::size_t initial_size,
78	39x	storage_ptr upstream) noexcept
79	39x	: buffer_{
80		nullptr, 0, 0, nullptr}
81	78x	, next_size_(round_pow2(initial_size))
82	39x	, upstream_(std::move(upstream))
83		{
84	39x	}
85
86	10x	monotonic_resource::
87		monotonic_resource(
88		unsigned char* buffer,
89		std::size_t size,
90	10x	storage_ptr upstream) noexcept
91	10x	: buffer_{
92		buffer, size, size, nullptr}
93	20x	, next_size_(next_pow2(size))
94	10x	, upstream_(std::move(upstream))
95		{
96	10x	}
97
98		void
99	50x	monotonic_resource::
100		release() noexcept
101		{
102	50x	auto p = head_;
103	88x	while(p != &buffer_)
104		{
105	38x	auto next = p->next;
106	38x	upstream_->deallocate(p,
107	38x	sizeof(block) + p->size);
108	38x	p = next;
109		}
110	50x	buffer_.p = reinterpret_cast<
111	50x	unsigned char*>(buffer_.p) - (
112	50x	buffer_.size - buffer_.avail);
113	50x	buffer_.avail = buffer_.size;
114	50x	head_ = &buffer_;
115	50x	}
116
117		void*
118	129502x	monotonic_resource::
119		do_allocate(
120		std::size_t n,
121		std::size_t align)
122		{
123	129502x	auto p = std::align(align, n, head_->p, head_->avail);
124	129502x	if(p)
125		{
126	129464x	head_->p = reinterpret_cast<
127	129464x	unsigned char*>(p) + n;
128	129464x	head_->avail -= n;
129	129464x	return p;
130		}
131
132	38x	if(next_size_ < n)
133	3x	next_size_ = round_pow2(n);
134	38x	auto b = ::new(upstream_->allocate(
135	38x	sizeof(block) + next_size_)) block;
136	38x	b->p = b + 1;
137	38x	b->avail = next_size_;
138	38x	b->size = next_size_;
139	38x	b->next = head_;
140	38x	head_ = b;
141	38x	next_size_ = next_pow2(next_size_);
142
143	38x	p = std::align(align, n, head_->p, head_->avail);
144	38x	BOOST_ASSERT(p);
145	38x	head_->p = reinterpret_cast<
146	38x	unsigned char*>(p) + n;
147	38x	head_->avail -= n;
148	38x	return p;
149		}
150
151		void
152	29x	monotonic_resource::
153		do_deallocate(
154		void*,
155		std::size_t,
156		std::size_t)
157		{
158		// do nothing
159	29x	}
160
161		bool
162	✗	monotonic_resource::
163		do_is_equal(
164		memory_resource const& mr) const noexcept
165		{
166	✗	return this == &mr;
167		}
168
169		} // namespace json
170		} // namespace boost
171
172		#endif
173