detail/default_resource.hpp

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1		//
2		// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
3		//
4		// Distributed under the Boost Software License, Version 1.0. (See accompanying
5		// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6		//
7		// Official repository: https://github.com/boostorg/json
8		//
9
10		#ifndef BOOST_JSON_DEFAULT_RESOURCE_HPP
11		#define BOOST_JSON_DEFAULT_RESOURCE_HPP
12
13		#include <boost/json/detail/config.hpp>
14		#include <boost/container/pmr/memory_resource.hpp>
15
16		namespace boost {
17		namespace json {
18		namespace detail {
19
20		#ifdef _MSC_VER
21		#pragma warning(push)
22		#pragma warning(disable: 4251) // class needs to have dll-interface to be used by clients of class
23		#pragma warning(disable: 4275) // non dll-interface class used as base for dll-interface class
24		#endif
25
26		// A simple memory resource that uses operator new and delete.
27		class
28		BOOST_SYMBOL_VISIBLE
29		BOOST_JSON_DECL
30		default_resource final
31		: public container::pmr::memory_resource
32		{
33		union holder;
34
35		#ifndef BOOST_JSON_WEAK_CONSTINIT
36		# ifndef BOOST_JSON_NO_DESTROY
37		static holder instance_;
38		# else
39		BOOST_JSON_NO_DESTROY
40		static default_resource instance_;
41		# endif
42		#endif
43
44		public:
45		static
46		container::pmr::memory_resource*
47	530672	get() noexcept
48		{
49		#ifdef BOOST_JSON_WEAK_CONSTINIT
50		static default_resource instance_;
51		#endif
52		return reinterpret_cast<memory_resource*>(
53		reinterpret_cast<std::uintptr_t*>(
54	530672	&instance_));
55		}
56
57		~default_resource();
58
59		void*
60		do_allocate(
61		std::size_t n,
62		std::size_t) override;
63
64		void
65		do_deallocate(
66		void* p,
67		std::size_t,
68		std::size_t) override;
69
70		bool
71		do_is_equal(
72		memory_resource const& mr) const noexcept override;
73		};
74
75		#ifdef _MSC_VER
76		#pragma warning(pop)
77		#endif
78
79		union default_resource::
80		holder
81		{
82		#ifndef BOOST_JSON_WEAK_CONSTINIT
83		constexpr
84		#endif
85		holder()
86		: mr()
87		{
88		}
89
90	39	~holder()
91		{
92	39	}
93
94		default_resource mr;
95		};
96
97		} // detail
98		} // namespace json
99		} // namespace boost
100
101		#endif
102