libs/http/include/boost/http/detail/workspace.hpp

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1		//
2		// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
3		// Copyright (c) 2025 Mohammad Nejati
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/cppalliance/http
9		//
10
11		#ifndef BOOST_HTTP_DETAIL_WORKSPACE_HPP
12		#define BOOST_HTTP_DETAIL_WORKSPACE_HPP
13
14		#include <boost/http/detail/except.hpp>
15		#include <boost/assert.hpp>
16		#include <cstdlib>
17		#include <new>
18		#include <utility>
19		#include <stddef.h> // ::max_align_t
20
21		namespace boost {
22		namespace http {
23		namespace detail {
24
25		/** A contiguous buffer of storage used by algorithms.
26
27		Objects of this type retain ownership of a
28		contiguous buffer of storage allocated upon
29		construction. This storage is divided into
30		three regions:
31
32		@code
33		\| front \| free \| acquired \| back \|
34		@endcode
35
36		@li The reserved area, which starts at the
37		beginning of the buffer and can grow
38		upwards towards the end of the buffer.
39
40		@li The acquired area, which starts at the
41		end of the buffer and can grow downwards
42		towards the beginning of the buffer.
43
44		@li The unused area, which starts from the
45		end of the reserved area and stretches
46		until the beginning of the acquired area.
47		*/
48		class workspace
49		{
50		unsigned char* begin_ = nullptr;
51		unsigned char* front_ = nullptr;
52		unsigned char* head_ = nullptr;
53		unsigned char* back_ = nullptr;
54		unsigned char* end_ = nullptr;
55
56		template<class>
57		struct any_impl;
58		struct any;
59		struct undo;
60
61		public:
62		/** Return the number of aligned bytes required for T
63		*/
64		template<class T>
65		static
66		constexpr
67		std::size_t
68		space_needed();
69
70		/** Destructor.
71		*/
72		~workspace();
73
74		/** Constructor.
75
76		@param n The number of bytes of storage
77		to allocate for the internal buffer.
78		*/
79		explicit
80		workspace(
81		std::size_t n);
82
83		/** Constructor.
84		*/
85		workspace() = default;
86
87		/** Constructor.
88		*/
89		workspace(workspace&&) noexcept;
90
91		/** Assignment.
92		*/
93		workspace&
94		operator=(workspace&&) noexcept;
95
96		/** Allocate internal storage.
97
98		@throw std::logic_error this->size() > 0
99
100		@throw std::invalid_argument n == 0
101		*/
102		void
103		allocate(
104		std::size_t n);
105
106		/** Return a pointer to the unused area.
107		*/
108		unsigned char*
109	96708	data() noexcept
110		{
111	96708	return front_;
112		}
113
114		/** Return the size of the unused area.
115		*/
116		std::size_t
117	30850	size() const noexcept
118		{
119	30850	return head_ - front_;
120		}
121
122		/** Clear the contents while preserving capacity.
123		*/
124		BOOST_HTTP_DECL
125		void
126		clear() noexcept;
127
128		/** Convert unused storage to reserved storage.
129
130		@throw std::invalid_argument n >= this->size()
131		*/
132		BOOST_HTTP_DECL
133		unsigned char*
134		reserve_front(
135		std::size_t n);
136
137		/** Convert unused storage to reserved storage.
138
139		@return nullptr if n >= this->size()
140		*/
141		BOOST_HTTP_DECL
142		unsigned char*
143		try_reserve_front(
144		std::size_t n) noexcept;
145
146		template<class T, class... Args>
147		typename std::decay<T>::type&
148		emplace(Args&&... args);
149
150		template<class T>
151		T*
152		push_array(
153		std::size_t n,
154		T const& t);
155
156		BOOST_HTTP_DECL
157		unsigned char*
158		reserve_back(
159		std::size_t n);
160
161		private:
162		BOOST_HTTP_DECL
163		unsigned char*
164		bump_down(
165		std::size_t size,
166		std::size_t align);
167		};
168
169		} // detail
170		} // http
171		} // boost
172
173		#include <boost/http/detail/impl/workspace.hpp>
174
175		#endif
176