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1 : //
2 : // Copyright (c) 2023 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/cppalliance/buffers
8 : //
9 :
10 : #ifndef BOOST_BUFFERS_CIRCULAR_BUFFER_HPP
11 : #define BOOST_BUFFERS_CIRCULAR_BUFFER_HPP
12 :
13 : #include <boost/buffers/detail/config.hpp>
14 : #include <boost/buffers/buffer_pair.hpp>
15 : #include <boost/buffers/detail/except.hpp>
16 :
17 : namespace boost {
18 : namespace buffers {
19 :
20 : /** A circular buffer.
21 :
22 : This implements a fixed-size, circular
23 : buffer. Buffer sequences returned from
24 : @ref prepare and @ref data always have
25 : length two.
26 : */
27 : class circular_buffer
28 : {
29 : unsigned char* base_ = nullptr;
30 : std::size_t cap_ = 0;
31 : std::size_t in_pos_ = 0;
32 : std::size_t in_len_ = 0;
33 : std::size_t out_size_ = 0;
34 :
35 : public:
36 : /** The ConstBufferSequence used to
37 : represent the readable bytes.
38 : */
39 : using const_buffers_type =
40 : const_buffer_pair;
41 :
42 : /** The MutableBufferSequence used to
43 : represent the writable bytes.
44 : */
45 : using mutable_buffers_type =
46 : mutable_buffer_pair;
47 :
48 : /** Constructor.
49 : */
50 : circular_buffer() = default;
51 :
52 : /** Constructor.
53 : */
54 : circular_buffer(
55 : circular_buffer const&) = default;
56 :
57 : /** Constructor.
58 : */
59 8213 : circular_buffer(
60 : void* base,
61 : std::size_t capacity) noexcept
62 8213 : : base_(static_cast<
63 : unsigned char*>(base))
64 8213 : , cap_(capacity)
65 : {
66 8213 : }
67 :
68 : /** Constructor.
69 : */
70 2 : circular_buffer(
71 : void* base,
72 : std::size_t capacity,
73 : std::size_t initial_size)
74 2 : : base_(static_cast<
75 : unsigned char*>(base))
76 2 : , cap_(capacity)
77 2 : , in_len_(initial_size)
78 : {
79 2 : if(in_len_ > capacity)
80 1 : detail::throw_invalid_argument();
81 1 : }
82 :
83 : /** Assignment.
84 : */
85 : circular_buffer& operator=(
86 : circular_buffer const&) = default;
87 :
88 : /** Returns the number of readable bytes.
89 : */
90 : std::size_t
91 4119 : size() const noexcept
92 : {
93 4119 : return in_len_;
94 : }
95 :
96 : /** Returns the maximum sum of the input and
97 : output sequence sizes.
98 : */
99 : std::size_t
100 4102 : max_size() const noexcept
101 : {
102 4102 : return cap_;
103 : }
104 :
105 : /** Returns the number of writable bytes.
106 : */
107 : std::size_t
108 8199 : capacity() const noexcept
109 : {
110 8199 : return cap_ - in_len_;
111 : }
112 :
113 : /** Returns a constant buffer sequence representing
114 : the readable bytes.
115 : */
116 : BOOST_BUFFERS_DECL
117 : const_buffers_type
118 : data() const noexcept;
119 :
120 : /** Returns a mutable buffer sequence representing
121 : the writable bytes.
122 :
123 : All buffers sequences previously
124 : obtained using @ref prepare become
125 : invalid.
126 :
127 : @param n The desired number of bytes in
128 : the returned buffer sequence.
129 :
130 : @throw std::length_error if @ref size() + n
131 : exceeds @ref max_size().
132 : */
133 : BOOST_BUFFERS_DECL
134 : mutable_buffers_type
135 : prepare(std::size_t n);
136 :
137 : /** Append writable bytes to the readable bytes.
138 :
139 : Appends n bytes from the start of the
140 : writable bytes to the end of the
141 : readable bytes. The remainder of the
142 : writable bytes are discarded. If n is
143 : greater than the number of writable
144 : bytes, all writable bytes are appended
145 : to the readable bytes.
146 :
147 : All buffer sequences previously obtained
148 : using @ref prepare are invalidated.
149 :
150 : Buffer sequences previously obtained
151 : using @ref data remain valid.
152 :
153 : @param n The number of bytes to append. If
154 : this number is greater than the number
155 : of writable bytes, all writable bytes
156 : are appended.
157 : */
158 : BOOST_BUFFERS_DECL
159 : void
160 : commit(std::size_t n) noexcept;
161 :
162 : /** Remove bytes from beginning of the readable bytes.
163 :
164 : All buffers sequences previously
165 : obtained using @ref data are
166 : invalidated.
167 :
168 : Buffer sequences previously obtained
169 : using @ref prepare remain valid.
170 :
171 : @param n The number of bytes to remove.
172 : If this number is greater than the
173 : number of readable bytes, all readable
174 : bytes are removed.
175 : */
176 : BOOST_BUFFERS_DECL
177 : void
178 : consume(std::size_t n) noexcept;
179 : };
180 :
181 : } // buffers
182 : } // boost
183 :
184 : #endif
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