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1 | // |
2 | // third_party_lib.cpp | |
3 | // ~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
b32b8144 | 5 | // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
7c673cae FG |
6 | // |
7 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
8 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
9 | // | |
10 | ||
11 | #include <boost/asio.hpp> | |
12 | #include <boost/array.hpp> | |
13 | #include <boost/bind.hpp> | |
14 | #include <boost/shared_ptr.hpp> | |
15 | #include <boost/enable_shared_from_this.hpp> | |
16 | #include <iostream> | |
17 | ||
18 | using boost::asio::ip::tcp; | |
19 | ||
20 | namespace third_party_lib { | |
21 | ||
22 | // Simulation of a third party library that wants to perform read and write | |
23 | // operations directly on a socket. It needs to be polled to determine whether | |
24 | // it requires a read or write operation, and notified when the socket is ready | |
25 | // for reading or writing. | |
26 | class session | |
27 | { | |
28 | public: | |
29 | session(tcp::socket& socket) | |
30 | : socket_(socket), | |
31 | state_(reading) | |
32 | { | |
33 | } | |
34 | ||
35 | // Returns true if the third party library wants to be notified when the | |
36 | // socket is ready for reading. | |
37 | bool want_read() const | |
38 | { | |
39 | return state_ == reading; | |
40 | } | |
41 | ||
42 | // Notify that third party library that it should perform its read operation. | |
43 | void do_read(boost::system::error_code& ec) | |
44 | { | |
45 | if (std::size_t len = socket_.read_some(boost::asio::buffer(data_), ec)) | |
46 | { | |
47 | write_buffer_ = boost::asio::buffer(data_, len); | |
48 | state_ = writing; | |
49 | } | |
50 | } | |
51 | ||
52 | // Returns true if the third party library wants to be notified when the | |
53 | // socket is ready for writing. | |
54 | bool want_write() const | |
55 | { | |
56 | return state_ == writing; | |
57 | } | |
58 | ||
59 | // Notify that third party library that it should perform its write operation. | |
60 | void do_write(boost::system::error_code& ec) | |
61 | { | |
62 | if (std::size_t len = socket_.write_some( | |
63 | boost::asio::buffer(write_buffer_), ec)) | |
64 | { | |
65 | write_buffer_ = write_buffer_ + len; | |
66 | state_ = boost::asio::buffer_size(write_buffer_) > 0 ? writing : reading; | |
67 | } | |
68 | } | |
69 | ||
70 | private: | |
71 | tcp::socket& socket_; | |
72 | enum { reading, writing } state_; | |
73 | boost::array<char, 128> data_; | |
74 | boost::asio::const_buffer write_buffer_; | |
75 | }; | |
76 | ||
77 | } // namespace third_party_lib | |
78 | ||
79 | // The glue between asio's sockets and the third party library. | |
80 | class connection | |
81 | : public boost::enable_shared_from_this<connection> | |
82 | { | |
83 | public: | |
84 | typedef boost::shared_ptr<connection> pointer; | |
85 | ||
b32b8144 | 86 | static pointer create(boost::asio::io_context& io_context) |
7c673cae | 87 | { |
b32b8144 | 88 | return pointer(new connection(io_context)); |
7c673cae FG |
89 | } |
90 | ||
91 | tcp::socket& socket() | |
92 | { | |
93 | return socket_; | |
94 | } | |
95 | ||
96 | void start() | |
97 | { | |
98 | // Put the socket into non-blocking mode. | |
99 | socket_.non_blocking(true); | |
100 | ||
101 | start_operations(); | |
102 | } | |
103 | ||
104 | private: | |
b32b8144 FG |
105 | connection(boost::asio::io_context& io_context) |
106 | : socket_(io_context), | |
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107 | session_impl_(socket_), |
108 | read_in_progress_(false), | |
109 | write_in_progress_(false) | |
110 | { | |
111 | } | |
112 | ||
113 | void start_operations() | |
114 | { | |
115 | // Start a read operation if the third party library wants one. | |
116 | if (session_impl_.want_read() && !read_in_progress_) | |
117 | { | |
118 | read_in_progress_ = true; | |
b32b8144 | 119 | socket_.async_wait(tcp::socket::wait_read, |
7c673cae FG |
120 | boost::bind(&connection::handle_read, |
121 | shared_from_this(), | |
122 | boost::asio::placeholders::error)); | |
123 | } | |
124 | ||
125 | // Start a write operation if the third party library wants one. | |
126 | if (session_impl_.want_write() && !write_in_progress_) | |
127 | { | |
128 | write_in_progress_ = true; | |
b32b8144 | 129 | socket_.async_wait(tcp::socket::wait_write, |
7c673cae FG |
130 | boost::bind(&connection::handle_write, |
131 | shared_from_this(), | |
132 | boost::asio::placeholders::error)); | |
133 | } | |
134 | } | |
135 | ||
136 | void handle_read(boost::system::error_code ec) | |
137 | { | |
138 | read_in_progress_ = false; | |
139 | ||
140 | // Notify third party library that it can perform a read. | |
141 | if (!ec) | |
142 | session_impl_.do_read(ec); | |
143 | ||
144 | // The third party library successfully performed a read on the socket. | |
145 | // Start new read or write operations based on what it now wants. | |
146 | if (!ec || ec == boost::asio::error::would_block) | |
147 | start_operations(); | |
148 | ||
149 | // Otherwise, an error occurred. Closing the socket cancels any outstanding | |
150 | // asynchronous read or write operations. The connection object will be | |
151 | // destroyed automatically once those outstanding operations complete. | |
152 | else | |
153 | socket_.close(); | |
154 | } | |
155 | ||
156 | void handle_write(boost::system::error_code ec) | |
157 | { | |
158 | write_in_progress_ = false; | |
159 | ||
160 | // Notify third party library that it can perform a write. | |
161 | if (!ec) | |
162 | session_impl_.do_write(ec); | |
163 | ||
164 | // The third party library successfully performed a write on the socket. | |
165 | // Start new read or write operations based on what it now wants. | |
166 | if (!ec || ec == boost::asio::error::would_block) | |
167 | start_operations(); | |
168 | ||
169 | // Otherwise, an error occurred. Closing the socket cancels any outstanding | |
170 | // asynchronous read or write operations. The connection object will be | |
171 | // destroyed automatically once those outstanding operations complete. | |
172 | else | |
173 | socket_.close(); | |
174 | } | |
175 | ||
176 | private: | |
177 | tcp::socket socket_; | |
178 | third_party_lib::session session_impl_; | |
179 | bool read_in_progress_; | |
180 | bool write_in_progress_; | |
181 | }; | |
182 | ||
183 | class server | |
184 | { | |
185 | public: | |
b32b8144 FG |
186 | server(boost::asio::io_context& io_context, unsigned short port) |
187 | : acceptor_(io_context, tcp::endpoint(tcp::v4(), port)) | |
7c673cae FG |
188 | { |
189 | start_accept(); | |
190 | } | |
191 | ||
192 | private: | |
193 | void start_accept() | |
194 | { | |
195 | connection::pointer new_connection = | |
b32b8144 | 196 | connection::create(acceptor_.get_executor().context()); |
7c673cae FG |
197 | |
198 | acceptor_.async_accept(new_connection->socket(), | |
199 | boost::bind(&server::handle_accept, this, new_connection, | |
200 | boost::asio::placeholders::error)); | |
201 | } | |
202 | ||
203 | void handle_accept(connection::pointer new_connection, | |
204 | const boost::system::error_code& error) | |
205 | { | |
206 | if (!error) | |
207 | { | |
208 | new_connection->start(); | |
209 | } | |
210 | ||
211 | start_accept(); | |
212 | } | |
213 | ||
214 | tcp::acceptor acceptor_; | |
215 | }; | |
216 | ||
217 | int main(int argc, char* argv[]) | |
218 | { | |
219 | try | |
220 | { | |
221 | if (argc != 2) | |
222 | { | |
223 | std::cerr << "Usage: third_party_lib <port>\n"; | |
224 | return 1; | |
225 | } | |
226 | ||
b32b8144 | 227 | boost::asio::io_context io_context; |
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228 | |
229 | using namespace std; // For atoi. | |
b32b8144 | 230 | server s(io_context, atoi(argv[1])); |
7c673cae | 231 | |
b32b8144 | 232 | io_context.run(); |
7c673cae FG |
233 | } |
234 | catch (std::exception& e) | |
235 | { | |
236 | std::cerr << "Exception: " << e.what() << "\n"; | |
237 | } | |
238 | ||
239 | return 0; | |
240 | } |