corosio

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src/corosio/src/detail/select/sockets.hpp
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1 //
2 // Copyright (c) 2026 Steve Gerbino
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/corosio
8 //
9
10 #ifndef BOOST_COROSIO_DETAIL_SELECT_SOCKETS_HPP
11 #define BOOST_COROSIO_DETAIL_SELECT_SOCKETS_HPP
12
13 #include <boost/corosio/detail/platform.hpp>
14
15 #if BOOST_COROSIO_HAS_SELECT
16
17 #include <boost/corosio/detail/config.hpp>
18 #include <boost/corosio/tcp_socket.hpp>
19 #include <boost/capy/ex/executor_ref.hpp>
20 #include <boost/capy/ex/execution_context.hpp>
21 #include "src/detail/intrusive.hpp"
22 #include "src/detail/socket_service.hpp"
23
24 #include "src/detail/select/op.hpp"
25 #include "src/detail/select/scheduler.hpp"
26
27 #include <memory>
28 #include <mutex>
29 #include <unordered_map>
30
31 /*
32 select Socket Implementation
33 ============================
34
35 This mirrors the epoll_sockets design for behavioral consistency.
36 Each I/O operation follows the same pattern:
37 1. Try the syscall immediately (non-blocking socket)
38 2. If it succeeds or fails with a real error, post to completion queue
39 3. If EAGAIN/EWOULDBLOCK, register with select scheduler and wait
40
41 Cancellation
42 ------------
43 See op.hpp for the completion/cancellation race handling via the
44 `registered` atomic. cancel() must complete pending operations (post
45 them with cancelled flag) so coroutines waiting on them can resume.
46 close_socket() calls cancel() first to ensure this.
47
48 Impl Lifetime with shared_ptr
49 -----------------------------
50 Socket impls use enable_shared_from_this. The service owns impls via
51 shared_ptr maps (socket_ptrs_) keyed by raw pointer for O(1) lookup and
52 removal. When a user calls close(), we call cancel() which posts pending
53 ops to the scheduler.
54
55 CRITICAL: The posted ops must keep the impl alive until they complete.
56 Otherwise the scheduler would process a freed op (use-after-free). The
57 cancel() method captures shared_from_this() into op.impl_ptr before
58 posting. When the op completes, impl_ptr is cleared, allowing the impl
59 to be destroyed if no other references exist.
60
61 Service Ownership
62 -----------------
63 select_socket_service owns all socket impls. destroy_impl() removes the
64 shared_ptr from the map, but the impl may survive if ops still hold
65 impl_ptr refs. shutdown() closes all sockets and clears the map; any
66 in-flight ops will complete and release their refs.
67 */
68
69 namespace boost::corosio::detail {
70
71 class select_socket_service;
72 class select_socket_impl;
73
74 /// Socket implementation for select backend.
75 class select_socket_impl
76 : public tcp_socket::socket_impl
77 , public std::enable_shared_from_this<select_socket_impl>
78 , public intrusive_list<select_socket_impl>::node
79 {
80 friend class select_socket_service;
81
82 public:
83 explicit select_socket_impl(select_socket_service& svc) noexcept;
84
85 void release() override;
86
87 std::coroutine_handle<> connect(
88 std::coroutine_handle<>,
89 capy::executor_ref,
90 endpoint,
91 std::stop_token,
92 std::error_code*) override;
93
94 std::coroutine_handle<> read_some(
95 std::coroutine_handle<>,
96 capy::executor_ref,
97 io_buffer_param,
98 std::stop_token,
99 std::error_code*,
100 std::size_t*) override;
101
102 std::coroutine_handle<> write_some(
103 std::coroutine_handle<>,
104 capy::executor_ref,
105 io_buffer_param,
106 std::stop_token,
107 std::error_code*,
108 std::size_t*) override;
109
110 std::error_code shutdown(tcp_socket::shutdown_type what) noexcept override;
111
112 ✗ native_handle_type native_handle() const noexcept override { return fd_; }
113
114 // Socket options
115 std::error_code set_no_delay(bool value) noexcept override;
116 bool no_delay(std::error_code& ec) const noexcept override;
117
118 std::error_code set_keep_alive(bool value) noexcept override;
119 bool keep_alive(std::error_code& ec) const noexcept override;
120
121 std::error_code set_receive_buffer_size(int size) noexcept override;
122 int receive_buffer_size(std::error_code& ec) const noexcept override;
123
124 std::error_code set_send_buffer_size(int size) noexcept override;
125 int send_buffer_size(std::error_code& ec) const noexcept override;
126
127 std::error_code set_linger(bool enabled, int timeout) noexcept override;
128 tcp_socket::linger_options linger(std::error_code& ec) const noexcept override;
129
130 16 endpoint local_endpoint() const noexcept override { return local_endpoint_; }
131 16 endpoint remote_endpoint() const noexcept override { return remote_endpoint_; }
132 bool is_open() const noexcept { return fd_ >= 0; }
133 void cancel() noexcept override;
134 void cancel_single_op(select_op& op) noexcept;
135 void close_socket() noexcept;
136 2676 void set_socket(int fd) noexcept { fd_ = fd; }
137 5352 void set_endpoints(endpoint local, endpoint remote) noexcept
138 {
139 5352 local_endpoint_ = local;
140 5352 remote_endpoint_ = remote;
141 5352 }
142
143 select_connect_op conn_;
144 select_read_op rd_;
145 select_write_op wr_;
146
147 private:
148 select_socket_service& svc_;
149 int fd_ = -1;
150 endpoint local_endpoint_;
151 endpoint remote_endpoint_;
152 };
153
154 /** State for select socket service. */
155 class select_socket_state
156 {
157 public:
158 133 explicit select_socket_state(select_scheduler& sched) noexcept
159 133 : sched_(sched)
160 {
161 133 }
162
163 select_scheduler& sched_;
164 std::mutex mutex_;
165 intrusive_list<select_socket_impl> socket_list_;
166 std::unordered_map<select_socket_impl*, std::shared_ptr<select_socket_impl>> socket_ptrs_;
167 };
168
169 /** select socket service implementation.
170
171 Inherits from socket_service to enable runtime polymorphism.
172 Uses key_type = socket_service for service lookup.
173 */
174 class select_socket_service : public socket_service
175 {
176 public:
177 explicit select_socket_service(capy::execution_context& ctx);
178 ~select_socket_service();
179
180 select_socket_service(select_socket_service const&) = delete;
181 select_socket_service& operator=(select_socket_service const&) = delete;
182
183 void shutdown() override;
184
185 tcp_socket::socket_impl& create_impl() override;
186 void destroy_impl(tcp_socket::socket_impl& impl) override;
187 std::error_code open_socket(tcp_socket::socket_impl& impl) override;
188
189 8482 select_scheduler& scheduler() const noexcept { return state_->sched_; }
190 void post(select_op* op);
191 void work_started() noexcept;
192 void work_finished() noexcept;
193
194 private:
195 std::unique_ptr<select_socket_state> state_;
196 };
197
198 // Backward compatibility alias
199 using select_sockets = select_socket_service;
200
201 } // namespace boost::corosio::detail
202
203 #endif // BOOST_COROSIO_HAS_SELECT
204
205 #endif // BOOST_COROSIO_DETAIL_SELECT_SOCKETS_HPP
206