TLA Line data Source code
1 : //
2 : // Copyright (c) 2026 Michael Vandeberg
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_CONNECT_HPP
11 : #define BOOST_COROSIO_CONNECT_HPP
12 :
13 : #include <boost/corosio/detail/config.hpp>
14 :
15 : #include <boost/capy/cond.hpp>
16 : #include <boost/capy/io_result.hpp>
17 : #include <boost/capy/task.hpp>
18 :
19 : #include <concepts>
20 : #include <iterator>
21 : #include <ranges>
22 : #include <system_error>
23 : #include <utility>
24 :
25 : /*
26 : Range-based composed connect operation.
27 :
28 : These free functions try each endpoint in a range (or iterator pair)
29 : in order, returning on the first successful connect. Between attempts
30 : the socket is closed so that the next attempt can auto-open with the
31 : correct address family (e.g. going from IPv4 to IPv6 candidates).
32 :
33 : The iteration semantics follow Boost.Asio's range/iterator async_connect:
34 : on success, the successful endpoint (or its iterator) is returned; on
35 : all-fail, the last attempt's error code is returned; on an empty range
36 : (or when a connect_condition rejects every candidate),
37 : std::errc::no_such_device_or_address is returned, matching the error
38 : the resolver uses for "no results" in posix_resolver_service.
39 :
40 : The operation is a plain coroutine; cancellation is propagated to the
41 : inner per-endpoint connect via the affine awaitable protocol on io_env.
42 : */
43 :
44 : namespace boost::corosio {
45 :
46 : namespace detail {
47 :
48 : /* Always-true connect condition used by the overloads that take no
49 : user-supplied predicate. Kept at namespace-detail scope so it has a
50 : stable linkage name across translation units. */
51 : struct default_connect_condition
52 : {
53 : template<class Endpoint>
54 HIT 20 : bool operator()(std::error_code const&, Endpoint const&) const noexcept
55 : {
56 20 : return true;
57 : }
58 : };
59 :
60 : } // namespace detail
61 :
62 : /* Forward declarations so the non-condition overloads can delegate
63 : to the condition overloads via qualified lookup (qualified calls
64 : bind to the overload set visible at definition, not instantiation). */
65 :
66 : template<class Socket, std::ranges::input_range Range, class ConnectCondition>
67 : requires std::convertible_to<
68 : std::ranges::range_reference_t<Range>,
69 : typename Socket::endpoint_type> &&
70 : std::predicate<
71 : ConnectCondition&,
72 : std::error_code const&,
73 : typename Socket::endpoint_type const&>
74 : capy::task<capy::io_result<typename Socket::endpoint_type>>
75 : connect(Socket& s, Range endpoints, ConnectCondition cond);
76 :
77 : template<class Socket, std::input_iterator Iter, class ConnectCondition>
78 : requires std::convertible_to<
79 : std::iter_reference_t<Iter>,
80 : typename Socket::endpoint_type> &&
81 : std::predicate<
82 : ConnectCondition&,
83 : std::error_code const&,
84 : typename Socket::endpoint_type const&>
85 : capy::task<capy::io_result<Iter>>
86 : connect(Socket& s, Iter begin, Iter end, ConnectCondition cond);
87 :
88 : /** Asynchronously connect a socket by trying each endpoint in a range.
89 :
90 : Each candidate is tried in order. Before each attempt the socket is
91 : closed (so the next `connect` auto-opens with the candidate's
92 : address family). On first successful connect, the operation
93 : completes with the connected endpoint.
94 :
95 : @par Cancellation
96 : Supports cancellation via the affine awaitable protocol. If a
97 : per-endpoint connect completes with `capy::cond::canceled` the
98 : operation completes immediately with that error and does not try
99 : further endpoints.
100 :
101 : @param s The socket to connect. Must have a `connect(endpoint)`
102 : member returning an awaitable, plus `close()` and `is_open()`.
103 : If the socket is already open, it will be closed before the
104 : first attempt.
105 : @param endpoints A range of candidate endpoints. Taken by value
106 : so temporaries (e.g. `resolver_results` returned from
107 : `resolver::resolve`) remain alive for the coroutine's lifetime.
108 :
109 : @return An awaitable completing with
110 : `capy::io_result<typename Socket::endpoint_type>`:
111 : - on success: default error_code and the connected endpoint;
112 : - on failure of all attempts: the error from the last attempt
113 : and a default-constructed endpoint;
114 : - on empty range: `std::errc::no_such_device_or_address` and a
115 : default-constructed endpoint.
116 :
117 : @note The socket is closed and re-opened before each attempt, so
118 : any socket options set by the caller (e.g. `no_delay`,
119 : `reuse_address`) are lost. Apply options after this operation
120 : completes.
121 :
122 : @throws std::system_error if auto-opening the socket fails during
123 : an attempt (inherits the contract of `Socket::connect`).
124 :
125 : @par Example
126 : @code
127 : resolver r(ioc);
128 : auto [rec, results] = co_await r.resolve("www.boost.org", "80");
129 : if (rec) co_return;
130 : tcp_socket s(ioc);
131 : auto [cec, ep] = co_await corosio::connect(s, results);
132 : @endcode
133 : */
134 : template<class Socket, std::ranges::input_range Range>
135 : requires std::convertible_to<
136 : std::ranges::range_reference_t<Range>,
137 : typename Socket::endpoint_type>
138 : capy::task<capy::io_result<typename Socket::endpoint_type>>
139 12 : connect(Socket& s, Range endpoints)
140 : {
141 : return corosio::connect(
142 12 : s, std::move(endpoints), detail::default_connect_condition{});
143 : }
144 :
145 : /** Asynchronously connect a socket by trying each endpoint in a range,
146 : filtered by a user-supplied condition.
147 :
148 : For each candidate the condition is invoked as
149 : `cond(last_ec, ep)` where `last_ec` is the error from the most
150 : recent attempt (default-constructed before the first attempt). If
151 : the condition returns `false` the candidate is skipped; otherwise a
152 : connect is attempted.
153 :
154 : @param s The socket to connect. See the non-condition overload for
155 : requirements.
156 : @param endpoints A range of candidate endpoints.
157 : @param cond A predicate invocable with
158 : `(std::error_code const&, typename Socket::endpoint_type const&)`
159 : returning a value contextually convertible to `bool`.
160 :
161 : @return Same as the non-condition overload. If every candidate is
162 : rejected, completes with `std::errc::no_such_device_or_address`.
163 :
164 : @throws std::system_error if auto-opening the socket fails.
165 : */
166 : template<class Socket, std::ranges::input_range Range, class ConnectCondition>
167 : requires std::convertible_to<
168 : std::ranges::range_reference_t<Range>,
169 : typename Socket::endpoint_type> &&
170 : std::predicate<
171 : ConnectCondition&,
172 : std::error_code const&,
173 : typename Socket::endpoint_type const&>
174 : capy::task<capy::io_result<typename Socket::endpoint_type>>
175 16 : connect(Socket& s, Range endpoints, ConnectCondition cond)
176 : {
177 : using endpoint_type = typename Socket::endpoint_type;
178 :
179 : std::error_code last_ec;
180 :
181 : for (auto&& e : endpoints)
182 : {
183 : endpoint_type ep = e;
184 :
185 : if (!cond(static_cast<std::error_code const&>(last_ec),
186 : static_cast<endpoint_type const&>(ep)))
187 : continue;
188 :
189 : if (s.is_open())
190 : s.close();
191 :
192 : auto [ec] = co_await s.connect(ep);
193 :
194 : if (!ec)
195 : co_return {std::error_code{}, std::move(ep)};
196 :
197 : if (ec == capy::cond::canceled)
198 : co_return {ec, endpoint_type{}};
199 :
200 : last_ec = ec;
201 : }
202 :
203 : if (!last_ec)
204 : last_ec = std::make_error_code(std::errc::no_such_device_or_address);
205 :
206 : co_return {last_ec, endpoint_type{}};
207 32 : }
208 :
209 : /** Asynchronously connect a socket by trying each endpoint in an
210 : iterator range.
211 :
212 : Behaves like the range overload, except the return value carries
213 : the iterator to the successfully connected endpoint on success, or
214 : `end` on failure. This mirrors Boost.Asio's iterator-based
215 : `async_connect`.
216 :
217 : @param s The socket to connect.
218 : @param begin The first candidate.
219 : @param end One past the last candidate.
220 :
221 : @return An awaitable completing with `capy::io_result<Iter>`:
222 : - on success: default error_code and the iterator of the
223 : successful endpoint;
224 : - on failure of all attempts: the error from the last attempt
225 : and `end`;
226 : - on empty range: `std::errc::no_such_device_or_address` and
227 : `end`.
228 :
229 : @throws std::system_error if auto-opening the socket fails.
230 : */
231 : template<class Socket, std::input_iterator Iter>
232 : requires std::convertible_to<
233 : std::iter_reference_t<Iter>,
234 : typename Socket::endpoint_type>
235 : capy::task<capy::io_result<Iter>>
236 4 : connect(Socket& s, Iter begin, Iter end)
237 : {
238 : return corosio::connect(
239 : s,
240 4 : std::move(begin),
241 4 : std::move(end),
242 4 : detail::default_connect_condition{});
243 : }
244 :
245 : /** Asynchronously connect a socket by trying each endpoint in an
246 : iterator range, filtered by a user-supplied condition.
247 :
248 : @param s The socket to connect.
249 : @param begin The first candidate.
250 : @param end One past the last candidate.
251 : @param cond A predicate invocable with
252 : `(std::error_code const&, typename Socket::endpoint_type const&)`.
253 :
254 : @return Same as the plain iterator overload. If every candidate is
255 : rejected, completes with `std::errc::no_such_device_or_address`.
256 :
257 : @throws std::system_error if auto-opening the socket fails.
258 : */
259 : template<class Socket, std::input_iterator Iter, class ConnectCondition>
260 : requires std::convertible_to<
261 : std::iter_reference_t<Iter>,
262 : typename Socket::endpoint_type> &&
263 : std::predicate<
264 : ConnectCondition&,
265 : std::error_code const&,
266 : typename Socket::endpoint_type const&>
267 : capy::task<capy::io_result<Iter>>
268 4 : connect(Socket& s, Iter begin, Iter end, ConnectCondition cond)
269 : {
270 : using endpoint_type = typename Socket::endpoint_type;
271 :
272 : std::error_code last_ec;
273 :
274 : for (Iter it = begin; it != end; ++it)
275 : {
276 : endpoint_type ep = *it;
277 :
278 : if (!cond(static_cast<std::error_code const&>(last_ec),
279 : static_cast<endpoint_type const&>(ep)))
280 : continue;
281 :
282 : if (s.is_open())
283 : s.close();
284 :
285 : auto [ec] = co_await s.connect(ep);
286 :
287 : if (!ec)
288 : co_return {std::error_code{}, std::move(it)};
289 :
290 : if (ec == capy::cond::canceled)
291 : co_return {ec, std::move(end)};
292 :
293 : last_ec = ec;
294 : }
295 :
296 : if (!last_ec)
297 : last_ec = std::make_error_code(std::errc::no_such_device_or_address);
298 :
299 : co_return {last_ec, std::move(end)};
300 8 : }
301 :
302 : } // namespace boost::corosio
303 :
304 : #endif
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