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 : Because the range is owned by the coroutine, passing an lvalue
109 : copies it; since `resolver_results` is a
110 : `std::vector<resolver_entry>`, that is a deep copy of every entry.
111 : Pass an rvalue (`std::move(results)`) or use the iterator overload
112 : (`connect(s, results.begin(), results.end())`) to avoid the copy.
113 :
114 : @return An awaitable completing with
115 : `capy::io_result<typename Socket::endpoint_type>`:
116 : - on success: default error_code and the connected endpoint;
117 : - on failure of all attempts: the error from the last attempt
118 : and a default-constructed endpoint;
119 : - on empty range: `std::errc::no_such_device_or_address` and a
120 : default-constructed endpoint.
121 :
122 : @note The socket is closed and re-opened before each attempt, so
123 : any socket options set by the caller (e.g. `no_delay`,
124 : `reuse_address`) are lost. Apply options after this operation
125 : completes.
126 :
127 : @throws std::system_error if auto-opening the socket fails during
128 : an attempt (inherits the contract of `Socket::connect`).
129 :
130 : @par Example
131 : @code
132 : resolver r(ioc);
133 : auto [rec, results] = co_await r.resolve("www.boost.org", "80");
134 : if (rec) co_return;
135 : tcp_socket s(ioc);
136 : auto [cec, ep] = co_await corosio::connect(s, results);
137 : @endcode
138 : */
139 : template<class Socket, std::ranges::input_range Range>
140 : requires std::convertible_to<
141 : std::ranges::range_reference_t<Range>,
142 : typename Socket::endpoint_type>
143 : capy::task<capy::io_result<typename Socket::endpoint_type>>
144 12 : connect(Socket& s, Range endpoints)
145 : {
146 : return corosio::connect(
147 12 : s, std::move(endpoints), detail::default_connect_condition{});
148 : }
149 :
150 : /** Asynchronously connect a socket by trying each endpoint in a range,
151 : filtered by a user-supplied condition.
152 :
153 : For each candidate the condition is invoked as
154 : `cond(last_ec, ep)` where `last_ec` is the error from the most
155 : recent attempt (default-constructed before the first attempt). If
156 : the condition returns `false` the candidate is skipped; otherwise a
157 : connect is attempted.
158 :
159 : @param s The socket to connect. See the non-condition overload for
160 : requirements.
161 : @param endpoints A range of candidate endpoints, taken by value. See
162 : the non-condition overload for the deep-copy caveat when passing
163 : an lvalue `resolver_results`.
164 : @param cond A predicate invocable with
165 : `(std::error_code const&, typename Socket::endpoint_type const&)`
166 : returning a value contextually convertible to `bool`.
167 :
168 : @return Same as the non-condition overload. If every candidate is
169 : rejected, completes with `std::errc::no_such_device_or_address`.
170 :
171 : @throws std::system_error if auto-opening the socket fails.
172 : */
173 : template<class Socket, std::ranges::input_range Range, class ConnectCondition>
174 : requires std::convertible_to<
175 : std::ranges::range_reference_t<Range>,
176 : typename Socket::endpoint_type> &&
177 : std::predicate<
178 : ConnectCondition&,
179 : std::error_code const&,
180 : typename Socket::endpoint_type const&>
181 : capy::task<capy::io_result<typename Socket::endpoint_type>>
182 16 : connect(Socket& s, Range endpoints, ConnectCondition cond)
183 : {
184 : using endpoint_type = typename Socket::endpoint_type;
185 :
186 : std::error_code last_ec;
187 :
188 : for (auto&& e : endpoints)
189 : {
190 : endpoint_type ep = e;
191 :
192 : if (!cond(static_cast<std::error_code const&>(last_ec),
193 : static_cast<endpoint_type const&>(ep)))
194 : continue;
195 :
196 : if (s.is_open())
197 : s.close();
198 :
199 : auto [ec] = co_await s.connect(ep);
200 :
201 : if (!ec)
202 : co_return {std::error_code{}, std::move(ep)};
203 :
204 : if (ec == capy::cond::canceled)
205 : co_return {ec, endpoint_type{}};
206 :
207 : last_ec = ec;
208 : }
209 :
210 : if (!last_ec)
211 : last_ec = std::make_error_code(std::errc::no_such_device_or_address);
212 :
213 : co_return {last_ec, endpoint_type{}};
214 32 : }
215 :
216 : /** Asynchronously connect a socket by trying each endpoint in an
217 : iterator range.
218 :
219 : Behaves like the range overload, except the return value carries
220 : the iterator to the successfully connected endpoint on success, or
221 : `end` on failure. This mirrors Boost.Asio's iterator-based
222 : `async_connect`.
223 :
224 : @param s The socket to connect.
225 : @param begin The first candidate.
226 : @param end One past the last candidate.
227 :
228 : @return An awaitable completing with `capy::io_result<Iter>`:
229 : - on success: default error_code and the iterator of the
230 : successful endpoint;
231 : - on failure of all attempts: the error from the last attempt
232 : and `end`;
233 : - on empty range: `std::errc::no_such_device_or_address` and
234 : `end`.
235 :
236 : @throws std::system_error if auto-opening the socket fails.
237 : */
238 : template<class Socket, std::input_iterator Iter>
239 : requires std::convertible_to<
240 : std::iter_reference_t<Iter>,
241 : typename Socket::endpoint_type>
242 : capy::task<capy::io_result<Iter>>
243 4 : connect(Socket& s, Iter begin, Iter end)
244 : {
245 : return corosio::connect(
246 : s,
247 4 : std::move(begin),
248 4 : std::move(end),
249 4 : detail::default_connect_condition{});
250 : }
251 :
252 : /** Asynchronously connect a socket by trying each endpoint in an
253 : iterator range, filtered by a user-supplied condition.
254 :
255 : @param s The socket to connect.
256 : @param begin The first candidate.
257 : @param end One past the last candidate.
258 : @param cond A predicate invocable with
259 : `(std::error_code const&, typename Socket::endpoint_type const&)`.
260 :
261 : @return Same as the plain iterator overload. If every candidate is
262 : rejected, completes with `std::errc::no_such_device_or_address`.
263 :
264 : @throws std::system_error if auto-opening the socket fails.
265 : */
266 : template<class Socket, std::input_iterator Iter, class ConnectCondition>
267 : requires std::convertible_to<
268 : std::iter_reference_t<Iter>,
269 : typename Socket::endpoint_type> &&
270 : std::predicate<
271 : ConnectCondition&,
272 : std::error_code const&,
273 : typename Socket::endpoint_type const&>
274 : capy::task<capy::io_result<Iter>>
275 4 : connect(Socket& s, Iter begin, Iter end, ConnectCondition cond)
276 : {
277 : using endpoint_type = typename Socket::endpoint_type;
278 :
279 : std::error_code last_ec;
280 :
281 : for (Iter it = begin; it != end; ++it)
282 : {
283 : endpoint_type ep = *it;
284 :
285 : if (!cond(static_cast<std::error_code const&>(last_ec),
286 : static_cast<endpoint_type const&>(ep)))
287 : continue;
288 :
289 : if (s.is_open())
290 : s.close();
291 :
292 : auto [ec] = co_await s.connect(ep);
293 :
294 : if (!ec)
295 : co_return {std::error_code{}, std::move(it)};
296 :
297 : if (ec == capy::cond::canceled)
298 : co_return {ec, std::move(end)};
299 :
300 : last_ec = ec;
301 : }
302 :
303 : if (!last_ec)
304 : last_ec = std::make_error_code(std::errc::no_such_device_or_address);
305 :
306 : co_return {last_ec, std::move(end)};
307 8 : }
308 :
309 : } // namespace boost::corosio
310 :
311 : #endif
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