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_LOCAL_STREAM_ACCEPTOR_HPP
11 : #define BOOST_COROSIO_LOCAL_STREAM_ACCEPTOR_HPP
12 :
13 : #include <boost/corosio/detail/config.hpp>
14 : #include <boost/corosio/detail/except.hpp>
15 : #include <boost/corosio/detail/op_base.hpp>
16 : #include <boost/corosio/wait_type.hpp>
17 : #include <boost/corosio/io/io_object.hpp>
18 : #include <boost/capy/io_result.hpp>
19 : #include <boost/corosio/local_endpoint.hpp>
20 : #include <boost/corosio/local_stream.hpp>
21 : #include <boost/corosio/local_stream_socket.hpp>
22 : #include <boost/capy/ex/executor_ref.hpp>
23 : #include <boost/capy/ex/execution_context.hpp>
24 : #include <boost/capy/ex/io_env.hpp>
25 : #include <boost/capy/concept/executor.hpp>
26 :
27 : #include <system_error>
28 :
29 : #include <cassert>
30 : #include <concepts>
31 : #include <coroutine>
32 : #include <cstddef>
33 : #include <stop_token>
34 : #include <type_traits>
35 :
36 : namespace boost::corosio {
37 :
38 : /** Options for @ref local_stream_acceptor::bind().
39 :
40 : Controls filesystem cleanup behavior before binding
41 : to a Unix domain socket path.
42 : */
43 : enum class bind_option
44 : {
45 : none,
46 : /// Unlink the socket path before binding (ignored for abstract paths).
47 : unlink_existing
48 : };
49 :
50 : /** An asynchronous Unix domain stream acceptor for coroutine I/O.
51 :
52 : This class provides asynchronous Unix domain stream accept
53 : operations that return awaitable types. The acceptor binds
54 : to a local endpoint (filesystem path or abstract name) and
55 : listens for incoming connections.
56 :
57 : The library does NOT automatically unlink the socket path
58 : on close. Callers are responsible for removing the socket
59 : file before bind (via @ref bind_option::unlink_existing) or
60 : after close.
61 :
62 : @par Thread Safety
63 : Distinct objects: Safe.@n
64 : Shared objects: Unsafe. An acceptor must not have concurrent
65 : accept operations.
66 :
67 : @par Example
68 : @par !example bind_listen_accept
69 : */
70 : class BOOST_COROSIO_DECL local_stream_acceptor : public io_object
71 : {
72 : struct wait_awaitable : detail::void_op_base<wait_awaitable>
73 : {
74 : local_stream_acceptor& acc_;
75 : wait_type w_;
76 :
77 HIT 8 : wait_awaitable(local_stream_acceptor& acc, wait_type w) noexcept
78 16 : : acc_(acc)
79 8 : , w_(w)
80 : {
81 8 : }
82 :
83 : std::coroutine_handle<>
84 6 : dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
85 : {
86 6 : return acc_.get().wait(h, ex, w_, token_, &ec_);
87 : }
88 : };
89 :
90 : struct move_accept_awaitable : detail::void_op_base<move_accept_awaitable>
91 : {
92 : local_stream_acceptor& acc_;
93 : mutable io_object::implementation* peer_impl_ = nullptr;
94 :
95 6 : explicit move_accept_awaitable(local_stream_acceptor& acc) noexcept
96 6 : : acc_(acc)
97 : {
98 6 : }
99 :
100 : [[nodiscard]] capy::io_result<local_stream_socket>
101 6 : await_resume() const noexcept
102 : {
103 6 : if (this->ec_ || !peer_impl_)
104 4 : return {this->ec_, local_stream_socket()};
105 :
106 2 : local_stream_socket peer(acc_.ctx_);
107 2 : reset_peer_impl(peer, peer_impl_);
108 2 : return {this->ec_, std::move(peer)};
109 2 : }
110 :
111 : std::coroutine_handle<>
112 4 : dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
113 : {
114 12 : return acc_.get().accept(
115 12 : h, ex, this->token_, &this->ec_, &peer_impl_);
116 : }
117 : };
118 :
119 : struct accept_awaitable : detail::void_op_base<accept_awaitable>
120 : {
121 : local_stream_acceptor& acc_;
122 : local_stream_socket& peer_;
123 : mutable io_object::implementation* peer_impl_ = nullptr;
124 :
125 29 : accept_awaitable(
126 : local_stream_acceptor& acc, local_stream_socket& peer) noexcept
127 58 : : acc_(acc)
128 29 : , peer_(peer)
129 : {
130 29 : }
131 :
132 27 : [[nodiscard]] capy::io_result<> await_resume() const noexcept
133 : {
134 27 : if (!this->ec_ && peer_impl_)
135 17 : peer_.h_.reset(peer_impl_);
136 27 : return {this->ec_};
137 : }
138 :
139 : std::coroutine_handle<>
140 25 : dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
141 : {
142 75 : return acc_.get().accept(
143 75 : h, ex, this->token_, &this->ec_, &peer_impl_);
144 : }
145 : };
146 :
147 : public:
148 : /** Destructor.
149 :
150 : Closes the acceptor if open, cancelling any pending operations.
151 : */
152 : ~local_stream_acceptor() override;
153 :
154 : /** Construct an acceptor from an execution context.
155 :
156 : @param ctx The execution context that will own this acceptor.
157 : */
158 : explicit local_stream_acceptor(capy::execution_context& ctx);
159 :
160 : /** Convenience constructor: open + bind + listen.
161 :
162 : Creates a fully-bound listening acceptor in a single
163 : expression, throwing the codes the piecewise `open()` +
164 : `bind()` + `listen()` path returns.
165 :
166 : @param ctx The execution context that will own this acceptor.
167 : @param ep The local endpoint to bind to.
168 : @param backlog The maximum pending connection queue length.
169 :
170 : @throws std::system_error on open, bind, or listen failure.
171 : */
172 : local_stream_acceptor(
173 : capy::execution_context& ctx,
174 : corosio::local_endpoint ep,
175 : int backlog = 128);
176 :
177 : /** Construct an acceptor from an executor.
178 :
179 : The acceptor is associated with the executor's context.
180 :
181 : @param ex The executor whose context will own the acceptor.
182 :
183 : @tparam Ex A type satisfying @ref capy::Executor. Must not
184 : be `local_stream_acceptor` itself (disables implicit
185 : conversion from move).
186 : */
187 : template<class Ex>
188 : requires(!std::
189 : same_as<std::remove_cvref_t<Ex>, local_stream_acceptor>) &&
190 : capy::Executor<Ex>
191 : explicit local_stream_acceptor(Ex const& ex)
192 : : local_stream_acceptor(ex.context())
193 : {
194 : }
195 :
196 : /** Convenience constructor from an executor.
197 :
198 : @param ex The executor whose context will own the acceptor.
199 : @param ep The local endpoint to bind to.
200 : @param backlog The maximum pending connection queue length.
201 :
202 : @throws std::system_error on open, bind, or listen failure.
203 : */
204 : template<class Ex>
205 : requires capy::Executor<Ex>
206 : local_stream_acceptor(
207 : Ex const& ex, corosio::local_endpoint ep, int backlog = 128)
208 : : local_stream_acceptor(ex.context(), std::move(ep), backlog)
209 : {
210 : }
211 :
212 : /** Move constructor.
213 :
214 : Transfers ownership of the acceptor resources.
215 :
216 : @param other The acceptor to move from.
217 :
218 : @pre No awaitables returned by @p other's methods exist.
219 : @pre The execution context associated with @p other must
220 : outlive this acceptor.
221 : */
222 2 : local_stream_acceptor(local_stream_acceptor&& other) noexcept
223 2 : : local_stream_acceptor(other.ctx_, std::move(other))
224 : {
225 2 : }
226 :
227 : /** Move assignment operator.
228 :
229 : Closes any existing acceptor and transfers ownership.
230 : Both acceptors must share the same execution context.
231 :
232 : @param other The acceptor to move from.
233 :
234 : @return Reference to this acceptor.
235 :
236 : @pre `&ctx_ == &other.ctx_` (same execution context).
237 : @pre No awaitables returned by either `*this` or @p other's
238 : methods exist.
239 : */
240 : local_stream_acceptor& operator=(local_stream_acceptor&& other) noexcept
241 : {
242 : assert(
243 : &ctx_ == &other.ctx_ &&
244 : "move-assign requires the same execution_context");
245 : if (this != &other)
246 : {
247 : close();
248 : io_object::operator=(std::move(other));
249 : }
250 : return *this;
251 : }
252 :
253 : local_stream_acceptor(local_stream_acceptor const&) = delete;
254 : local_stream_acceptor& operator=(local_stream_acceptor const&) = delete;
255 :
256 : /** Create the acceptor socket.
257 :
258 : Failures such as descriptor exhaustion are normal runtime
259 : conditions and are reported through the returned error code.
260 :
261 : @param proto The protocol. Defaults to local_stream{}.
262 :
263 : @return The error code, empty on success.
264 : */
265 : [[nodiscard]] std::error_code open(local_stream proto = {}) noexcept;
266 :
267 : /** Bind to a local endpoint.
268 :
269 : @param ep The local endpoint (path) to bind to.
270 : @param opt Bind options. Pass bind_option::unlink_existing
271 : to unlink the socket path before binding (ignored for
272 : abstract sockets and empty endpoints).
273 :
274 : @return An error code on failure, empty on success.
275 :
276 : A closed acceptor reports `errc::bad_file_descriptor`.
277 : */
278 : [[nodiscard]] std::error_code bind(
279 : corosio::local_endpoint ep,
280 : bind_option opt = bind_option::none) noexcept;
281 :
282 : /** Start listening for incoming connections.
283 :
284 : @param backlog The maximum pending connection queue length.
285 :
286 : @return An error code on failure, empty on success.
287 :
288 : A closed acceptor reports `errc::bad_file_descriptor`.
289 : */
290 : [[nodiscard]] std::error_code listen(int backlog = 128) noexcept;
291 :
292 : /** Close the acceptor.
293 :
294 : Cancels any pending accept operations and releases the
295 : underlying socket. Has no effect if the acceptor is not
296 : open.
297 :
298 : @post is_open() == false
299 : */
300 : void close() noexcept;
301 :
302 : /// Check if the acceptor has an open socket handle.
303 489 : bool is_open() const noexcept
304 : {
305 489 : return h_ && get().is_open();
306 : }
307 :
308 : /** Initiate an asynchronous accept into an existing socket.
309 :
310 : Completes when a new connection is available. On success
311 : @p peer is reset to the accepted connection. Only one
312 : accept may be in flight at a time.
313 :
314 : @param peer The socket to receive the accepted connection.
315 :
316 : @par Cancellation
317 : Supports cancellation via stop_token or cancel().
318 : On cancellation, yields `capy::cond::canceled` and
319 : @p peer is not modified.
320 :
321 : @return An awaitable that completes with io_result<>.
322 :
323 : A closed acceptor reports `errc::bad_file_descriptor`.
324 : */
325 29 : [[nodiscard]] auto accept(local_stream_socket& peer)
326 : {
327 29 : accept_awaitable aw(*this, peer);
328 29 : if (!is_open())
329 2 : aw.ec_ = make_error_code(std::errc::bad_file_descriptor);
330 29 : return aw;
331 : }
332 :
333 : /** Wait for an incoming connection or readiness condition.
334 :
335 : Suspends until the listen socket is ready in the
336 : requested direction. For `wait_type::read`, completion
337 : signals that a subsequent @ref accept will succeed
338 : without blocking; a connection already queued when the
339 : wait begins completes it immediately. No connection is
340 : consumed.
341 :
342 : @note `wait_type::write` is not usable on an acceptor:
343 : writability carries no meaning for a listening socket, so
344 : the wait fails with `errc::operation_not_supported` on
345 : every backend.
346 :
347 : @param w The wait direction.
348 :
349 : @return An awaitable that completes with `io_result<>`.
350 :
351 : A closed acceptor completes with `errc::bad_file_descriptor`.
352 :
353 : @par Preconditions
354 : This acceptor must outlive the returned awaitable.
355 : */
356 8 : [[nodiscard]] auto wait(wait_type w)
357 : {
358 8 : wait_awaitable aw(*this, w);
359 8 : if (!is_open())
360 2 : aw.ec_ = make_error_code(std::errc::bad_file_descriptor);
361 8 : return aw;
362 : }
363 :
364 : /** Initiate an asynchronous accept, returning the socket.
365 :
366 : Completes when a new connection is available. Only one
367 : accept may be in flight at a time.
368 :
369 : @par Cancellation
370 : Supports cancellation via stop_token or cancel().
371 : On cancellation, yields `capy::cond::canceled` with
372 : a default-constructed socket.
373 :
374 : @return An awaitable that completes with
375 : io_result<local_stream_socket>.
376 :
377 : A closed acceptor reports `errc::bad_file_descriptor`.
378 : On failure the returned socket is default-constructed and
379 : may only be destroyed or assigned.
380 : */
381 6 : [[nodiscard]] auto accept()
382 : {
383 6 : move_accept_awaitable aw(*this);
384 6 : if (!is_open())
385 2 : aw.ec_ = make_error_code(std::errc::bad_file_descriptor);
386 6 : return aw;
387 : }
388 :
389 : /** Cancel pending asynchronous accept operations.
390 :
391 : Outstanding accept operations complete with
392 : @c capy::cond::canceled. Safe to call when no
393 : operations are pending (no-op).
394 : */
395 : void cancel() noexcept;
396 :
397 : /** Release ownership of the native socket handle.
398 :
399 : Deregisters the acceptor from the reactor and cancels
400 : pending operations without closing the descriptor. The
401 : caller takes ownership of the returned handle.
402 :
403 : @return The native handle.
404 :
405 : @throws std::system_error `errc::bad_file_descriptor` if the
406 : acceptor is not open.
407 :
408 : @post is_open() == false
409 : */
410 : native_handle_type release();
411 :
412 : /** Get the native socket handle.
413 :
414 : @return The native socket handle, or -1/INVALID_SOCKET if not
415 : open.
416 :
417 : @par Preconditions
418 : None. May be called on closed acceptors.
419 : */
420 : native_handle_type native_handle() const noexcept;
421 :
422 : /** Assign an existing native socket to this acceptor.
423 :
424 : Adopts a listening socket created outside the library —
425 : received from a service manager, inherited, or made natively —
426 : and registers it with the backend. The socket must be a
427 : listening stream socket in the local IPC family. Adoption
428 : never alters the descriptor's flags or options: on POSIX the
429 : fd must already be non-blocking, and on Windows the socket
430 : must be overlapped-capable.
431 :
432 : Adoption does not verify listen state; @ref accept reports the
433 : error if the socket is not listening.
434 :
435 : If this object is already open, pending operations complete
436 : with `errc::operation_canceled` and the held socket is closed
437 : before the new one is adopted.
438 :
439 : @par Exception Safety
440 : Strong guarantee on validation failure: the object is
441 : unchanged. If backend registration fails, the object either
442 : retains its previous socket or is left closed, depending on
443 : the backend. In all failure cases the caller retains
444 : ownership of `fd`.
445 :
446 : @param fd The native socket to adopt. On success the object
447 : owns it and will close it.
448 :
449 : @return The error code, empty on success. Validation and
450 : registration failures are normal runtime conditions when
451 : adopting foreign descriptors.
452 : */
453 : [[nodiscard]] std::error_code assign(native_handle_type fd) noexcept;
454 :
455 : /** Return the local endpoint the acceptor is bound to.
456 :
457 : Returns a default-constructed (empty) endpoint if the
458 : acceptor is not open or not yet bound. Safe to call in
459 : any state.
460 : */
461 : corosio::local_endpoint local_endpoint() const noexcept;
462 :
463 : /** Set a socket option on the acceptor.
464 :
465 : Applies a type-safe socket option to the underlying socket.
466 : The option type encodes the protocol level and option name.
467 :
468 : @param opt The option to set.
469 :
470 : @tparam Option A socket option type providing static
471 : `level()` and `name()` members, and `data()` / `size()`
472 : accessors.
473 :
474 : @throws std::system_error `errc::bad_file_descriptor` if the
475 : acceptor is not open; otherwise thrown on failure.
476 : */
477 : template<class Option>
478 6 : void set_option(Option const& opt)
479 : {
480 6 : if (!is_open())
481 2 : detail::throw_system_error(
482 4 : make_error_code(std::errc::bad_file_descriptor),
483 : "local_stream_acceptor::set_option");
484 4 : std::error_code ec = get().set_option(
485 : Option::level(), Option::name(), opt.data(), opt.size());
486 4 : if (ec)
487 2 : detail::throw_system_error(ec, "local_stream_acceptor::set_option");
488 2 : }
489 :
490 : /** Get a socket option from the acceptor.
491 :
492 : Retrieves the current value of a type-safe socket option.
493 :
494 : @return The current option value.
495 :
496 : @tparam Option A socket option type providing static
497 : `level()` and `name()` members, and `data()` / `size()`
498 : / `resize()` members.
499 :
500 : @throws std::system_error `errc::bad_file_descriptor` if the
501 : acceptor is not open; otherwise thrown on failure.
502 : */
503 : template<class Option>
504 6 : Option get_option() const
505 : {
506 6 : if (!is_open())
507 2 : detail::throw_system_error(
508 4 : make_error_code(std::errc::bad_file_descriptor),
509 : "local_stream_acceptor::get_option");
510 4 : Option opt{};
511 4 : std::size_t sz = opt.size();
512 : std::error_code ec =
513 4 : get().get_option(Option::level(), Option::name(), opt.data(), &sz);
514 4 : if (ec)
515 2 : detail::throw_system_error(ec, "local_stream_acceptor::get_option");
516 2 : opt.resize(sz);
517 2 : return opt;
518 : }
519 :
520 : /** Backend hooks for local stream acceptor operations.
521 :
522 : Platform backends derive from this to implement
523 : accept, option, and lifecycle management.
524 : */
525 : struct implementation : io_object::implementation
526 : {
527 : /** Initiate an asynchronous accept.
528 :
529 : On completion the backend sets @p *ec and, on
530 : success, stores a pointer to the new socket
531 : implementation in @p *impl_out.
532 :
533 : @param h Coroutine handle to resume.
534 : @param ex Executor for dispatching the completion.
535 : @param token Stop token for cancellation.
536 : @param ec Output error code.
537 : @param impl_out Output pointer for the accepted socket.
538 : @return Coroutine handle to resume immediately.
539 : */
540 : virtual std::coroutine_handle<> accept(
541 : std::coroutine_handle<>,
542 : capy::executor_ref,
543 : std::stop_token,
544 : std::error_code*,
545 : io_object::implementation**) = 0;
546 :
547 : /** Initiate an asynchronous wait for acceptor readiness.
548 :
549 : Completes when the listen socket becomes ready for
550 : the specified direction. No connection is consumed.
551 : */
552 : virtual std::coroutine_handle<> wait(
553 : std::coroutine_handle<> h,
554 : capy::executor_ref ex,
555 : wait_type w,
556 : std::stop_token token,
557 : std::error_code* ec) = 0;
558 :
559 : /// Return the cached local endpoint.
560 : virtual corosio::local_endpoint local_endpoint() const noexcept = 0;
561 :
562 : /// Return whether the underlying socket is open.
563 : virtual bool is_open() const noexcept = 0;
564 :
565 : /// Return the native handle, or the platform sentinel if closed.
566 : virtual native_handle_type native_handle() const noexcept = 0;
567 :
568 : /// Release and return the native handle without closing.
569 : virtual native_handle_type release_socket() noexcept = 0;
570 :
571 : /// Cancel pending accept operations.
572 : virtual void cancel() noexcept = 0;
573 :
574 : /// Set a raw socket option.
575 : virtual std::error_code set_option(
576 : int level,
577 : int optname,
578 : void const* data,
579 : std::size_t size) noexcept = 0;
580 :
581 : /// Get a raw socket option.
582 : virtual std::error_code
583 : get_option(int level, int optname, void* data, std::size_t* size)
584 : const noexcept = 0;
585 : };
586 :
587 : protected:
588 18 : local_stream_acceptor(handle h, capy::execution_context& ctx) noexcept
589 18 : : io_object(std::move(h))
590 18 : , ctx_(ctx)
591 : {
592 18 : }
593 :
594 2 : local_stream_acceptor(
595 : capy::execution_context& ctx, local_stream_acceptor&& other) noexcept
596 2 : : io_object(std::move(other))
597 2 : , ctx_(ctx)
598 : {
599 2 : }
600 :
601 8 : static void reset_peer_impl(
602 : local_stream_socket& peer, io_object::implementation* impl) noexcept
603 : {
604 8 : if (impl)
605 8 : peer.h_.reset(impl);
606 8 : }
607 :
608 : private:
609 : capy::execution_context& ctx_;
610 :
611 564 : inline implementation& get() const noexcept
612 : {
613 564 : return *static_cast<implementation*>(h_.get());
614 : }
615 : };
616 :
617 : } // namespace boost::corosio
618 :
619 : #endif // BOOST_COROSIO_LOCAL_STREAM_ACCEPTOR_HPP
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