Line data Source code
1 : //
2 : // Copyright (c) 2025 Vinnie Falco (vinnie dot falco at gmail dot com)
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/capy
8 : //
9 :
10 : #ifndef BOOST_CAPY_IO_ANY_READ_SOURCE_HPP
11 : #define BOOST_CAPY_IO_ANY_READ_SOURCE_HPP
12 :
13 : #include <boost/capy/detail/config.hpp>
14 : #include <boost/capy/detail/await_suspend_helper.hpp>
15 : #include <boost/capy/buffers.hpp>
16 : #include <boost/capy/buffers/buffer_array.hpp>
17 : #include <boost/capy/buffers/buffer_param.hpp>
18 : #include <boost/capy/concept/io_awaitable.hpp>
19 : #include <boost/capy/concept/read_source.hpp>
20 : #include <boost/capy/coro.hpp>
21 : #include <boost/capy/ex/executor_ref.hpp>
22 : #include <boost/capy/io_result.hpp>
23 : #include <boost/capy/io_task.hpp>
24 :
25 : #include <concepts>
26 : #include <coroutine>
27 : #include <cstddef>
28 : #include <new>
29 : #include <span>
30 : #include <stop_token>
31 : #include <system_error>
32 : #include <utility>
33 :
34 : namespace boost {
35 : namespace capy {
36 :
37 : /** Type-erased wrapper for any ReadSource.
38 :
39 : This class provides type erasure for any type satisfying the
40 : @ref ReadSource concept, enabling runtime polymorphism for
41 : source read operations. It uses cached awaitable storage to achieve
42 : zero steady-state allocation after construction.
43 :
44 : The wrapper supports two construction modes:
45 : - **Owning**: Pass by value to transfer ownership. The wrapper
46 : allocates storage and owns the source.
47 : - **Reference**: Pass a pointer to wrap without ownership. The
48 : pointed-to source must outlive this wrapper.
49 :
50 : @par Awaitable Preallocation
51 : The constructor preallocates storage for the type-erased awaitable.
52 : This reserves all virtual address space at server startup
53 : so memory usage can be measured up front, rather than
54 : allocating piecemeal as traffic arrives.
55 :
56 : @par Immediate Completion
57 : Operations complete immediately without suspending when the
58 : buffer sequence is empty, or when the underlying source's
59 : awaitable reports readiness via `await_ready`.
60 :
61 : @par Thread Safety
62 : Not thread-safe. Concurrent operations on the same wrapper
63 : are undefined behavior.
64 :
65 : @par Example
66 : @code
67 : // Owning - takes ownership of the source
68 : any_read_source rs(some_source{args...});
69 :
70 : // Reference - wraps without ownership
71 : some_source source;
72 : any_read_source rs(&source);
73 :
74 : mutable_buffer buf(data, size);
75 : auto [ec, n] = co_await rs.read(std::span(&buf, 1));
76 : @endcode
77 :
78 : @see any_read_stream, ReadSource
79 : */
80 : class any_read_source
81 : {
82 : struct vtable;
83 : struct awaitable_ops;
84 :
85 : template<ReadSource S>
86 : struct vtable_for_impl;
87 :
88 : void* source_ = nullptr;
89 : vtable const* vt_ = nullptr;
90 : void* cached_awaitable_ = nullptr;
91 : void* storage_ = nullptr;
92 : awaitable_ops const* active_ops_ = nullptr;
93 :
94 : public:
95 : /** Destructor.
96 :
97 : Destroys the owned source (if any) and releases the cached
98 : awaitable storage.
99 : */
100 : ~any_read_source();
101 :
102 : /** Default constructor.
103 :
104 : Constructs an empty wrapper. Operations on a default-constructed
105 : wrapper result in undefined behavior.
106 : */
107 : any_read_source() = default;
108 :
109 : /** Non-copyable.
110 :
111 : The awaitable cache is per-instance and cannot be shared.
112 : */
113 : any_read_source(any_read_source const&) = delete;
114 : any_read_source& operator=(any_read_source const&) = delete;
115 :
116 : /** Move constructor.
117 :
118 : Transfers ownership of the wrapped source (if owned) and
119 : cached awaitable storage from `other`. After the move, `other` is
120 : in a default-constructed state.
121 :
122 : @param other The wrapper to move from.
123 : */
124 1 : any_read_source(any_read_source&& other) noexcept
125 1 : : source_(std::exchange(other.source_, nullptr))
126 1 : , vt_(std::exchange(other.vt_, nullptr))
127 1 : , cached_awaitable_(std::exchange(other.cached_awaitable_, nullptr))
128 1 : , storage_(std::exchange(other.storage_, nullptr))
129 1 : , active_ops_(std::exchange(other.active_ops_, nullptr))
130 : {
131 1 : }
132 :
133 : /** Move assignment operator.
134 :
135 : Destroys any owned source and releases existing resources,
136 : then transfers ownership from `other`.
137 :
138 : @param other The wrapper to move from.
139 : @return Reference to this wrapper.
140 : */
141 : any_read_source&
142 : operator=(any_read_source&& other) noexcept;
143 :
144 : /** Construct by taking ownership of a ReadSource.
145 :
146 : Allocates storage and moves the source into this wrapper.
147 : The wrapper owns the source and will destroy it.
148 :
149 : @param s The source to take ownership of.
150 : */
151 : template<ReadSource S>
152 : requires (!std::same_as<std::decay_t<S>, any_read_source>)
153 : any_read_source(S s);
154 :
155 : /** Construct by wrapping a ReadSource without ownership.
156 :
157 : Wraps the given source by pointer. The source must remain
158 : valid for the lifetime of this wrapper.
159 :
160 : @param s Pointer to the source to wrap.
161 : */
162 : template<ReadSource S>
163 : any_read_source(S* s);
164 :
165 : /** Check if the wrapper contains a valid source.
166 :
167 : @return `true` if wrapping a source, `false` if default-constructed
168 : or moved-from.
169 : */
170 : bool
171 27 : has_value() const noexcept
172 : {
173 27 : return source_ != nullptr;
174 : }
175 :
176 : /** Check if the wrapper contains a valid source.
177 :
178 : @return `true` if wrapping a source, `false` if default-constructed
179 : or moved-from.
180 : */
181 : explicit
182 8 : operator bool() const noexcept
183 : {
184 8 : return has_value();
185 : }
186 :
187 : /** Initiate a partial read operation.
188 :
189 : Reads one or more bytes into the provided buffer sequence.
190 : May fill less than the full sequence.
191 :
192 : @param buffers The buffer sequence to read into.
193 :
194 : @return An awaitable yielding `(error_code,std::size_t)`.
195 :
196 : @par Immediate Completion
197 : The operation completes immediately without suspending
198 : the calling coroutine when:
199 : @li The buffer sequence is empty, returning `{error_code{}, 0}`.
200 : @li The underlying source's awaitable reports immediate
201 : readiness via `await_ready`.
202 :
203 : @note This is a partial operation and may not process the
204 : entire buffer sequence. Use @ref read for guaranteed
205 : complete transfer.
206 :
207 : @par Preconditions
208 : The wrapper must contain a valid source (`has_value() == true`).
209 : The caller must not call this function again after a prior
210 : call returned an error (including EOF).
211 : */
212 : template<MutableBufferSequence MB>
213 : auto
214 : read_some(MB buffers);
215 :
216 : /** Initiate a complete read operation.
217 :
218 : Reads data into the provided buffer sequence by forwarding
219 : to the underlying source's `read` operation. Large buffer
220 : sequences are processed in windows, with each window
221 : forwarded as a separate `read` call to the underlying source.
222 : The operation completes when the entire buffer sequence is
223 : filled, end-of-file is reached, or an error occurs.
224 :
225 : @param buffers The buffer sequence to read into.
226 :
227 : @return An awaitable yielding `(error_code,std::size_t)`.
228 :
229 : @par Immediate Completion
230 : The operation completes immediately without suspending
231 : the calling coroutine when:
232 : @li The buffer sequence is empty, returning `{error_code{}, 0}`.
233 : @li The underlying source's `read` awaitable reports
234 : immediate readiness via `await_ready`.
235 :
236 : @par Postconditions
237 : Exactly one of the following is true on return:
238 : @li **Success**: `!ec` and `n == buffer_size(buffers)`.
239 : The entire buffer was filled.
240 : @li **End-of-stream or Error**: `ec` and `n` indicates
241 : the number of bytes transferred before the failure.
242 :
243 : @par Preconditions
244 : The wrapper must contain a valid source (`has_value() == true`).
245 : The caller must not call this function again after a prior
246 : call returned an error (including EOF).
247 : */
248 : template<MutableBufferSequence MB>
249 : io_task<std::size_t>
250 : read(MB buffers);
251 :
252 : protected:
253 : /** Rebind to a new source after move.
254 :
255 : Updates the internal pointer to reference a new source object.
256 : Used by owning wrappers after move assignment when the owned
257 : object has moved to a new location.
258 :
259 : @param new_source The new source to bind to. Must be the same
260 : type as the original source.
261 :
262 : @note Terminates if called with a source of different type
263 : than the original.
264 : */
265 : template<ReadSource S>
266 : void
267 : rebind(S& new_source) noexcept
268 : {
269 : if(vt_ != &vtable_for_impl<S>::value)
270 : std::terminate();
271 : source_ = &new_source;
272 : }
273 :
274 : private:
275 : auto
276 : read_(std::span<mutable_buffer const> buffers);
277 : };
278 :
279 : //----------------------------------------------------------
280 :
281 : // ordered by call sequence for cache line coherence
282 : struct any_read_source::awaitable_ops
283 : {
284 : bool (*await_ready)(void*);
285 : coro (*await_suspend)(void*, coro, executor_ref, std::stop_token);
286 : io_result<std::size_t> (*await_resume)(void*);
287 : void (*destroy)(void*) noexcept;
288 : };
289 :
290 : // ordered by call frequency for cache line coherence
291 : struct any_read_source::vtable
292 : {
293 : awaitable_ops const* (*construct_read_some_awaitable)(
294 : void* source,
295 : void* storage,
296 : std::span<mutable_buffer const> buffers);
297 : awaitable_ops const* (*construct_read_awaitable)(
298 : void* source,
299 : void* storage,
300 : std::span<mutable_buffer const> buffers);
301 : std::size_t awaitable_size;
302 : std::size_t awaitable_align;
303 : void (*destroy)(void*) noexcept;
304 : };
305 :
306 : template<ReadSource S>
307 : struct any_read_source::vtable_for_impl
308 : {
309 : using ReadSomeAwaitable = decltype(std::declval<S&>().read_some(
310 : std::span<mutable_buffer const>{}));
311 : using ReadAwaitable = decltype(std::declval<S&>().read(
312 : std::span<mutable_buffer const>{}));
313 :
314 : static void
315 6 : do_destroy_impl(void* source) noexcept
316 : {
317 6 : static_cast<S*>(source)->~S();
318 6 : }
319 :
320 : static awaitable_ops const*
321 52 : construct_read_some_awaitable_impl(
322 : void* source,
323 : void* storage,
324 : std::span<mutable_buffer const> buffers)
325 : {
326 52 : auto& s = *static_cast<S*>(source);
327 52 : ::new(storage) ReadSomeAwaitable(s.read_some(buffers));
328 :
329 : static constexpr awaitable_ops ops = {
330 52 : +[](void* p) {
331 52 : return static_cast<ReadSomeAwaitable*>(p)->await_ready();
332 : },
333 2 : +[](void* p, coro h, executor_ref ex, std::stop_token token) {
334 4 : return detail::call_await_suspend(
335 2 : static_cast<ReadSomeAwaitable*>(p), h, ex, token);
336 : },
337 50 : +[](void* p) {
338 50 : return static_cast<ReadSomeAwaitable*>(p)->await_resume();
339 : },
340 54 : +[](void* p) noexcept {
341 2 : static_cast<ReadSomeAwaitable*>(p)->~ReadSomeAwaitable();
342 : }
343 : };
344 52 : return &ops;
345 : }
346 :
347 : static awaitable_ops const*
348 116 : construct_read_awaitable_impl(
349 : void* source,
350 : void* storage,
351 : std::span<mutable_buffer const> buffers)
352 : {
353 116 : auto& s = *static_cast<S*>(source);
354 116 : ::new(storage) ReadAwaitable(s.read(buffers));
355 :
356 : static constexpr awaitable_ops ops = {
357 116 : +[](void* p) {
358 116 : return static_cast<ReadAwaitable*>(p)->await_ready();
359 : },
360 0 : +[](void* p, coro h, executor_ref ex, std::stop_token token) {
361 0 : return detail::call_await_suspend(
362 0 : static_cast<ReadAwaitable*>(p), h, ex, token);
363 : },
364 116 : +[](void* p) {
365 116 : return static_cast<ReadAwaitable*>(p)->await_resume();
366 : },
367 116 : +[](void* p) noexcept {
368 0 : static_cast<ReadAwaitable*>(p)->~ReadAwaitable();
369 : }
370 : };
371 116 : return &ops;
372 : }
373 :
374 : static constexpr std::size_t max_awaitable_size =
375 : sizeof(ReadSomeAwaitable) > sizeof(ReadAwaitable)
376 : ? sizeof(ReadSomeAwaitable)
377 : : sizeof(ReadAwaitable);
378 : static constexpr std::size_t max_awaitable_align =
379 : alignof(ReadSomeAwaitable) > alignof(ReadAwaitable)
380 : ? alignof(ReadSomeAwaitable)
381 : : alignof(ReadAwaitable);
382 :
383 : static constexpr vtable value = {
384 : &construct_read_some_awaitable_impl,
385 : &construct_read_awaitable_impl,
386 : max_awaitable_size,
387 : max_awaitable_align,
388 : &do_destroy_impl
389 : };
390 : };
391 :
392 : //----------------------------------------------------------
393 :
394 : inline
395 145 : any_read_source::~any_read_source()
396 : {
397 145 : if(storage_)
398 : {
399 6 : vt_->destroy(source_);
400 6 : ::operator delete(storage_);
401 : }
402 145 : if(cached_awaitable_)
403 : {
404 139 : if(active_ops_)
405 1 : active_ops_->destroy(cached_awaitable_);
406 139 : ::operator delete(cached_awaitable_);
407 : }
408 145 : }
409 :
410 : inline any_read_source&
411 4 : any_read_source::operator=(any_read_source&& other) noexcept
412 : {
413 4 : if(this != &other)
414 : {
415 3 : if(storage_)
416 : {
417 0 : vt_->destroy(source_);
418 0 : ::operator delete(storage_);
419 : }
420 3 : if(cached_awaitable_)
421 : {
422 2 : if(active_ops_)
423 1 : active_ops_->destroy(cached_awaitable_);
424 2 : ::operator delete(cached_awaitable_);
425 : }
426 3 : source_ = std::exchange(other.source_, nullptr);
427 3 : vt_ = std::exchange(other.vt_, nullptr);
428 3 : cached_awaitable_ = std::exchange(other.cached_awaitable_, nullptr);
429 3 : storage_ = std::exchange(other.storage_, nullptr);
430 3 : active_ops_ = std::exchange(other.active_ops_, nullptr);
431 : }
432 4 : return *this;
433 : }
434 :
435 : template<ReadSource S>
436 : requires (!std::same_as<std::decay_t<S>, any_read_source>)
437 6 : any_read_source::any_read_source(S s)
438 6 : : vt_(&vtable_for_impl<S>::value)
439 : {
440 : struct guard {
441 : any_read_source* self;
442 : bool committed = false;
443 6 : ~guard() {
444 6 : if(!committed && self->storage_) {
445 0 : self->vt_->destroy(self->source_);
446 0 : ::operator delete(self->storage_);
447 0 : self->storage_ = nullptr;
448 0 : self->source_ = nullptr;
449 : }
450 6 : }
451 6 : } g{this};
452 :
453 6 : storage_ = ::operator new(sizeof(S));
454 6 : source_ = ::new(storage_) S(std::move(s));
455 :
456 : // Preallocate the awaitable storage
457 6 : cached_awaitable_ = ::operator new(vt_->awaitable_size);
458 :
459 6 : g.committed = true;
460 6 : }
461 :
462 : template<ReadSource S>
463 135 : any_read_source::any_read_source(S* s)
464 135 : : source_(s)
465 135 : , vt_(&vtable_for_impl<S>::value)
466 : {
467 : // Preallocate the awaitable storage
468 135 : cached_awaitable_ = ::operator new(vt_->awaitable_size);
469 135 : }
470 :
471 : //----------------------------------------------------------
472 :
473 : template<MutableBufferSequence MB>
474 : auto
475 54 : any_read_source::read_some(MB buffers)
476 : {
477 : struct awaitable
478 : {
479 : any_read_source* self_;
480 : mutable_buffer_array<detail::max_iovec_> ba_;
481 :
482 54 : awaitable(any_read_source* self, MB const& buffers)
483 54 : : self_(self)
484 54 : , ba_(buffers)
485 : {
486 54 : }
487 :
488 : bool
489 54 : await_ready() const noexcept
490 : {
491 54 : return ba_.to_span().empty();
492 : }
493 :
494 : coro
495 52 : await_suspend(coro h, executor_ref ex, std::stop_token token)
496 : {
497 52 : self_->active_ops_ = self_->vt_->construct_read_some_awaitable(
498 52 : self_->source_,
499 52 : self_->cached_awaitable_,
500 52 : ba_.to_span());
501 :
502 52 : if(self_->active_ops_->await_ready(self_->cached_awaitable_))
503 50 : return h;
504 :
505 4 : return self_->active_ops_->await_suspend(
506 2 : self_->cached_awaitable_, h, ex, token);
507 : }
508 :
509 : io_result<std::size_t>
510 52 : await_resume()
511 : {
512 52 : if(ba_.to_span().empty())
513 2 : return {{}, 0};
514 :
515 : struct guard {
516 : any_read_source* self;
517 50 : ~guard() {
518 50 : self->active_ops_->destroy(self->cached_awaitable_);
519 50 : self->active_ops_ = nullptr;
520 50 : }
521 50 : } g{self_};
522 50 : return self_->active_ops_->await_resume(
523 50 : self_->cached_awaitable_);
524 50 : }
525 : };
526 54 : return awaitable(this, buffers);
527 : }
528 :
529 : inline auto
530 116 : any_read_source::read_(std::span<mutable_buffer const> buffers)
531 : {
532 : struct awaitable
533 : {
534 : any_read_source* self_;
535 : std::span<mutable_buffer const> buffers_;
536 :
537 : bool
538 116 : await_ready() const noexcept
539 : {
540 116 : return false;
541 : }
542 :
543 : coro
544 116 : await_suspend(coro h, executor_ref ex, std::stop_token token)
545 : {
546 232 : self_->active_ops_ = self_->vt_->construct_read_awaitable(
547 116 : self_->source_,
548 116 : self_->cached_awaitable_,
549 : buffers_);
550 :
551 116 : if(self_->active_ops_->await_ready(self_->cached_awaitable_))
552 116 : return h;
553 :
554 0 : return self_->active_ops_->await_suspend(
555 0 : self_->cached_awaitable_, h, ex, token);
556 : }
557 :
558 : io_result<std::size_t>
559 116 : await_resume()
560 : {
561 : struct guard {
562 : any_read_source* self;
563 116 : ~guard() {
564 116 : self->active_ops_->destroy(self->cached_awaitable_);
565 116 : self->active_ops_ = nullptr;
566 116 : }
567 116 : } g{self_};
568 116 : return self_->active_ops_->await_resume(
569 200 : self_->cached_awaitable_);
570 116 : }
571 : };
572 116 : return awaitable{this, buffers};
573 : }
574 :
575 : template<MutableBufferSequence MB>
576 : io_task<std::size_t>
577 110 : any_read_source::read(MB buffers)
578 : {
579 : buffer_param bp(buffers);
580 : std::size_t total = 0;
581 :
582 : for(;;)
583 : {
584 : auto bufs = bp.data();
585 : if(bufs.empty())
586 : break;
587 :
588 : auto [ec, n] = co_await read_(bufs);
589 : total += n;
590 : if(ec)
591 : co_return {ec, total};
592 : bp.consume(n);
593 : }
594 :
595 : co_return {{}, total};
596 220 : }
597 :
598 : } // namespace capy
599 : } // namespace boost
600 :
601 : #endif
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