. /include/boost/corosio /io_context.hpp
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1   // 1   //
2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) 2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3   // Copyright (c) 2026 Steve Gerbino 3   // Copyright (c) 2026 Steve Gerbino
4   // Copyright (c) 2026 Michael Vandeberg 4   // Copyright (c) 2026 Michael Vandeberg
5   // 5   //
6   // Distributed under the Boost Software License, Version 1.0. (See accompanying 6   // Distributed under the Boost Software License, Version 1.0. (See accompanying
7   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 7   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8   // 8   //
9   // Official repository: https://github.com/cppalliance/corosio 9   // Official repository: https://github.com/cppalliance/corosio
10   // 10   //
11   11  
12   #ifndef BOOST_COROSIO_IO_CONTEXT_HPP 12   #ifndef BOOST_COROSIO_IO_CONTEXT_HPP
13   #define BOOST_COROSIO_IO_CONTEXT_HPP 13   #define BOOST_COROSIO_IO_CONTEXT_HPP
14   14  
15   #include <boost/corosio/detail/config.hpp> 15   #include <boost/corosio/detail/config.hpp>
16   #include <boost/corosio/detail/continuation_op.hpp> 16   #include <boost/corosio/detail/continuation_op.hpp>
17   #include <boost/corosio/detail/platform.hpp> 17   #include <boost/corosio/detail/platform.hpp>
18   #include <boost/corosio/detail/scheduler.hpp> 18   #include <boost/corosio/detail/scheduler.hpp>
19   #include <boost/capy/continuation.hpp> 19   #include <boost/capy/continuation.hpp>
20   #include <boost/capy/ex/execution_context.hpp> 20   #include <boost/capy/ex/execution_context.hpp>
21   21  
22   #include <chrono> 22   #include <chrono>
23   #include <coroutine> 23   #include <coroutine>
24   #include <cstddef> 24   #include <cstddef>
25   #include <limits> 25   #include <limits>
26   #include <thread> 26   #include <thread>
27   27  
28   namespace boost::corosio { 28   namespace boost::corosio {
29   29  
30   /** Runtime tuning options for @ref io_context. 30   /** Runtime tuning options for @ref io_context.
31   31  
32   All fields have defaults that match the library's built-in 32   All fields have defaults that match the library's built-in
33   values, so constructing a default `io_context_options` produces 33   values, so constructing a default `io_context_options` produces
34   identical behavior to an unconfigured context. 34   identical behavior to an unconfigured context.
35   35  
36   Options that apply only to a specific backend family are 36   Options that apply only to a specific backend family are
37   silently ignored when the active backend does not support them. 37   silently ignored when the active backend does not support them.
38   38  
39   @par Example 39   @par Example
40   @code 40   @code
41   io_context_options opts; 41   io_context_options opts;
42   opts.max_events_per_poll = 256; // larger batch per syscall 42   opts.max_events_per_poll = 256; // larger batch per syscall
43   opts.inline_budget_max = 32; // more speculative completions 43   opts.inline_budget_max = 32; // more speculative completions
44   opts.thread_pool_size = 4; // more file-I/O workers 44   opts.thread_pool_size = 4; // more file-I/O workers
45   45  
46   io_context ioc(opts); 46   io_context ioc(opts);
47   @endcode 47   @endcode
48   48  
49   @see io_context, native_io_context 49   @see io_context, native_io_context
50   */ 50   */
51   struct io_context_options 51   struct io_context_options
52   { 52   {
53   /** Maximum events fetched per reactor poll call. 53   /** Maximum events fetched per reactor poll call.
54   54  
55   Controls the buffer size passed to `epoll_wait()` or 55   Controls the buffer size passed to `epoll_wait()` or
56   `kevent()`. Larger values reduce syscall frequency under 56   `kevent()`. Larger values reduce syscall frequency under
57   high load; smaller values improve fairness between 57   high load; smaller values improve fairness between
58   connections. Ignored on IOCP and select backends. 58   connections. Ignored on IOCP and select backends.
59   */ 59   */
60   unsigned max_events_per_poll = 128; 60   unsigned max_events_per_poll = 128;
61   61  
62   /** Starting inline completion budget per handler chain. 62   /** Starting inline completion budget per handler chain.
63   63  
64   After a posted handler executes, the reactor grants this 64   After a posted handler executes, the reactor grants this
65   many speculative inline completions before forcing a 65   many speculative inline completions before forcing a
66   re-queue. Applies to reactor backends only. 66   re-queue. Applies to reactor backends only.
67   */ 67   */
68   unsigned inline_budget_initial = 2; 68   unsigned inline_budget_initial = 2;
69   69  
70   /** Hard ceiling on adaptive inline budget ramp-up. 70   /** Hard ceiling on adaptive inline budget ramp-up.
71   71  
72   The budget doubles each cycle it is fully consumed, up to 72   The budget doubles each cycle it is fully consumed, up to
73   this limit. Applies to reactor backends only. 73   this limit. Applies to reactor backends only.
74   */ 74   */
75   unsigned inline_budget_max = 16; 75   unsigned inline_budget_max = 16;
76   76  
77   /** Inline budget when no other thread assists the reactor. 77   /** Inline budget when no other thread assists the reactor.
78   78  
79   When only one thread is running the event loop, this 79   When only one thread is running the event loop, this
80   value caps the inline budget to preserve fairness. 80   value caps the inline budget to preserve fairness.
81   Applies to reactor backends only. 81   Applies to reactor backends only.
82   */ 82   */
83   unsigned unassisted_budget = 4; 83   unsigned unassisted_budget = 4;
84   84  
85   /** Maximum `GetQueuedCompletionStatus` timeout in milliseconds. 85   /** Maximum `GetQueuedCompletionStatus` timeout in milliseconds.
86   86  
87   Bounds how long the IOCP scheduler blocks between timer 87   Bounds how long the IOCP scheduler blocks between timer
88   rechecks. Lower values improve timer responsiveness at the 88   rechecks. Lower values improve timer responsiveness at the
89   cost of more syscalls. Applies to IOCP only. 89   cost of more syscalls. Applies to IOCP only.
90   */ 90   */
91   unsigned gqcs_timeout_ms = 500; 91   unsigned gqcs_timeout_ms = 500;
92   92  
93   /** Thread pool size for blocking I/O (file I/O, DNS resolution). 93   /** Thread pool size for blocking I/O (file I/O, DNS resolution).
94   94  
95   Sets the number of worker threads in the shared thread pool 95   Sets the number of worker threads in the shared thread pool
96   used by POSIX file services and DNS resolution. Must be at 96   used by POSIX file services and DNS resolution. Must be at
97   least 1. Applies to POSIX backends only; ignored on IOCP 97   least 1. Applies to POSIX backends only; ignored on IOCP
98   where file I/O uses native overlapped I/O. 98   where file I/O uses native overlapped I/O.
99   */ 99   */
100   unsigned thread_pool_size = 1; 100   unsigned thread_pool_size = 1;
101   101  
102   /** Enable single-threaded mode (disable scheduler locking). 102   /** Enable single-threaded mode (disable scheduler locking).
103   103  
104   When true, the scheduler skips all mutex lock/unlock and 104   When true, the scheduler skips all mutex lock/unlock and
105   condition variable operations on the hot path. This 105   condition variable operations on the hot path. This
106   eliminates synchronization overhead when only one thread 106   eliminates synchronization overhead when only one thread
107   calls `run()`. 107   calls `run()`.
108   108  
109   @par Restrictions 109   @par Restrictions
110   - Only one thread may call `run()` (or any run variant). 110   - Only one thread may call `run()` (or any run variant).
111   - Posting work from another thread is undefined behavior. 111   - Posting work from another thread is undefined behavior.
112   - DNS resolution returns `operation_not_supported`. 112   - DNS resolution returns `operation_not_supported`.
113   - POSIX file I/O returns `operation_not_supported`. 113   - POSIX file I/O returns `operation_not_supported`.
114   - Signal sets should not be shared across contexts. 114   - Signal sets should not be shared across contexts.
115   */ 115   */
116   bool single_threaded = false; 116   bool single_threaded = false;
117   }; 117   };
118   118  
119   namespace detail { 119   namespace detail {
120   class timer_service; 120   class timer_service;
121   struct timer_service_access; 121   struct timer_service_access;
122   } // namespace detail 122   } // namespace detail
123   123  
124   /** An I/O context for running asynchronous operations. 124   /** An I/O context for running asynchronous operations.
125   125  
126   The io_context provides an execution environment for async 126   The io_context provides an execution environment for async
127   operations. It maintains a queue of pending work items and 127   operations. It maintains a queue of pending work items and
128   processes them when `run()` is called. 128   processes them when `run()` is called.
129   129  
130   The default and unsigned constructors select the platform's 130   The default and unsigned constructors select the platform's
131   native backend: 131   native backend:
132   - Windows: IOCP 132   - Windows: IOCP
133   - Linux: epoll 133   - Linux: epoll
134   - BSD/macOS: kqueue 134   - BSD/macOS: kqueue
135   - Other POSIX: select 135   - Other POSIX: select
136   136  
137   The template constructor accepts a backend tag value to 137   The template constructor accepts a backend tag value to
138   choose a specific backend at compile time: 138   choose a specific backend at compile time:
139   139  
140   @par Example 140   @par Example
141   @code 141   @code
142   io_context ioc; // platform default 142   io_context ioc; // platform default
143   io_context ioc2(corosio::epoll); // explicit backend 143   io_context ioc2(corosio::epoll); // explicit backend
144   @endcode 144   @endcode
145   145  
146   @par Thread Safety 146   @par Thread Safety
147   Distinct objects: Safe.@n 147   Distinct objects: Safe.@n
148   Shared objects: Safe, if using a concurrency hint greater 148   Shared objects: Safe, if using a concurrency hint greater
149   than 1. 149   than 1.
150   150  
151   @see epoll_t, select_t, kqueue_t, iocp_t 151   @see epoll_t, select_t, kqueue_t, iocp_t
152   */ 152   */
153   class BOOST_COROSIO_DECL io_context : public capy::execution_context 153   class BOOST_COROSIO_DECL io_context : public capy::execution_context
154   { 154   {
155   friend struct detail::timer_service_access; 155   friend struct detail::timer_service_access;
156   156  
157   /// Pre-create services that depend on options (before construct). 157   /// Pre-create services that depend on options (before construct).
158   void apply_options_pre_(io_context_options const& opts); 158   void apply_options_pre_(io_context_options const& opts);
159   159  
160   /// Apply runtime tuning to the scheduler (after construct). 160   /// Apply runtime tuning to the scheduler (after construct).
161   void apply_options_post_(io_context_options const& opts); 161   void apply_options_post_(io_context_options const& opts);
162   162  
163   protected: 163   protected:
164   detail::timer_service* timer_svc_ = nullptr; 164   detail::timer_service* timer_svc_ = nullptr;
165   detail::scheduler* sched_; 165   detail::scheduler* sched_;
166   166  
167   public: 167   public:
168   /** The executor type for this context. */ 168   /** The executor type for this context. */
169   class executor_type; 169   class executor_type;
170   170  
171   /** Construct with default concurrency and platform backend. */ 171   /** Construct with default concurrency and platform backend. */
172   io_context(); 172   io_context();
173   173  
174   /** Construct with a concurrency hint and platform backend. 174   /** Construct with a concurrency hint and platform backend.
175   175  
176   @param concurrency_hint Hint for the number of threads 176   @param concurrency_hint Hint for the number of threads
177   that will call `run()`. 177   that will call `run()`.
178   */ 178   */
179   explicit io_context(unsigned concurrency_hint); 179   explicit io_context(unsigned concurrency_hint);
180   180  
181   /** Construct with runtime tuning options and platform backend. 181   /** Construct with runtime tuning options and platform backend.
182   182  
183   @param opts Runtime options controlling scheduler and 183   @param opts Runtime options controlling scheduler and
184   service behavior. 184   service behavior.
185   @param concurrency_hint Hint for the number of threads 185   @param concurrency_hint Hint for the number of threads
186   that will call `run()`. 186   that will call `run()`.
187   */ 187   */
188   explicit io_context( 188   explicit io_context(
189   io_context_options const& opts, 189   io_context_options const& opts,
190   unsigned concurrency_hint = std::thread::hardware_concurrency()); 190   unsigned concurrency_hint = std::thread::hardware_concurrency());
191   191  
192   /** Construct with an explicit backend tag. 192   /** Construct with an explicit backend tag.
193   193  
194   @param backend The backend tag value selecting the I/O 194   @param backend The backend tag value selecting the I/O
195   multiplexer (e.g. `corosio::epoll`). 195   multiplexer (e.g. `corosio::epoll`).
196   @param concurrency_hint Hint for the number of threads 196   @param concurrency_hint Hint for the number of threads
197   that will call `run()`. 197   that will call `run()`.
198   */ 198   */
199   template<class Backend> 199   template<class Backend>
200   requires requires { Backend::construct; } 200   requires requires { Backend::construct; }
HITCBC 201   478 explicit io_context( 201   478 explicit io_context(
202   Backend backend, 202   Backend backend,
203   unsigned concurrency_hint = std::thread::hardware_concurrency()) 203   unsigned concurrency_hint = std::thread::hardware_concurrency())
204   : capy::execution_context(this) 204   : capy::execution_context(this)
HITCBC 205   478 , sched_(nullptr) 205   478 , sched_(nullptr)
206   { 206   {
207   (void)backend; 207   (void)backend;
HITCBC 208   478 sched_ = &Backend::construct(*this, concurrency_hint); 208   478 sched_ = &Backend::construct(*this, concurrency_hint);
HITCBC 209   478 } 209   478 }
210   210  
211   /** Construct with an explicit backend tag and runtime options. 211   /** Construct with an explicit backend tag and runtime options.
212   212  
213   @param backend The backend tag value selecting the I/O 213   @param backend The backend tag value selecting the I/O
214   multiplexer (e.g. `corosio::epoll`). 214   multiplexer (e.g. `corosio::epoll`).
215   @param opts Runtime options controlling scheduler and 215   @param opts Runtime options controlling scheduler and
216   service behavior. 216   service behavior.
217   @param concurrency_hint Hint for the number of threads 217   @param concurrency_hint Hint for the number of threads
218   that will call `run()`. 218   that will call `run()`.
219   */ 219   */
220   template<class Backend> 220   template<class Backend>
221   requires requires { Backend::construct; } 221   requires requires { Backend::construct; }
222   explicit io_context( 222   explicit io_context(
223   Backend backend, 223   Backend backend,
224   io_context_options const& opts, 224   io_context_options const& opts,
225   unsigned concurrency_hint = std::thread::hardware_concurrency()) 225   unsigned concurrency_hint = std::thread::hardware_concurrency())
226   : capy::execution_context(this) 226   : capy::execution_context(this)
227   , sched_(nullptr) 227   , sched_(nullptr)
228   { 228   {
229   (void)backend; 229   (void)backend;
230   apply_options_pre_(opts); 230   apply_options_pre_(opts);
231   sched_ = &Backend::construct(*this, concurrency_hint); 231   sched_ = &Backend::construct(*this, concurrency_hint);
232   apply_options_post_(opts); 232   apply_options_post_(opts);
233   } 233   }
234   234  
235   ~io_context(); 235   ~io_context();
236   236  
237   io_context(io_context const&) = delete; 237   io_context(io_context const&) = delete;
238   io_context& operator=(io_context const&) = delete; 238   io_context& operator=(io_context const&) = delete;
239   239  
240   /** Return an executor for this context. 240   /** Return an executor for this context.
241   241  
242   The returned executor can be used to dispatch coroutines 242   The returned executor can be used to dispatch coroutines
243   and post work items to this context. 243   and post work items to this context.
244   244  
245   @return An executor associated with this context. 245   @return An executor associated with this context.
246   */ 246   */
247   executor_type get_executor() const noexcept; 247   executor_type get_executor() const noexcept;
248   248  
249   /** Signal the context to stop processing. 249   /** Signal the context to stop processing.
250   250  
251   This causes `run()` to return as soon as possible. Any pending 251   This causes `run()` to return as soon as possible. Any pending
252   work items remain queued. 252   work items remain queued.
253   */ 253   */
HITCBC 254   5 void stop() 254   5 void stop()
255   { 255   {
HITCBC 256   5 sched_->stop(); 256   5 sched_->stop();
HITCBC 257   5 } 257   5 }
258   258  
259   /** Return whether the context has been stopped. 259   /** Return whether the context has been stopped.
260   260  
261   @return `true` if `stop()` has been called and `restart()` 261   @return `true` if `stop()` has been called and `restart()`
262   has not been called since. 262   has not been called since.
263   */ 263   */
HITCBC 264   62 bool stopped() const noexcept 264   62 bool stopped() const noexcept
265   { 265   {
HITCBC 266   62 return sched_->stopped(); 266   62 return sched_->stopped();
267   } 267   }
268   268  
269   /** Restart the context after being stopped. 269   /** Restart the context after being stopped.
270   270  
271   This function must be called before `run()` can be called 271   This function must be called before `run()` can be called
272   again after `stop()` has been called. 272   again after `stop()` has been called.
273   */ 273   */
HITCBC 274   111 void restart() 274   111 void restart()
275   { 275   {
HITCBC 276   111 sched_->restart(); 276   111 sched_->restart();
HITCBC 277   111 } 277   111 }
278   278  
279   /** Process all pending work items. 279   /** Process all pending work items.
280   280  
281   This function blocks until all pending work items have been 281   This function blocks until all pending work items have been
282   executed or `stop()` is called. The context is stopped 282   executed or `stop()` is called. The context is stopped
283   when there is no more outstanding work. 283   when there is no more outstanding work.
284   284  
285   @note The context must be restarted with `restart()` before 285   @note The context must be restarted with `restart()` before
286   calling this function again after it returns. 286   calling this function again after it returns.
287   287  
288   @return The number of handlers executed. 288   @return The number of handlers executed.
289   */ 289   */
HITCBC 290   432 std::size_t run() 290   432 std::size_t run()
291   { 291   {
HITCBC 292   432 return sched_->run(); 292   432 return sched_->run();
293   } 293   }
294   294  
295   /** Process at most one pending work item. 295   /** Process at most one pending work item.
296   296  
297   This function blocks until one work item has been executed 297   This function blocks until one work item has been executed
298   or `stop()` is called. The context is stopped when there 298   or `stop()` is called. The context is stopped when there
299   is no more outstanding work. 299   is no more outstanding work.
300   300  
301   @note The context must be restarted with `restart()` before 301   @note The context must be restarted with `restart()` before
302   calling this function again after it returns. 302   calling this function again after it returns.
303   303  
304   @return The number of handlers executed (0 or 1). 304   @return The number of handlers executed (0 or 1).
305   */ 305   */
HITCBC 306   2 std::size_t run_one() 306   2 std::size_t run_one()
307   { 307   {
HITCBC 308   2 return sched_->run_one(); 308   2 return sched_->run_one();
309   } 309   }
310   310  
311   /** Process work items for the specified duration. 311   /** Process work items for the specified duration.
312   312  
313   This function blocks until work items have been executed for 313   This function blocks until work items have been executed for
314   the specified duration, or `stop()` is called. The context 314   the specified duration, or `stop()` is called. The context
315   is stopped when there is no more outstanding work. 315   is stopped when there is no more outstanding work.
316   316  
317   @note The context must be restarted with `restart()` before 317   @note The context must be restarted with `restart()` before
318   calling this function again after it returns. 318   calling this function again after it returns.
319   319  
320   @param rel_time The duration for which to process work. 320   @param rel_time The duration for which to process work.
321   321  
322   @return The number of handlers executed. 322   @return The number of handlers executed.
323   */ 323   */
324   template<class Rep, class Period> 324   template<class Rep, class Period>
HITCBC 325   9 std::size_t run_for(std::chrono::duration<Rep, Period> const& rel_time) 325   9 std::size_t run_for(std::chrono::duration<Rep, Period> const& rel_time)
326   { 326   {
HITCBC 327   9 return run_until(std::chrono::steady_clock::now() + rel_time); 327   9 return run_until(std::chrono::steady_clock::now() + rel_time);
328   } 328   }
329   329  
330   /** Process work items until the specified time. 330   /** Process work items until the specified time.
331   331  
332   This function blocks until the specified time is reached 332   This function blocks until the specified time is reached
333   or `stop()` is called. The context is stopped when there 333   or `stop()` is called. The context is stopped when there
334   is no more outstanding work. 334   is no more outstanding work.
335   335  
336   @note The context must be restarted with `restart()` before 336   @note The context must be restarted with `restart()` before
337   calling this function again after it returns. 337   calling this function again after it returns.
338   338  
339   @param abs_time The time point until which to process work. 339   @param abs_time The time point until which to process work.
340   340  
341   @return The number of handlers executed. 341   @return The number of handlers executed.
342   */ 342   */
343   template<class Clock, class Duration> 343   template<class Clock, class Duration>
344   std::size_t 344   std::size_t
HITCBC 345   9 run_until(std::chrono::time_point<Clock, Duration> const& abs_time) 345   9 run_until(std::chrono::time_point<Clock, Duration> const& abs_time)
346   { 346   {
HITCBC 347   9 std::size_t n = 0; 347   9 std::size_t n = 0;
HITCBC 348   58 while (run_one_until(abs_time)) 348   58 while (run_one_until(abs_time))
HITCBC 349   49 if (n != (std::numeric_limits<std::size_t>::max)()) 349   49 if (n != (std::numeric_limits<std::size_t>::max)())
HITCBC 350   49 ++n; 350   49 ++n;
HITCBC 351   9 return n; 351   9 return n;
352   } 352   }
353   353  
354   /** Process at most one work item for the specified duration. 354   /** Process at most one work item for the specified duration.
355   355  
356   This function blocks until one work item has been executed, 356   This function blocks until one work item has been executed,
357   the specified duration has elapsed, or `stop()` is called. 357   the specified duration has elapsed, or `stop()` is called.
358   The context is stopped when there is no more outstanding work. 358   The context is stopped when there is no more outstanding work.
359   359  
360   @note The context must be restarted with `restart()` before 360   @note The context must be restarted with `restart()` before
361   calling this function again after it returns. 361   calling this function again after it returns.
362   362  
363   @param rel_time The duration for which the call may block. 363   @param rel_time The duration for which the call may block.
364   364  
365   @return The number of handlers executed (0 or 1). 365   @return The number of handlers executed (0 or 1).
366   */ 366   */
367   template<class Rep, class Period> 367   template<class Rep, class Period>
HITCBC 368   3 std::size_t run_one_for(std::chrono::duration<Rep, Period> const& rel_time) 368   3 std::size_t run_one_for(std::chrono::duration<Rep, Period> const& rel_time)
369   { 369   {
HITCBC 370   3 return run_one_until(std::chrono::steady_clock::now() + rel_time); 370   3 return run_one_until(std::chrono::steady_clock::now() + rel_time);
371   } 371   }
372   372  
373   /** Process at most one work item until the specified time. 373   /** Process at most one work item until the specified time.
374   374  
375   This function blocks until one work item has been executed, 375   This function blocks until one work item has been executed,
376   the specified time is reached, or `stop()` is called. 376   the specified time is reached, or `stop()` is called.
377   The context is stopped when there is no more outstanding work. 377   The context is stopped when there is no more outstanding work.
378   378  
379   @note The context must be restarted with `restart()` before 379   @note The context must be restarted with `restart()` before
380   calling this function again after it returns. 380   calling this function again after it returns.
381   381  
382   @param abs_time The time point until which the call may block. 382   @param abs_time The time point until which the call may block.
383   383  
384   @return The number of handlers executed (0 or 1). 384   @return The number of handlers executed (0 or 1).
385   */ 385   */
386   template<class Clock, class Duration> 386   template<class Clock, class Duration>
387   std::size_t 387   std::size_t
HITCBC 388   63 run_one_until(std::chrono::time_point<Clock, Duration> const& abs_time) 388   63 run_one_until(std::chrono::time_point<Clock, Duration> const& abs_time)
389   { 389   {
HITCBC 390   63 typename Clock::time_point now = Clock::now(); 390   63 typename Clock::time_point now = Clock::now();
HITCBC 391   104 while (now < abs_time) 391   104 while (now < abs_time)
392   { 392   {
HITCBC 393   102 auto rel_time = abs_time - now; 393   102 auto rel_time = abs_time - now;
HITCBC 394   102 if (rel_time > std::chrono::seconds(1)) 394   102 if (rel_time > std::chrono::seconds(1))
MISUBC 395   ✗ rel_time = std::chrono::seconds(1); 395   ✗ rel_time = std::chrono::seconds(1);
396   396  
HITCBC 397   102 std::size_t s = sched_->wait_one( 397   102 std::size_t s = sched_->wait_one(
398   static_cast<long>( 398   static_cast<long>(
HITCBC 399   102 std::chrono::duration_cast<std::chrono::microseconds>( 399   102 std::chrono::duration_cast<std::chrono::microseconds>(
400   rel_time) 400   rel_time)
HITCBC 401   102 .count())); 401   102 .count()));
402   402  
HITCBC 403   102 if (s || stopped()) 403   102 if (s || stopped())
HITCBC 404   61 return s; 404   61 return s;
405   405  
HITCBC 406   41 now = Clock::now(); 406   41 now = Clock::now();
407   } 407   }
HITCBC 408   2 return 0; 408   2 return 0;
409   } 409   }
410   410  
411   /** Process all ready work items without blocking. 411   /** Process all ready work items without blocking.
412   412  
413   This function executes all work items that are ready to run 413   This function executes all work items that are ready to run
414   without blocking for more work. The context is stopped 414   without blocking for more work. The context is stopped
415   when there is no more outstanding work. 415   when there is no more outstanding work.
416   416  
417   @note The context must be restarted with `restart()` before 417   @note The context must be restarted with `restart()` before
418   calling this function again after it returns. 418   calling this function again after it returns.
419   419  
420   @return The number of handlers executed. 420   @return The number of handlers executed.
421   */ 421   */
HITCBC 422   6 std::size_t poll() 422   6 std::size_t poll()
423   { 423   {
HITCBC 424   6 return sched_->poll(); 424   6 return sched_->poll();
425   } 425   }
426   426  
427   /** Process at most one ready work item without blocking. 427   /** Process at most one ready work item without blocking.
428   428  
429   This function executes at most one work item that is ready 429   This function executes at most one work item that is ready
430   to run without blocking for more work. The context is 430   to run without blocking for more work. The context is
431   stopped when there is no more outstanding work. 431   stopped when there is no more outstanding work.
432   432  
433   @note The context must be restarted with `restart()` before 433   @note The context must be restarted with `restart()` before
434   calling this function again after it returns. 434   calling this function again after it returns.
435   435  
436   @return The number of handlers executed (0 or 1). 436   @return The number of handlers executed (0 or 1).
437   */ 437   */
HITCBC 438   4 std::size_t poll_one() 438   4 std::size_t poll_one()
439   { 439   {
HITCBC 440   4 return sched_->poll_one(); 440   4 return sched_->poll_one();
441   } 441   }
442   }; 442   };
443   443  
444   /** An executor for dispatching work to an I/O context. 444   /** An executor for dispatching work to an I/O context.
445   445  
446   The executor provides the interface for posting work items and 446   The executor provides the interface for posting work items and
447   dispatching coroutines to the associated context. It satisfies 447   dispatching coroutines to the associated context. It satisfies
448   the `capy::Executor` concept. 448   the `capy::Executor` concept.
449   449  
450   Executors are lightweight handles that can be copied and compared 450   Executors are lightweight handles that can be copied and compared
451   for equality. Two executors compare equal if they refer to the 451   for equality. Two executors compare equal if they refer to the
452   same context. 452   same context.
453   453  
454   @par Thread Safety 454   @par Thread Safety
455   Distinct objects: Safe.@n 455   Distinct objects: Safe.@n
456   Shared objects: Safe. 456   Shared objects: Safe.
457   */ 457   */
458   class io_context::executor_type 458   class io_context::executor_type
459   { 459   {
460   io_context* ctx_ = nullptr; 460   io_context* ctx_ = nullptr;
461   461  
462   public: 462   public:
463   /** Default constructor. 463   /** Default constructor.
464   464  
465   Constructs an executor not associated with any context. 465   Constructs an executor not associated with any context.
466   */ 466   */
467   executor_type() = default; 467   executor_type() = default;
468   468  
469   /** Construct an executor from a context. 469   /** Construct an executor from a context.
470   470  
471   @param ctx The context to associate with this executor. 471   @param ctx The context to associate with this executor.
472   */ 472   */
HITCBC 473   668 explicit executor_type(io_context& ctx) noexcept : ctx_(&ctx) {} 473   668 explicit executor_type(io_context& ctx) noexcept : ctx_(&ctx) {}
474   474  
475   /** Return a reference to the associated execution context. 475   /** Return a reference to the associated execution context.
476   476  
477   @return Reference to the context. 477   @return Reference to the context.
478   */ 478   */
HITCBC 479   1341 io_context& context() const noexcept 479   1343 io_context& context() const noexcept
480   { 480   {
HITCBC 481   1341 return *ctx_; 481   1343 return *ctx_;
482   } 482   }
483   483  
484   /** Check if the current thread is running this executor's context. 484   /** Check if the current thread is running this executor's context.
485   485  
486   @return `true` if `run()` is being called on this thread. 486   @return `true` if `run()` is being called on this thread.
487   */ 487   */
HITCBC 488   1353 bool running_in_this_thread() const noexcept 488   1355 bool running_in_this_thread() const noexcept
489   { 489   {
HITCBC 490   1353 return ctx_->sched_->running_in_this_thread(); 490   1355 return ctx_->sched_->running_in_this_thread();
491   } 491   }
492   492  
493   /** Informs the executor that work is beginning. 493   /** Informs the executor that work is beginning.
494   494  
495   Must be paired with `on_work_finished()`. 495   Must be paired with `on_work_finished()`.
496   */ 496   */
HITCBC 497   1498 void on_work_started() const noexcept 497   1500 void on_work_started() const noexcept
498   { 498   {
HITCBC 499   1498 ctx_->sched_->work_started(); 499   1500 ctx_->sched_->work_started();
HITCBC 500   1498 } 500   1500 }
501   501  
502   /** Informs the executor that work has completed. 502   /** Informs the executor that work has completed.
503   503  
504   @par Preconditions 504   @par Preconditions
505   A preceding call to `on_work_started()` on an equal executor. 505   A preceding call to `on_work_started()` on an equal executor.
506   */ 506   */
HITCBC 507   1472 void on_work_finished() const noexcept 507   1474 void on_work_finished() const noexcept
508   { 508   {
HITCBC 509   1472 ctx_->sched_->work_finished(); 509   1474 ctx_->sched_->work_finished();
HITCBC 510   1472 } 510   1474 }
511   511  
512   /** Dispatch a continuation. 512   /** Dispatch a continuation.
513   513  
514   Returns a handle for symmetric transfer. If called from 514   Returns a handle for symmetric transfer. If called from
515   within `run()`, returns `c.h`. Otherwise posts the 515   within `run()`, returns `c.h`. Otherwise posts the
516   enclosing continuation_op as a scheduler_op for later 516   enclosing continuation_op as a scheduler_op for later
517   execution and returns `std::noop_coroutine()`. 517   execution and returns `std::noop_coroutine()`.
518   518  
519   @param c The continuation to dispatch. Must be the `cont` 519   @param c The continuation to dispatch. Must be the `cont`
520   member of a `detail::continuation_op`. 520   member of a `detail::continuation_op`.
521   521  
522   @return A handle for symmetric transfer or `std::noop_coroutine()`. 522   @return A handle for symmetric transfer or `std::noop_coroutine()`.
523   */ 523   */
HITCBC 524   1351 std::coroutine_handle<> dispatch(capy::continuation& c) const 524   1353 std::coroutine_handle<> dispatch(capy::continuation& c) const
525   { 525   {
HITCBC 526   1351 if (running_in_this_thread()) 526   1353 if (running_in_this_thread())
HITCBC 527   591 return c.h; 527   593 return c.h;
HITCBC 528   760 post(c); 528   760 post(c);
HITCBC 529   760 return std::noop_coroutine(); 529   760 return std::noop_coroutine();
530   } 530   }
531   531  
532   /** Post a continuation for deferred execution. 532   /** Post a continuation for deferred execution.
533   533  
534   If the continuation is backed by a continuation_op 534   If the continuation is backed by a continuation_op
535   (tagged), posts it directly as a scheduler_op — zero 535   (tagged), posts it directly as a scheduler_op — zero
536   heap allocation. Otherwise falls back to the 536   heap allocation. Otherwise falls back to the
537   heap-allocating post(coroutine_handle<>) path. 537   heap-allocating post(coroutine_handle<>) path.
538   */ 538   */
HITCBC 539   7763 void post(capy::continuation& c) const 539   8975 void post(capy::continuation& c) const
540   { 540   {
HITCBC 541   7763 auto* op = detail::continuation_op::try_from_continuation(c); 541   8975 auto* op = detail::continuation_op::try_from_continuation(c);
HITCBC 542   7763 if (op) 542   8975 if (op)
HITCBC 543   7000 ctx_->sched_->post(op); 543   8212 ctx_->sched_->post(op);
544   else 544   else
HITCBC 545   763 ctx_->sched_->post(c.h); 545   763 ctx_->sched_->post(c.h);
HITCBC 546   7763 } 546   8975 }
547   547  
548   /** Post a bare coroutine handle for deferred execution. 548   /** Post a bare coroutine handle for deferred execution.
549   549  
550   Heap-allocates a scheduler_op to wrap the handle. Prefer 550   Heap-allocates a scheduler_op to wrap the handle. Prefer
551   posting through a continuation_op-backed continuation when 551   posting through a continuation_op-backed continuation when
552   the continuation has suitable lifetime. 552   the continuation has suitable lifetime.
553   553  
554   @param h The coroutine handle to post. 554   @param h The coroutine handle to post.
555   */ 555   */
HITCBC 556   1426 void post(std::coroutine_handle<> h) const 556   1426 void post(std::coroutine_handle<> h) const
557   { 557   {
HITCBC 558   1426 ctx_->sched_->post(h); 558   1426 ctx_->sched_->post(h);
HITCBC 559   1426 } 559   1426 }
560   560  
561   /** Compare two executors for equality. 561   /** Compare two executors for equality.
562   562  
563   @return `true` if both executors refer to the same context. 563   @return `true` if both executors refer to the same context.
564   */ 564   */
HITCBC 565   1 bool operator==(executor_type const& other) const noexcept 565   1 bool operator==(executor_type const& other) const noexcept
566   { 566   {
HITCBC 567   1 return ctx_ == other.ctx_; 567   1 return ctx_ == other.ctx_;
568   } 568   }
569   569  
570   /** Compare two executors for inequality. 570   /** Compare two executors for inequality.
571   571  
572   @return `true` if the executors refer to different contexts. 572   @return `true` if the executors refer to different contexts.
573   */ 573   */
574   bool operator!=(executor_type const& other) const noexcept 574   bool operator!=(executor_type const& other) const noexcept
575   { 575   {
576   return ctx_ != other.ctx_; 576   return ctx_ != other.ctx_;
577   } 577   }
578   }; 578   };
579   579  
580   inline io_context::executor_type 580   inline io_context::executor_type
HITCBC 581   668 io_context::get_executor() const noexcept 581   668 io_context::get_executor() const noexcept
582   { 582   {
HITCBC 583   668 return executor_type(const_cast<io_context&>(*this)); 583   668 return executor_type(const_cast<io_context&>(*this));
584   } 584   }
585   585  
586   } // namespace boost::corosio 586   } // namespace boost::corosio
587   587  
588   #endif // BOOST_COROSIO_IO_CONTEXT_HPP 588   #endif // BOOST_COROSIO_IO_CONTEXT_HPP