1   
//
1   
//
2   
// Copyright (c) 2026 Steve Gerbino
2   
// Copyright (c) 2026 Steve Gerbino
3   
//
3   
//
4   
// Distributed under the Boost Software License, Version 1.0. (See accompanying
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)
5   
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   
//
6   
//
7   
// Official repository: https://github.com/cppalliance/corosio
7   
// Official repository: https://github.com/cppalliance/corosio
8   
//
8   
//
9  
9  
10   
#ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
10   
#ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
11   
#define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
11   
#define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
12  
12  
13   
#include <boost/corosio/detail/platform.hpp>
13   
#include <boost/corosio/detail/platform.hpp>
14  
14  
15   
#if BOOST_COROSIO_HAS_SELECT
15   
#if BOOST_COROSIO_HAS_SELECT
16  
16  
17   
#include <boost/corosio/detail/config.hpp>
17   
#include <boost/corosio/detail/config.hpp>
18   
#include <boost/capy/ex/execution_context.hpp>
18   
#include <boost/capy/ex/execution_context.hpp>
19  
19  
20   
#include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp>
20   
#include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp>
21  
21  
22   
#include <boost/corosio/native/detail/select/select_op.hpp>
22   
#include <boost/corosio/native/detail/select/select_op.hpp>
23   
#include <boost/corosio/detail/timer_service.hpp>
23   
#include <boost/corosio/detail/timer_service.hpp>
24   
#include <boost/corosio/native/detail/make_err.hpp>
24   
#include <boost/corosio/native/detail/make_err.hpp>
25   
#include <boost/corosio/native/detail/posix/posix_resolver_service.hpp>
25   
#include <boost/corosio/native/detail/posix/posix_resolver_service.hpp>
26   
#include <boost/corosio/native/detail/posix/posix_signal_service.hpp>
26   
#include <boost/corosio/native/detail/posix/posix_signal_service.hpp>
27   
#include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp>
27   
#include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp>
28   
#include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp>
28   
#include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp>
29  
29  
30   
#include <boost/corosio/detail/except.hpp>
30   
#include <boost/corosio/detail/except.hpp>
31  
31  
32   
#include <sys/select.h>
32   
#include <sys/select.h>
33   
#include <unistd.h>
33   
#include <unistd.h>
34   
#include <errno.h>
34   
#include <errno.h>
35   
#include <fcntl.h>
35   
#include <fcntl.h>
36  
36  
37   
#include <atomic>
37   
#include <atomic>
38   
#include <chrono>
38   
#include <chrono>
39   
#include <cstdint>
39   
#include <cstdint>
40   
#include <limits>
40   
#include <limits>
41   
#include <mutex>
41   
#include <mutex>
42   
#include <unordered_map>
42   
#include <unordered_map>
43  
43  
44   
namespace boost::corosio::detail {
44   
namespace boost::corosio::detail {
45  
45  
46   
struct select_op;
46   
struct select_op;
47   
struct select_descriptor_state;
47   
struct select_descriptor_state;
48  
48  
49   
/** POSIX scheduler using select() for I/O multiplexing.
49   
/** POSIX scheduler using select() for I/O multiplexing.
50  
50  
51   
    This scheduler implements the scheduler interface using the POSIX select()
51   
    This scheduler implements the scheduler interface using the POSIX select()
52   
    call for I/O event notification. It inherits the shared reactor threading
52   
    call for I/O event notification. It inherits the shared reactor threading
53 - 
    model from reactor_scheduler_base: signal state machine, inline completion
53 + 
    model from reactor_scheduler: signal state machine, inline completion
54   
    budget, work counting, and the do_one event loop.
54   
    budget, work counting, and the do_one event loop.
55  
55  
56   
    The design mirrors epoll_scheduler for behavioral consistency:
56   
    The design mirrors epoll_scheduler for behavioral consistency:
57   
    - Same single-reactor thread coordination model
57   
    - Same single-reactor thread coordination model
58   
    - Same deferred I/O pattern (reactor marks ready; workers do I/O)
58   
    - Same deferred I/O pattern (reactor marks ready; workers do I/O)
59   
    - Same timer integration pattern
59   
    - Same timer integration pattern
60  
60  
61   
    Known Limitations:
61   
    Known Limitations:
62   
    - FD_SETSIZE (~1024) limits maximum concurrent connections
62   
    - FD_SETSIZE (~1024) limits maximum concurrent connections
63   
    - O(n) scanning: rebuilds fd_sets each iteration
63   
    - O(n) scanning: rebuilds fd_sets each iteration
64   
    - Level-triggered only (no edge-triggered mode)
64   
    - Level-triggered only (no edge-triggered mode)
65  
65  
66   
    @par Thread Safety
66   
    @par Thread Safety
67   
    All public member functions are thread-safe.
67   
    All public member functions are thread-safe.
68   
*/
68   
*/
69 - 
class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler_base
69 + 
class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler
70   
{
70   
{
71   
public:
71   
public:
72   
    /** Construct the scheduler.
72   
    /** Construct the scheduler.
73  
73  
74   
        Creates a self-pipe for reactor interruption.
74   
        Creates a self-pipe for reactor interruption.
75  
75  
76   
        @param ctx Reference to the owning execution_context.
76   
        @param ctx Reference to the owning execution_context.
77   
        @param concurrency_hint Hint for expected thread count (unused).
77   
        @param concurrency_hint Hint for expected thread count (unused).
78   
    */
78   
    */
79   
    select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1);
79   
    select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1);
80  
80  
81   
    /// Destroy the scheduler.
81   
    /// Destroy the scheduler.
82   
    ~select_scheduler() override;
82   
    ~select_scheduler() override;
83  
83  
84   
    select_scheduler(select_scheduler const&)            = delete;
84   
    select_scheduler(select_scheduler const&)            = delete;
85   
    select_scheduler& operator=(select_scheduler const&) = delete;
85   
    select_scheduler& operator=(select_scheduler const&) = delete;
86  
86  
87   
    /// Shut down the scheduler, draining pending operations.
87   
    /// Shut down the scheduler, draining pending operations.
88   
    void shutdown() override;
88   
    void shutdown() override;
89  
89  
90   
    /** Return the maximum file descriptor value supported.
90   
    /** Return the maximum file descriptor value supported.
91  
91  
92   
        Returns FD_SETSIZE - 1, the maximum fd value that can be
92   
        Returns FD_SETSIZE - 1, the maximum fd value that can be
93   
        monitored by select(). Operations with fd >= FD_SETSIZE
93   
        monitored by select(). Operations with fd >= FD_SETSIZE
94   
        will fail with EINVAL.
94   
        will fail with EINVAL.
95  
95  
96   
        @return The maximum supported file descriptor value.
96   
        @return The maximum supported file descriptor value.
97   
    */
97   
    */
98   
    static constexpr int max_fd() noexcept
98   
    static constexpr int max_fd() noexcept
99   
    {
99   
    {
100   
        return FD_SETSIZE - 1;
100   
        return FD_SETSIZE - 1;
101   
    }
101   
    }
102  
102  
103   
    /** Register a descriptor for persistent monitoring.
103   
    /** Register a descriptor for persistent monitoring.
104  
104  
105   
        The fd is added to the registered_descs_ map and will be
105   
        The fd is added to the registered_descs_ map and will be
106   
        included in subsequent select() calls. The reactor is
106   
        included in subsequent select() calls. The reactor is
107   
        interrupted so a blocked select() rebuilds its fd_sets.
107   
        interrupted so a blocked select() rebuilds its fd_sets.
108  
108  
109   
        @param fd The file descriptor to register.
109   
        @param fd The file descriptor to register.
110   
        @param desc Pointer to descriptor state for this fd.
110   
        @param desc Pointer to descriptor state for this fd.
111   
    */
111   
    */
112   
    void register_descriptor(int fd, select_descriptor_state* desc) const;
112   
    void register_descriptor(int fd, select_descriptor_state* desc) const;
113  
113  
114   
    /** Deregister a persistently registered descriptor.
114   
    /** Deregister a persistently registered descriptor.
115  
115  
116   
        @param fd The file descriptor to deregister.
116   
        @param fd The file descriptor to deregister.
117   
    */
117   
    */
118   
    void deregister_descriptor(int fd) const;
118   
    void deregister_descriptor(int fd) const;
119  
119  
120   
    /** Interrupt the reactor so it rebuilds its fd_sets.
120   
    /** Interrupt the reactor so it rebuilds its fd_sets.
121  
121  
122   
        Called when a write or connect op is registered after
122   
        Called when a write or connect op is registered after
123   
        the reactor's snapshot was taken. Without this, select()
123   
        the reactor's snapshot was taken. Without this, select()
124   
        may block not watching for writability on the fd.
124   
        may block not watching for writability on the fd.
125   
    */
125   
    */
126   
    void notify_reactor() const;
126   
    void notify_reactor() const;
127  
127  
128   
private:
128   
private:
129   
    void
129   
    void
130   
    run_task(lock_type& lock, context_type* ctx,
130   
    run_task(lock_type& lock, context_type* ctx,
131   
        long timeout_us) override;
131   
        long timeout_us) override;
132   
    void interrupt_reactor() const override;
132   
    void interrupt_reactor() const override;
133   
    long calculate_timeout(long requested_timeout_us) const;
133   
    long calculate_timeout(long requested_timeout_us) const;
134  
134  
135   
    // Self-pipe for interrupting select()
135   
    // Self-pipe for interrupting select()
136   
    int pipe_fds_[2]; // [0]=read, [1]=write
136   
    int pipe_fds_[2]; // [0]=read, [1]=write
137  
137  
138   
    // Per-fd tracking for fd_set building
138   
    // Per-fd tracking for fd_set building
139   
    mutable std::unordered_map<int, select_descriptor_state*> registered_descs_;
139   
    mutable std::unordered_map<int, select_descriptor_state*> registered_descs_;
140   
    mutable int max_fd_ = -1;
140   
    mutable int max_fd_ = -1;
141   
};
141   
};
142  
142  
143   
inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
143   
inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
144   
    : pipe_fds_{-1, -1}
144   
    : pipe_fds_{-1, -1}
145   
    , max_fd_(-1)
145   
    , max_fd_(-1)
146   
{
146   
{
147   
    if (::pipe(pipe_fds_) < 0)
147   
    if (::pipe(pipe_fds_) < 0)
148   
        detail::throw_system_error(make_err(errno), "pipe");
148   
        detail::throw_system_error(make_err(errno), "pipe");
149  
149  
150   
    for (int i = 0; i < 2; ++i)
150   
    for (int i = 0; i < 2; ++i)
151   
    {
151   
    {
152   
        int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
152   
        int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
153   
        if (flags == -1)
153   
        if (flags == -1)
154   
        {
154   
        {
155   
            int errn = errno;
155   
            int errn = errno;
156   
            ::close(pipe_fds_[0]);
156   
            ::close(pipe_fds_[0]);
157   
            ::close(pipe_fds_[1]);
157   
            ::close(pipe_fds_[1]);
158   
            detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
158   
            detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
159   
        }
159   
        }
160   
        if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
160   
        if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
161   
        {
161   
        {
162   
            int errn = errno;
162   
            int errn = errno;
163   
            ::close(pipe_fds_[0]);
163   
            ::close(pipe_fds_[0]);
164   
            ::close(pipe_fds_[1]);
164   
            ::close(pipe_fds_[1]);
165   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
165   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
166   
        }
166   
        }
167   
        if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
167   
        if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
168   
        {
168   
        {
169   
            int errn = errno;
169   
            int errn = errno;
170   
            ::close(pipe_fds_[0]);
170   
            ::close(pipe_fds_[0]);
171   
            ::close(pipe_fds_[1]);
171   
            ::close(pipe_fds_[1]);
172   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
172   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
173   
        }
173   
        }
174   
    }
174   
    }
175  
175  
176   
    timer_svc_ = &get_timer_service(ctx, *this);
176   
    timer_svc_ = &get_timer_service(ctx, *this);
177   
    timer_svc_->set_on_earliest_changed(
177   
    timer_svc_->set_on_earliest_changed(
178   
        timer_service::callback(this, [](void* p) {
178   
        timer_service::callback(this, [](void* p) {
179   
            static_cast<select_scheduler*>(p)->interrupt_reactor();
179   
            static_cast<select_scheduler*>(p)->interrupt_reactor();
180   
        }));
180   
        }));
181  
181  
182   
    get_resolver_service(ctx, *this);
182   
    get_resolver_service(ctx, *this);
183   
    get_signal_service(ctx, *this);
183   
    get_signal_service(ctx, *this);
184   
    get_stream_file_service(ctx, *this);
184   
    get_stream_file_service(ctx, *this);
185   
    get_random_access_file_service(ctx, *this);
185   
    get_random_access_file_service(ctx, *this);
186  
186  
187   
    completed_ops_.push(&task_op_);
187   
    completed_ops_.push(&task_op_);
188   
}
188   
}
189  
189  
190   
inline select_scheduler::~select_scheduler()
190   
inline select_scheduler::~select_scheduler()
191   
{
191   
{
192   
    if (pipe_fds_[0] >= 0)
192   
    if (pipe_fds_[0] >= 0)
193   
        ::close(pipe_fds_[0]);
193   
        ::close(pipe_fds_[0]);
194   
    if (pipe_fds_[1] >= 0)
194   
    if (pipe_fds_[1] >= 0)
195   
        ::close(pipe_fds_[1]);
195   
        ::close(pipe_fds_[1]);
196   
}
196   
}
197  
197  
198   
inline void
198   
inline void
199   
select_scheduler::shutdown()
199   
select_scheduler::shutdown()
200   
{
200   
{
201   
    shutdown_drain();
201   
    shutdown_drain();
202  
202  
203   
    if (pipe_fds_[1] >= 0)
203   
    if (pipe_fds_[1] >= 0)
204   
        interrupt_reactor();
204   
        interrupt_reactor();
205   
}
205   
}
206  
206  
207   
inline void
207   
inline void
208   
select_scheduler::register_descriptor(
208   
select_scheduler::register_descriptor(
209   
    int fd, select_descriptor_state* desc) const
209   
    int fd, select_descriptor_state* desc) const
210   
{
210   
{
211   
    if (fd < 0 || fd >= FD_SETSIZE)
211   
    if (fd < 0 || fd >= FD_SETSIZE)
212   
        detail::throw_system_error(make_err(EINVAL), "select: fd out of range");
212   
        detail::throw_system_error(make_err(EINVAL), "select: fd out of range");
213  
213  
214   
    desc->registered_events = reactor_event_read | reactor_event_write;
214   
    desc->registered_events = reactor_event_read | reactor_event_write;
215   
    desc->fd                = fd;
215   
    desc->fd                = fd;
216   
    desc->scheduler_        = this;
216   
    desc->scheduler_        = this;
217   
    desc->mutex.set_enabled(!single_threaded_);
217   
    desc->mutex.set_enabled(!single_threaded_);
218   
    desc->ready_events_.store(0, std::memory_order_relaxed);
218   
    desc->ready_events_.store(0, std::memory_order_relaxed);
219  
219  
220   
    {
220   
    {
221   
        conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
221   
        conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
222   
        desc->impl_ref_.reset();
222   
        desc->impl_ref_.reset();
223   
        desc->read_ready  = false;
223   
        desc->read_ready  = false;
224   
        desc->write_ready = false;
224   
        desc->write_ready = false;
225   
    }
225   
    }
226  
226  
227   
    {
227   
    {
228   
        mutex_type::scoped_lock lock(mutex_);
228   
        mutex_type::scoped_lock lock(mutex_);
229   
        registered_descs_[fd] = desc;
229   
        registered_descs_[fd] = desc;
230   
        if (fd > max_fd_)
230   
        if (fd > max_fd_)
231   
            max_fd_ = fd;
231   
            max_fd_ = fd;
232   
    }
232   
    }
233  
233  
234   
    interrupt_reactor();
234   
    interrupt_reactor();
235   
}
235   
}
236  
236  
237   
inline void
237   
inline void
238   
select_scheduler::deregister_descriptor(int fd) const
238   
select_scheduler::deregister_descriptor(int fd) const
239   
{
239   
{
240   
    mutex_type::scoped_lock lock(mutex_);
240   
    mutex_type::scoped_lock lock(mutex_);
241  
241  
242   
    auto it = registered_descs_.find(fd);
242   
    auto it = registered_descs_.find(fd);
243   
    if (it == registered_descs_.end())
243   
    if (it == registered_descs_.end())
244   
        return;
244   
        return;
245  
245  
246   
    registered_descs_.erase(it);
246   
    registered_descs_.erase(it);
247  
247  
248   
    if (fd == max_fd_)
248   
    if (fd == max_fd_)
249   
    {
249   
    {
250   
        max_fd_ = pipe_fds_[0];
250   
        max_fd_ = pipe_fds_[0];
251   
        for (auto& [registered_fd, state] : registered_descs_)
251   
        for (auto& [registered_fd, state] : registered_descs_)
252   
        {
252   
        {
253   
            if (registered_fd > max_fd_)
253   
            if (registered_fd > max_fd_)
254   
                max_fd_ = registered_fd;
254   
                max_fd_ = registered_fd;
255   
        }
255   
        }
256   
    }
256   
    }
257   
}
257   
}
258  
258  
259   
inline void
259   
inline void
260   
select_scheduler::notify_reactor() const
260   
select_scheduler::notify_reactor() const
261   
{
261   
{
262   
    interrupt_reactor();
262   
    interrupt_reactor();
263   
}
263   
}
264  
264  
265   
inline void
265   
inline void
266   
select_scheduler::interrupt_reactor() const
266   
select_scheduler::interrupt_reactor() const
267   
{
267   
{
268   
    char byte               = 1;
268   
    char byte               = 1;
269   
    [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
269   
    [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
270   
}
270   
}
271  
271  
272   
inline long
272   
inline long
273   
select_scheduler::calculate_timeout(long requested_timeout_us) const
273   
select_scheduler::calculate_timeout(long requested_timeout_us) const
274   
{
274   
{
275   
    if (requested_timeout_us == 0)
275   
    if (requested_timeout_us == 0)
276   
        return 0;
276   
        return 0;
277  
277  
278   
    auto nearest = timer_svc_->nearest_expiry();
278   
    auto nearest = timer_svc_->nearest_expiry();
279   
    if (nearest == timer_service::time_point::max())
279   
    if (nearest == timer_service::time_point::max())
280   
        return requested_timeout_us;
280   
        return requested_timeout_us;
281  
281  
282   
    auto now = std::chrono::steady_clock::now();
282   
    auto now = std::chrono::steady_clock::now();
283   
    if (nearest <= now)
283   
    if (nearest <= now)
284   
        return 0;
284   
        return 0;
285  
285  
286   
    auto timer_timeout_us =
286   
    auto timer_timeout_us =
287   
        std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
287   
        std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
288   
            .count();
288   
            .count();
289  
289  
290   
    constexpr auto long_max =
290   
    constexpr auto long_max =
291   
        static_cast<long long>((std::numeric_limits<long>::max)());
291   
        static_cast<long long>((std::numeric_limits<long>::max)());
292   
    auto capped_timer_us =
292   
    auto capped_timer_us =
293   
        (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
293   
        (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
294   
                              static_cast<long long>(0)),
294   
                              static_cast<long long>(0)),
295   
                   long_max);
295   
                   long_max);
296  
296  
297   
    if (requested_timeout_us < 0)
297   
    if (requested_timeout_us < 0)
298   
        return static_cast<long>(capped_timer_us);
298   
        return static_cast<long>(capped_timer_us);
299  
299  
300   
    return static_cast<long>(
300   
    return static_cast<long>(
301   
        (std::min)(static_cast<long long>(requested_timeout_us),
301   
        (std::min)(static_cast<long long>(requested_timeout_us),
302   
                   capped_timer_us));
302   
                   capped_timer_us));
303   
}
303   
}
304  
304  
305   
inline void
305   
inline void
306   
select_scheduler::run_task(
306   
select_scheduler::run_task(
307   
    lock_type& lock, context_type* ctx, long timeout_us)
307   
    lock_type& lock, context_type* ctx, long timeout_us)
308   
{
308   
{
309   
    long effective_timeout_us =
309   
    long effective_timeout_us =
310   
        task_interrupted_ ? 0 : calculate_timeout(timeout_us);
310   
        task_interrupted_ ? 0 : calculate_timeout(timeout_us);
311  
311  
312   
    // Snapshot registered descriptors while holding lock.
312   
    // Snapshot registered descriptors while holding lock.
313   
    // Record which fds need write monitoring to avoid a hot loop:
313   
    // Record which fds need write monitoring to avoid a hot loop:
314   
    // select is level-triggered so writable sockets (nearly always
314   
    // select is level-triggered so writable sockets (nearly always
315   
    // writable) would cause select() to return immediately every
315   
    // writable) would cause select() to return immediately every
316   
    // iteration if unconditionally added to write_fds.
316   
    // iteration if unconditionally added to write_fds.
317   
    struct fd_entry
317   
    struct fd_entry
318   
    {
318   
    {
319   
        int fd;
319   
        int fd;
320   
        select_descriptor_state* desc;
320   
        select_descriptor_state* desc;
321   
        bool needs_write;
321   
        bool needs_write;
322   
    };
322   
    };
323   
    fd_entry snapshot[FD_SETSIZE];
323   
    fd_entry snapshot[FD_SETSIZE];
324   
    int snapshot_count = 0;
324   
    int snapshot_count = 0;
325  
325  
326   
    for (auto& [fd, desc] : registered_descs_)
326   
    for (auto& [fd, desc] : registered_descs_)
327   
    {
327   
    {
328   
        if (snapshot_count < FD_SETSIZE)
328   
        if (snapshot_count < FD_SETSIZE)
329   
        {
329   
        {
330   
            conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
330   
            conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
331   
            snapshot[snapshot_count].fd   = fd;
331   
            snapshot[snapshot_count].fd   = fd;
332   
            snapshot[snapshot_count].desc = desc;
332   
            snapshot[snapshot_count].desc = desc;
333   
            snapshot[snapshot_count].needs_write =
333   
            snapshot[snapshot_count].needs_write =
334   
                (desc->write_op || desc->connect_op);
334   
                (desc->write_op || desc->connect_op);
335   
            ++snapshot_count;
335   
            ++snapshot_count;
336   
        }
336   
        }
337   
    }
337   
    }
338  
338  
339   
    if (lock.owns_lock())
339   
    if (lock.owns_lock())
340   
        lock.unlock();
340   
        lock.unlock();
341  
341  
342   
    task_cleanup on_exit{this, &lock, ctx};
342   
    task_cleanup on_exit{this, &lock, ctx};
343  
343  
344   
    fd_set read_fds, write_fds, except_fds;
344   
    fd_set read_fds, write_fds, except_fds;
345   
    FD_ZERO(&read_fds);
345   
    FD_ZERO(&read_fds);
346   
    FD_ZERO(&write_fds);
346   
    FD_ZERO(&write_fds);
347   
    FD_ZERO(&except_fds);
347   
    FD_ZERO(&except_fds);
348  
348  
349   
    FD_SET(pipe_fds_[0], &read_fds);
349   
    FD_SET(pipe_fds_[0], &read_fds);
350   
    int nfds = pipe_fds_[0];
350   
    int nfds = pipe_fds_[0];
351  
351  
352   
    for (int i = 0; i < snapshot_count; ++i)
352   
    for (int i = 0; i < snapshot_count; ++i)
353   
    {
353   
    {
354   
        int fd = snapshot[i].fd;
354   
        int fd = snapshot[i].fd;
355   
        FD_SET(fd, &read_fds);
355   
        FD_SET(fd, &read_fds);
356   
        if (snapshot[i].needs_write)
356   
        if (snapshot[i].needs_write)
357   
            FD_SET(fd, &write_fds);
357   
            FD_SET(fd, &write_fds);
358   
        FD_SET(fd, &except_fds);
358   
        FD_SET(fd, &except_fds);
359   
        if (fd > nfds)
359   
        if (fd > nfds)
360   
            nfds = fd;
360   
            nfds = fd;
361   
    }
361   
    }
362  
362  
363   
    struct timeval tv;
363   
    struct timeval tv;
364   
    struct timeval* tv_ptr = nullptr;
364   
    struct timeval* tv_ptr = nullptr;
365   
    if (effective_timeout_us >= 0)
365   
    if (effective_timeout_us >= 0)
366   
    {
366   
    {
367   
        tv.tv_sec  = effective_timeout_us / 1000000;
367   
        tv.tv_sec  = effective_timeout_us / 1000000;
368   
        tv.tv_usec = effective_timeout_us % 1000000;
368   
        tv.tv_usec = effective_timeout_us % 1000000;
369   
        tv_ptr     = &tv;
369   
        tv_ptr     = &tv;
370   
    }
370   
    }
371  
371  
372   
    int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
372   
    int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
373  
373  
374   
    // EINTR: signal interrupted select(), just retry.
374   
    // EINTR: signal interrupted select(), just retry.
375   
    // EBADF: an fd was closed between snapshot and select(); retry
375   
    // EBADF: an fd was closed between snapshot and select(); retry
376   
    // with a fresh snapshot from registered_descs_.
376   
    // with a fresh snapshot from registered_descs_.
377   
    if (ready < 0)
377   
    if (ready < 0)
378   
    {
378   
    {
379   
        if (errno == EINTR || errno == EBADF)
379   
        if (errno == EINTR || errno == EBADF)
380   
            return;
380   
            return;
381   
        detail::throw_system_error(make_err(errno), "select");
381   
        detail::throw_system_error(make_err(errno), "select");
382   
    }
382   
    }
383  
383  
384   
    // Process timers outside the lock
384   
    // Process timers outside the lock
385   
    timer_svc_->process_expired();
385   
    timer_svc_->process_expired();
386  
386  
387   
    op_queue local_ops;
387   
    op_queue local_ops;
388  
388  
389   
    if (ready > 0)
389   
    if (ready > 0)
390   
    {
390   
    {
391   
        if (FD_ISSET(pipe_fds_[0], &read_fds))
391   
        if (FD_ISSET(pipe_fds_[0], &read_fds))
392   
        {
392   
        {
393   
            char buf[256];
393   
            char buf[256];
394   
            while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
394   
            while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
395   
            {
395   
            {
396   
            }
396   
            }
397   
        }
397   
        }
398  
398  
399   
        for (int i = 0; i < snapshot_count; ++i)
399   
        for (int i = 0; i < snapshot_count; ++i)
400   
        {
400   
        {
401   
            int fd                        = snapshot[i].fd;
401   
            int fd                        = snapshot[i].fd;
402   
            select_descriptor_state* desc = snapshot[i].desc;
402   
            select_descriptor_state* desc = snapshot[i].desc;
403  
403  
404   
            std::uint32_t flags = 0;
404   
            std::uint32_t flags = 0;
405   
            if (FD_ISSET(fd, &read_fds))
405   
            if (FD_ISSET(fd, &read_fds))
406   
                flags |= reactor_event_read;
406   
                flags |= reactor_event_read;
407   
            if (FD_ISSET(fd, &write_fds))
407   
            if (FD_ISSET(fd, &write_fds))
408   
                flags |= reactor_event_write;
408   
                flags |= reactor_event_write;
409   
            if (FD_ISSET(fd, &except_fds))
409   
            if (FD_ISSET(fd, &except_fds))
410   
                flags |= reactor_event_error;
410   
                flags |= reactor_event_error;
411  
411  
412   
            if (flags == 0)
412   
            if (flags == 0)
413   
                continue;
413   
                continue;
414  
414  
415   
            desc->add_ready_events(flags);
415   
            desc->add_ready_events(flags);
416  
416  
417   
            bool expected = false;
417   
            bool expected = false;
418   
            if (desc->is_enqueued_.compare_exchange_strong(
418   
            if (desc->is_enqueued_.compare_exchange_strong(
419   
                    expected, true, std::memory_order_release,
419   
                    expected, true, std::memory_order_release,
420   
                    std::memory_order_relaxed))
420   
                    std::memory_order_relaxed))
421   
            {
421   
            {
422   
                local_ops.push(desc);
422   
                local_ops.push(desc);
423   
            }
423   
            }
424   
        }
424   
        }
425   
    }
425   
    }
426  
426  
427   
    lock.lock();
427   
    lock.lock();
428  
428  
429   
    if (!local_ops.empty())
429   
    if (!local_ops.empty())
430   
        completed_ops_.splice(local_ops);
430   
        completed_ops_.splice(local_ops);
431   
}
431   
}
432  
432  
433   
} // namespace boost::corosio::detail
433   
} // namespace boost::corosio::detail
434  
434  
435   
#endif // BOOST_COROSIO_HAS_SELECT
435   
#endif // BOOST_COROSIO_HAS_SELECT
436  
436  
437   
#endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
437   
#endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP