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_base: 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_base
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(std::unique_lock<std::mutex>& lock, context_type* ctx) override;
130 + 
    run_task(std::unique_lock<std::mutex>& lock, context_type* ctx,
 
131 + 
        long timeout_us) override;
131   
    void interrupt_reactor() const override;
132   
    void interrupt_reactor() const override;
132   
    long calculate_timeout(long requested_timeout_us) const;
133   
    long calculate_timeout(long requested_timeout_us) const;
133  
134  
134   
    // Self-pipe for interrupting select()
135   
    // Self-pipe for interrupting select()
135   
    int pipe_fds_[2]; // [0]=read, [1]=write
136   
    int pipe_fds_[2]; // [0]=read, [1]=write
136  
137  
137   
    // Per-fd tracking for fd_set building
138   
    // Per-fd tracking for fd_set building
138   
    mutable std::unordered_map<int, select_descriptor_state*> registered_descs_;
139   
    mutable std::unordered_map<int, select_descriptor_state*> registered_descs_;
139   
    mutable int max_fd_ = -1;
140   
    mutable int max_fd_ = -1;
140   
};
141   
};
141  
142  
142   
inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
143   
inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
143   
    : pipe_fds_{-1, -1}
144   
    : pipe_fds_{-1, -1}
144   
    , max_fd_(-1)
145   
    , max_fd_(-1)
145   
{
146   
{
146   
    if (::pipe(pipe_fds_) < 0)
147   
    if (::pipe(pipe_fds_) < 0)
147   
        detail::throw_system_error(make_err(errno), "pipe");
148   
        detail::throw_system_error(make_err(errno), "pipe");
148  
149  
149   
    for (int i = 0; i < 2; ++i)
150   
    for (int i = 0; i < 2; ++i)
150   
    {
151   
    {
151   
        int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
152   
        int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
152   
        if (flags == -1)
153   
        if (flags == -1)
153   
        {
154   
        {
154   
            int errn = errno;
155   
            int errn = errno;
155   
            ::close(pipe_fds_[0]);
156   
            ::close(pipe_fds_[0]);
156   
            ::close(pipe_fds_[1]);
157   
            ::close(pipe_fds_[1]);
157   
            detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
158   
            detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
158   
        }
159   
        }
159   
        if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
160   
        if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
160   
        {
161   
        {
161   
            int errn = errno;
162   
            int errn = errno;
162   
            ::close(pipe_fds_[0]);
163   
            ::close(pipe_fds_[0]);
163   
            ::close(pipe_fds_[1]);
164   
            ::close(pipe_fds_[1]);
164   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
165   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
165   
        }
166   
        }
166   
        if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
167   
        if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
167   
        {
168   
        {
168   
            int errn = errno;
169   
            int errn = errno;
169   
            ::close(pipe_fds_[0]);
170   
            ::close(pipe_fds_[0]);
170   
            ::close(pipe_fds_[1]);
171   
            ::close(pipe_fds_[1]);
171   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
172   
            detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
172   
        }
173   
        }
173   
    }
174   
    }
174  
175  
175   
    timer_svc_ = &get_timer_service(ctx, *this);
176   
    timer_svc_ = &get_timer_service(ctx, *this);
176   
    timer_svc_->set_on_earliest_changed(
177   
    timer_svc_->set_on_earliest_changed(
177   
        timer_service::callback(this, [](void* p) {
178   
        timer_service::callback(this, [](void* p) {
178   
            static_cast<select_scheduler*>(p)->interrupt_reactor();
179   
            static_cast<select_scheduler*>(p)->interrupt_reactor();
179   
        }));
180   
        }));
180  
181  
181   
    get_resolver_service(ctx, *this);
182   
    get_resolver_service(ctx, *this);
182   
    get_signal_service(ctx, *this);
183   
    get_signal_service(ctx, *this);
183   
    get_stream_file_service(ctx, *this);
184   
    get_stream_file_service(ctx, *this);
184   
    get_random_access_file_service(ctx, *this);
185   
    get_random_access_file_service(ctx, *this);
185  
186  
186   
    completed_ops_.push(&task_op_);
187   
    completed_ops_.push(&task_op_);
187   
}
188   
}
188  
189  
189   
inline select_scheduler::~select_scheduler()
190   
inline select_scheduler::~select_scheduler()
190   
{
191   
{
191   
    if (pipe_fds_[0] >= 0)
192   
    if (pipe_fds_[0] >= 0)
192   
        ::close(pipe_fds_[0]);
193   
        ::close(pipe_fds_[0]);
193   
    if (pipe_fds_[1] >= 0)
194   
    if (pipe_fds_[1] >= 0)
194   
        ::close(pipe_fds_[1]);
195   
        ::close(pipe_fds_[1]);
195   
}
196   
}
196  
197  
197   
inline void
198   
inline void
198   
select_scheduler::shutdown()
199   
select_scheduler::shutdown()
199   
{
200   
{
200   
    shutdown_drain();
201   
    shutdown_drain();
201  
202  
202   
    if (pipe_fds_[1] >= 0)
203   
    if (pipe_fds_[1] >= 0)
203   
        interrupt_reactor();
204   
        interrupt_reactor();
204   
}
205   
}
205  
206  
206   
inline void
207   
inline void
207   
select_scheduler::register_descriptor(
208   
select_scheduler::register_descriptor(
208   
    int fd, select_descriptor_state* desc) const
209   
    int fd, select_descriptor_state* desc) const
209   
{
210   
{
210   
    if (fd < 0 || fd >= FD_SETSIZE)
211   
    if (fd < 0 || fd >= FD_SETSIZE)
211   
        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");
212  
213  
213   
    desc->registered_events = reactor_event_read | reactor_event_write;
214   
    desc->registered_events = reactor_event_read | reactor_event_write;
214   
    desc->fd                = fd;
215   
    desc->fd                = fd;
215   
    desc->scheduler_        = this;
216   
    desc->scheduler_        = this;
216   
    desc->ready_events_.store(0, std::memory_order_relaxed);
217   
    desc->ready_events_.store(0, std::memory_order_relaxed);
217  
218  
218   
    {
219   
    {
219   
        std::lock_guard lock(desc->mutex);
220   
        std::lock_guard lock(desc->mutex);
220   
        desc->impl_ref_.reset();
221   
        desc->impl_ref_.reset();
221   
        desc->read_ready  = false;
222   
        desc->read_ready  = false;
222   
        desc->write_ready = false;
223   
        desc->write_ready = false;
223   
    }
224   
    }
224  
225  
225   
    {
226   
    {
226   
        std::lock_guard lock(mutex_);
227   
        std::lock_guard lock(mutex_);
227   
        registered_descs_[fd] = desc;
228   
        registered_descs_[fd] = desc;
228   
        if (fd > max_fd_)
229   
        if (fd > max_fd_)
229   
            max_fd_ = fd;
230   
            max_fd_ = fd;
230   
    }
231   
    }
231  
232  
232   
    interrupt_reactor();
233   
    interrupt_reactor();
233   
}
234   
}
234  
235  
235   
inline void
236   
inline void
236   
select_scheduler::deregister_descriptor(int fd) const
237   
select_scheduler::deregister_descriptor(int fd) const
237   
{
238   
{
238   
    std::lock_guard lock(mutex_);
239   
    std::lock_guard lock(mutex_);
239  
240  
240   
    auto it = registered_descs_.find(fd);
241   
    auto it = registered_descs_.find(fd);
241   
    if (it == registered_descs_.end())
242   
    if (it == registered_descs_.end())
242   
        return;
243   
        return;
243  
244  
244   
    registered_descs_.erase(it);
245   
    registered_descs_.erase(it);
245  
246  
246   
    if (fd == max_fd_)
247   
    if (fd == max_fd_)
247   
    {
248   
    {
248   
        max_fd_ = pipe_fds_[0];
249   
        max_fd_ = pipe_fds_[0];
249   
        for (auto& [registered_fd, state] : registered_descs_)
250   
        for (auto& [registered_fd, state] : registered_descs_)
250   
        {
251   
        {
251   
            if (registered_fd > max_fd_)
252   
            if (registered_fd > max_fd_)
252   
                max_fd_ = registered_fd;
253   
                max_fd_ = registered_fd;
253   
        }
254   
        }
254   
    }
255   
    }
255   
}
256   
}
256  
257  
257   
inline void
258   
inline void
258   
select_scheduler::notify_reactor() const
259   
select_scheduler::notify_reactor() const
259   
{
260   
{
260   
    interrupt_reactor();
261   
    interrupt_reactor();
261   
}
262   
}
262  
263  
263   
inline void
264   
inline void
264   
select_scheduler::interrupt_reactor() const
265   
select_scheduler::interrupt_reactor() const
265   
{
266   
{
266   
    char byte               = 1;
267   
    char byte               = 1;
267   
    [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
268   
    [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
268   
}
269   
}
269  
270  
270   
inline long
271   
inline long
271   
select_scheduler::calculate_timeout(long requested_timeout_us) const
272   
select_scheduler::calculate_timeout(long requested_timeout_us) const
272   
{
273   
{
273   
    if (requested_timeout_us == 0)
274   
    if (requested_timeout_us == 0)
274   
        return 0;
275   
        return 0;
275  
276  
276   
    auto nearest = timer_svc_->nearest_expiry();
277   
    auto nearest = timer_svc_->nearest_expiry();
277   
    if (nearest == timer_service::time_point::max())
278   
    if (nearest == timer_service::time_point::max())
278   
        return requested_timeout_us;
279   
        return requested_timeout_us;
279  
280  
280   
    auto now = std::chrono::steady_clock::now();
281   
    auto now = std::chrono::steady_clock::now();
281   
    if (nearest <= now)
282   
    if (nearest <= now)
282   
        return 0;
283   
        return 0;
283  
284  
284   
    auto timer_timeout_us =
285   
    auto timer_timeout_us =
285   
        std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
286   
        std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
286   
            .count();
287   
            .count();
287  
288  
288   
    constexpr auto long_max =
289   
    constexpr auto long_max =
289   
        static_cast<long long>((std::numeric_limits<long>::max)());
290   
        static_cast<long long>((std::numeric_limits<long>::max)());
290   
    auto capped_timer_us =
291   
    auto capped_timer_us =
291   
        (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
292   
        (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
292   
                              static_cast<long long>(0)),
293   
                              static_cast<long long>(0)),
293   
                   long_max);
294   
                   long_max);
294  
295  
295   
    if (requested_timeout_us < 0)
296   
    if (requested_timeout_us < 0)
296   
        return static_cast<long>(capped_timer_us);
297   
        return static_cast<long>(capped_timer_us);
297  
298  
298   
    return static_cast<long>(
299   
    return static_cast<long>(
299   
        (std::min)(static_cast<long long>(requested_timeout_us),
300   
        (std::min)(static_cast<long long>(requested_timeout_us),
300   
                   capped_timer_us));
301   
                   capped_timer_us));
301   
}
302   
}
302  
303  
303   
inline void
304   
inline void
304   
select_scheduler::run_task(
305   
select_scheduler::run_task(
305 - 
    std::unique_lock<std::mutex>& lock, context_type* ctx)
306 + 
    std::unique_lock<std::mutex>& lock, context_type* ctx, long timeout_us)
306   
{
307   
{
307 - 
    long effective_timeout_us = task_interrupted_ ? 0 : calculate_timeout(-1);
308 + 
    long effective_timeout_us =
 
309 + 
        task_interrupted_ ? 0 : calculate_timeout(timeout_us);
308  
310  
309   
    // Snapshot registered descriptors while holding lock.
311   
    // Snapshot registered descriptors while holding lock.
310   
    // Record which fds need write monitoring to avoid a hot loop:
312   
    // Record which fds need write monitoring to avoid a hot loop:
311   
    // select is level-triggered so writable sockets (nearly always
313   
    // select is level-triggered so writable sockets (nearly always
312   
    // writable) would cause select() to return immediately every
314   
    // writable) would cause select() to return immediately every
313   
    // iteration if unconditionally added to write_fds.
315   
    // iteration if unconditionally added to write_fds.
314   
    struct fd_entry
316   
    struct fd_entry
315   
    {
317   
    {
316   
        int fd;
318   
        int fd;
317   
        select_descriptor_state* desc;
319   
        select_descriptor_state* desc;
318   
        bool needs_write;
320   
        bool needs_write;
319   
    };
321   
    };
320   
    fd_entry snapshot[FD_SETSIZE];
322   
    fd_entry snapshot[FD_SETSIZE];
321   
    int snapshot_count = 0;
323   
    int snapshot_count = 0;
322  
324  
323   
    for (auto& [fd, desc] : registered_descs_)
325   
    for (auto& [fd, desc] : registered_descs_)
324   
    {
326   
    {
325   
        if (snapshot_count < FD_SETSIZE)
327   
        if (snapshot_count < FD_SETSIZE)
326   
        {
328   
        {
327   
            std::lock_guard desc_lock(desc->mutex);
329   
            std::lock_guard desc_lock(desc->mutex);
328   
            snapshot[snapshot_count].fd   = fd;
330   
            snapshot[snapshot_count].fd   = fd;
329   
            snapshot[snapshot_count].desc = desc;
331   
            snapshot[snapshot_count].desc = desc;
330   
            snapshot[snapshot_count].needs_write =
332   
            snapshot[snapshot_count].needs_write =
331   
                (desc->write_op || desc->connect_op);
333   
                (desc->write_op || desc->connect_op);
332   
            ++snapshot_count;
334   
            ++snapshot_count;
333   
        }
335   
        }
334   
    }
336   
    }
335  
337  
336   
    if (lock.owns_lock())
338   
    if (lock.owns_lock())
337   
        lock.unlock();
339   
        lock.unlock();
338  
340  
339   
    task_cleanup on_exit{this, &lock, ctx};
341   
    task_cleanup on_exit{this, &lock, ctx};
340  
342  
341   
    fd_set read_fds, write_fds, except_fds;
343   
    fd_set read_fds, write_fds, except_fds;
342   
    FD_ZERO(&read_fds);
344   
    FD_ZERO(&read_fds);
343   
    FD_ZERO(&write_fds);
345   
    FD_ZERO(&write_fds);
344   
    FD_ZERO(&except_fds);
346   
    FD_ZERO(&except_fds);
345  
347  
346   
    FD_SET(pipe_fds_[0], &read_fds);
348   
    FD_SET(pipe_fds_[0], &read_fds);
347   
    int nfds = pipe_fds_[0];
349   
    int nfds = pipe_fds_[0];
348  
350  
349   
    for (int i = 0; i < snapshot_count; ++i)
351   
    for (int i = 0; i < snapshot_count; ++i)
350   
    {
352   
    {
351   
        int fd = snapshot[i].fd;
353   
        int fd = snapshot[i].fd;
352   
        FD_SET(fd, &read_fds);
354   
        FD_SET(fd, &read_fds);
353   
        if (snapshot[i].needs_write)
355   
        if (snapshot[i].needs_write)
354   
            FD_SET(fd, &write_fds);
356   
            FD_SET(fd, &write_fds);
355   
        FD_SET(fd, &except_fds);
357   
        FD_SET(fd, &except_fds);
356   
        if (fd > nfds)
358   
        if (fd > nfds)
357   
            nfds = fd;
359   
            nfds = fd;
358   
    }
360   
    }
359  
361  
360   
    struct timeval tv;
362   
    struct timeval tv;
361   
    struct timeval* tv_ptr = nullptr;
363   
    struct timeval* tv_ptr = nullptr;
362   
    if (effective_timeout_us >= 0)
364   
    if (effective_timeout_us >= 0)
363   
    {
365   
    {
364   
        tv.tv_sec  = effective_timeout_us / 1000000;
366   
        tv.tv_sec  = effective_timeout_us / 1000000;
365   
        tv.tv_usec = effective_timeout_us % 1000000;
367   
        tv.tv_usec = effective_timeout_us % 1000000;
366   
        tv_ptr     = &tv;
368   
        tv_ptr     = &tv;
367   
    }
369   
    }
368  
370  
369   
    int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
371   
    int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
370  
372  
371   
    // EINTR: signal interrupted select(), just retry.
373   
    // EINTR: signal interrupted select(), just retry.
372   
    // EBADF: an fd was closed between snapshot and select(); retry
374   
    // EBADF: an fd was closed between snapshot and select(); retry
373   
    // with a fresh snapshot from registered_descs_.
375   
    // with a fresh snapshot from registered_descs_.
374   
    if (ready < 0)
376   
    if (ready < 0)
375   
    {
377   
    {
376   
        if (errno == EINTR || errno == EBADF)
378   
        if (errno == EINTR || errno == EBADF)
377   
            return;
379   
            return;
378   
        detail::throw_system_error(make_err(errno), "select");
380   
        detail::throw_system_error(make_err(errno), "select");
379   
    }
381   
    }
380  
382  
381   
    // Process timers outside the lock
383   
    // Process timers outside the lock
382   
    timer_svc_->process_expired();
384   
    timer_svc_->process_expired();
383  
385  
384   
    op_queue local_ops;
386   
    op_queue local_ops;
385  
387  
386   
    if (ready > 0)
388   
    if (ready > 0)
387   
    {
389   
    {
388   
        if (FD_ISSET(pipe_fds_[0], &read_fds))
390   
        if (FD_ISSET(pipe_fds_[0], &read_fds))
389   
        {
391   
        {
390   
            char buf[256];
392   
            char buf[256];
391   
            while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
393   
            while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
392   
            {
394   
            {
393   
            }
395   
            }
394   
        }
396   
        }
395  
397  
396   
        for (int i = 0; i < snapshot_count; ++i)
398   
        for (int i = 0; i < snapshot_count; ++i)
397   
        {
399   
        {
398   
            int fd                        = snapshot[i].fd;
400   
            int fd                        = snapshot[i].fd;
399   
            select_descriptor_state* desc = snapshot[i].desc;
401   
            select_descriptor_state* desc = snapshot[i].desc;
400  
402  
401   
            std::uint32_t flags = 0;
403   
            std::uint32_t flags = 0;
402   
            if (FD_ISSET(fd, &read_fds))
404   
            if (FD_ISSET(fd, &read_fds))
403   
                flags |= reactor_event_read;
405   
                flags |= reactor_event_read;
404   
            if (FD_ISSET(fd, &write_fds))
406   
            if (FD_ISSET(fd, &write_fds))
405   
                flags |= reactor_event_write;
407   
                flags |= reactor_event_write;
406   
            if (FD_ISSET(fd, &except_fds))
408   
            if (FD_ISSET(fd, &except_fds))
407   
                flags |= reactor_event_error;
409   
                flags |= reactor_event_error;
408  
410  
409   
            if (flags == 0)
411   
            if (flags == 0)
410   
                continue;
412   
                continue;
411  
413  
412   
            desc->add_ready_events(flags);
414   
            desc->add_ready_events(flags);
413  
415  
414   
            bool expected = false;
416   
            bool expected = false;
415   
            if (desc->is_enqueued_.compare_exchange_strong(
417   
            if (desc->is_enqueued_.compare_exchange_strong(
416   
                    expected, true, std::memory_order_release,
418   
                    expected, true, std::memory_order_release,
417   
                    std::memory_order_relaxed))
419   
                    std::memory_order_relaxed))
418   
            {
420   
            {
419   
                local_ops.push(desc);
421   
                local_ops.push(desc);
420   
            }
422   
            }
421   
        }
423   
        }
422   
    }
424   
    }
423  
425  
424   
    lock.lock();
426   
    lock.lock();
425  
427  
426   
    if (!local_ops.empty())
428   
    if (!local_ops.empty())
427   
        completed_ops_.splice(local_ops);
429   
        completed_ops_.splice(local_ops);
428   
}
430   
}
429  
431  
430   
} // namespace boost::corosio::detail
432   
} // namespace boost::corosio::detail
431  
433  
432   
#endif // BOOST_COROSIO_HAS_SELECT
434   
#endif // BOOST_COROSIO_HAS_SELECT
433  
435  
434   
#endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
436   
#endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP