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//
 
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// Copyright (c) 2026 Steve Gerbino
 
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//
 
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
 
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
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//
 
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// Official repository: https://github.com/cppalliance/corosio
 
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//
 
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#ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_OP_HPP
 
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#define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_OP_HPP
 
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#include <boost/corosio/detail/platform.hpp>
 
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#if BOOST_COROSIO_HAS_SELECT
 
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#include <boost/corosio/native/detail/reactor/reactor_op.hpp>
 
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#include <boost/corosio/native/detail/reactor/reactor_descriptor_state.hpp>
 
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#include <errno.h>
 
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#include <fcntl.h>
 
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#include <sys/socket.h>
 
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#include <unistd.h>
 
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/*
 
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    File descriptors are registered with the select scheduler once (via
 
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    select_descriptor_state) and stay registered until closed.
 
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    select() is level-triggered but the descriptor_state pattern
 
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    (designed for edge-triggered) works correctly: is_enqueued_ CAS
 
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    prevents double-enqueue, add_ready_events is idempotent, and
 
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    EAGAIN ops stay parked until the next select() re-reports readiness.
 
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    cancel() captures shared_from_this() into op.impl_ptr to prevent
 
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    use-after-free when the socket is closed with pending ops.
 
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    Writes use sendmsg(MSG_NOSIGNAL) on Linux. On macOS/BSD where
 
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    MSG_NOSIGNAL may be absent, SO_NOSIGPIPE is set at socket creation
 
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    and accepted-socket setup instead.
 
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*/
 
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namespace boost::corosio::detail {
 
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// Forward declarations
 
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class select_tcp_socket;
 
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class select_tcp_acceptor;
 
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struct select_op;
 
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// Forward declaration
 
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class select_scheduler;
 
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/// Per-descriptor state for persistent select registration.
 
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struct select_descriptor_state final : reactor_descriptor_state
 
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{};
 
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/// select base operation — thin wrapper over reactor_op.
 
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struct select_op : reactor_op<select_tcp_socket, select_tcp_acceptor>
 
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{
 
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    void operator()() override;
 
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};
 
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/// select connect operation.
 
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struct select_connect_op final : reactor_connect_op<select_op>
 
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{
 
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    void operator()() override;
 
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    void cancel() noexcept override;
 
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};
 
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/// select scatter-read operation.
 
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struct select_read_op final : reactor_read_op<select_op>
 
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{
 
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    void cancel() noexcept override;
 
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};
 
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/** Provides sendmsg() with EINTR retry for select writes.
 
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    Uses MSG_NOSIGNAL where available (Linux). On platforms without
 
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    it (macOS/BSD), SO_NOSIGPIPE is set at socket creation time
 
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    and flags=0 is used here.
 
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*/
 
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struct select_write_policy
 
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{
 
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    static ssize_t write(int fd, iovec* iovecs, int count) noexcept
 
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    {
 
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        msghdr msg{};
 
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        msg.msg_iov    = iovecs;
 
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        msg.msg_iovlen = static_cast<std::size_t>(count);
 
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#ifdef MSG_NOSIGNAL
 
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        constexpr int send_flags = MSG_NOSIGNAL;
 
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#else
 
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        constexpr int send_flags = 0;
 
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#endif
 
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        ssize_t n;
 
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        do
 
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        {
 
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            n = ::sendmsg(fd, &msg, send_flags);
 
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        }
 
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        while (n < 0 && errno == EINTR);
 
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        return n;
 
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    }
 
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};
 
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/// select gather-write operation.
 
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struct select_write_op final : reactor_write_op<select_op, select_write_policy>
 
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{
 
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    void cancel() noexcept override;
 
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};
 
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/** Provides accept() + fcntl(O_NONBLOCK|FD_CLOEXEC) with FD_SETSIZE check.
 
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    Uses accept() instead of accept4() for broader POSIX compatibility.
 
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*/
 
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struct select_accept_policy
 
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{
 
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    static int do_accept(
 
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        int fd, sockaddr_storage& peer, socklen_t& addrlen_out) noexcept
 
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    {
 
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        addrlen_out = sizeof(peer);
 
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        int new_fd;
 
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        do
 
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        {
 
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            addrlen_out = sizeof(peer);
 
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            new_fd = ::accept(
 
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                fd, reinterpret_cast<sockaddr*>(&peer), &addrlen_out);
 
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        }
 
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        while (new_fd < 0 && errno == EINTR);
 
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        if (new_fd < 0)
 
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            return new_fd;
 
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        if (new_fd >= FD_SETSIZE)
 
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        {
 
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            ::close(new_fd);
 
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            errno = EINVAL;
 
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            return -1;
 
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        }
 
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        int flags = ::fcntl(new_fd, F_GETFL, 0);
 
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        if (flags == -1)
 
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        {
 
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            int err = errno;
 
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            ::close(new_fd);
 
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            errno = err;
 
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            return -1;
 
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        }
 
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        if (::fcntl(new_fd, F_SETFL, flags | O_NONBLOCK) == -1)
 
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        {
 
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            int err = errno;
 
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            ::close(new_fd);
 
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            errno = err;
 
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            return -1;
 
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        }
 
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        if (::fcntl(new_fd, F_SETFD, FD_CLOEXEC) == -1)
 
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        {
 
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            int err = errno;
 
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            ::close(new_fd);
 
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            errno = err;
 
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            return -1;
 
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        }
 
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#ifdef SO_NOSIGPIPE
 
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        int one = 1;
 
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        if (::setsockopt(new_fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one)) ==
 
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            -1)
 
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        {
 
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            int err = errno;
 
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            ::close(new_fd);
 
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            errno = err;
 
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            return -1;
 
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        }
 
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#endif
 
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        return new_fd;
 
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    }
 
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};
 
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/// select accept operation.
 
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struct select_accept_op final
 
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    : reactor_accept_op<select_op, select_accept_policy>
 
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{
 
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    void operator()() override;
 
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    void cancel() noexcept override;
 
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};
 
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} // namespace boost::corosio::detail
 
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#endif // BOOST_COROSIO_HAS_SELECT
 
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#endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_OP_HPP