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/*
* Copyright 2003-2021 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "SocketEvent.hxx"
#include "Loop.hxx"
#include "event/Features.h"
#include <cassert>
#include <utility>
#ifdef USE_EPOLL
#include <cerrno>
#endif
void
SocketEvent::Open(SocketDescriptor _fd) noexcept
{
assert(_fd.IsDefined());
assert(!fd.IsDefined());
assert(GetScheduledFlags() == 0);
fd = _fd;
}
void
SocketEvent::Close() noexcept
{
if (!fd.IsDefined())
return;
/* closing the socket automatically unregisters it from epoll,
so we can omit the epoll_ctl(EPOLL_CTL_DEL) call and save
one system call */
if (std::exchange(scheduled_flags, 0) != 0) {
#ifdef HAVE_THREADED_EVENT_LOOP
/* can't use this optimization in multi-threaded
programs, because all file descriptors get
duplicated in forked processes, leaving them
registered in epoll, which could cause the parent
to crash */
loop.RemoveFD(fd.Get(), *this);
#else
loop.AbandonFD(*this);
#endif
}
fd.Close();
}
void
SocketEvent::Abandon() noexcept
{
if (std::exchange(scheduled_flags, 0) != 0)
loop.AbandonFD(*this);
fd = SocketDescriptor::Undefined();
}
bool
SocketEvent::Schedule(unsigned flags) noexcept
{
if (flags != 0)
flags |= IMPLICIT_FLAGS;
if (flags == GetScheduledFlags())
return true;
assert(IsDefined());
bool success;
if (scheduled_flags == 0)
success = loop.AddFD(fd.Get(), flags, *this);
else if (flags == 0)
success = loop.RemoveFD(fd.Get(), *this);
else
success = loop.ModifyFD(fd.Get(), flags, *this);
if (success)
scheduled_flags = flags;
#ifdef USE_EPOLL
else if (errno == EBADF || errno == ENOENT)
/* the socket was probably closed by somebody else
(EBADF) or a new file descriptor with the same
number was created but not registered already
(ENOENT) - we can assume that there are no
scheduled events */
/* note that when this happens, we're actually lucky
that it has failed - imagine another thread may
meanwhile have created something on the same file
descriptor number, and has registered it; the
epoll_ctl() call above would then have succeeded,
but broke the other thread's epoll registration */
scheduled_flags = 0;
#endif
return success;
}
void
SocketEvent::Dispatch() noexcept
{
const unsigned flags = std::exchange(ready_flags, 0) &
GetScheduledFlags();
if (flags != 0)
callback(flags);
}