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/*
* Copyright 2003-2018 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.
*/
#ifndef MPD_MULTI_SOCKET_MONITOR_HXX
#define MPD_MULTI_SOCKET_MONITOR_HXX
#include "check.h"
#include "IdleMonitor.hxx"
#include "TimerEvent.hxx"
#include "SocketMonitor.hxx"
#include "util/Compiler.h"
#include <forward_list>
#include <iterator>
#include <assert.h>
#ifndef _WIN32
struct pollfd;
#endif
class EventLoop;
/**
* Similar to #SocketMonitor, but monitors multiple sockets. To use
* it, implement the methods PrepareSockets() and DispatchSockets().
* In PrepareSockets(), use UpdateSocketList() and AddSocket().
* DispatchSockets() will be called if at least one socket is ready.
*/
class MultiSocketMonitor : IdleMonitor
{
class SingleFD final : public SocketMonitor {
MultiSocketMonitor &multi;
unsigned revents;
public:
SingleFD(MultiSocketMonitor &_multi, SocketDescriptor _fd,
unsigned events) noexcept
:SocketMonitor(_fd, _multi.GetEventLoop()),
multi(_multi), revents(0) {
Schedule(events);
}
SocketDescriptor GetSocket() const noexcept {
return SocketMonitor::GetSocket();
}
unsigned GetEvents() const noexcept {
return SocketMonitor::GetScheduledFlags();
}
void SetEvents(unsigned _events) noexcept {
revents &= _events;
SocketMonitor::Schedule(_events);
}
unsigned GetReturnedEvents() const noexcept {
return revents;
}
void ClearReturnedEvents() noexcept {
revents = 0;
}
protected:
bool OnSocketReady(unsigned flags) noexcept override {
revents = flags;
multi.SetReady();
return true;
}
};
friend class SingleFD;
TimerEvent timeout_event;
/**
* DispatchSockets() should be called.
*/
bool ready = false;
/**
* PrepareSockets() should be called.
*
* Note that this doesn't need to be initialized by the
* constructor; this class is activated with the first
* InvalidateSockets() call, which initializes this flag.
*/
bool refresh;
std::forward_list<SingleFD> fds;
public:
static constexpr unsigned READ = SocketMonitor::READ;
static constexpr unsigned WRITE = SocketMonitor::WRITE;
static constexpr unsigned ERROR = SocketMonitor::ERROR;
static constexpr unsigned HANGUP = SocketMonitor::HANGUP;
MultiSocketMonitor(EventLoop &_loop) noexcept;
using IdleMonitor::GetEventLoop;
/**
* Clear the socket list and disable all #EventLoop
* registrations. Run this in the #EventLoop thread before
* destroying this object.
*
* Later, this object can be reused and reactivated by calling
* InvalidateSockets().
*
* Note that this class doesn't have a destructor which calls
* this method, because this would be racy and thus pointless:
* at the time ~MultiSocketMonitor() is called, our virtual
* methods have been morphed to be pure again, and in the
* meantime the #EventLoop thread could invoke those pure
* methods.
*/
void Reset() noexcept;
/**
* Invalidate the socket list. A call to PrepareSockets() is
* scheduled which will then update the list.
*/
void InvalidateSockets() noexcept {
refresh = true;
IdleMonitor::Schedule();
}
/**
* Add one socket to the list of monitored sockets.
*
* May only be called from PrepareSockets().
*/
void AddSocket(SocketDescriptor fd, unsigned events) noexcept {
fds.emplace_front(*this, fd, events);
}
/**
* Remove all sockets.
*
* May only be called from PrepareSockets().
*/
void ClearSocketList() noexcept;
/**
* Update the known sockets by invoking the given function for
* each one; its return value is the events bit mask. A
* return value of 0 means the socket will be removed from the
* list.
*
* May only be called from PrepareSockets().
*/
template<typename E>
void UpdateSocketList(E &&e) noexcept {
for (auto prev = fds.before_begin(), end = fds.end(),
i = std::next(prev);
i != end; i = std::next(prev)) {
assert(i->GetEvents() != 0);
unsigned events = e(i->GetSocket());
if (events != 0) {
i->SetEvents(events);
prev = i;
} else {
fds.erase_after(prev);
}
}
}
#ifndef _WIN32
/**
* Replace the socket list with the given file descriptors.
* The given pollfd array will be modified by this method.
*
* May only be called from PrepareSockets().
*/
void ReplaceSocketList(pollfd *pfds, unsigned n) noexcept;
#endif
protected:
/**
* Override this method and update the socket registrations.
* To do that, call AddSocket(), ClearSocketList(),
* UpdateSocketList() and ReplaceSocketList().
*
* @return timeout or a negative value for no timeout
*/
virtual std::chrono::steady_clock::duration PrepareSockets() noexcept = 0;
/**
* At least one socket is ready or the timeout has expired.
* This method should be used to perform I/O.
*/
virtual void DispatchSockets() noexcept = 0;
private:
void SetReady() noexcept {
ready = true;
IdleMonitor::Schedule();
}
void Prepare() noexcept;
void OnTimeout() noexcept {
SetReady();
IdleMonitor::Schedule();
}
virtual void OnIdle() noexcept final;
};
#endif
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