event: introduce generic API for internal event loop

Makefile.am

@@ -306,6 +306,8 @@ libsystem_a_SOURCES = \
 
 libevent_a_SOURCES = \
 	src/event/WakeFD.hxx \
+	src/event/PollGroup.hxx \
+	src/event/PollGroupEPoll.hxx \
 	src/event/SignalMonitor.hxx src/event/SignalMonitor.cxx \
 	src/event/TimeoutMonitor.hxx src/event/TimeoutMonitor.cxx \
 	src/event/IdleMonitor.hxx src/event/IdleMonitor.cxx \

src/event/Loop.cxx

@@ -33,9 +33,6 @@ EventLoop::EventLoop(Default)
 	:SocketMonitor(*this),
 	 now_ms(::MonotonicClockMS()),
 	 quit(false),
-#ifdef USE_EPOLL
-	 n_events(0),
-#endif
 	 thread(ThreadId::Null())
 {
 	SocketMonitor::Open(wake_fd.Get());
@@ -60,23 +57,18 @@ EventLoop::Break()
 		AddCall([this]() { Break(); });
 }
 
-void
-EventLoop::Abandon(SocketMonitor &m)
+bool
+EventLoop::Abandon(int _fd, SocketMonitor &m)
 {
-#ifdef USE_EPOLL
-	for (unsigned i = 0, n = n_events; i < n; ++i)
-		if (events[i].data.ptr == &m)
-			events[i].events = 0;
-#endif
+	poll_result.Clear(&m);
+	return poll_group.Abandon(_fd);
 }
 
 bool
 EventLoop::RemoveFD(int _fd, SocketMonitor &m)
 {
-#ifdef USE_EPOLL
-	Abandon(m);
-	return epoll.Remove(_fd);
-#endif
+	poll_result.Clear(&m);
+	return poll_group.Remove(_fd);
 }
 
 void
@@ -168,34 +160,29 @@ EventLoop::Run()
 			   timeout */
 			continue;
 
-#ifdef USE_EPOLL
 		/* wait for new event */
 
-		const int n = epoll.Wait(events, MAX_EVENTS, timeout_ms);
-		n_events = std::max(n, 0);
+		poll_group.ReadEvents(poll_result, timeout_ms);
 
 		now_ms = ::MonotonicClockMS();
 
 		assert(!quit);
 
 		/* invoke sockets */
-
-		for (int i = 0; i < n; ++i) {
-			const auto &e = events[i];
-
-			if (e.events != 0) {
-				SocketMonitor &m = *(SocketMonitor *)e.data.ptr;
-				m.Dispatch(e.events);
+		for (int i = 0; i < poll_result.GetSize(); ++i) {
+			auto events = poll_result.GetEvents(i);
+			if (events != 0) {
+				auto m = (SocketMonitor *)poll_result.GetObject(i);
+				m->Dispatch(events);
 
 				if (quit)
 					break;
 			}
 		}
 
-		n_events = 0;
-#endif
-	} while (!quit);
+		poll_result.Reset();
 
+	} while (!quit);
 #endif
 
 #ifdef USE_GLIB_EVENTLOOP

src/event/Loop.hxx

@@ -25,10 +25,7 @@
 #include "Compiler.h"
 
 #ifdef USE_INTERNAL_EVENTLOOP
-#ifdef USE_EPOLL
-#include "system/EPollFD.hxx"
-#endif
-
+#include "PollGroup.hxx"
 #include "thread/Mutex.hxx"
 #include "WakeFD.hxx"
 #include "SocketMonitor.hxx"
@@ -99,13 +96,8 @@ class EventLoop final
 
 	bool quit;
 
-#ifdef USE_EPOLL
-	EPollFD epoll;
-	static constexpr unsigned MAX_EVENTS = 16;
-	unsigned n_events;
-	epoll_event events[MAX_EVENTS];
-#endif
-
+	PollGroup poll_group;
+	PollResult poll_result;
 #endif
 
 #ifdef USE_GLIB_EVENTLOOP
@@ -140,15 +132,11 @@ public:
 	void Break();
 
 	bool AddFD(int _fd, unsigned flags, SocketMonitor &m) {
-#ifdef USE_EPOLL
-		return epoll.Add(_fd, flags, &m);
-#endif
+		return poll_group.Add(_fd, flags, &m);
 	}
 
 	bool ModifyFD(int _fd, unsigned flags, SocketMonitor &m) {
-#ifdef USE_EPOLL
-		return epoll.Modify(_fd, flags, &m);
-#endif
+		return poll_group.Modify(_fd, flags, &m);
 	}
 
 	/**
@@ -156,7 +144,7 @@ public:
 	 * has been closed.  This is like RemoveFD(), but does not
 	 * attempt to use #EPOLL_CTL_DEL.
 	 */
-	void Abandon(SocketMonitor &m);
+	bool Abandon(int fd, SocketMonitor &m);
 
 	bool RemoveFD(int fd, SocketMonitor &m);
 

src/event/PollGroup.hxx

+/*
+ * Copyright (C) 2003-2013 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_EVENT_POLLGROUP_HXX
+#define MPD_EVENT_POLLGROUP_HXX
+
+#ifdef USE_EPOLL
+#include "PollGroupEPoll.hxx"
+typedef PollResultEPoll PollResult;
+typedef PollGroupEPoll  PollGroup;
+#endif
+
+#endif

src/event/PollGroupEPoll.hxx

+/*
+ * Copyright (C) 2003-2013 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_EVENT_POLLGROUP_EPOLL_HXX
+#define MPD_EVENT_POLLGROUP_EPOLL_HXX
+
+#include "check.h"
+
+#include "Compiler.h"
+#include "system/EPollFD.hxx"
+
+#include <array>
+#include <algorithm>
+
+class PollResultEPoll
+{
+	friend class PollGroupEPoll;
+
+	std::array<epoll_event, 16> events;
+	int n_events;
+public:
+	PollResultEPoll() : n_events(0) { }
+
+	int GetSize() const { return n_events; }
+	unsigned GetEvents(int i) { return events[i].events; }
+	void *GetObject(int i) { return events[i].data.ptr; }
+	void Reset() { n_events = 0; }
+
+	void Clear(void *obj) {
+		for (int i = 0; i < n_events; ++i)
+			if (events[i].data.ptr == obj)
+				events[i].events = 0;
+	}
+};
+
+class PollGroupEPoll
+{
+	EPollFD epoll;
+
+	PollGroupEPoll(PollGroupEPoll &) = delete;
+	PollGroupEPoll &operator=(PollGroupEPoll &) = delete;
+public:
+	static constexpr unsigned READ = EPOLLIN;
+	static constexpr unsigned WRITE = EPOLLOUT;
+	static constexpr unsigned ERROR = EPOLLERR;
+	static constexpr unsigned HANGUP = EPOLLHUP;
+
+	PollGroupEPoll() = default;
+
+	void ReadEvents(PollResultEPoll &result, int timeout_ms) {
+		int ret = epoll.Wait(result.events.data(), result.events.size(),
+				     timeout_ms);
+		result.n_events = std::max(0, ret);
+	}
+
+	bool Add(int fd, unsigned events, void *obj) {
+		return epoll.Add(fd, events, obj);
+	}
+
+	bool Modify(int fd, unsigned events, void *obj) {
+		return epoll.Modify(fd, events, obj);
+	}
+
+	bool Remove(int fd) {
+		return epoll.Remove(fd);
+	}
+
+	bool Abandon(gcc_unused int fd) {
+		// Nothing to do in this implementation.
+		// Closed descriptors are automatically unregistered.
+		return true;
+	}
+};
+
+#endif

src/event/SocketMonitor.cxx

@@ -158,8 +158,9 @@ SocketMonitor::Abandon()
 	assert(IsDefined());
 
 #ifdef USE_INTERNAL_EVENTLOOP
+	int old_fd = fd;
 	fd = -1;
-	loop.Abandon(*this);
+	loop.Abandon(old_fd, *this);
 #else
 	Steal();
 #endif

src/event/SocketMonitor.hxx

@@ -23,9 +23,7 @@
 #include "check.h"
 
 #ifdef USE_INTERNAL_EVENTLOOP
-#ifdef USE_EPOLL
-#include <sys/epoll.h>
-#endif
+#include "PollGroup.hxx"
 #endif
 
 #ifdef USE_GLIB_EVENTLOOP
@@ -79,12 +77,10 @@ class SocketMonitor {
 
 public:
 #ifdef USE_INTERNAL_EVENTLOOP
-#ifdef USE_EPOLL
-	static constexpr unsigned READ = EPOLLIN;
-	static constexpr unsigned WRITE = EPOLLOUT;
-	static constexpr unsigned ERROR = EPOLLERR;
-	static constexpr unsigned HANGUP = EPOLLHUP;
-#endif
+	static constexpr unsigned READ = PollGroup::READ;
+	static constexpr unsigned WRITE = PollGroup::WRITE;
+	static constexpr unsigned ERROR = PollGroup::ERROR;
+	static constexpr unsigned HANGUP = PollGroup::HANGUP;
 #endif
 
 #ifdef USE_GLIB_EVENTLOOP