event/SocketMonitor: refactor to SocketEvent

Similar to commits 1686f4e857 and
30a5dd267b

src/db/plugins/ProxyDatabasePlugin.cxx

@@ -42,7 +42,7 @@
 #include "util/ScopeExit.hxx"
 #include "util/RuntimeError.hxx"
 #include "protocol/Ack.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "event/IdleEvent.hxx"
 #include "Log.hxx"
 
@@ -85,7 +85,8 @@ public:
 	}
 };
 
-class ProxyDatabase final : public Database, SocketMonitor {
+class ProxyDatabase final : public Database {
+	SocketEvent socket_event;
 	IdleEvent idle_event;
 
 	DatabaseListener &listener;
@@ -149,10 +150,8 @@ private:
 
 	void Disconnect() noexcept;
 
+	void OnSocketReady(unsigned flags) noexcept;
 	void OnIdle() noexcept;
-
-	/* virtual methods from SocketMonitor */
-	bool OnSocketReady(unsigned flags) noexcept override;
 };
 
 static constexpr struct {
@@ -446,7 +445,7 @@ SendGroup(mpd_connection *connection, ConstBuffer<TagType> group)
 ProxyDatabase::ProxyDatabase(EventLoop &_loop, DatabaseListener &_listener,
 			     const ConfigBlock &block)
 	:Database(proxy_db_plugin),
-	 SocketMonitor(_loop),
+	 socket_event(_loop, BIND_THIS_METHOD(OnSocketReady)),
 	 idle_event(_loop, BIND_THIS_METHOD(OnIdle)),
 	 listener(_listener),
 	 host(block.GetBlockValue("host", "")),
@@ -527,7 +526,7 @@ ProxyDatabase::Connect()
 	idle_received = ~0U;
 	is_idle = false;
 
-	SocketMonitor::Open(SocketDescriptor(mpd_async_get_fd(mpd_connection_get_async(connection))));
+	socket_event.Open(SocketDescriptor(mpd_async_get_fd(mpd_connection_get_async(connection))));
 	idle_event.Schedule();
 }
 
@@ -574,13 +573,13 @@ ProxyDatabase::Disconnect() noexcept
 	assert(connection != nullptr);
 
 	idle_event.Cancel();
-	SocketMonitor::Steal();
+	socket_event.Steal();
 
 	mpd_connection_free(connection);
 	connection = nullptr;
 }
 
-bool
+void
 ProxyDatabase::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 {
 	assert(connection != nullptr);
@@ -588,8 +587,8 @@ ProxyDatabase::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 	if (!is_idle) {
 		// TODO: can this happen?
 		idle_event.Schedule();
-		SocketMonitor::Cancel();
+		socket_event.Cancel();
-		return true;
+		return;
 	}
 
 	auto idle = (unsigned)mpd_recv_idle(connection, false);
@@ -599,7 +598,7 @@ ProxyDatabase::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 		} catch (...) {
 			LogError(std::current_exception());
 			Disconnect();
-			return false;
+			return;
 		}
 	}
 
@@ -607,8 +606,7 @@ ProxyDatabase::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 	idle_received |= idle;
 	is_idle = false;
 	idle_event.Schedule();
-	SocketMonitor::Cancel();
+	socket_event.Cancel();
-	return true;
 }
 
 void
@@ -636,14 +634,14 @@ ProxyDatabase::OnIdle() noexcept
 			LogError(std::current_exception());
 		}
 
-		SocketMonitor::Steal();
+		socket_event.Steal();
 		mpd_connection_free(connection);
 		connection = nullptr;
 		return;
 	}
 
 	is_idle = true;
-	SocketMonitor::ScheduleRead();
+	socket_event.ScheduleRead();
 }
 
 const LightSong *

src/db/update/InotifySource.cxx

@@ -30,14 +30,14 @@
 
 #include <sys/inotify.h>
 
-bool
+void
 InotifySource::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 {
 	uint8_t buffer[4096];
 	static_assert(sizeof(buffer) >= sizeof(struct inotify_event) + NAME_MAX + 1,
 		      "inotify buffer too small");
 
-	auto ifd = GetSocket().ToFileDescriptor();
+	auto ifd = socket_event.GetSocket().ToFileDescriptor();
 	ssize_t nbytes = ifd.Read(buffer, sizeof(buffer));
 	if (nbytes < 0)
 		FatalSystemError("Failed to read from inotify");
@@ -63,8 +63,6 @@ InotifySource::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 		callback(event->wd, event->mask, name, callback_ctx);
 		p += sizeof(*event) + event->len;
 	}
-
-	return true;
 }
 
 static FileDescriptor
@@ -79,17 +77,17 @@ InotifyInit()
 
 InotifySource::InotifySource(EventLoop &_loop,
 			     mpd_inotify_callback_t _callback, void *_ctx)
-	:SocketMonitor(SocketDescriptor::FromFileDescriptor(InotifyInit()),
+	:socket_event(_loop, BIND_THIS_METHOD(OnSocketReady),
-		       _loop),
+		      SocketDescriptor::FromFileDescriptor(InotifyInit())),
 	 callback(_callback), callback_ctx(_ctx)
 {
-	ScheduleRead();
+	socket_event.ScheduleRead();
 }
 
 int
 InotifySource::Add(const char *path_fs, unsigned mask)
 {
-	auto ifd = GetSocket().ToFileDescriptor();
+	auto ifd = socket_event.GetSocket().ToFileDescriptor();
 	int wd = inotify_add_watch(ifd.Get(), path_fs, mask);
 	if (wd < 0)
 		throw MakeErrno("inotify_add_watch() has failed");
@@ -100,7 +98,7 @@ InotifySource::Add(const char *path_fs, unsigned mask)
 void
 InotifySource::Remove(unsigned wd) noexcept
 {
-	auto ifd = GetSocket().ToFileDescriptor();
+	auto ifd = socket_event.GetSocket().ToFileDescriptor();
 	int ret = inotify_rm_watch(ifd.Get(), wd);
 	if (ret < 0 && errno != EINVAL)
 		LogErrno(inotify_domain, "inotify_rm_watch() has failed");

src/db/update/InotifySource.hxx

@@ -20,12 +20,14 @@
 #ifndef MPD_INOTIFY_SOURCE_HXX
 #define MPD_INOTIFY_SOURCE_HXX
 
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 
 typedef void (*mpd_inotify_callback_t)(int wd, unsigned mask,
 				       const char *name, void *ctx);
 
-class InotifySource final : private SocketMonitor {
+class InotifySource final {
+	SocketEvent socket_event;
+
 	mpd_inotify_callback_t callback;
 	void *callback_ctx;
 
@@ -43,7 +45,7 @@ public:
 		      mpd_inotify_callback_t callback, void *ctx);
 
 	~InotifySource() noexcept {
-		Close();
+		socket_event.Close();
 	}
 
 	/**
@@ -63,7 +65,7 @@ public:
 	void Remove(unsigned wd) noexcept;
 
 private:
-	bool OnSocketReady(unsigned flags) noexcept override;
+	void OnSocketReady(unsigned flags) noexcept;
 };
 
 #endif

src/event/BufferedSocket.cxx

@@ -69,7 +69,7 @@ BufferedSocket::ResumeInput() noexcept
 	while (true) {
 		const auto buffer = input.Read();
 		if (buffer.empty()) {
-			ScheduleRead();
+			event.ScheduleRead();
 			return true;
 		}
 
@@ -81,11 +81,11 @@ BufferedSocket::ResumeInput() noexcept
 				return false;
 			}
 
-			ScheduleRead();
+			event.ScheduleRead();
 			return true;
 
 		case InputResult::PAUSE:
-			CancelRead();
+			event.CancelRead();
 			return true;
 
 		case InputResult::AGAIN:
@@ -97,25 +97,23 @@ BufferedSocket::ResumeInput() noexcept
 	}
 }
 
-bool
+void
 BufferedSocket::OnSocketReady(unsigned flags) noexcept
 {
 	assert(IsDefined());
 
-	if (gcc_unlikely(flags & (ERROR|HANGUP))) {
+	if (gcc_unlikely(flags & (SocketEvent::ERROR|SocketEvent::HANGUP))) {
 		OnSocketClosed();
-		return false;
+		return;
 	}
 
-	if (flags & READ) {
+	if (flags & SocketEvent::READ) {
 		assert(!input.IsFull());
 
 		if (!ReadToBuffer() || !ResumeInput())
-			return false;
+			return;
 
 		if (!input.IsFull())
-			ScheduleRead();
+			event.ScheduleRead();
 	}
-
-	return true;
 }

src/event/BufferedSocket.hxx

@@ -20,7 +20,7 @@
 #ifndef MPD_BUFFERED_SOCKET_HXX
 #define MPD_BUFFERED_SOCKET_HXX
 
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "util/StaticFifoBuffer.hxx"
 
 #include <cassert>
@@ -30,20 +30,37 @@
 class EventLoop;
 
 /**
- * A #SocketMonitor specialization that adds an input buffer.
+ * A #SocketEvent specialization that adds an input buffer.
  */
-class BufferedSocket : protected SocketMonitor {
+class BufferedSocket {
 	StaticFifoBuffer<uint8_t, 8192> input;
 
+protected:
+	SocketEvent event;
+
 public:
+	using ssize_t = SocketEvent::ssize_t;
+
 	BufferedSocket(SocketDescriptor _fd, EventLoop &_loop) noexcept
-		:SocketMonitor(_fd, _loop) {
+		:event(_loop, BIND_THIS_METHOD(OnSocketReady), _fd) {
-		ScheduleRead();
+		event.ScheduleRead();
 	}
 
-	using SocketMonitor::GetEventLoop;
+	auto &GetEventLoop() const noexcept {
-	using SocketMonitor::IsDefined;
+		return event.GetEventLoop();
-	using SocketMonitor::Close;
+	}
+
+	bool IsDefined() const noexcept {
+		return event.IsDefined();
+	}
+
+	auto GetSocket() const noexcept {
+		return event.GetSocket();
+	}
+
+	void Close() noexcept {
+		event.Close();
+	}
 
 private:
 	/**
@@ -116,8 +133,7 @@ protected:
 	virtual void OnSocketError(std::exception_ptr ep) noexcept = 0;
 	virtual void OnSocketClosed() noexcept = 0;
 
-	/* virtual methods from class SocketMonitor */
+	virtual void OnSocketReady(unsigned flags) noexcept;
-	bool OnSocketReady(unsigned flags) noexcept override;
 };
 
 #endif

src/event/FullyBufferedSocket.cxx

@@ -35,7 +35,7 @@ FullyBufferedSocket::DirectWrite(const void *data, size_t length) noexcept
 			return 0;
 
 		idle_event.Cancel();
-		BufferedSocket::Cancel();
+		event.Cancel();
 
 		if (IsSocketErrorClosed(code))
 			OnSocketClosed();
@@ -54,7 +54,7 @@ FullyBufferedSocket::Flush() noexcept
 	const auto data = output.Read();
 	if (data.empty()) {
 		idle_event.Cancel();
-		CancelWrite();
+		event.CancelWrite();
 		return true;
 	}
 
@@ -66,7 +66,7 @@ FullyBufferedSocket::Flush() noexcept
 
 	if (output.empty()) {
 		idle_event.Cancel();
-		CancelWrite();
+		event.CancelWrite();
 	}
 
 	return true;
@@ -92,23 +92,23 @@ FullyBufferedSocket::Write(const void *data, size_t length) noexcept
 	return true;
 }
 
-bool
+void
 FullyBufferedSocket::OnSocketReady(unsigned flags) noexcept
 {
-	if (flags & WRITE) {
+	if (flags & SocketEvent::WRITE) {
 		assert(!output.empty());
 		assert(!idle_event.IsActive());
 
 		if (!Flush())
-			return false;
+			return;
 	}
 
-	return BufferedSocket::OnSocketReady(flags);
+	BufferedSocket::OnSocketReady(flags);
 }
 
 void
 FullyBufferedSocket::OnIdle() noexcept
 {
 	if (Flush() && !output.empty())
-		ScheduleWrite();
+		event.ScheduleWrite();
 }

src/event/FullyBufferedSocket.hxx

@@ -69,10 +69,10 @@ protected:
 	 */
 	bool Write(const void *data, size_t length) noexcept;
 
-	/* virtual methods from class SocketMonitor */
-	bool OnSocketReady(unsigned flags) noexcept override;
-
 	void OnIdle() noexcept;
+
+	/* virtual methods from class BufferedSocket */
+	void OnSocketReady(unsigned flags) noexcept override;
 };
 
 #endif

src/event/Loop.cxx

@@ -19,7 +19,7 @@
 
 #include "Loop.hxx"
 #include "TimerEvent.hxx"
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "IdleEvent.hxx"
 #include "util/ScopeExit.hxx"
 
@@ -47,7 +47,7 @@ EventLoop::EventLoop(
 		     )
 	:
 #ifdef HAVE_THREADED_EVENT_LOOP
-	SocketMonitor(*this),
+	wake_event(*this, BIND_THIS_METHOD(OnSocketReady)),
 	 thread(_thread),
 	 /* if this instance is hosted by an EventThread (no ThreadId
 	    known yet) then we're not yet alive until the thread is
@@ -59,7 +59,7 @@ EventLoop::EventLoop(
 	 quit(false)
 {
 #ifdef HAVE_THREADED_EVENT_LOOP
-	SocketMonitor::Open(SocketDescriptor(wake_fd.Get()));
+	wake_event.Open(SocketDescriptor(wake_fd.Get()));
 #endif
 }
 
@@ -198,7 +198,7 @@ EventLoop::Run() noexcept
 	assert(alive);
 	assert(busy);
 
-	SocketMonitor::Schedule(SocketMonitor::READ);
+	wake_event.Schedule(SocketEvent::READ);
 #endif
 
 #ifdef HAVE_URING
@@ -214,7 +214,7 @@ EventLoop::Run() noexcept
 
 #ifdef HAVE_THREADED_EVENT_LOOP
 	AtScopeExit(this) {
-		SocketMonitor::Cancel();
+		wake_event.Cancel();
 	};
 #endif
 
@@ -262,9 +262,9 @@ EventLoop::Run() noexcept
 
 		ready_sockets.clear();
 		for (size_t i = 0; i < poll_result.GetSize(); ++i) {
-			auto &sm = *(SocketMonitor *)poll_result.GetObject(i);
+			auto &s = *(SocketEvent *)poll_result.GetObject(i);
-			sm.SetReadyFlags(poll_result.GetEvents(i));
+			s.SetReadyFlags(poll_result.GetEvents(i));
-			ready_sockets.push_back(sm);
+			ready_sockets.push_back(s);
 		}
 
 		now = std::chrono::steady_clock::now();
@@ -339,7 +339,7 @@ EventLoop::HandleDeferred() noexcept
 	}
 }
 
-bool
+void
 EventLoop::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 {
 	assert(IsInside());
@@ -348,8 +348,6 @@ EventLoop::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 
 	const std::lock_guard<Mutex> lock(mutex);
 	HandleDeferred();
-
-	return true;
 }
 
 #endif

src/event/Loop.hxx

@@ -22,7 +22,7 @@
 
 #include "Chrono.hxx"
 #include "PollGroup.hxx"
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "event/Features.h"
 #include "util/Compiler.h"
 
@@ -56,15 +56,13 @@ class DeferEvent;
  * thread that runs it, except where explicitly documented as
  * thread-safe.
  *
- * @see SocketMonitor, MultiSocketMonitor, TimerEvent, IdleEvent
+ * @see SocketEvent, MultiSocketMonitor, TimerEvent, IdleEvent
  */
 class EventLoop final
-#ifdef HAVE_THREADED_EVENT_LOOP
-	: SocketMonitor
-#endif
 {
 #ifdef HAVE_THREADED_EVENT_LOOP
 	WakeFD wake_fd;
+	SocketEvent wake_event;
 #endif
 
 	struct TimerCompare {
@@ -96,14 +94,14 @@ class EventLoop final
 #endif
 
 	using ReadySocketList =
-		boost::intrusive::list<SocketMonitor,
+		boost::intrusive::list<SocketEvent,
-				       boost::intrusive::member_hook<SocketMonitor,
+				       boost::intrusive::member_hook<SocketEvent,
-								     SocketMonitor::ReadyListHook,
+								     SocketEvent::ReadyListHook,
-								     &SocketMonitor::ready_siblings>,
+								     &SocketEvent::ready_siblings>,
 				       boost::intrusive::constant_time_size<false>>;
 
 	/**
-	 * A linked list of #SocketMonitor instances which have a
+	 * A linked list of #SocketEvent instances which have a
 	 * non-zero "ready_flags" field, and need to be dispatched.
 	 */
 	ReadySocketList ready_sockets;
@@ -190,7 +188,7 @@ public:
 	 */
 	void Break() noexcept;
 
-	bool AddFD(int _fd, unsigned flags, SocketMonitor &m) noexcept {
+	bool AddFD(int _fd, unsigned flags, SocketEvent &m) noexcept {
 #ifdef HAVE_THREADED_EVENT_LOOP
 		assert(!IsAlive() || IsInside());
 #endif
@@ -198,7 +196,7 @@ public:
 		return poll_group.Add(_fd, flags, &m);
 	}
 
-	bool ModifyFD(int _fd, unsigned flags, SocketMonitor &m) noexcept {
+	bool ModifyFD(int _fd, unsigned flags, SocketEvent &m) noexcept {
 #ifdef HAVE_THREADED_EVENT_LOOP
 		assert(!IsAlive() || IsInside());
 #endif
@@ -207,7 +205,7 @@ public:
 	}
 
 	/**
-	 * Remove the given #SocketMonitor after the file descriptor
+	 * Remove the given #SocketEvent after the file descriptor
 	 * has been closed.  This is like RemoveFD(), but does not
 	 * attempt to use #EPOLL_CTL_DEL.
 	 */
@@ -261,7 +259,7 @@ private:
 	Event::Duration HandleTimers() noexcept;
 
 #ifdef HAVE_THREADED_EVENT_LOOP
-	bool OnSocketReady(unsigned flags) noexcept override;
+	void OnSocketReady(unsigned flags) noexcept;
 #endif
 
 public:

src/event/MultiSocketMonitor.hxx

@@ -22,7 +22,7 @@
 
 #include "IdleEvent.hxx"
 #include "TimerEvent.hxx"
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "event/Features.h"
 
 #include <cassert>
@@ -36,35 +36,43 @@ struct pollfd;
 class EventLoop;
 
 /**
- * Similar to #SocketMonitor, but monitors multiple sockets.  To use
+ * Similar to #SocketEvent, 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
 {
-	class SingleFD final : public SocketMonitor {
+	class SingleFD final {
 		MultiSocketMonitor &multi;
 
+		SocketEvent event;
+
 		unsigned revents;
 
 	public:
 		SingleFD(MultiSocketMonitor &_multi,
 			 SocketDescriptor _fd) noexcept
-			:SocketMonitor(_fd, _multi.GetEventLoop()),
+			:multi(_multi),
-			multi(_multi), revents(0) {}
+			 event(multi.GetEventLoop(),
+			       BIND_THIS_METHOD(OnSocketReady), _fd),
+			 revents(0) {}
 
 		SocketDescriptor GetSocket() const noexcept {
-			return SocketMonitor::GetSocket();
+			return event.GetSocket();
 		}
 
 		unsigned GetEvents() const noexcept {
-			return SocketMonitor::GetScheduledFlags();
+			return event.GetScheduledFlags();
 		}
 
 		void SetEvents(unsigned _events) noexcept {
 			revents &= _events;
-			SocketMonitor::Schedule(_events);
+			event.Schedule(_events);
+		}
+
+		bool Schedule(unsigned events) noexcept {
+			return event.Schedule(events);
 		}
 
 		unsigned GetReturnedEvents() const noexcept {
@@ -75,11 +83,10 @@ class MultiSocketMonitor
 			revents = 0;
 		}
 
-	protected:
+	private:
-		bool OnSocketReady(unsigned flags) noexcept override {
+		void OnSocketReady(unsigned flags) noexcept {
 			revents = flags;
 			multi.SetReady();
-			return true;
 		}
 	};
 
@@ -119,11 +126,6 @@ class MultiSocketMonitor
 #endif
 
 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;
 
 	EventLoop &GetEventLoop() const noexcept {

src/event/ServerSocket.cxx

@@ -29,7 +29,7 @@
 #include "net/Resolver.hxx"
 #include "net/AddressInfo.hxx"
 #include "net/ToString.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/Domain.hxx"
@@ -43,9 +43,11 @@
 #include <sys/stat.h>
 #endif
 
-class ServerSocket::OneServerSocket final : private SocketMonitor {
+class ServerSocket::OneServerSocket final {
 	ServerSocket &parent;
 
+	SocketEvent event;
+
 	const unsigned serial;
 
 #ifdef HAVE_UN
@@ -59,8 +61,9 @@ public:
 	OneServerSocket(EventLoop &_loop, ServerSocket &_parent,
 			unsigned _serial,
 			A &&_address) noexcept
-		:SocketMonitor(_loop),
+		:parent(_parent),
-		 parent(_parent), serial(_serial),
+		 event(_loop, BIND_THIS_METHOD(OnSocketReady)),
+		 serial(_serial),
 #ifdef HAVE_UN
 		 path(nullptr),
 #endif
@@ -88,10 +91,15 @@ public:
 	}
 #endif
 
+	bool IsDefined() const noexcept {
+		return event.IsDefined();
+	}
+
 	void Open();
 
-	using SocketMonitor::IsDefined;
+	void Close() noexcept {
-	using SocketMonitor::Close;
+		event.Close();
+	}
 
 	[[nodiscard]] gcc_pure
 	std::string ToString() const noexcept {
@@ -99,14 +107,14 @@ public:
 	}
 
 	void SetFD(UniqueSocketDescriptor _fd) noexcept {
-		SocketMonitor::Open(_fd.Release());
+		event.Open(_fd.Release());
-		SocketMonitor::ScheduleRead();
+		event.ScheduleRead();
 	}
 
 	void Accept() noexcept;
 
 private:
-	bool OnSocketReady(unsigned flags) noexcept override;
+	void OnSocketReady(unsigned flags) noexcept;
 };
 
 static constexpr Domain server_socket_domain("server_socket");
@@ -140,7 +148,7 @@ inline void
 ServerSocket::OneServerSocket::Accept() noexcept
 {
 	StaticSocketAddress peer_address;
-	UniqueSocketDescriptor peer_fd(GetSocket().AcceptNonBlock(peer_address));
+	UniqueSocketDescriptor peer_fd(event.GetSocket().AcceptNonBlock(peer_address));
 	if (!peer_fd.IsDefined()) {
 		const SocketErrorMessage msg;
 		FormatError(server_socket_domain,
@@ -160,11 +168,10 @@ ServerSocket::OneServerSocket::Accept() noexcept
 	parent.OnAccept(std::move(peer_fd), peer_address, uid);
 }
 
-bool
+void
 ServerSocket::OneServerSocket::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
 {
 	Accept();
-	return true;
 }
 
 inline void

src/event/SignalMonitor.cxx

@@ -22,7 +22,7 @@
 
 #ifndef _WIN32
 
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "util/Manual.hxx"
 #include "system/Error.hxx"
 
@@ -44,33 +44,37 @@
 #include <pthread.h>
 #endif
 
-class SignalMonitor final : private SocketMonitor {
+class SignalMonitor final {
 #ifdef USE_SIGNALFD
 	SignalFD fd;
 #else
 	WakeFD fd;
 #endif
 
+	SocketEvent event;
+
 public:
 	explicit SignalMonitor(EventLoop &_loop)
-		:SocketMonitor(_loop) {
+		:event(_loop, BIND_THIS_METHOD(OnSocketReady)) {
 #ifndef USE_SIGNALFD
-		SocketMonitor::Open(SocketDescriptor(fd.Get()));
+		event.Open(SocketDescriptor(fd.Get()));
-		SocketMonitor::ScheduleRead();
+		event.ScheduleRead();
 #endif
 	}
 
-	using SocketMonitor::GetEventLoop;
+	auto &GetEventLoop() const noexcept {
+		return event.GetEventLoop();
+	}
 
 #ifdef USE_SIGNALFD
 	void Update(sigset_t &mask) noexcept {
-		const bool was_open = SocketMonitor::IsDefined();
+		const bool was_open = event.IsDefined();
 
 		fd.Create(mask);
 
 		if (!was_open) {
-			SocketMonitor::Open(SocketDescriptor(fd.Get()));
+			event.Open(SocketDescriptor(fd.Get()));
-			SocketMonitor::ScheduleRead();
+			event.ScheduleRead();
 		}
 	}
 #else
@@ -80,7 +84,7 @@ public:
 #endif
 
 private:
-	bool OnSocketReady(unsigned flags) noexcept override;
+	void OnSocketReady(unsigned flags) noexcept;
 };
 
 /* this should be enough - is it? */
@@ -195,7 +199,7 @@ SignalMonitorRegister(int signo, SignalHandler handler)
 #endif
 }
 
-bool
+void
 SignalMonitor::OnSocketReady(unsigned) noexcept
 {
 #ifdef USE_SIGNALFD
@@ -213,8 +217,6 @@ SignalMonitor::OnSocketReady(unsigned) noexcept
 		if (signal_pending[i].exchange(false))
 			signal_handlers[i]();
 #endif
-
-	return true;
 }
 
 #endif

src/event/SocketEvent.cxx

@@ -17,7 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "Loop.hxx"
 #include "event/Features.h"
 
@@ -29,23 +29,23 @@
 #endif
 
 void
-SocketMonitor::Dispatch() noexcept
+SocketEvent::Dispatch() noexcept
 {
 	const unsigned flags = std::exchange(ready_flags, 0) &
 		(GetScheduledFlags() | IMPLICIT_FLAGS);
 
 	if (flags != 0)
-		OnSocketReady(flags);
+		callback(flags);
 }
 
-SocketMonitor::~SocketMonitor() noexcept
+SocketEvent::~SocketEvent() noexcept
 {
 	if (IsDefined())
 		Cancel();
 }
 
 void
-SocketMonitor::Open(SocketDescriptor _fd) noexcept
+SocketEvent::Open(SocketDescriptor _fd) noexcept
 {
 	assert(!fd.IsDefined());
 	assert(_fd.IsDefined());
@@ -54,7 +54,7 @@ SocketMonitor::Open(SocketDescriptor _fd) noexcept
 }
 
 SocketDescriptor
-SocketMonitor::Steal() noexcept
+SocketEvent::Steal() noexcept
 {
 	assert(IsDefined());
 
@@ -64,13 +64,13 @@ SocketMonitor::Steal() noexcept
 }
 
 void
-SocketMonitor::Close() noexcept
+SocketEvent::Close() noexcept
 {
 	Steal().Close();
 }
 
 bool
-SocketMonitor::Schedule(unsigned flags) noexcept
+SocketEvent::Schedule(unsigned flags) noexcept
 {
 	assert(IsDefined());
 

src/event/SocketEvent.hxx

@@ -17,11 +17,12 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef MPD_SOCKET_MONITOR_HXX
+#ifndef MPD_SOCKET_EVENT_HXX
-#define MPD_SOCKET_MONITOR_HXX
+#define MPD_SOCKET_EVENT_HXX
 
 #include "PollGroup.hxx"
 #include "net/SocketDescriptor.hxx"
+#include "util/BindMethod.hxx"
 
 #include <boost/intrusive/list_hook.hpp>
 
@@ -34,8 +35,8 @@ class EventLoop;
 /**
  * Monitor events on a socket.  Call Schedule() to announce events
  * you're interested in, or Cancel() to cancel your subscription.  The
- * #EventLoop will invoke virtual method OnSocketReady() as soon as
+ * #EventLoop will invoke the callback as soon as any of the
- * any of the subscribed events are ready.
+ * subscribed events are ready.
  *
  * This class does not feel responsible for closing the socket.  Call
  * Close() to do it manually.
@@ -44,14 +45,18 @@ class EventLoop;
  * thread that runs the #EventLoop, except where explicitly documented
  * as thread-safe.
  */
-class SocketMonitor {
+class SocketEvent {
 	friend class EventLoop;
 
+	EventLoop &loop;
+
 	using ReadyListHook = boost::intrusive::list_member_hook<boost::intrusive::link_mode<boost::intrusive::auto_unlink>>;
 	ReadyListHook ready_siblings;
 
+	using Callback = BoundMethod<void(unsigned events) noexcept>;
+	const Callback callback;
+
 	SocketDescriptor fd = SocketDescriptor::Undefined();
-	EventLoop &loop;
 
 	/**
 	 * A bit mask of events that is currently registered in the
@@ -80,13 +85,13 @@ public:
 
 	typedef std::make_signed<size_t>::type ssize_t;
 
-	explicit SocketMonitor(EventLoop &_loop) noexcept
+	SocketEvent(EventLoop &_loop, Callback _callback,
-		:loop(_loop) {}
+		    SocketDescriptor _fd=SocketDescriptor::Undefined()) noexcept
+		:loop(_loop),
+		 callback(_callback),
+		 fd(_fd) {}
 
-	SocketMonitor(SocketDescriptor _fd, EventLoop &_loop) noexcept
+	~SocketEvent() noexcept;
-		:fd(_fd), loop(_loop) {}
-
-	~SocketMonitor() noexcept;
 
 	auto &GetEventLoop() const noexcept {
 		return loop;
@@ -148,12 +153,6 @@ public:
 		Schedule(GetScheduledFlags() & ~WRITE);
 	}
 
-protected:
-	/**
-	 * @return false if the socket has been closed
-	 */
-	virtual bool OnSocketReady(unsigned flags) noexcept = 0;
-
 public:
 	void Dispatch() noexcept;
 };

src/event/UringManager.cxx

@@ -22,15 +22,13 @@
 
 namespace Uring {
 
-bool
+void
 Manager::OnSocketReady(unsigned) noexcept
 {
 	try {
 		DispatchCompletions();
-		return true;
 	} catch (...) {
 		PrintException(std::current_exception());
-		return false;
 	}
 }
 

src/event/UringManager.hxx

@@ -19,23 +19,24 @@
 
 #pragma once
 
-#include "SocketMonitor.hxx"
+#include "SocketEvent.hxx"
 #include "IdleEvent.hxx"
 #include "io/uring/Queue.hxx"
 
 namespace Uring {
 
-class Manager final : public Queue, SocketMonitor {
+class Manager final : public Queue {
+	SocketEvent event;
 	IdleEvent idle_event;
 
 public:
 	explicit Manager(EventLoop &event_loop)
 		:Queue(1024, 0),
-		 SocketMonitor(SocketDescriptor::FromFileDescriptor(GetFileDescriptor()),
+		 event(event_loop, BIND_THIS_METHOD(OnSocketReady),
-			       event_loop),
+		       SocketDescriptor::FromFileDescriptor(GetFileDescriptor())),
 		 idle_event(event_loop, BIND_THIS_METHOD(OnIdle))
 	{
-		SocketMonitor::ScheduleRead();
+		event.ScheduleRead();
 	}
 
 	void Push(struct io_uring_sqe &sqe,
@@ -45,7 +46,7 @@ public:
 	}
 
 private:
-	bool OnSocketReady(unsigned flags) noexcept override;
+	void OnSocketReady(unsigned flags) noexcept;
 	void OnIdle() noexcept;
 };
 

src/event/meson.build

@@ -26,7 +26,7 @@ event = static_library(
   'IdleEvent.cxx',
   'DeferEvent.cxx',
   'MaskMonitor.cxx',
-  'SocketMonitor.cxx',
+  'SocketEvent.cxx',
   'BufferedSocket.cxx',
   'FullyBufferedSocket.cxx',
   'MultiSocketMonitor.cxx',

src/lib/curl/Global.cxx

@@ -31,7 +31,7 @@
 #include "Request.hxx"
 #include "Log.hxx"
 #include "event/Loop.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/Domain.hxx"
 
@@ -42,12 +42,15 @@ static constexpr Domain curlm_domain("curlm");
 /**
  * Monitor for one socket created by CURL.
  */
-class CurlSocket final : SocketMonitor {
+class CurlSocket final {
 	CurlGlobal &global;
 
+	SocketEvent socket_event;
+
 public:
 	CurlSocket(CurlGlobal &_global, EventLoop &_loop, SocketDescriptor _fd)
-		:SocketMonitor(_fd, _loop), global(_global) {}
+		:global(_global),
+		 socket_event(_loop, BIND_THIS_METHOD(OnSocketReady), _fd) {}
 
 	~CurlSocket() noexcept {
 		/* TODO: sometimes, CURL uses CURL_POLL_REMOVE after
@@ -59,6 +62,10 @@ public:
 		   better solution? */
 	}
 
+	auto &GetEventLoop() const noexcept {
+		return socket_event.GetEventLoop();
+	}
+
 	/**
 	 * Callback function for CURLMOPT_SOCKETFUNCTION.
 	 */
@@ -66,13 +73,17 @@ public:
 				  curl_socket_t s, int action,
 				  void *userp, void *socketp) noexcept;
 
-	bool OnSocketReady(unsigned flags) noexcept override;
-
 private:
+	SocketDescriptor GetSocket() const noexcept {
+		return socket_event.GetSocket();
+	}
+
+	void OnSocketReady(unsigned flags) noexcept;
+
 	static constexpr int FlagsToCurlCSelect(unsigned flags) noexcept {
-		return (flags & (READ | HANGUP) ? CURL_CSELECT_IN : 0) |
+		return (flags & (SocketEvent::READ | SocketEvent::HANGUP) ? CURL_CSELECT_IN : 0) |
-			(flags & WRITE ? CURL_CSELECT_OUT : 0) |
+			(flags & SocketEvent::WRITE ? CURL_CSELECT_OUT : 0) |
-			(flags & ERROR ? CURL_CSELECT_ERR : 0);
+			(flags & SocketEvent::ERROR ? CURL_CSELECT_ERR : 0);
 	}
 
 	gcc_const
@@ -82,13 +93,13 @@ private:
 			return 0;
 
 		case CURL_POLL_IN:
-			return READ;
+			return SocketEvent::READ;
 
 		case CURL_POLL_OUT:
-			return WRITE;
+			return SocketEvent::WRITE;
 
 		case CURL_POLL_INOUT:
-			return READ|WRITE;
+			return SocketEvent::READ|SocketEvent::WRITE;
 		}
 
 		assert(false);
@@ -130,17 +141,16 @@ CurlSocket::SocketFunction([[maybe_unused]] CURL *easy,
 
 	unsigned flags = CurlPollToFlags(action);
 	if (flags != 0)
-		cs->Schedule(flags);
+		cs->socket_event.Schedule(flags);
 	return 0;
 }
 
-bool
+void
 CurlSocket::OnSocketReady(unsigned flags) noexcept
 {
 	assert(GetEventLoop().IsInside());
 
 	global.SocketAction(GetSocket().Get(), FlagsToCurlCSelect(flags));
-	return true;
 }
 
 void

src/lib/dbus/Watch.cxx

@@ -1,5 +1,5 @@
 /*
- * Copyright 2007-2018 Content Management AG
+ * Copyright 2007-2020 CM4all GmbH
  * All rights reserved.
  *
  * author: Max Kellermann <mk@cm4all.com>
@@ -36,8 +36,8 @@ namespace ODBus {
 
 WatchManager::Watch::Watch(EventLoop &event_loop,
 			   WatchManager &_parent, DBusWatch &_watch) noexcept
-	:SocketMonitor(event_loop),
+	:parent(_parent), watch(_watch),
-	 parent(_parent), watch(_watch)
+	 event(event_loop, BIND_THIS_METHOD(OnSocketReady))
 {
 	Toggled();
 }
@@ -45,30 +45,30 @@ WatchManager::Watch::Watch(EventLoop &event_loop,
 static constexpr unsigned
 DbusToLibevent(unsigned flags) noexcept
 {
-	return ((flags & DBUS_WATCH_READABLE) != 0) * SocketMonitor::READ |
+	return ((flags & DBUS_WATCH_READABLE) != 0) * SocketEvent::READ |
-		((flags & DBUS_WATCH_WRITABLE) != 0) * SocketMonitor::WRITE;
+		((flags & DBUS_WATCH_WRITABLE) != 0) * SocketEvent::WRITE;
 }
 
 void
 WatchManager::Watch::Toggled() noexcept
 {
-	if (SocketMonitor::IsDefined())
+	if (event.IsDefined())
-		SocketMonitor::Cancel();
+		event.Cancel();
 
 	if (dbus_watch_get_enabled(&watch)) {
-		SocketMonitor::Open(SocketDescriptor(dbus_watch_get_unix_fd(&watch)));
+		event.Open(SocketDescriptor(dbus_watch_get_unix_fd(&watch)));
-		SocketMonitor::Schedule(DbusToLibevent(dbus_watch_get_flags(&watch)));
+		event.Schedule(DbusToLibevent(dbus_watch_get_flags(&watch)));
 	}
 }
 
 static constexpr unsigned
 LibeventToDbus(unsigned flags) noexcept
 {
-	return ((flags & SocketMonitor::READ) != 0) * DBUS_WATCH_READABLE |
+	return ((flags & SocketEvent::READ) != 0) * DBUS_WATCH_READABLE |
-		((flags & SocketMonitor::WRITE) != 0) * DBUS_WATCH_WRITABLE;
+		((flags & SocketEvent::WRITE) != 0) * DBUS_WATCH_WRITABLE;
 }
 
-bool
+void
 WatchManager::Watch::OnSocketReady(unsigned events) noexcept
 {
 	/* copy the "parent" reference to the stack, because the
@@ -79,7 +79,6 @@ WatchManager::Watch::OnSocketReady(unsigned events) noexcept
 	dbus_watch_handle(&watch, LibeventToDbus(events));
 
 	_parent.ScheduleDispatch();
-	return true;
 }
 
 void

src/lib/dbus/Watch.hxx

@@ -1,5 +1,5 @@
 /*
- * Copyright 2007-2018 Content Management AG
+ * Copyright 2007-2020 CM4all GmbH
  * All rights reserved.
  *
  * author: Max Kellermann <mk@cm4all.com>
@@ -34,7 +34,7 @@
 #define ODBUS_WATCH_HXX
 
 #include "Connection.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "event/DeferEvent.hxx"
 
 #include <dbus/dbus.h>
@@ -58,9 +58,10 @@ class WatchManager {
 
 	Connection connection;
 
-	class Watch final : SocketMonitor {
+	class Watch {
 		WatchManager &parent;
 		DBusWatch &watch;
+		SocketEvent event;
 
 	public:
 		Watch(EventLoop &event_loop, WatchManager &_parent,
@@ -69,7 +70,7 @@ class WatchManager {
 		void Toggled() noexcept;
 
 	private:
-		bool OnSocketReady(unsigned flags) noexcept override;
+		void OnSocketReady(unsigned flags) noexcept;
 	};
 
 	std::map<DBusWatch *, Watch> watches;

src/lib/nfs/Connection.cxx

@@ -183,17 +183,17 @@ NfsConnection::CancellableCallback::Callback(int err,
 static constexpr unsigned
 libnfs_to_events(int i) noexcept
 {
-	return ((i & POLLIN) ? SocketMonitor::READ : 0) |
+	return ((i & POLLIN) ? SocketEvent::READ : 0) |
-		((i & POLLOUT) ? SocketMonitor::WRITE : 0);
+		((i & POLLOUT) ? SocketEvent::WRITE : 0);
 }
 
 static constexpr int
 events_to_libnfs(unsigned i) noexcept
 {
-	return ((i & SocketMonitor::READ) ? POLLIN : 0) |
+	return ((i & SocketEvent::READ) ? POLLIN : 0) |
-		((i & SocketMonitor::WRITE) ? POLLOUT : 0) |
+		((i & SocketEvent::WRITE) ? POLLOUT : 0) |
-		((i & SocketMonitor::HANGUP) ? POLLHUP : 0) |
+		((i & SocketEvent::HANGUP) ? POLLHUP : 0) |
-		((i & SocketMonitor::ERROR) ? POLLERR : 0);
+		((i & SocketEvent::ERROR) ? POLLERR : 0);
 }
 
 NfsConnection::~NfsConnection() noexcept
@@ -403,8 +403,8 @@ NfsConnection::DestroyContext() noexcept
 	   new leases */
 	defer_new_lease.Cancel();
 
-	if (SocketMonitor::IsDefined())
+	if (socket_event.IsDefined())
-		SocketMonitor::Steal();
+		socket_event.Steal();
 
 	callbacks.ForEach([](CancellableCallback &c){
 			c.PrepareDestroyContext();
@@ -434,25 +434,25 @@ NfsConnection::ScheduleSocket() noexcept
 
 	const int which_events = nfs_which_events(context);
 
-	if (which_events == POLLOUT && SocketMonitor::IsDefined())
+	if (which_events == POLLOUT && socket_event.IsDefined())
 		/* kludge: if libnfs asks only for POLLOUT, it means
 		   that it is currently waiting for the connect() to
 		   finish - rpc_reconnect_requeue() may have been
 		   called from inside nfs_service(); we must now
 		   unregister the old socket and register the new one
 		   instead */
-		SocketMonitor::Steal();
+		socket_event.Steal();
 
-	if (!SocketMonitor::IsDefined()) {
+	if (!socket_event.IsDefined()) {
 		SocketDescriptor _fd(nfs_get_fd(context));
 		if (!_fd.IsDefined())
 			return;
 
 		_fd.EnableCloseOnExec();
-		SocketMonitor::Open(_fd);
+		socket_event.Open(_fd);
 	}
 
-	SocketMonitor::Schedule(libnfs_to_events(which_events));
+	socket_event.Schedule(libnfs_to_events(which_events));
 }
 
 inline int
@@ -480,16 +480,14 @@ NfsConnection::Service(unsigned flags) noexcept
 	return result;
 }
 
-bool
+void
 NfsConnection::OnSocketReady(unsigned flags) noexcept
 {
 	assert(GetEventLoop().IsInside());
 	assert(deferred_close.empty());
 
-	bool closed = false;
-
 	const bool was_mounted = mount_finished;
-	if (!mount_finished || (flags & SocketMonitor::HANGUP) != 0)
+	if (!mount_finished || (flags & SocketEvent::HANGUP) != 0)
 		/* until the mount is finished, the NFS client may use
 		   various sockets, therefore we unregister and
 		   re-register it each time */
@@ -497,7 +495,7 @@ NfsConnection::OnSocketReady(unsigned flags) noexcept
 		   which is a sure sign that libnfs will close the
 		   socket, which can lead to a race condition if
 		   epoll_ctl() is called later */
-		SocketMonitor::Steal();
+		socket_event.Steal();
 
 	const int result = Service(flags);
 
@@ -509,7 +507,6 @@ NfsConnection::OnSocketReady(unsigned flags) noexcept
 	if (!was_mounted && mount_finished) {
 		if (postponed_mount_error) {
 			DestroyContext();
-			closed = true;
 			BroadcastMountError(std::move(postponed_mount_error));
 		} else if (result == 0)
 			BroadcastMountSuccess();
@@ -521,7 +518,6 @@ NfsConnection::OnSocketReady(unsigned flags) noexcept
 		BroadcastError(std::make_exception_ptr(e));
 
 		DestroyContext();
-		closed = true;
 	} else if (nfs_get_fd(context) < 0) {
 		/* this happens when rpc_reconnect_requeue() is called
 		   after the connection broke, but autoreconnect was
@@ -535,7 +531,6 @@ NfsConnection::OnSocketReady(unsigned flags) noexcept
 		BroadcastError(std::make_exception_ptr(e));
 
 		DestroyContext();
-		closed = true;
 	}
 
 	assert(context == nullptr || nfs_get_fd(context) >= 0);
@@ -547,8 +542,6 @@ NfsConnection::OnSocketReady(unsigned flags) noexcept
 
 	if (context != nullptr)
 		ScheduleSocket();
-
-	return !closed;
 }
 
 inline void

src/lib/nfs/Connection.hxx

@@ -21,7 +21,7 @@
 #define MPD_NFS_CONNECTION_HXX
 
 #include "Cancellable.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "event/TimerEvent.hxx"
 #include "event/DeferEvent.hxx"
 #include "util/Compiler.h"
@@ -40,7 +40,7 @@ class NfsLease;
 /**
  * An asynchronous connection to a NFS server.
  */
-class NfsConnection : SocketMonitor {
+class NfsConnection {
 	class CancellableCallback : public CancellablePointer<NfsCallback> {
 		NfsConnection &connection;
 
@@ -93,6 +93,7 @@ class NfsConnection : SocketMonitor {
 		void Callback(int err, void *data) noexcept;
 	};
 
+	SocketEvent socket_event;
 	DeferEvent defer_new_lease;
 	TimerEvent mount_timeout_event;
 
@@ -141,7 +142,7 @@ public:
 	gcc_nonnull_all
 	NfsConnection(EventLoop &_loop,
 		      const char *_server, const char *_export_name) noexcept
-		:SocketMonitor(_loop),
+		:socket_event(_loop, BIND_THIS_METHOD(OnSocketReady)),
 		 defer_new_lease(_loop, BIND_THIS_METHOD(RunDeferred)),
 		 mount_timeout_event(_loop, BIND_THIS_METHOD(OnMountTimeout)),
 		 server(_server), export_name(_export_name),
@@ -152,6 +153,10 @@ public:
 	 */
 	~NfsConnection() noexcept;
 
+	auto &GetEventLoop() const noexcept {
+		return socket_event.GetEventLoop();
+	}
+
 	gcc_pure
 	const char *GetServer() const noexcept {
 		return server.c_str();
@@ -162,8 +167,6 @@ public:
 		return export_name.c_str();
 	}
 
-	using SocketMonitor::GetEventLoop;
-
 	/**
 	 * Ensure that the connection is established.  The connection
 	 * is kept up while at least one #NfsLease is registered.
@@ -231,8 +234,7 @@ private:
 	 */
 	int Service(unsigned flags) noexcept;
 
-	/* virtual methods from SocketMonitor */
+	void OnSocketReady(unsigned flags) noexcept;
-	bool OnSocketReady(unsigned flags) noexcept override;
 
 	/* callback for #mount_timeout_event */
 	void OnMountTimeout() noexcept;

src/output/plugins/httpd/HttpdClient.cxx

@@ -216,7 +216,7 @@ HttpdClient::CancelQueue() noexcept
 	ClearQueue();
 
 	if (current_page == nullptr)
-		CancelWrite();
+		event.CancelWrite();
 }
 
 ssize_t
@@ -259,7 +259,7 @@ HttpdClient::TryWrite() noexcept
 			/* another thread has removed the event source
 			   while this thread was waiting for
 			   httpd.mutex */
-			CancelWrite();
+			event.CancelWrite();
 			return true;
 		}
 
@@ -354,7 +354,7 @@ HttpdClient::TryWrite() noexcept
 			if (pages.empty())
 				/* all pages are sent: remove the
 				   event source */
-				CancelWrite();
+				event.CancelWrite();
 		}
 	}
 
@@ -377,7 +377,7 @@ HttpdClient::PushPage(PagePtr page) noexcept
 	queue_size += page->GetSize();
 	pages.emplace(std::move(page));
 
-	ScheduleWrite();
+	event.ScheduleWrite();
 }
 
 void
@@ -389,17 +389,14 @@ HttpdClient::PushMetaData(PagePtr page) noexcept
 	metadata_sent = false;
 }
 
-bool
+void
 HttpdClient::OnSocketReady(unsigned flags) noexcept
 {
-	if (!BufferedSocket::OnSocketReady(flags))
+	if (flags & SocketEvent::WRITE)
-		return false;
-
-	if (flags & WRITE)
 		if (!TryWrite())
-			return false;
+			return;
 
-	return true;
+	BufferedSocket::OnSocketReady(flags);
 }
 
 BufferedSocket::InputResult

src/output/plugins/httpd/HttpdClient.hxx

@@ -196,8 +196,8 @@ private:
 	void ClearQueue() noexcept;
 
 protected:
-	/* virtual methods from class SocketMonitor */
+	/* virtual methods from class BufferedSocket */
-	bool OnSocketReady(unsigned flags) noexcept override;
+	void OnSocketReady(unsigned flags) noexcept override;
 
 	InputResult OnSocketInput(void *data, size_t length) noexcept override;
 	void OnSocketError(std::exception_ptr ep) noexcept override;

src/zeroconf/AvahiPoll.cxx

@@ -18,28 +18,29 @@
  */
 
 #include "AvahiPoll.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "event/TimerEvent.hxx"
 #include "time/Convert.hxx"
 
 static unsigned
 FromAvahiWatchEvent(AvahiWatchEvent e)
 {
-	return (e & AVAHI_WATCH_IN ? SocketMonitor::READ : 0) |
+	return (e & AVAHI_WATCH_IN ? SocketEvent::READ : 0) |
-		(e & AVAHI_WATCH_OUT ? SocketMonitor::WRITE : 0);
+		(e & AVAHI_WATCH_OUT ? SocketEvent::WRITE : 0);
 }
 
 static AvahiWatchEvent
 ToAvahiWatchEvent(unsigned e)
 {
-	return AvahiWatchEvent((e & SocketMonitor::READ ? AVAHI_WATCH_IN : 0) |
+	return AvahiWatchEvent((e & SocketEvent::READ ? AVAHI_WATCH_IN : 0) |
-			       (e & SocketMonitor::WRITE ? AVAHI_WATCH_OUT : 0) |
+			       (e & SocketEvent::WRITE ? AVAHI_WATCH_OUT : 0) |
-			       (e & SocketMonitor::ERROR ? AVAHI_WATCH_ERR : 0) |
+			       (e & SocketEvent::ERROR ? AVAHI_WATCH_ERR : 0) |
-			       (e & SocketMonitor::HANGUP ? AVAHI_WATCH_HUP : 0));
+			       (e & SocketEvent::HANGUP ? AVAHI_WATCH_HUP : 0));
 }
 
-struct AvahiWatch final : private SocketMonitor {
+struct AvahiWatch final {
-private:
+	SocketEvent event;
+
 	const AvahiWatchCallback callback;
 	void *const userdata;
 
@@ -49,14 +50,14 @@ public:
 	AvahiWatch(SocketDescriptor _fd, AvahiWatchEvent _event,
 		   AvahiWatchCallback _callback, void *_userdata,
 		   EventLoop &_loop)
-		:SocketMonitor(_fd, _loop),
+		:event(_loop, BIND_THIS_METHOD(OnSocketReady), _fd),
 		 callback(_callback), userdata(_userdata),
 		 received(AvahiWatchEvent(0)) {
-		Schedule(FromAvahiWatchEvent(_event));
+		event.Schedule(FromAvahiWatchEvent(_event));
 	}
 
 	static void WatchUpdate(AvahiWatch *w, AvahiWatchEvent event) {
-		w->Schedule(FromAvahiWatchEvent(event));
+		w->event.Schedule(FromAvahiWatchEvent(event));
 	}
 
 	static AvahiWatchEvent WatchGetEvents(AvahiWatch *w) {
@@ -68,12 +69,10 @@ public:
 	}
 
 private:
-	/* virtual methods from class SocketMonitor */
+	void OnSocketReady(unsigned flags) noexcept {
-	bool OnSocketReady(unsigned flags) noexcept override {
 		received = ToAvahiWatchEvent(flags);
-		callback(this, GetSocket().Get(), received, userdata);
+		callback(this, event.GetSocket().Get(), received, userdata);
 		received = AvahiWatchEvent(0);
-		return true;
 	}
 };
 

src/zeroconf/ZeroconfBonjour.cxx

@@ -20,7 +20,7 @@
 #include "ZeroconfBonjour.hxx"
 #include "ZeroconfInternal.hxx"
 #include "Listen.hxx"
-#include "event/SocketMonitor.hxx"
+#include "event/SocketEvent.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
 #include "util/Compiler.h"
@@ -31,15 +31,19 @@
 
 static constexpr Domain bonjour_domain("bonjour");
 
-class BonjourMonitor final : public SocketMonitor {
+class BonjourMonitor final {
 	DNSServiceRef service_ref;
 
+	SocketEvent socket_event;
+
 public:
 	BonjourMonitor(EventLoop &_loop, DNSServiceRef _service_ref)
-		:SocketMonitor(SocketDescriptor(DNSServiceRefSockFD(_service_ref)),
+		:service_ref(_service_ref),
-			       _loop),
+		 socket_event(SocketDescriptor(DNSServiceRefSockFD(service_ref)),
-		 service_ref(_service_ref) {
+			      BIND_THIS_METHOD(OnSocketReady),
-		ScheduleRead();
+			      _loop)
+	{
+		socket_event.ScheduleRead();
 	}
 
 	~BonjourMonitor() {
@@ -48,9 +52,8 @@ public:
 
 protected:
 	/* virtual methods from class SocketMonitor */
-	bool OnSocketReady([[maybe_unused]] unsigned flags) noexcept override {
+	void OnSocketReady([[maybe_unused]] unsigned flags) noexcept override {
 		DNSServiceProcessResult(service_ref);
-		return true;
 	}
 };