event/SocketEvent: add ScheduleImplicit(), Is{Read,Write}Pending()

src/event/SocketEvent.cxx

@@ -95,6 +95,16 @@ SocketEvent::Schedule(unsigned flags) noexcept
 }
 
 void
+SocketEvent::ScheduleImplicit() noexcept
+{
+	assert(IsDefined());
+	assert(scheduled_flags == 0);
+
+	scheduled_flags = IMPLICIT_FLAGS;
+	loop.AddFD(fd.Get(), scheduled_flags, *this);
+}
+
+void
 SocketEvent::Dispatch() noexcept
 {
 	const unsigned flags = std::exchange(ready_flags, 0) &

src/event/SocketEvent.hxx

@@ -167,6 +167,21 @@ public:
 		Schedule(GetScheduledFlags() & ~WRITE);
 	}
 
+	/**
+	 * Schedule only the #IMPLICIT_FLAGS without #READ and #WRITE.
+	 * This is not possible with Schedule(), and no other
+	 * ScheduleX()/CancelX() method may be called on this object.
+	 */
+	void ScheduleImplicit() noexcept;
+
+	bool IsReadPending() const noexcept {
+		return GetScheduledFlags() & READ;
+	}
+
+	bool IsWritePending() const noexcept {
+		return GetScheduledFlags() & WRITE;
+	}
+
 public:
 	void Dispatch() noexcept;
 };