event/{Coarse,Fine,Far}TimerEvent: aliases for TimerEvent

Preparing for a variant of TimerEvent with coarse 1-second
granularity, but cheaper (with a timer wheel).

src/event/Chrono.hxx

@@ -25,7 +25,7 @@
 namespace Event {
 
 /**
- * The clock used by class #EventLoop and class #TimerEvent.
+ * The clock used by classes #EventLoop, #CoarseTimerEvent and #FineTimerEvent.
  */
 using Clock = std::chrono::steady_clock;
 

src/event/CoarseTimerEvent.hxx

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2007-2021 CM4all GmbH
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "TimerEvent.hxx"
+
+/**
+ * This class invokes a callback function after a certain amount of
+ * time.  Use Schedule() to start the timer or Cancel() to cancel it.
+ *
+ * Unlike #FineTimerEvent, this class has a granularity of about 1
+ * second, and is optimized for timeouts between 1 and 60 seconds
+ * which are often canceled before they expire (i.e. optimized for
+ * fast insertion and deletion, at the cost of granularity).
+ *
+ * This class is not thread-safe, all methods must be called from the
+ * thread that runs the #EventLoop, except where explicitly documented
+ * as thread-safe.
+ */
+using CoarseTimerEvent = TimerEvent;
+// TODO: implement

src/event/FarTimerEvent.hxx

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2007-2021 CM4all GmbH
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "FineTimerEvent.hxx"
+
+/**
+ * A coarse timer event which schedules far into the future.  Use this
+ * when you need a coarse resolution, but the supported time span of
+ * #CoarseTimerEvent is not enough.  For example, a good use case is
+ * timers which fire only every few minutes and do periodic cleanup.
+ *
+ * Right now, this is just an alias for #FineTimerEvent.  This class
+ * supports arbitrary time spans, but uses a high-resolution timer.
+ * Eventually, we may turn this into a timer wheel with minute
+ * resolution.
+ */
+using FarTimerEvent = FineTimerEvent;

src/event/FineTimerEvent.hxx

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2007-2021 CM4all GmbH
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "TimerEvent.hxx"
+
+/**
+ * This class invokes a callback function after a certain amount of
+ * time.  Use Schedule() to start the timer or Cancel() to cancel it.
+ *
+ * Unlike #CoarseTimerEvent, this class uses a high-resolution timer,
+ * but at the cost of more expensive insertion and deletion.
+ *
+ * This class is not thread-safe, all methods must be called from the
+ * thread that runs the #EventLoop, except where explicitly documented
+ * as thread-safe.
+ */
+using FineTimerEvent = TimerEvent;
+// TODO: implement

src/event/MultiSocketMonitor.hxx

@@ -21,7 +21,7 @@
 #define MPD_MULTI_SOCKET_MONITOR_HXX
 
 #include "IdleEvent.hxx"
-#include "TimerEvent.hxx"
+#include "FineTimerEvent.hxx"
 #include "SocketEvent.hxx"
 #include "event/Features.h"
 
@@ -92,7 +92,8 @@ class MultiSocketMonitor
 
 	IdleEvent idle_event;
 
-	TimerEvent timeout_event;
+	// TODO: switch to CoarseTimerEvent?  ... not yet because the ALSA plugin needs exact timeouts
+	FineTimerEvent timeout_event;
 
 	/**
 	 * DispatchSockets() should be called.