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+/*
+ * Copyright (C) 2003-2014 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_PERIOD_CLOCK_HXX
+#define MPD_PERIOD_CLOCK_HXX
+
+#include "Clock.hxx"
+
+/**
+ * This is a stopwatch which saves the timestamp of an event, and can
+ * check whether a specified time span has passed since then.
+ */
+class PeriodClock {
+protected:
+ typedef unsigned Stamp;
+
+private:
+ Stamp last;
+
+public:
+ /**
+ * Initializes the object, setting the last time stamp to "0",
+ * i.e. a Check() will always succeed. If you do not want this
+ * default behaviour, call Update() immediately after creating the
+ * object.
+ */
+ constexpr
+ PeriodClock():last(0) {}
+
+protected:
+ static Stamp GetNow() {
+ return MonotonicClockMS();
+ }
+
+ constexpr int Elapsed(Stamp now) const {
+ return last == 0
+ ? -1
+ : now - last;
+ }
+
+ constexpr bool Check(Stamp now, unsigned duration) const {
+ return now >= last + duration;
+ }
+
+ void Update(Stamp now) {
+ last = now;
+ }
+
+public:
+ bool IsDefined() const {
+ return last != 0;
+ }
+
+ /**
+ * Resets the clock.
+ */
+ void Reset() {
+ last = 0;
+ }
+
+ /**
+ * Returns the number of milliseconds elapsed since the last
+ * update(). Returns -1 if update() was never called.
+ */
+ int Elapsed() const {
+ return Elapsed(GetNow());
+ }
+
+ /**
+ * Combines a call to Elapsed() and Update().
+ */
+ int ElapsedUpdate() {
+ const auto now = GetNow();
+ int result = Elapsed(now);
+ Update(now);
+ return result;
+ }
+
+ /**
+ * Checks whether the specified duration has passed since the last
+ * update.
+ *
+ * @param duration the duration in milliseconds
+ */
+ bool Check(unsigned duration) const {
+ return Check(GetNow(), duration);
+ }
+
+ /**
+ * Updates the time stamp, setting it to the current clock.
+ */
+ void Update() {
+ Update(GetNow());
+ }
+
+ /**
+ * Updates the time stamp, setting it to the current clock plus the
+ * specified offset.
+ */
+ void UpdateWithOffset(int offset) {
+ Update(GetNow() + offset);
+ }
+
+ /**
+ * Checks whether the specified duration has passed since the last
+ * update. If yes, it updates the time stamp.
+ *
+ * @param duration the duration in milliseconds
+ */
+ bool CheckUpdate(unsigned duration) {
+ Stamp now = GetNow();
+ if (Check(now, duration)) {
+ Update(now);
+ return true;
+ } else
+ return false;
+ }
+
+ /**
+ * Checks whether the specified duration has passed since the last
+ * update. After that, it updates the time stamp.
+ *
+ * @param duration the duration in milliseconds
+ */
+ bool CheckAlwaysUpdate(unsigned duration) {
+ Stamp now = GetNow();
+ bool ret = Check(now, duration);
+ Update(now);
+ return ret;
+ }
+};
+
+#endif