1 files changed, 149 insertions, 0 deletions
diff --git a/src/system/PeriodClock.hxx b/src/system/PeriodClock.hxx
new file mode 100644
index 000000000..1ba74ece2
--- /dev/null
+++ b/src/system/PeriodClock.hxx
@@ -0,0 +1,149 @@
+/*
+ * 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