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/*
* Copyright 2003-2016 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 <chrono>
/**
* 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 {
public:
typedef std::chrono::steady_clock::duration Duration;
typedef Duration Delta;
typedef std::chrono::steady_clock::time_point 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() {}
protected:
static Stamp GetNow() {
return std::chrono::steady_clock::now();
}
constexpr Delta Elapsed(Stamp now) const {
return last == Stamp()
? Delta(-1)
: Delta(now - last);
}
constexpr bool Check(Stamp now, Duration duration) const {
return now >= last + duration;
}
void Update(Stamp now) {
last = now;
}
public:
constexpr bool IsDefined() const {
return last > Stamp();
}
/**
* Resets the clock.
*/
void Reset() {
last = Stamp();
}
/**
* Returns the time elapsed since the last update(). Returns
* a negative value if update() was never called.
*/
Delta Elapsed() const {
return Elapsed(GetNow());
}
/**
* Combines a call to Elapsed() and Update().
*/
Delta ElapsedUpdate() {
const auto now = GetNow();
const auto result = Elapsed(now);
Update(now);
return result;
}
/**
* Checks whether the specified duration has passed since the last
* update.
*
* @param duration the duration
*/
bool Check(Duration 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(Delta 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(Duration 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(Duration duration) {
Stamp now = GetNow();
bool ret = Check(now, duration);
Update(now);
return ret;
}
};
#endif
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