/**
*
*/
package net.varkhan.base.management.metric;
/**
* <b>.</b>
* <p/>
*
* @author varkhan
* @date Nov 25, 2010
* @time 7:36:03 PM
*/
public class SamplingTimer implements Timer {
private final Time time;
private final long rate;
private volatile long tick;
private volatile long curr;
private volatile long last;
private volatile long start;
private volatile long stop;
public SamplingTimer(Time time, long rate) {
this.time=time;
this.rate=rate;
reset();
}
public void reset() {
last=curr=time.time();
// Stack the happens-before statements in the right order: mark as stopped, then update the start time, then ticks
stop=curr;
start=curr;
tick=0;
}
public void start() {
if(start<=stop) {
last=curr;
curr=time.time();
long delta=curr-stop;
// Stack the happens-before statements in the right order: mark as started, then update the start time, then ticks
// curr >= stop >= start => start + curr - stop >= start => start > stop after update
stop=start-1;
start+=delta;
tick=0;
}
}
public void stop() {
stop=time.time();
}
public long time() {
if(start<stop) return stop-start;
if(++tick>=rate) {
last=curr;
curr=time.time();
tick=0;
return curr-start;
}
return curr-start+(curr-last)*tick/rate;
}
}