Time.java

package backtype.storm.utils;

import java.util.concurrent.atomic.AtomicLong;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.log4j.Logger;


public class Time {
    public static Logger LOG = Logger.getLogger(Time.class);    
    
    private static AtomicBoolean simulating = new AtomicBoolean(false);
    //TODO: should probably use weak references here or something
    private static Map<Thread, AtomicLong> threadSleepTimes;
    private static final Object sleepTimesLock = new Object();
    
    private static AtomicLong simulatedCurrTimeMs; //should this be a thread local that's allowed to keep advancing?
    
    public static void startSimulating() {
        simulating.set(true);
        simulatedCurrTimeMs = new AtomicLong(0);
        threadSleepTimes = new ConcurrentHashMap<Thread, AtomicLong>();
    }
    
    public static void stopSimulating() {
        simulating.set(false);             
        threadSleepTimes = null;  
    }
    
    public static boolean isSimulating() {
        return simulating.get();
    }
    
    public static void sleepUntil(long targetTimeMs) throws InterruptedException {
        if(simulating.get()) {
            try {
                synchronized(sleepTimesLock) {
                    threadSleepTimes.put(Thread.currentThread(), new AtomicLong(targetTimeMs));
                }
                while(simulatedCurrTimeMs.get() < targetTimeMs) {
                    Thread.sleep(10);
                }
            } finally {
                synchronized(sleepTimesLock) {
                    threadSleepTimes.remove(Thread.currentThread());
                }
            }
        } else {
            long sleepTime = targetTimeMs-currentTimeMillis();
            if(sleepTime>0) 
                Thread.sleep(sleepTime);
        }
    }
    
    public static void sleep(long ms) throws InterruptedException {
        sleepUntil(currentTimeMillis()+ms);
    }
    
    public static long currentTimeMillis() {
        if(simulating.get()) {
            return simulatedCurrTimeMs.get();
        } else {
            return System.currentTimeMillis();
        }
    }
    
    public static void advanceTime(long ms) {
        if(!simulating.get()) throw new IllegalStateException("Cannot simulate time unless in simulation mode");
        simulatedCurrTimeMs.set(simulatedCurrTimeMs.get() + ms);
    }
    
    public static boolean isThreadWaiting(Thread t) {
        if(!simulating.get()) throw new IllegalStateException("Must be in simulation mode");
        AtomicLong time;
        synchronized(sleepTimesLock) {
            time = threadSleepTimes.get(t);
        }
        return !t.isAlive() || time!=null && currentTimeMillis() < time.longValue();
    }    
}