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OLamportLock.java
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OLamportLock.java
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package lab2try1;
import java.util.*;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
public class OLamportLock implements ImprovedBakeryLock{
private final Integer threads = 10;
private final ArrayList<Integer> tickets = new ArrayList<>(threads);
private final ArrayList<Boolean> entering = new ArrayList<>(threads);
private final Integer ticketBound = 10;
private final TreeSet<Integer> freeUsedTickets = new TreeSet<>();
private final Semaphore fillCount = new Semaphore(ticketBound);
private Boolean isInitialized = false;
OLamportLock(){
synchronized(isInitialized){
if(!isInitialized){
for(int i = 0; i < threads; i++){
tickets.add(-1);
entering.add(false);
freeUsedTickets.add(i + 1);
}
isInitialized = true;
}
}
}
@Override
public void lock(Integer pid){
try{
fillCount.acquire();
}
catch(InterruptedException me){
}
actualLock(pid);
}
@Override
public void lockInterruptibly(Integer pid) throws InterruptedException{
fillCount.acquire();
actualLock(pid);
}
@Override
public boolean tryLock(Integer pid){
Boolean result = fillCount.tryAcquire();
if(!result){
return false;
}
actualLock(pid);
return true;
}
@Override
public boolean tryLock(Integer pid, long time, TimeUnit unit) throws InterruptedException{
Boolean result = fillCount.tryAcquire(time, unit);
if(!result){
return false;
}
actualLock(pid);
return true;
}
@Override
public void unlock(Integer pid){
Integer freeTicket = tickets.get(pid);
tickets.set(pid, -1);
synchronized(freeUsedTickets){
freeUsedTickets.add(freeTicket);
}
fillCount.release();
System.out.println("Thread #" + pid + " exited....");
// System.out.println("UNLOCK: " + freeUsedTickets);
}
@Override
public Condition newCondition() throws UnsupportedOperationException{
throw new UnsupportedOperationException();
}
private void actualLock(Integer pid){
Integer curTicket;
entering.set(pid, true);
System.out.println(pid + " entered");
synchronized(freeUsedTickets){
curTicket = freeUsedTickets.pollFirst();
tickets.set(pid, curTicket);
}
entering.set(pid, false);
System.out.println("Thread #" + pid + " got ticket: " + tickets.get(pid));
for(int i = 0; i < threads; i++){
if(i != pid){
while(entering.get(i)) { Thread.yield();}
while(tickets.get(i) < tickets.get(pid) && tickets.get(i) != -1){ Thread.yield(); }
// if(tickets.get(i).equals(tickets.get(pid))){ // just to prove that there is no duplicates
// System.out.println("WARNING!!! DUPLICATE FOR " + pid + " IN " + i);
// }
}
}
}
}