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DependencyQueue.java
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DependencyQueue.java
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package org.imdea.vcd.queue;
import java.util.ArrayList;
import java.util.List;
import org.imdea.vcd.queue.clock.ExceptionSet;
import org.imdea.vcd.queue.clock.Clock;
/**
*
* Some methods are copied from java.util.LinkedList.
*
* @author Vitor Enes
* @param <E>
*/
public class DependencyQueue<E extends DepBox> {
Node<E> first;
Node<E> last;
private Clock<ExceptionSet> delivered;
public DependencyQueue(Integer nodeNumber) {
this.delivered = Clock.eclock(nodeNumber);
}
public DependencyQueue(Clock<ExceptionSet> delivered) {
this.delivered = delivered;
}
public List<E> add(E e) {
System.out.println("Adding " + e);
Node<E> pred = findPredecessor(e);
Node<E> succ = findSuccessor(e);
if (pred == null && succ == null) {
linkFirst(e);
} else if (pred == null) {
linkAfter(e, succ);
} else if (succ == null) {
linkBefore(e, pred);
} else if (succ.next == pred) {
// insert in between both
linkBetween(e, pred, succ);
} else {
// found cycle: merge all
merge(e, pred, succ);
}
List<E> result = new ArrayList<>();
boolean flag = true;
while (first != null && flag) {
Node<E> candidate = first;
// copy 'delivered' clock
Clock<ExceptionSet> nextDelivered = (Clock<ExceptionSet>) delivered.clone();
// NOTE function 'canDeliver' mutates 'nextDelivered' clock
flag = candidate.item.canDeliver(nextDelivered);
if (flag) {
// update delivered clock
this.delivered = nextDelivered;
// add to results
result.add(candidate.item);
// update first
first = first.next;
if (first == null) {
last = null;
} else {
first.prev = null;
}
}
}
System.out.println("final queue:");
System.out.println(this);
return result;
}
/**
* Find predecessor of e in the queue.
*/
private Node<E> findPredecessor(E e) {
Node<E> it = first;
while (it != null) {
if (e.before(it.item)) {
return it;
}
it = it.next;
}
return null;
}
/**
* Find successor of e in the queue.
*/
private Node<E> findSuccessor(E e) {
Node<E> it = last;
while (it != null) {
if (it.item.before(e)) {
return it;
}
it = it.prev;
}
return null;
}
/**
* Links e as first element.
*/
private void linkFirst(E e) {
final Node<E> f = first;
final Node<E> newNode = new Node<>(null, e, f);
first = newNode;
if (f == null) {
last = newNode;
} else {
f.prev = newNode;
}
}
/**
* Inserts element e before non-null Node succ.
*/
void linkBefore(E e, Node<E> succ) {
// assert n != null;
final Node<E> pred = succ.prev;
final Node<E> newNode = new Node<>(pred, e, succ);
succ.prev = newNode;
if (pred == null) {
first = newNode;
} else {
pred.next = newNode;
}
}
/**
* Inserts element e after non-null Node pred.
*/
void linkAfter(E e, Node<E> pred) {
// assert n != null;
final Node<E> succ = pred.next;
final Node<E> newNode = new Node<>(pred, e, succ);
pred.next = newNode;
if (succ == null) {
last = newNode;
} else {
succ.prev = newNode;
}
}
/**
* Inserts element e between Node pred and Node succ.
*/
void linkBetween(E e, Node<E> pred, Node<E> succ) {
final Node<E> newNode = new Node<>(pred, e, succ);
if (pred == null) {
first = newNode;
} else {
pred.next = newNode;
}
if (succ == null) {
last = newNode;
} else {
succ.prev = newNode;
}
}
/**
* Merge e with all from Node a to Node b.
*/
void merge(E e, Node<E> a, Node<E> b) {
Node<E> pred = a.prev;
Node<E> succ = b.next;
// merge a with e
e.merge(a.item);
while (a.next != b.next) {
// while not pointing to the same element, merge
a = a.next;
e.merge(a.item);
}
linkBetween(e, pred, succ);
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
Node<E> it = first;
int i = 0;
while (it != null) {
if (i > 0) {
sb.append("\n");
}
sb.append(i)
.append("> ")
.append(it.item.toString());
it = it.next;
i++;
}
if (i == 0) {
sb.append("[empty]");
}
return sb.toString();
}
private static class Node<E> {
Node<E> prev;
E item;
Node<E> next;
Node(Node<E> prev, E element, Node<E> next) {
this.prev = prev;
this.item = element;
this.next = next;
}
}
}