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package org.eclipse.viatra.solver.data.map.internal;
import org.eclipse.viatra.solver.data.map.Cursor;
import org.eclipse.viatra.solver.data.map.DiffCursor;
/**
* A cursor representing the difference between two states of a map.
* @author Oszkar Semerath
*
*/
public class MapDiffCursor<KEY,VALUE> implements DiffCursor<KEY, VALUE> {
/**
* Default value representing missing elements.
*/
VALUE defaultValue;
MapCursor<KEY,VALUE> cursor1;
MapCursor<KEY,VALUE> cursor2;
// Values
KEY key;
VALUE value1;
VALUE value2;
// State
/**
* Positive number if cursor 1 is behind, negative number if cursor 2 is behind, and 0 if they are at the same position.
*/
int cursorRelation;
public MapDiffCursor(VALUE defaultValue, Cursor<KEY, VALUE> cursor1, Cursor<KEY, VALUE> cursor2) {
super();
this.defaultValue = defaultValue;
this.cursor1 = (MapCursor<KEY, VALUE>) cursor1;
this.cursor2 = (MapCursor<KEY, VALUE>) cursor2;
this.updateState();
this.moveToConsistentState();
}
public KEY getKey() {
return key;
}
public VALUE getValue1() {
return value1;
}
public VALUE getValue2() {
return value2;
}
public boolean isTerminated() {
return cursor1.isTerminated() && cursor2.isTerminated();
}
protected void updateState() {
this.cursorRelation = MapCursor.compare(cursor1, cursor2);
if(cursorRelation > 0 || cursor2.isTerminated()) {
this.key = cursor1.getKey();
this.value1 = cursor1.getValue();
this.value2 = defaultValue;
} else if(cursorRelation < 0|| cursor1.isTerminated()){
this.key = cursor2.getKey();
this.value1 = defaultValue;
this.value2 = cursor1.getValue();
} else {
// cursor1 = cursor2
if(!cursor1.getKey().equals(cursor2.getKey())) {
throw new IllegalStateException(
"Cursor comarison tells that they are in the same state, but keys are different. " + cursor1.getKey() + " - " + cursor2.getKey());
}
this.key = cursor1.getKey();
this.value1 = cursor1.getValue();
this.value2 = defaultValue;
}
}
protected boolean canStop() {
return this.value1 != this.value2;
}
protected void moveOne() {
if(isTerminated()) {
throw new IllegalStateException("DiffCursor tries to move when terminated!");
}
if(this.cursorRelation > 0 || cursor2.isTerminated()) {
cursor1.move();
} else if(this.cursorRelation < 0 || cursor1.isTerminated()) {
cursor2.move();
} else {
cursor1.move();
cursor2.move();
}
updateState();
}
protected void moveToConsistentState() {
while(!canStop() && !isTerminated()) {
moveOne();
}
}
public void move() {
if(!isTerminated()) {
moveOne();
moveToConsistentState();
}
}
}
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