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package org.eclipse.viatra.solver.data.map.internal;
import java.util.List;
import java.util.stream.Stream;
import org.eclipse.viatra.solver.data.map.ContinousHashProvider;
import org.eclipse.viatra.solver.data.map.Cursor;
import org.eclipse.viatra.solver.data.map.DiffCursor;
import org.eclipse.viatra.solver.data.map.VersionedMap;
/**
* A cursor representing the difference between two states of a map.
*
* @author Oszkar Semerath
*
*/
public class MapDiffCursor<K, V> implements DiffCursor<K, V>, Cursor<K, V> {
/**
* Default value representing missing elements.
*/
private V defaultValue;
private MapCursor<K, V> cursor1;
private MapCursor<K, V> cursor2;
private ContinousHashProvider<? super K> hashProvider;
// Values
private K key;
private V fromValue;
private V toValue;
// State
/**
* Positive number if cursor 1 is behind, negative number if cursor 2 is behind,
* and 0 if they are at the same position.
*/
private int cursorRelation;
private HashClash hashClash = HashClash.NONE;
public MapDiffCursor(ContinousHashProvider<? super K> hashProvider, V defaultValue, Cursor<K, V> cursor1,
Cursor<K, V> cursor2) {
super();
this.hashProvider = hashProvider;
this.defaultValue = defaultValue;
this.cursor1 = (MapCursor<K, V>) cursor1;
this.cursor2 = (MapCursor<K, V>) cursor2;
}
@Override
public K getKey() {
return key;
}
@Override
public V getFromValue() {
return fromValue;
}
@Override
public V getToValue() {
return toValue;
}
@Override
public V getValue() {
return getToValue();
}
public boolean isTerminated() {
return cursor1.isTerminated() && cursor2.isTerminated();
}
@Override
public boolean isDirty() {
return this.cursor1.isDirty() || this.cursor2.isDirty();
}
@Override
public List<VersionedMap<?, ?>> getDependingMaps() {
return Stream.concat(cursor1.getDependingMaps().stream(), cursor2.getDependingMaps().stream()).toList();
}
protected void updateState() {
if (!isTerminated()) {
this.cursorRelation = MapCursor.compare(cursor1, cursor2);
if (cursorRelation > 0 || cursor2.isTerminated()) {
this.key = cursor1.getKey();
this.fromValue = cursor1.getValue();
this.toValue = defaultValue;
} else if (cursorRelation < 0 || cursor1.isTerminated()) {
this.key = cursor2.getKey();
this.fromValue = defaultValue;
this.toValue = cursor1.getValue();
} else {
// cursor1 = cursor2
if (cursor1.getKey().equals(cursor2.getKey())) {
this.key = cursor1.getKey();
this.fromValue = cursor1.getValue();
this.toValue = defaultValue;
} else {
resolveHashClashWithFirstEntry();
}
}
}
}
protected void resolveHashClashWithFirstEntry() {
int compareResult = this.hashProvider.compare(cursor1.key, cursor2.key);
if (compareResult < 0) {
this.hashClash = HashClash.STUCK_CURSOR_2;
this.cursorRelation = 0;
this.key = cursor1.key;
this.fromValue = cursor1.value;
this.toValue = defaultValue;
} else if (compareResult > 0) {
this.hashClash = HashClash.STUCK_CURSOR_1;
this.cursorRelation = 0;
this.key = cursor2.key;
this.fromValue = defaultValue;
this.toValue = cursor2.value;
} else {
throw new IllegalArgumentException("Inconsistent compare result for diffcursor");
}
}
protected boolean isInHashClash() {
return this.hashClash != HashClash.NONE;
}
protected void resolveHashClashWithSecondEntry() {
switch (this.hashClash) {
case STUCK_CURSOR_1:
this.hashClash = HashClash.NONE;
this.cursorRelation = 0;
this.key = cursor1.key;
this.fromValue = cursor1.value;
this.toValue = defaultValue;
break;
case STUCK_CURSOR_2:
this.hashClash = HashClash.NONE;
this.cursorRelation = 0;
this.key = cursor2.key;
this.fromValue = defaultValue;
this.toValue = cursor2.value;
break;
default:
throw new IllegalArgumentException("Inconsistent compare result for diffcursor");
}
}
protected boolean sameValues() {
if (this.fromValue == null) {
return this.toValue == null;
} else {
return this.fromValue.equals(this.toValue);
}
}
protected boolean moveOne() {
if (isTerminated()) {
return false;
}
if (this.cursorRelation > 0 || cursor2.isTerminated()) {
return cursor1.move();
} else if (this.cursorRelation < 0 || cursor1.isTerminated()) {
return cursor2.move();
} else {
boolean moved1 = cursor1.move();
boolean moved2 = cursor2.move();
return moved1 && moved2;
}
}
private boolean skipNode() {
if (isTerminated()) {
throw new IllegalStateException("DiffCursor tries to skip when terminated!");
}
boolean update1 = cursor1.skipCurrentNode();
boolean update2 = cursor2.skipCurrentNode();
updateState();
return update1 && update2;
}
protected boolean moveToConsistentState() {
if (!isTerminated()) {
boolean changed;
boolean lastResult = true;
do {
changed = false;
if (MapCursor.sameSubnode(cursor1, cursor2)) {
lastResult = skipNode();
changed = true;
}
if (sameValues()) {
lastResult = moveOne();
changed = true;
}
updateState();
} while (changed && !isTerminated());
return lastResult;
} else {
return false;
}
}
public boolean move() {
if (!isTerminated()) {
if (isInHashClash()) {
this.resolveHashClashWithSecondEntry();
return true;
} else {
if (moveOne()) {
return moveToConsistentState();
} else {
return false;
}
}
} else
return false;
}
}
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