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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.search.predicate.index;
import com.yahoo.search.predicate.SubqueryBitmap;
/**
* Wraps a posting list of compressed NOT-features.
* The compression works by implying an interval of size 1 after each
* stored interval, unless the next interval starts with 16 bits of 0,
* in which case the current interval is extended to the next.
*
* @author Magnar Nedland
* @author bjorncs
*/
public class ZstarCompressedPostingList extends MultiIntervalPostingList {
private final PredicateIntervalStore store;
private int[] currentIntervals;
private int currentIntervalIndex;
private int prevInterval;
private int currentInterval;
/**
* @param docIds Posting list as a stream.
*/
public ZstarCompressedPostingList(PredicateIntervalStore store, int[] docIds, int[] dataRefs) {
super(docIds, dataRefs, SubqueryBitmap.ALL_SUBQUERIES);
this.store = store;
}
@Override
protected boolean prepareIntervals(int dataRef) {
currentIntervals = store.get(dataRef);
currentIntervalIndex = 0;
return nextInterval();
}
@Override
public boolean nextInterval() {
int nextInterval = -1;
if (currentIntervalIndex < currentIntervals.length) {
nextInterval = currentIntervals[currentIntervalIndex];
}
if (prevInterval != 0) {
if (Interval.isZStar2Interval(nextInterval)) {
this.currentInterval = Interval.combineZStarIntervals(prevInterval, nextInterval);
++currentIntervalIndex;
} else {
int end = Interval.getZStar1End(prevInterval);
this.currentInterval = Interval.fromZStar1Boundaries(end, end + 1);
}
prevInterval = 0;
return true;
} else if (nextInterval != -1) {
this.currentInterval = nextInterval;
++currentIntervalIndex;
prevInterval = nextInterval;
return true;
}
return false;
}
@Override
public int getInterval() {
return currentInterval;
}
}
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