package org.apache.lucene.search.spans;
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.PriorityQueue;
class NearSpans implements Spans {
private SpanNearQuery query;
private List ordered = new ArrayList(); // spans in query order
private int slop; // from query
private boolean inOrder; // from query
private SpansCell first; // linked list of spans
private SpansCell last; // sorted by doc only
private int totalLength; // sum of current lengths
private CellQueue queue; // sorted queue of spans
private SpansCell max; // max element in queue
private boolean more = true; // true iff not done
private boolean firstTime = true; // true before first next()
private class CellQueue extends PriorityQueue {
public CellQueue(int size) {
initialize(size);
}
protected final boolean lessThan(Object o1, Object o2) {
SpansCell spans1 = (SpansCell)o1;
SpansCell spans2 = (SpansCell)o2;
if (spans1.doc() == spans2.doc()) {
if (spans1.start() == spans2.start()) {
if (spans1.end() == spans2.end()) {
return spans1.index > spans2.index;
} else {
return spans1.end() < spans2.end();
}
} else {
return spans1.start() < spans2.start();
}
} else {
return spans1.doc() < spans2.doc();
}
}
}
/** Wraps a Spans, and can be used to form a linked list. */
private class SpansCell implements Spans {
private Spans spans;
private SpansCell next;
private int length = -1;
private int index;
public SpansCell(Spans spans, int index) {
this.spans = spans;
this.index = index;
}
public boolean next() throws IOException {
if (length != -1) // subtract old length
totalLength -= length;
boolean more = spans.next(); // move to next
if (more) {
length = end() - start(); // compute new length
totalLength += length; // add new length to total
if (max == null || doc() > max.doc() || // maintain max
(doc() == max.doc() && end() > max.end()))
max = this;
}
return more;
}
public boolean skipTo(int target) throws IOException {
if (length != -1) // subtract old length
totalLength -= length;
boolean more = spans.skipTo(target); // skip
if (more) {
length = end() - start(); // compute new length
totalLength += length; // add new length to total
if (max == null || doc() > max.doc() || // maintain max
(doc() == max.doc() && end() > max.end()))
max = this;
}
return more;
}
public int doc() { return spans.doc(); }
public int start() { return spans.start(); }
public int end() { return spans.end(); }
public String toString() { return spans.toString() + "#" + index; }
}
public NearSpans(SpanNearQuery query, IndexReader reader)
throws IOException {
this.query = query;
this.slop = query.getSlop();
this.inOrder = query.isInOrder();
SpanQuery[] clauses = query.getClauses(); // initialize spans & list
queue = new CellQueue(clauses.length);
for (int i = 0; i < clauses.length; i++) {
SpansCell cell = // construct clause spans
new SpansCell(clauses[i].getSpans(reader), i);
ordered.add(cell); // add to ordered
}
}
public boolean next() throws IOException {
if (firstTime) {
initList(true);
listToQueue(); // initialize queue
firstTime = false;
} else if (more) {
more = min().next(); // trigger further scanning
if (more)
queue.adjustTop(); // maintain queue
}
while (more) {
boolean queueStale = false;
if (min().doc() != max.doc()) { // maintain list
queueToList();
queueStale = true;
}
// skip to doc w/ all clauses
while (more && first.doc() < last.doc()) {
more = first.skipTo(last.doc()); // skip first upto last
firstToLast(); // and move it to the end
queueStale = true;
}
if (!more) return false;
// found doc w/ all clauses
if (queueStale) { // maintain the queue
listToQueue();
queueStale = false;
}
if (atMatch())
return true;
// trigger further scanning
if (inOrder && checkSlop()) {
/* There is a non ordered match within slop and an ordered match is needed. */
more = firstNonOrderedNextToPartialList();
if (more) {
partialListToQueue();
}
} else {
more = min().next();
if (more) {
queue.adjustTop(); // maintain queue
}
}
}
return false; // no more matches
}
public boolean skipTo(int target) throws IOException {
if (firstTime) { // initialize
initList(false);
for (SpansCell cell = first; more && cell!=null; cell=cell.next) {
more = cell.skipTo(target); // skip all
}
if (more) {
listToQueue();
}
firstTime = false;
} else { // normal case
while (more && min().doc() < target) { // skip as needed
more = min().skipTo(target);
if (more)
queue.adjustTop();
}
}
if (more) {
if (atMatch()) // at a match?
return true;
return next(); // no, scan
}
return false;
}
private SpansCell min() { return (SpansCell)queue.top(); }
public int doc() { return min().doc(); }
public int start() { return min().start(); }
public int end() { return max.end(); }
public String toString() {
return "spans("+query.toString()+")@"+
(firstTime?"START":(more?(doc()+":"+start()+"-"+end()):"END"));
}
private void initList(boolean next) throws IOException {
for (int i = 0; more && i < ordered.size(); i++) {
SpansCell cell = (SpansCell)ordered.get(i);
if (next)
more = cell.next(); // move to first entry
if (more) {
addToList(cell); // add to list
}
}
}
private void addToList(SpansCell cell) {
if (last != null) { // add next to end of list
last.next = cell;
} else
first = cell;
last = cell;
cell.next = null;
}
private void firstToLast() {
last.next = first; // move first to end of list
last = first;
first = first.next;
last.next = null;
}
private void queueToList() {
last = first = null;
while (queue.top() != null) {
addToList((SpansCell)queue.pop());
}
}
private boolean firstNonOrderedNextToPartialList() throws IOException {
/* Creates a partial list consisting of first non ordered and earlier.
* Returns first non ordered .next().
*/
last = first = null;
int orderedIndex = 0;
while (queue.top() != null) {
SpansCell cell = (SpansCell)queue.pop();
addToList(cell);
if (cell.index == orderedIndex) {
orderedIndex++;
} else {
return cell.next();
// FIXME: continue here, rename to eg. checkOrderedMatch():
// when checkSlop() and not ordered, repeat cell.next().
// when checkSlop() and ordered, add to list and repeat queue.pop()
// without checkSlop(): no match, rebuild the queue from the partial list.
// When queue is empty and checkSlop() and ordered there is a match.
}
}
throw new RuntimeException("Unexpected: ordered");
}
private void listToQueue() {
queue.clear(); // rebuild queue
partialListToQueue();
}
private void partialListToQueue() {
for (SpansCell cell = first; cell != null; cell = cell.next) {
queue.put(cell); // add to queue from list
}
}
private boolean atMatch() {
return (min().doc() == max.doc())
&& checkSlop()
&& (!inOrder || matchIsOrdered());
}
private boolean checkSlop() {
int matchLength = max.end() - min().start();
return (matchLength - totalLength) <= slop;
}
private boolean matchIsOrdered() {
int lastStart = -1;
for (int i = 0; i < ordered.size(); i++) {
int start = ((SpansCell)ordered.get(i)).start();
if (!(start > lastStart))
return false;
lastStart = start;
}
return true;
}
}
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