package org.apache.lucene.util;
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.util.ArrayList;
import java.util.List;
import org.apache.lucene.index.IndexReader;
/**
* Common util methods for dealing with {@link IndexReader}s.
*
*/
public class ReaderUtil {
/**
* Gathers sub-readers from reader into a List.
*
* @param allSubReaders
* @param reader
*/
public static void gatherSubReaders(List<IndexReader> allSubReaders, IndexReader reader) {
IndexReader[] subReaders = reader.getSequentialSubReaders();
if (subReaders == null) {
// Add the reader itself, and do not recurse
allSubReaders.add(reader);
} else {
for (int i = 0; i < subReaders.length; i++) {
gatherSubReaders(allSubReaders, subReaders[i]);
}
}
}
/**
* Returns sub IndexReader that contains the given document id.
*
* @param doc id of document
* @param reader parent reader
* @return sub reader of parent which contains the specified doc id
*/
public static IndexReader subReader(int doc, IndexReader reader) {
List<IndexReader> subReadersList = new ArrayList<IndexReader>();
ReaderUtil.gatherSubReaders(subReadersList, reader);
IndexReader[] subReaders = subReadersList
.toArray(new IndexReader[subReadersList.size()]);
int[] docStarts = new int[subReaders.length];
int maxDoc = 0;
for (int i = 0; i < subReaders.length; i++) {
docStarts[i] = maxDoc;
maxDoc += subReaders[i].maxDoc();
}
return subReaders[ReaderUtil.subIndex(doc, docStarts)];
}
/**
* Returns sub-reader subIndex from reader.
*
* @param reader parent reader
* @param subIndex index of desired sub reader
* @return the subreader at subIndex
*/
public static IndexReader subReader(IndexReader reader, int subIndex) {
List<IndexReader> subReadersList = new ArrayList<IndexReader>();
ReaderUtil.gatherSubReaders(subReadersList, reader);
IndexReader[] subReaders = subReadersList
.toArray(new IndexReader[subReadersList.size()]);
return subReaders[subIndex];
}
/**
* Returns index of the searcher/reader for document <code>n</code> in the
* array used to construct this searcher/reader.
*/
public static int subIndex(int n, int[] docStarts) { // find
// searcher/reader for doc n:
int size = docStarts.length;
int lo = 0; // search starts array
int hi = size - 1; // for first element less than n, return its index
while (hi >= lo) {
int mid = (lo + hi) >>> 1;
int midValue = docStarts[mid];
if (n < midValue)
hi = mid - 1;
else if (n > midValue)
lo = mid + 1;
else { // found a match
while (mid + 1 < size && docStarts[mid + 1] == midValue) {
mid++; // scan to last match
}
return mid;
}
}
return hi;
}
}