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 java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexReader.AtomicReaderContext;
import org.apache.lucene.index.IndexReader.CompositeReaderContext;
import org.apache.lucene.index.IndexReader.ReaderContext;
/**
* Common util methods for dealing with {@link IndexReader}s.
*
* @lucene.internal
*/
public final class ReaderUtil {
private ReaderUtil() {} // no instance
public static class Slice {
public static final Slice[] EMPTY_ARRAY = new Slice[0];
public final int start;
public final int length;
public final int readerIndex;
public Slice(int start, int length, int readerIndex) {
this.start = start;
this.length = length;
this.readerIndex = readerIndex;
}
@Override
public String toString() {
return "slice start=" + start + " length=" + length + " readerIndex=" + readerIndex;
}
}
/**
* Gathers sub-readers from reader into a List. See
* {@link Gather} for are more general way to gather
* whatever you need to, per reader.
*
* @lucene.experimental
*
* @param allSubReaders
* @param reader
*/
public static void gatherSubReaders(final List<IndexReader> allSubReaders, IndexReader reader) {
try {
new Gather(reader) {
@Override
protected void add(int base, IndexReader r) {
allSubReaders.add(r);
}
}.run();
} catch (IOException ioe) {
// won't happen
throw new RuntimeException(ioe);
}
}
/** Recursively visits all sub-readers of a reader. You
* should subclass this and override the add method to
* gather what you need.
*
* @lucene.experimental */
public static abstract class Gather {
private final IndexReader topReader;
public Gather(IndexReader r) {
topReader = r;
}
public int run() throws IOException {
return run(0, topReader);
}
public int run(int docBase) throws IOException {
return run(docBase, topReader);
}
private int run(int base, IndexReader reader) throws IOException {
IndexReader[] subReaders = reader.getSequentialSubReaders();
if (subReaders == null) {
// atomic reader
add(base, reader);
base += reader.maxDoc();
} else {
// composite reader
for (int i = 0; i < subReaders.length; i++) {
base = run(base, subReaders[i]);
}
}
return base;
}
protected abstract void add(int base, IndexReader r) throws IOException;
}
/**
* 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[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];
}
public static ReaderContext buildReaderContext(IndexReader reader) {
return new ReaderContextBuilder(reader).build();
}
public static class ReaderContextBuilder {
private final IndexReader reader;
private final AtomicReaderContext[] leaves;
private int leafOrd = 0;
private int leafDocBase = 0;
public ReaderContextBuilder(IndexReader reader) {
this.reader = reader;
leaves = new AtomicReaderContext[numLeaves(reader)];
}
public ReaderContext build() {
return build(null, reader, 0, 0);
}
private ReaderContext build(CompositeReaderContext parent, IndexReader reader, int ord, int docBase) {
IndexReader[] sequentialSubReaders = reader.getSequentialSubReaders();
if (sequentialSubReaders == null) {
AtomicReaderContext atomic = new AtomicReaderContext(parent, reader, ord, docBase, leafOrd, leafDocBase);
leaves[leafOrd++] = atomic;
leafDocBase += reader.maxDoc();
return atomic;
} else {
ReaderContext[] children = new ReaderContext[sequentialSubReaders.length];
final CompositeReaderContext newParent;
if (parent == null) {
newParent = new CompositeReaderContext(reader, children, leaves);
} else {
newParent = new CompositeReaderContext(parent, reader, ord, docBase, children);
}
int newDocBase = 0;
for (int i = 0; i < sequentialSubReaders.length; i++) {
build(newParent, sequentialSubReaders[i], i, newDocBase);
newDocBase += sequentialSubReaders[i].maxDoc();
}
return newParent;
}
}
private int numLeaves(IndexReader reader) {
final int[] numLeaves = new int[1];
try {
new Gather(reader) {
@Override
protected void add(int base, IndexReader r) {
numLeaves[0]++;
}
}.run();
} catch (IOException ioe) {
// won't happen
throw new RuntimeException(ioe);
}
return numLeaves[0];
}
}
/**
* Returns the context's leaves or the context itself as the only element of
* the returned array. If the context's #leaves() method returns
* <code>null</code> the given context must be an instance of
* {@link AtomicReaderContext}
*/
public static AtomicReaderContext[] leaves(ReaderContext context) {
assert context != null && context.isTopLevel : "context must be non-null & top-level";
final AtomicReaderContext[] leaves = context.leaves();
if (leaves == null) {
assert context.isAtomic : "top-level context without leaves must be atomic";
return new AtomicReaderContext[] { (AtomicReaderContext) context };
}
return leaves;
}
/**
* Walks up the reader tree and return the given context's top level reader
* context, or in other words the reader tree's root context.
*/
public static ReaderContext getTopLevelContext(ReaderContext context) {
while (context.parent != null) {
context = context.parent;
}
return context;
}
/**
* 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;
}
/**
* 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, AtomicReaderContext[] leaves) { // find
// searcher/reader for doc n:
int size = leaves.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 = leaves[mid].docBase;
if (n < midValue)
hi = mid - 1;
else if (n > midValue)
lo = mid + 1;
else { // found a match
while (mid + 1 < size && leaves[mid + 1].docBase == midValue) {
mid++; // scan to last match
}
return mid;
}
}
return hi;
}
}