org.apache.lucene.index.ReaderUtil.java Source code

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Here is the source code for org.apache.lucene.index.ReaderUtil.java

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/*
 * 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.
 */
package org.apache.lucene.index;

import java.util.List;

/**
 * Common util methods for dealing with {@link IndexReader}s and {@link IndexReaderContext}s.
 *
 * @lucene.internal
 */
public final class ReaderUtil {

    private ReaderUtil() {
    } // no instance

    /**
     * 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 IndexReaderContext getTopLevelContext(IndexReaderContext 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, List<LeafReaderContext> leaves) { // find
        // searcher/reader for doc n:
        int size = leaves.size();
        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.get(mid).docBase;
            if (n < midValue)
                hi = mid - 1;
            else if (n > midValue)
                lo = mid + 1;
            else { // found a match
                while (mid + 1 < size && leaves.get(mid + 1).docBase == midValue) {
                    mid++; // scan to last match
                }
                return mid;
            }
        }
        return hi;
    }
}