cn.hbu.cs.esearch.util.ArrayDocIdSet.java Source code

Introduction

Here is the source code for cn.hbu.cs.esearch.util.ArrayDocIdSet.java

Source

/*
 * 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 cn.hbu.cs.esearch.util;

import java.io.IOException;

import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.DocIdSetIterator;

public class ArrayDocIdSet extends DocIdSet {
    private final int[] docIds;
    private final int lengthMinusone;

    public ArrayDocIdSet(int[] docids) {
        docIds = docids;
        if (docids != null) {
            lengthMinusone = docids.length - 1;
        } else {
            lengthMinusone = -1;
        }
    }

    final private static int binarySearch(int[] a, int key) {
        return binarySearch(a, key, 0, a.length - 1);
    }

    final private static int binarySearch(int[] a, int key, int low, int high) {
        while (low <= high) {
            int mid = (low + high) >>> 1;
            int midVal = a[mid];
            int cmp;

            cmp = midVal - key;

            if (cmp < 0) {
                low = mid + 1;
            } else if (cmp > 0) {
                high = mid - 1;
            } else {
                return mid;
            }
        }
        return -(low + 1);
    }

    @Override
    public DocIdSetIterator iterator() {
        return new DocIdSetIterator() {
            int doc = -1;
            int current = -1;
            int largest = lengthMinusone;

            @Override
            public int docID() {
                return doc;
            }

            @Override
            public int nextDoc() throws IOException {
                if (current < lengthMinusone) {
                    current++;
                    doc = docIds[current];
                    return doc;
                }
                return DocIdSetIterator.NO_MORE_DOCS;
            }

            @Override
            public int advance(int target) throws IOException {
                int idx = current < 0 ? binarySearch(docIds, target)
                        : binarySearch(docIds, target, current, largest);
                if (idx < 0) {
                    idx = -(idx + 1);
                    if (idx >= docIds.length) {
                        return DocIdSetIterator.NO_MORE_DOCS;
                    }
                }
                current = idx;
                doc = docIds[current];
                return doc;
            }

            @Override
            public long cost() {
                // TODO Auto-generated method stub
                return 0;
            }
        };
    }
}