ArrayDocIdSet.java

package proj.zoie.api.impl.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.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;
      }
    };
  }
}