org.apache.lucene.util.BitSetIterator.java Source code

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Here is the source code for org.apache.lucene.util.BitSetIterator.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.util;

import org.apache.lucene.search.DocIdSetIterator;

/**
 * A {@link DocIdSetIterator} which iterates over set bits in a
 * bit set.
 * @lucene.internal
 */
public class BitSetIterator extends DocIdSetIterator {

    private static <T extends BitSet> T getBitSet(DocIdSetIterator iterator, Class<? extends T> clazz) {
        if (iterator instanceof BitSetIterator) {
            BitSet bits = ((BitSetIterator) iterator).bits;
            assert bits != null;
            if (clazz.isInstance(bits)) {
                return clazz.cast(bits);
            }
        }
        return null;
    }

    /** If the provided iterator wraps a {@link FixedBitSet}, returns it, otherwise returns null. */
    public static FixedBitSet getFixedBitSetOrNull(DocIdSetIterator iterator) {
        return getBitSet(iterator, FixedBitSet.class);
    }

    /** If the provided iterator wraps a {@link SparseFixedBitSet}, returns it, otherwise returns null. */
    public static SparseFixedBitSet getSparseFixedBitSetOrNull(DocIdSetIterator iterator) {
        return getBitSet(iterator, SparseFixedBitSet.class);
    }

    private final BitSet bits;
    private final int length;
    private final long cost;
    private int doc = -1;

    /** Sole constructor. */
    public BitSetIterator(BitSet bits, long cost) {
        if (cost < 0) {
            throw new IllegalArgumentException("cost must be >= 0, got " + cost);
        }
        this.bits = bits;
        this.length = bits.length();
        this.cost = cost;
    }

    /** Return the wrapped {@link BitSet}. */
    public BitSet getBitSet() {
        return bits;
    }

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

    /** Set the current doc id that this iterator is on. */
    public void setDocId(int docId) {
        this.doc = docId;
    }

    @Override
    public int nextDoc() {
        return advance(doc + 1);
    }

    @Override
    public int advance(int target) {
        if (target >= length) {
            return doc = NO_MORE_DOCS;
        }
        return doc = bits.nextSetBit(target);
    }

    @Override
    public long cost() {
        return cost;
    }

}