rangescan.java

jsr170接口的java实现。是个apache的开源项目。

/*
 * 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.jackrabbit.core.query.lucene;

import org.apache.lucene.index.Term;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.FilteredTermEnum;

import java.io.IOException;

/**
 * <code>RangeScan</code> implements a range scan on terms.
 */
class RangeScan extends FilteredTermEnum {

    private final Term upper;

    private boolean endEnum = false;

    /**
     * Scans the index beginning at <code>lower</code> Term to <code>upper</code>.
     * @param reader the index reader;
     * @param lower the lower limit.
     * @param upper the upper limit.
     */
    RangeScan(IndexReader reader, Term lower, Term upper) throws IOException {
        this.upper = upper;
        setEnum(reader.terms(lower));
    }

    protected boolean termCompare(Term term) {
        int compare = term.compareTo(upper);
        if (compare > 0) {
            endEnum = true;
        }
        return compare <= 0;
    }

    public float difference() {
        return 1.0f;
    }

    protected boolean endEnum() {
        return endEnum;
    }
}