org.apache.lucene.search.vectorhighlight.SimpleBoundaryScanner.java Source code

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Here is the source code for org.apache.lucene.search.vectorhighlight.SimpleBoundaryScanner.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.search.vectorhighlight;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/**
 * Simple boundary scanner implementation that divides fragments
 * based on a set of separator characters.
 */
public class SimpleBoundaryScanner implements BoundaryScanner {

    public static final int DEFAULT_MAX_SCAN = 20;
    public static final Character[] DEFAULT_BOUNDARY_CHARS = { '.', ',', '!', '?', ' ', '\t', '\n' };

    protected int maxScan;
    protected Set<Character> boundaryChars;

    public SimpleBoundaryScanner() {
        this(DEFAULT_MAX_SCAN, DEFAULT_BOUNDARY_CHARS);
    }

    public SimpleBoundaryScanner(int maxScan) {
        this(maxScan, DEFAULT_BOUNDARY_CHARS);
    }

    public SimpleBoundaryScanner(Character[] boundaryChars) {
        this(DEFAULT_MAX_SCAN, boundaryChars);
    }

    public SimpleBoundaryScanner(int maxScan, Character[] boundaryChars) {
        this.maxScan = maxScan;
        this.boundaryChars = new HashSet<>();
        this.boundaryChars.addAll(Arrays.asList(boundaryChars));
    }

    public SimpleBoundaryScanner(int maxScan, Set<Character> boundaryChars) {
        this.maxScan = maxScan;
        this.boundaryChars = boundaryChars;
    }

    @Override
    public int findStartOffset(StringBuilder buffer, int start) {
        // avoid illegal start offset
        if (start > buffer.length() || start < 1)
            return start;
        int offset, count = maxScan;
        for (offset = start; offset > 0 && count > 0; count--) {
            // found?
            if (boundaryChars.contains(buffer.charAt(offset - 1)))
                return offset;
            offset--;
        }
        // if we scanned up to the start of the text, return it, it's a "boundary"
        if (offset == 0) {
            return 0;
        }
        // not found
        return start;
    }

    @Override
    public int findEndOffset(StringBuilder buffer, int start) {
        // avoid illegal start offset
        if (start > buffer.length() || start < 0)
            return start;
        int offset, count = maxScan;
        //for( offset = start; offset <= buffer.length() && count > 0; count-- ){
        for (offset = start; offset < buffer.length() && count > 0; count--) {
            // found?
            if (boundaryChars.contains(buffer.charAt(offset)))
                return offset;
            offset++;
        }
        // not found
        return start;
    }
}