org.apache.lucene.facet.taxonomy.DocValuesOrdinalsReader.java Source code

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Here is the source code for org.apache.lucene.facet.taxonomy.DocValuesOrdinalsReader.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.facet.taxonomy;

import java.io.IOException;

import org.apache.lucene.facet.FacetsConfig;
import org.apache.lucene.index.BinaryDocValues;
import org.apache.lucene.index.DocValues;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.util.ArrayUtil;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.IntsRef;

/** Decodes ordinals previously indexed into a BinaryDocValues field */
public class DocValuesOrdinalsReader extends OrdinalsReader {
    private final String field;

    /** Default constructor. */
    public DocValuesOrdinalsReader() {
        this(FacetsConfig.DEFAULT_INDEX_FIELD_NAME);
    }

    /** Create this, with the specified indexed field name. */
    public DocValuesOrdinalsReader(String field) {
        this.field = field;
    }

    @Override
    public OrdinalsSegmentReader getReader(LeafReaderContext context) throws IOException {
        BinaryDocValues values0 = context.reader().getBinaryDocValues(field);
        if (values0 == null) {
            values0 = DocValues.emptyBinary();
        }

        final BinaryDocValues values = values0;

        return new OrdinalsSegmentReader() {

            private int lastDocID;

            @Override
            public void get(int docID, IntsRef ordinals) throws IOException {
                if (docID < lastDocID) {
                    throw new AssertionError("docs out of order: lastDocID=" + lastDocID + " vs docID=" + docID);
                }
                lastDocID = docID;
                if (docID > values.docID()) {
                    values.advance(docID);
                }
                final BytesRef bytes;
                if (values.docID() == docID) {
                    bytes = values.binaryValue();
                } else {
                    bytes = new BytesRef(BytesRef.EMPTY_BYTES);
                }
                decode(bytes, ordinals);
            }
        };
    }

    @Override
    public String getIndexFieldName() {
        return field;
    }

    /** Subclass and override if you change the encoding. */
    protected void decode(BytesRef buf, IntsRef ordinals) {

        // grow the buffer up front, even if by a large number of values (buf.length)
        // that saves the need to check inside the loop for every decoded value if
        // the buffer needs to grow.
        if (ordinals.ints.length < buf.length) {
            ordinals.ints = ArrayUtil.grow(ordinals.ints, buf.length);
        }

        ordinals.offset = 0;
        ordinals.length = 0;

        // it is better if the decoding is inlined like so, and not e.g.
        // in a utility method
        int upto = buf.offset + buf.length;
        int value = 0;
        int offset = buf.offset;
        int prev = 0;
        while (offset < upto) {
            byte b = buf.bytes[offset++];
            if (b >= 0) {
                ordinals.ints[ordinals.length] = ((value << 7) | b) + prev;
                value = 0;
                prev = ordinals.ints[ordinals.length];
                ordinals.length++;
            } else {
                value = (value << 7) | (b & 0x7F);
            }
        }
    }
}