package org.apache.lucene.facet.taxonomy;
/*
* 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.facet.FacetsConfig;
import org.apache.lucene.index.AtomicReaderContext;
import org.apache.lucene.index.BinaryDocValues;
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(AtomicReaderContext context) throws IOException {
BinaryDocValues values0 = context.reader().getBinaryDocValues(field);
if (values0 == null) {
values0 = BinaryDocValues.EMPTY;
}
final BinaryDocValues values = values0;
return new OrdinalsSegmentReader() {
private final BytesRef bytes = new BytesRef(32);
@Override
public void get(int docID, IntsRef ordinals) throws IOException {
values.get(docID, bytes);
decode(bytes, ordinals);
}
};
}
@Override
public String getIndexFieldName() {
return field;
}
/** Subclass & 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);
}
}
}
}