package org.apache.lucene.util.encoding;
import java.io.IOException;
import java.io.OutputStream;
/*
* 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.
*/
/**
* An {@link IntEncoderFilter} which ensures only unique values are encoded. The
* implementation assumes the values given to {@link #encode(int)} are sorted.
* If this is not the case, you can chain this encoder with
* {@link SortingIntEncoder}.
*
* @lucene.experimental
*/
public final class UniqueValuesIntEncoder extends IntEncoderFilter {
/**
* Denotes an illegal value which we can use to init 'prev' to. Since all
* encoded values are integers, this value is init to MAX_INT+1 and is of type
* long. Therefore we are guaranteed not to get this value in encode.
*/
private static final long ILLEGAL_VALUE = Integer.MAX_VALUE + 1;
private long prev = ILLEGAL_VALUE;
/** Constructs a new instance with the given encoder. */
public UniqueValuesIntEncoder(IntEncoder encoder) {
super(encoder);
}
@Override
public void encode(int value) throws IOException {
if (prev != value) {
encoder.encode(value);
prev = value;
}
}
@Override
public IntDecoder createMatchingDecoder() {
return encoder.createMatchingDecoder();
}
@Override
public void reInit(OutputStream out) {
super.reInit(out);
prev = ILLEGAL_VALUE;
}
@Override
public String toString() {
return "Unique (" + encoder.toString() + ")";
}
}