/**
* Copyright The Apache Software Foundation
*
* 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.hadoop.hbase.io.hfile.bucket;
import java.io.Serializable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
/**
* Map from type T to int and vice-versa. Used for reducing bit field item
* counts.
*/
@InterfaceAudience.Private
public final class UniqueIndexMap<T> implements Serializable {
private static final long serialVersionUID = -1145635738654002342L;
ConcurrentHashMap<T, Integer> mForwardMap = new ConcurrentHashMap<>();
ConcurrentHashMap<Integer, T> mReverseMap = new ConcurrentHashMap<>();
AtomicInteger mIndex = new AtomicInteger(0);
// Map a length to an index. If we can't, allocate a new mapping. We might
// race here and get two entries with the same deserialiser. This is fine.
int map(T parameter) {
Integer ret = mForwardMap.get(parameter);
if (ret != null) return ret.intValue();
int nexti = mIndex.incrementAndGet();
assert (nexti < Short.MAX_VALUE);
mForwardMap.put(parameter, nexti);
mReverseMap.put(nexti, parameter);
return nexti;
}
T unmap(int leni) {
Integer len = Integer.valueOf(leni);
assert mReverseMap.containsKey(len);
return mReverseMap.get(len);
}
}