org.apache.tika.eval.db.AbstractDBBuffer Maven / Gradle / Ivy
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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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.tika.eval.db;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* Abstract buffer for map of values and unique ids.
*
* Use this for fast in memory lookups of smallish sets of values.
*
*/
abstract class AbstractDBBuffer {
private final Map m = new HashMap<>();
private final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
private final Lock r = rwl.readLock();
private final Lock w = rwl.writeLock();
private int numWrites = 0;
public int getId(String key) {
r.lock();
try {
Integer v = m.get(key);
if (v != null) {
return v;
}
} finally {
r.unlock();
}
try {
w.lock();
Integer v = m.get(key);
if (v != null) {
return v;
}
v = m.size()+1;
m.put(key, v);
write(v, key);
numWrites++;
return v;
} finally {
w.unlock();
}
}
public int getNumWrites() {
return numWrites;
}
//Odd to throw RuntimeException, I know. It should be
//catastrophic if this buffer can't write to the db.
public abstract void write(int id, String value) throws RuntimeException;
public abstract void close() throws SQLException;
}