org.bboxdb.network.client.SequenceNumberGenerator Maven / Gradle / Ivy
/*******************************************************************************
*
* Copyright (C) 2015-2018 the BBoxDB project
*
* Licensed 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.bboxdb.network.client;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
public class SequenceNumberGenerator {
/**
* The next unused free request id
*/
protected final AtomicInteger sequenceNumber = new AtomicInteger();
/**
* The used numbers
*/
protected final Set usedNumbers = new HashSet<>();
/**
* The amount of tried to find an empty sequence number
*/
private final static int MAX_TRIES = 10000;
public SequenceNumberGenerator() {
sequenceNumber.set(0);
}
/**
* Get the next free sequence number
*
* @return The sequence number
*/
public synchronized short getNextSequenceNummber() {
short nextNumber = (short) sequenceNumber.getAndIncrement();
int numberTry = 1;
// Check if sequence number is unused
while(usedNumbers.contains(nextNumber)) {
if(numberTry > MAX_TRIES) {
throw new IllegalArgumentException("Unable to get sequence number with tries: " + MAX_TRIES);
}
nextNumber = (short) sequenceNumber.getAndIncrement();
numberTry++;
}
usedNumbers.add(nextNumber);
return nextNumber;
}
/**
* Get the current sequence number
*
* @return The sequence number
*/
public short getLastGeneratedNumber() {
return sequenceNumber.shortValue();
}
/**
* Release the given sequence number
* @param sequenceNumber
* @return
*/
public synchronized boolean releaseNumber(final short sequenceNumber) {
return usedNumbers.remove(sequenceNumber);
}
/**
* Get the amount of used numbers
* @return
*/
public int getUsedNumbers() {
return usedNumbers.size();
}
}