DefaultMultiPartitionOracle.java

package ch.usi.paxosfs.partitioning;

import com.google.common.collect.Sets;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;

/**
 * This partitioning oracle will partition the path into the given number n (up to 8) of partitions. The partitioning works like this:
 * "/" - this is replicated by all partitions
 * "/1*" - everything under this path is in partition 1
 * "/2*" - everything under this path is in partition 2
 * ...
 * "/n*" - everything under this path is in partition n 
 * @author pacheco
 *
 */
public class DefaultMultiPartitionOracle implements PartitioningOracle {
	private int partitions;
	private HashMap<String, Set<Byte>> partitionMapping = new HashMap<>();
	private HashSet<Byte> allPartitions = new HashSet<>();
	
	private String firstElem(String path) {
		int elemEnd = path.indexOf("/", 1);
		if (elemEnd == -1) elemEnd = path.length();
		return path.substring(1, elemEnd);
	}
	
	public DefaultMultiPartitionOracle(int numberOfPartitions) {
		this.partitions = numberOfPartitions;
		for (byte i = 1; i <= partitions; i++) {
			partitionMapping.put(String.valueOf(i), Sets.newHashSet(Byte.valueOf(i)));
			allPartitions.add(Byte.valueOf(i));
		}
	}
	
	@Override
	public Set<Byte> partitionsOf(String path) {
        HashSet<Byte> reply = new HashSet<>();
		if (path.length() < 2) {
            reply.addAll(allPartitions);
        } else {
            Set<Byte> p;
            //p = partitionMapping.get(firstElem(path));
            p = partitionMapping.get(path.substring(1, 2));
            if (p == null) {
                reply.addAll(allPartitions);
            } else {
                reply.addAll(p);
            }
        }
        return reply;
	}
}