org.apache.cassandra.db.commitlog.ReplayPosition.java Source code

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Here is the source code for org.apache.cassandra.db.commitlog.ReplayPosition.java

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package org.apache.cassandra.db.commitlog;
/*
 * 
 * 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.
 * 
 */

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Comparator;

import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.common.collect.Ordering;

import org.apache.cassandra.io.ICompactSerializer2;
import org.apache.cassandra.io.sstable.SSTable;

public class ReplayPosition implements Comparable<ReplayPosition> {
    public static final ReplayPositionSerializer serializer = new ReplayPositionSerializer();

    // NONE is used for SSTables that are streamed from other nodes and thus have no relationship
    // with our local commitlog. The values satisfy the critera that
    //  - no real commitlog segment will have the given id
    //  - it will sort before any real replayposition, so it will be effectively ignored by getReplayPosition
    public static final ReplayPosition NONE = new ReplayPosition(-1, 0);

    /**
     * Convenience method to compute the replay position for a group of SSTables.
     * @param sstables
     * @return the most recent (highest) replay position
     */
    public static ReplayPosition getReplayPosition(Iterable<? extends SSTable> sstables) {
        if (Iterables.isEmpty(sstables))
            return NONE;

        Function<SSTable, ReplayPosition> f = new Function<SSTable, ReplayPosition>() {
            public ReplayPosition apply(SSTable sstable) {
                return sstable.replayPosition;
            }
        };
        Ordering<ReplayPosition> ordering = Ordering.from(ReplayPosition.comparator);
        return ordering.max(Iterables.transform(sstables, f));
    }

    public final long segment;
    public final int position;

    public static final Comparator<ReplayPosition> comparator = new Comparator<ReplayPosition>() {
        public int compare(ReplayPosition o1, ReplayPosition o2) {
            if (o1.segment != o2.segment)
                return new Long(o1.segment).compareTo(o2.segment);

            return new Integer(o1.position).compareTo(o2.position);
        }
    };

    public ReplayPosition(long segment, int position) {
        this.segment = segment;
        assert position >= 0;
        this.position = position;
    }

    public int compareTo(ReplayPosition other) {
        return comparator.compare(this, other);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (o == null || getClass() != o.getClass())
            return false;

        ReplayPosition that = (ReplayPosition) o;

        if (position != that.position)
            return false;
        return segment == that.segment;
    }

    @Override
    public int hashCode() {
        int result = (int) (segment ^ (segment >>> 32));
        result = 31 * result + position;
        return result;
    }

    @Override
    public String toString() {
        return "ReplayPosition(" + "segmentId=" + segment + ", position=" + position + ')';
    }

    public static class ReplayPositionSerializer implements ICompactSerializer2<ReplayPosition> {
        public void serialize(ReplayPosition rp, DataOutput dos) throws IOException {
            dos.writeLong(rp.segment);
            dos.writeInt(rp.position);
        }

        public ReplayPosition deserialize(DataInput dis) throws IOException {
            return new ReplayPosition(dis.readLong(), dis.readInt());
        }
    }
}