org.apache.cassandra.db.TimestampClock.java Source code

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

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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,
 * 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.cassandra.db;

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

import org.apache.log4j.Logger;
import org.apache.commons.lang.ArrayUtils;

import org.apache.cassandra.io.ICompactSerializer2;

/**
 * A simple clock composed of a timestamp.
 * The comparison is the timestamp comparison.
 */
public class TimestampClock implements IClock {
    private static Logger logger_ = Logger.getLogger(TimestampClock.class);
    public static TimestampClock MIN_VALUE = new TimestampClock(Long.MIN_VALUE);
    public static TimestampClock ZERO_VALUE = new TimestampClock(0);
    public static ICompactSerializer2<IClock> SERIALIZER = new TimestampClockSerializer();

    private final long timestamp;

    public TimestampClock(long timestamp) {
        this.timestamp = timestamp;
    }

    public long timestamp() {
        return timestamp;
    }

    public ClockRelationship compare(IClock other) {
        assert other instanceof TimestampClock : "Wrong class type.";

        long otherTimestamp = ((TimestampClock) other).timestamp();
        if (timestamp > otherTimestamp) {
            return ClockRelationship.GREATER_THAN;
        } else if (timestamp == otherTimestamp) {
            return ClockRelationship.EQUAL;
        }
        // timestamp < otherTimestamp
        return ClockRelationship.LESS_THAN;
    }

    public IClock getSuperset(List<IClock> otherClocks) {
        IClock max = this;

        for (IClock clock : otherClocks) {
            if (clock.compare(max) == ClockRelationship.GREATER_THAN) {
                max = clock;
            }
        }

        return max;
    }

    public int size() {
        return DBConstants.tsSize_;
    }

    public ClockType type() {
        return ClockType.Timestamp;
    }

    public void serialize(DataOutput out) throws IOException {
        SERIALIZER.serialize(this, out);
    }

    public String toString() {
        return Long.toString(timestamp);
    }

    @Override
    public boolean equals(Object o) {
        return o instanceof TimestampClock && compare((TimestampClock) o) == ClockRelationship.EQUAL;
    }

    @Override
    public int hashCode() {
        return (int) (timestamp ^ (timestamp >>> 32));
    }
}

class TimestampClockSerializer implements ICompactSerializer2<IClock> {
    public void serialize(IClock tc, DataOutput out) throws IOException {
        out.writeLong(((TimestampClock) tc).timestamp());
    }

    public IClock deserialize(DataInput in) throws IOException {
        return new TimestampClock(in.readLong());
    }
}