HMapSIW.java Source code

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Here is the source code for HMapSIW.java

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/*
 * Cloud9: A MapReduce Library for Hadoop
 * 
 * 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.
 */

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.hadoop.io.Writable;

/**
 * Writable representing a map where keys are Strings and values are ints. This
 * class is specialized for String objects to avoid the overhead that comes with
 * wrapping Strings inside <code>Text</code> objects.
 * 
 * @author Jimmy Lin
 */
public class HMapSIW extends HMapKI<String> implements Writable {
    private static final long serialVersionUID = -9179978557431493856L;

    /**
     * Creates a <code>HMapSIW</code> object.
     */
    public HMapSIW() {
        super();
    }

    /**
     * Deserializes the map.
     *
     * @param in source for raw byte representation
     */
    public void readFields(DataInput in) throws IOException {
        this.clear();

        int numEntries = in.readInt();
        if (numEntries == 0)
            return;

        for (int i = 0; i < numEntries; i++) {
            String k = in.readUTF();
            int v = in.readInt();
            put(k, v);
        }
    }

    /**
     * Serializes the map.
     *
     * @param out where to write the raw byte representation
     */
    public void write(DataOutput out) throws IOException {
        // Write out the number of entries in the map.
        out.writeInt(size());
        if (size() == 0)
            return;

        // Then write out each key/value pair.
        for (MapKI.Entry<String> e : entrySet()) {
            out.writeUTF(e.getKey());
            out.writeInt(e.getValue());
        }
    }

    /**
     * Returns the serialized representation of this object as a byte array.
     *
     * @return byte array representing the serialized representation of this object
     * @throws IOException
     */
    public byte[] serialize() throws IOException {
        ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
        DataOutputStream dataOut = new DataOutputStream(bytesOut);
        write(dataOut);

        return bytesOut.toByteArray();
    }

    /**
     * Creates a <code>HMapSIW</code> object from a <code>DataInput</code>.
     *
     * @param in source for reading the serialized representation
     * @return a newly-created <code>OHMapSIW</code> object
     * @throws IOException
     */
    public static HMapSIW create(DataInput in) throws IOException {
        HMapSIW m = new HMapSIW();
        m.readFields(in);

        return m;
    }

    /**
     * Creates a <code>HMapSIW</code> object from a byte array.
     *
     * @param bytes source for reading the serialized representation
     * @return a newly-created <code>OHMapSIW</code> object
     * @throws IOException
     */
    public static HMapSIW create(byte[] bytes) throws IOException {
        return create(new DataInputStream(new ByteArrayInputStream(bytes)));
    }
}