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// or more contributor license agreements.  See the NOTICE file
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// 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.doris.common.io;

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

/**
 * A serializable object which implements a simple, efficient, serialization 
 * protocol, based on {@link DataInput} and {@link DataOutput}.
 *
 * <p>Any <code>key</code> or <code>value</code> type in the Hadoop Map-Reduce
 * framework implements this interface.</p>
 * 
 * <p>Implementations typically implement a static <code>read(DataInput)</code>
 * method which constructs a new instance, calls {@link #readFields(DataInput)} 
 * and returns the instance.</p>
 * 
 * <p>Example:</p>
 * <p><blockquote><pre>
 *     public class MyWritable implements Writable {
 *       // Some data     
 *       private int counter;
 *       private long timestamp;
 *       
 *       public void write(DataOutput out) throws IOException {
 *         out.writeInt(counter);
 *         out.writeLong(timestamp);
 *       }
 *       
 *       public void readFields(DataInput in) throws IOException {
 *         counter = in.readInt();
 *         timestamp = in.readLong();
 *       }
 *       
 *       public static MyWritable read(DataInput in) throws IOException {
 *         MyWritable w = new MyWritable();
 *         w.readFields(in);
 *         return w;
 *       }
 *     }
 * </pre></blockquote></p>
 */
public interface Writable {
    /** 
     * Serialize the fields of this object to <code>out</code>.
     * 
     * @param out <code>DataOuput</code> to serialize this object into.
     * @throws IOException
     */
    void write(DataOutput out) throws IOException;

    /** 
     * Deserialize the fields of this object from <code>in</code>.  
     * 
     * <p>For efficiency, implementations should attempt to re-use storage in the 
     * existing object where possible.</p>
     * 
     * @param in <code>DataInput</code> to deseriablize this object from.
     * @throws IOException
     */
    void readFields(DataInput in) throws IOException;
}
