content: /*
   * 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.spark.network.protocol;
  
  import io.netty.buffer.ByteBuf;
  
  /**
   * Interface for an object which can be encoded into a ByteBuf. Multiple Encodable objects are
   * stored in a single, pre-allocated ByteBuf, so Encodables must also provide their length.
   *
   * Encodable objects should provide a static "decode(ByteBuf)" method which is invoked by
   * {@link MessageDecoder}. During decoding, if the object uses the ByteBuf as its data (rather than
   * just copying data from it), then you must retain() the ByteBuf.
   *
   * Additionally, when adding a new Encodable Message, add it to {@link Message.Type}.
   */
  public interface Encodable {
    /** Number of bytes of the encoded form of this object. */
    int encodedLength();
  
    /**
     * Serializes this object by writing into the given ByteBuf.
     * This method must write exactly encodedLength() bytes.
     */
    void encode(ByteBuf buf);
  }
  