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;
  
  import org.apache.spark.network.buffer.ManagedBuffer;
  
  /** An on-the-wire transmittable message. */
  public interface Message extends Encodable {
    /** Used to identify this request type. */
    Type type();
  
    /** An optional body for the message. */
    ManagedBuffer body();
  
    /** Whether to include the body of the message in the same frame as the message. */
    boolean isBodyInFrame();
  
    /** Preceding every serialized Message is its type, which allows us to deserialize it. */
    enum Type implements Encodable {
      ChunkFetchRequest(0), ChunkFetchSuccess(1), ChunkFetchFailure(2),
      RpcRequest(3), RpcResponse(4), RpcFailure(5),
      StreamRequest(6), StreamResponse(7), StreamFailure(8),
      OneWayMessage(9), User(-1);
  
      private final byte id;
  
      Type(int id) {
        assert id < 128 : "Cannot have more than 128 message types";
        this.id = (byte) id;
      }
  
      public byte id() { return id; }
  
      @Override public int encodedLength() { return 1; }
  
      @Override public void encode(ByteBuf buf) { buf.writeByte(id); }
  
      public static Type decode(ByteBuf buf) {
        byte id = buf.readByte();
        switch (id) {
          case 0: return ChunkFetchRequest;
          case 1: return ChunkFetchSuccess;
          case 2: return ChunkFetchFailure;
          case 3: return RpcRequest;
          case 4: return RpcResponse;
          case 5: return RpcFailure;
          case 6: return StreamRequest;
          case 7: return StreamResponse;
          case 8: return StreamFailure;
          case 9: return OneWayMessage;
          case -1: throw new IllegalArgumentException("User type messages cannot be decoded.");
          default: throw new IllegalArgumentException("Unknown message type: " + id);
        }
      }
    }
  }
  