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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.handler.codec.serialization;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.ObjectInputStream;
  import java.io.ObjectStreamClass;
  import java.io.StreamCorruptedException;
  
  class CompactObjectInputStream extends ObjectInputStream {
  
      private final ClassResolver classResolver;
  
      CompactObjectInputStream(InputStream in, ClassResolver classResolver) throws IOException {
          super(in);
          if (classResolver == null) {
              throw new NullPointerException("classResolver");
          }
          this.classResolver = classResolver;
      }
  
      @Override
      protected void readStreamHeader() throws IOException {
          int version = readByte() & 0xFF;
          if (version != STREAM_VERSION) {
              throw new StreamCorruptedException(
                      "Unsupported version: " + version);
          }
      }
  
      @Override
      protected ObjectStreamClass readClassDescriptor()
              throws IOException, ClassNotFoundException {
          int type = read();
          if (type < 0) {
              throw new EOFException();
          }
          switch (type) {
          case CompactObjectOutputStream.TYPE_FAT_DESCRIPTOR:
              return super.readClassDescriptor();
          case CompactObjectOutputStream.TYPE_THIN_DESCRIPTOR:
              String className = readUTF();
              Class<?> clazz = classResolver.resolve(className);
              ObjectStreamClass streamClass = ObjectStreamClass.lookup(clazz);
              if (streamClass == null) {
                  // If streamClass is null its very likely that we had an old netty version that was writing an
                  // interface with a thin descriptor. Fall back to use ObjectStreamClazz.lookupAny(..) to resolve
                  // it.
                  //
                  // This will only work on java6+ but if we hit this line its very likely that a user is upgrading
                  // from netty 3.2.x which was using the method before and so use java6+.
                  //
                  // See https://github.com/netty/netty/commit/6c2eba79d70a532822a0e38092faa9783d90906b
                  streamClass = ObjectStreamClass.lookupAny(clazz);
              }
              return streamClass;
          default:
              throw new StreamCorruptedException(
                      "Unexpected class descriptor type: " + type);
          }
      }
  
      @Override
      protected Class<?> resolveClass(ObjectStreamClass desc) throws IOException, ClassNotFoundException {
          Class<?> clazz;
          try {
              clazz = classResolver.resolve(desc.getName());
          } catch (ClassNotFoundException ex) {
              clazz = super.resolveClass(desc);
          }
  
          return clazz;
      }
  
  }