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Sourcecode: libjlayer-java version File versions  Download package

JavaLayerUtils.java

/*
 * 11/19/04       1.0 moved to LGPL.
 * 12/12/99       Initial version.  mdm@techie.com
 *-----------------------------------------------------------------------
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as published
 *   by the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *----------------------------------------------------------------------
 */

package javazoom.jl.decoder;

import java.io.IOException;
import java.io.InputStream;
import java.io.InvalidClassException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.lang.reflect.Array;

/**
 * The JavaLayerUtils class is not strictly part of the JavaLayer API.
 * It serves to provide useful methods and system-wide hooks.
 * 
 * @author MDM
 */
00038 public class JavaLayerUtils
{
      static private JavaLayerHook  hook = null;
      
      /**
       * Deserializes the object contained in the given input stream.
       * @param in      The input stream to deserialize an object from.
       * @param cls     The expected class of the deserialized object. 
       */
00047       static public Object deserialize(InputStream in, Class cls)
            throws IOException
      {
            if (cls==null)
                  throw new NullPointerException("cls");
            
            Object obj = deserialize(in, cls);
            if (!cls.isInstance(obj))
            {
                  throw new InvalidObjectException("type of deserialized instance not of required class.");
            }
            
            return obj;
      }
      
      /**
       * Deserializes an object from the given <code>InputStream</code>.
       * The deserialization is delegated to an <code>
       * ObjectInputStream</code> instance. 
       * 
       * @param in      The <code>InputStream</code> to deserialize an object
       *                      from.
       * 
       * @return The object deserialized from the stream. 
       * @exception IOException is thrown if there was a problem reading
       *          the underlying stream, or an object could not be deserialized
       *          from the stream.
       * 
       * @see java.io.ObjectInputStream
       */
00077       static public Object deserialize(InputStream in)
            throws IOException
      {
            if (in==null)
                  throw new NullPointerException("in");
            
            ObjectInputStream objIn = new ObjectInputStream(in);
            
            Object obj;
            
            try
            {
                  obj = objIn.readObject();
            }
            catch (ClassNotFoundException ex)
            {
                  throw new InvalidClassException(ex.toString());
            }
            
            return obj;
      }

      /**
       * Deserializes an array from a given <code>InputStream</code>.
       * 
       * @param in            The <code>InputStream</code> to 
       *                            deserialize an object from.
       *                      
       * @param elemType      The class denoting the type of the array
       *                            elements.
       * @param length  The expected length of the array, or -1 if
       *                            any length is expected.
       */
00110       static public Object deserializeArray(InputStream in, Class elemType, int length)
            throws IOException
      {
            if (elemType==null)
                  throw new NullPointerException("elemType");
            
            if (length<-1)
                  throw new IllegalArgumentException("length");
            
            Object obj = deserialize(in);
            
            Class cls = obj.getClass();
            
            
            if (!cls.isArray())
                  throw new InvalidObjectException("object is not an array");
            
            Class arrayElemType = cls.getComponentType();
            if (arrayElemType!=elemType)
                  throw new InvalidObjectException("unexpected array component type");
                        
            if (length != -1)
            {
                  int arrayLength = Array.getLength(obj);
                  if (arrayLength!=length)
                        throw new InvalidObjectException("array length mismatch");
            }
            
            return obj;
      }

      static public Object deserializeArrayResource(String name, Class elemType, int length)
            throws IOException
      {           
            InputStream str = getResourceAsStream(name);
            if (str==null)
                  throw new IOException("unable to load resource '"+name+"'");
            
            Object obj = deserializeArray(str, elemType, length);
            
            return obj;
      }     
      
      static public void serialize(OutputStream out, Object obj)
            throws IOException
      {
            if (out==null)
                  throw new NullPointerException("out");
            
            if (obj==null)
                  throw new NullPointerException("obj");
            
            ObjectOutputStream objOut = new ObjectOutputStream(out);
            objOut.writeObject(obj);
                        
      }

      /**
       * Sets the system-wide JavaLayer hook.
       */
00170       static synchronized public void setHook(JavaLayerHook hook0)            
      {
            hook = hook0;
      }
      
      static synchronized public JavaLayerHook getHook()
      {
            return hook;      
      }
      
      /**
       * Retrieves an InputStream for a named resource. 
       * 
       * @param name    The name of the resource. This must be a simple
       *                      name, and not a qualified package name.
       * 
       * @return        The InputStream for the named resource, or null if
       *                      the resource has not been found. If a hook has been 
       *                      provided, its getResourceAsStream() method is called
       *                      to retrieve the resource. 
       */
00191       static synchronized public InputStream getResourceAsStream(String name)
      {
            InputStream is = null;
            
            if (hook!=null)
            {
                  is = hook.getResourceAsStream(name);      
            }
            else
            {
                  Class cls = JavaLayerUtils.class;
                  is = cls.getResourceAsStream(name);
            }
            
            return is;        
      }
}

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