package org.jaudiotagger.audio.asf.io;

 import org.jaudiotagger.audio.asf.data.AsfExtendedHeader;

 import org.jaudiotagger.audio.asf.data.GUID;

 import org.jaudiotagger.audio.asf.util.Utils;

 import java.io.IOException;

 import java.io.InputStream;

 import java.math.BigInteger;

 import java.util.List;

 /**

  * This reader reads an ASF header extension object from an {@link InputStream} and creates an

  * {@link AsfExtendedHeader} object.<br>

  * 

  * @author Christian Laireiter

  */

 public class AsfExtHeaderReader extends ChunkContainerReader<AsfExtendedHeader>

 {

     /**

      * Creates a reader instance, which only utilizes the given list of chunk

      * readers.<br>

      * 

      * @param toRegister

      *            List of {@link ChunkReader} class instances, which are to be

      *            utilized by the instance.

      * @param readChunkOnce

      *            if <code>true</code>, each chunk type (identified by chunk

      *            GUID) will handled only once, if a reader is available, other

      *            chunks will be discarded.

      */

     public AsfExtHeaderReader(List<Class<? extends ChunkReader>> toRegister, boolean readChunkOnce)

     {

         super(toRegister, readChunkOnce);

     }

     /**

      * {@inheritDoc}

      */

     @Override

     protected AsfExtendedHeader createContainer(long streamPosition, BigInteger chunkLength, InputStream stream) throws IOException

     {

         Utils.readGUID(stream); // First reserved field (should be a specific GUID.

         Utils.readUINT16(stream); // Second reserved field (should always be 6)

         final long extensionSize = Utils.readUINT32(stream);

         assert extensionSize == 0 || extensionSize >= 24;

         assert chunkLength.subtract(BigInteger.valueOf(46)).longValue() == extensionSize;

         return new AsfExtendedHeader(streamPosition, chunkLength);

     }

     /**

      * {@inheritDoc}

      */

     public GUID getApplyingId()

     {

         return GUID.GUID_HEADER_EXTENSION;

     }

 }