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> {

     /**

      * The GUID this reader {@linkplain #getApplyingIds() applies to}

      */

     private final static GUID[] APPLYING = { GUID.GUID_HEADER_EXTENSION };

     /**

      * 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(

             final List<Class<? extends ChunkReader>> toRegister,

             final boolean readChunkOnce) {

         super(toRegister, readChunkOnce);

     }

     /**

      * {@inheritDoc}

      */

     public boolean canFail() {

         return false;

     }

     /**

      * {@inheritDoc}

      */

     @Override

     protected AsfExtendedHeader createContainer(final long streamPosition,

             final BigInteger chunkLength, final 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[] getApplyingIds() {

         return APPLYING.clone();

     }

 }