code: private InputStream decompress( UntarCompressionMethod compression, final File file, final InputStream istream )
  			throws IOException, ArchiverException
  	{
  		if ( compression == UntarCompressionMethod.GZIP )
  		{
  			return new GZIPInputStream( istream );
  		}
  		else if ( compression == UntarCompressionMethod.BZIP2 )
  		{
  			return new BZip2CompressorInputStream( istream );
  		}
          else if ( compression == UntarCompressionMethod.SNAPPY )
          {
              return new SnappyInputStream( istream );
          }
  		return istream;
  	}
docs: This method wraps the input stream with the
  corresponding decompression method
  
  @param file    provides location information for BuildException
  @param istream input stream
  @return input stream with on-the-fly decompression
  @throws IOException thrown by GZIPInputStream constructor