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VorbisCommentReader.javaAPI DocJaudiotagger 2.0.45857Wed Jun 08 11:59:18 BST 2011org.jaudiotagger.tag.vorbiscomment

VorbisCommentReader

public class VorbisCommentReader extends Object
Create the VorbisCommentTag by reading from the raw packet data

This is in the same format whether encoded with Ogg or Flac except the framing bit is only present when used within Ogg Vorbis 

From the http://xiph.org/vorbis/doc/Vorbis_I_spec.html#vorbis-spec-comment
Read decodes the packet data using the following algorithm:
[vendor_length] = read an unsigned integer of 32 bits
[vendor_string] = read a UTF-8 vector as [vendor_length] octets
[user_comment_list_length] = read an unsigned integer of 32 bits
iterate [user_comment_list_length] times {
5) [length] = read an unsigned integer of 32 bits
6) this iteration's user comment = read a UTF-8 vector as [length] octets
}
[framing_bit] = read a single bit as boolean
if ( [framing_bit] unset or end-of-packet ) then ERROR
done.

Fields Summary
public static Logger
logger
public static final int
FIELD_VENDOR_LENGTH_POS
public static final int
FIELD_VENDOR_STRING_POS
public static final int
FIELD_VENDOR_LENGTH_LENGTH
public static final int
FIELD_USER_COMMENT_LIST_LENGTH
public static final int
FIELD_COMMENT_LENGTH_LENGTH
private static final int
JAUDIOTAGGER_MAX_COMMENT_LENGTH
max comment length that jaudiotagger can handle, this isnt the maximum column length allowed but we dont dont allow comments larger than this because of problem with allocating memory (10MB shoudl be fine for all apps)
Constructors Summary
public VorbisCommentReader()
Methods Summary
public VorbisCommentTagread(byte[] rawdata, boolean isFramingBit)

param
rawdata
param
isFramingBit
return
logical representation of VorbisCommentTag
throws
IOException
throws
CannotReadException


        VorbisCommentTag tag = new VorbisCommentTag();

        byte[] b = new byte[FIELD_VENDOR_LENGTH_LENGTH];
        System.arraycopy(rawdata, FIELD_VENDOR_LENGTH_POS, b, FIELD_VENDOR_LENGTH_POS, FIELD_VENDOR_LENGTH_LENGTH);
        int pos = FIELD_VENDOR_LENGTH_LENGTH;
        int vendorStringLength = Utils.getIntLE(b);

        b = new byte[vendorStringLength];
        System.arraycopy(rawdata, pos, b, 0, vendorStringLength);
        pos += vendorStringLength;
        tag.setVendor(new String(b, VorbisHeader.CHARSET_UTF_8));
        logger.config("Vendor is:"+tag.getVendor());
        
        b = new byte[FIELD_USER_COMMENT_LIST_LENGTH];
        System.arraycopy(rawdata, pos, b, 0, FIELD_USER_COMMENT_LIST_LENGTH);
        pos += FIELD_USER_COMMENT_LIST_LENGTH;

        int userComments = Utils.getIntLE(b);
        logger.config("Number of user comments:" + userComments);
        
        for (int i = 0; i < userComments; i++)
        {
            b = new byte[FIELD_COMMENT_LENGTH_LENGTH];
            System.arraycopy(rawdata, pos, b, 0, FIELD_COMMENT_LENGTH_LENGTH);
            pos += FIELD_COMMENT_LENGTH_LENGTH;

            int commentLength = Utils.getIntLE(b);
            logger.config("Next Comment Length:" + commentLength);

            if(commentLength> JAUDIOTAGGER_MAX_COMMENT_LENGTH)
            {
                logger.warning(ErrorMessage.VORBIS_COMMENT_LENGTH_TOO_LARGE.getMsg(commentLength));
                break;
            }
            else if(commentLength>rawdata.length)
            {
                logger.warning(ErrorMessage.VORBIS_COMMENT_LENGTH_LARGE_THAN_HEADER.getMsg(commentLength,rawdata.length));
                break;
            }
            else
            {
                b = new byte[commentLength];
                System.arraycopy(rawdata, pos, b, 0, commentLength);
                pos += commentLength;

                VorbisCommentTagField fieldComment = new VorbisCommentTagField(b);
                logger.config("Adding:" + fieldComment.getId());
                tag.addField(fieldComment);
            }
        }

        //Check framing bit, only exists when vorbisComment used within OggVorbis       
        if (isFramingBit)
        {
            if ((rawdata[pos] & 0x01) != 1)
            {
                throw new CannotReadException(ErrorMessage.OGG_VORBIS_NO_FRAMING_BIT.getMsg((rawdata[pos] & 0x01)));
            }
        }
        return tag;