/// <summary>
/// Creates a <see cref="ByteVector"/> for the comment segment of this file
/// </summary>
/// <returns>
/// A <see cref="ByteVector"/> with the whole comment segment, if a comment tag
/// exists, otherwise null.
/// </returns>
private ByteVector RenderCOMSegment()
{
// check, if Comment is contained
JpegCommentTag com_tag = GetTag(TagTypes.JpegComment) as JpegCommentTag;
if (com_tag == null)
{
return(null);
}
// create comment data
ByteVector com_data =
ByteVector.FromString(com_tag.Value + "\0", StringType.Latin1);
uint segment_size = (uint)(2 + com_data.Count);
// do not render data segments, which cannot fit into the possible segment size
if (segment_size > ushort.MaxValue)
{
throw new Exception("Comment Segment is too big to render");
}
// create segment
ByteVector data = new ByteVector(new byte[] { 0xFF, (byte)Marker.COM });
data.Add(ByteVector.FromUShort((ushort)segment_size));
data.Add(com_data);
return(data);
}
/// <summary>
/// Reads a COM segment to find the JPEG comment.
/// </summary>
/// <param name="length">
/// The length of the segment that will be read.
/// </param>
private void ReadCOMSegment(int length)
{
if ((ImageTag.TagTypes & TagLib.TagTypes.JpegComment) != 0x00)
{
return;
}
long position = Tell;
JpegCommentTag com_tag;
if (length == 0)
{
com_tag = new JpegCommentTag();
}
else
{
ByteVector data = ReadBlock(length);
int terminator = data.Find("\0", 0);
if (terminator < 0)
{
com_tag = new JpegCommentTag(data.ToString());
}
else
{
com_tag = new JpegCommentTag(data.Mid(0, terminator).ToString());
}
}
ImageTag.AddTag(com_tag);
AddMetadataBlock(position - 4, length + 4);
}