/// <summary>
/// Looks for a tag starting at a specified position and moves
/// the cursor to its start position.
/// </summary>
/// <param name="position">
/// A <see cref="long" /> value reference specifying at what
/// position the potential tag starts. If a tag is found,
/// this value will be updated to the position at which the
/// found tag ends.
/// </param>
/// <returns>
/// A <see cref="TagLib.TagTypes" /> value specifying the
/// type of tag found at the specified position, or <see
/// cref="TagTypes.None" /> if no tag was found.
/// </returns>
TagTypes ReadTagInfo(ref long position)
{
file.Seek(position);
ByteVector data = file.ReadBlock(read_size);
try {
if (data.StartsWith(Ape.Footer.FileIdentifier))
{
Ape.Footer footer =
new Ape.Footer(data);
position += footer.CompleteTagSize;
return(TagTypes.Ape);
}
if (data.StartsWith(Id3v2.Header.FileIdentifier))
{
Id3v2.Header header =
new Id3v2.Header(data);
position += header.CompleteTagSize;
return(TagTypes.Id3v2);
}
} catch (CorruptFileException) {
}
return(TagTypes.None);
}
/// <summary>
/// Looks for a tag ending at a specified position and moves
/// the cursor to its start position.
/// </summary>
/// <param name="position">
/// A <see cref="long" /> value reference specifying at what
/// position the potential tag ends. If a tag is found,
/// this value will be updated to the position at which the
/// found tag starts.
/// </param>
/// <returns>
/// A <see cref="TagLib.TagTypes" /> value specifying the
/// type of tag found at the specified position, or <see
/// cref="TagTypes.None" /> if no tag was found.
/// </returns>
TagTypes ReadTagInfo(ref long position)
{
if (position - read_size < 0)
{
return(TagTypes.None);
}
file.Seek(position - read_size);
ByteVector data = file.ReadBlock(read_size);
try {
int offset = (int)(data.Count - Ape.Footer.Size);
if (data.ContainsAt(Ape.Footer.FileIdentifier, offset))
{
Ape.Footer footer = new Ape.Footer(data.Mid(offset));
// If the complete tag size is zero or
// the tag is a header, this indicates
// some sort of corruption.
if (footer.CompleteTagSize == 0 ||
(footer.Flags & Ape.FooterFlags.IsHeader) != 0)
{
return(TagTypes.None);
}
position -= footer.CompleteTagSize;
return(TagTypes.Ape);
}
offset = (int)(data.Count - Id3v2.Footer.Size);
if (data.ContainsAt(Id3v2.Footer.FileIdentifier,
offset))
{
var footer = new Id3v2.Footer(data.Mid(offset));
position -= footer.CompleteTagSize;
return(TagTypes.Id3v2);
}
if (data.StartsWith(Id3v1.Tag.FileIdentifier))
{
position -= Id3v1.Tag.Size;
return(TagTypes.Id3v1);
}
} catch (CorruptFileException) {
}
return(TagTypes.None);
}
