Negative offesets in mime.types

[Anonymous]

I'm trying to implement a filter for the Targa (tga) image type, and it turns out that the identifying information is at the end of the file.  I would like to perform a string match to identify the file, but I can't predict the offset from the beginning of the file to do this.  Does CUPS support the use of negative offsets in the mime.types file to make this happen?

 Thanks,
   Rob Jones