Reading results from dmd -profile

[cal]

I am trying to read the text file (trace.log) created by running 
the dmd profiler on some code, so that I can use demangle to make 
the output a bit more readable. I can read it in as a char[], but 
the whenever I try any string ops I get an exception because 
there are invalid UTF-8 sequences in the text.

So two questions: why does the output contain invalid UTF-8 
sequences, and what would be a good way to handle the invalid 
sequences, since I guess I need them for proper demangling?

Cheers