I think he's looking for Pascal source code to generate diff-data.
If you're using *NIX may be you can call the "diff" command and get it's output via a pipe. I can't remember how to create a pipe on Pascal but I'm sure it's possible.
If you actually need Pascal code to do the work, I did wrote a small program that does it. It was pretty simple and detects fairly differences but it's slower and less perfect than other tools, and I'm not sure it will work with binary data (I'd test it only with text data). It uses a sort of "incremental search". I found the algorithm incrementally: I did a simple diff-search program, then optimize it a bit, then a bit more, until I can't do it better. Most diff tools uses table-guided searches or matrix based algorithms much more complex than the mine. The sad thing is it was written in Spanish (naming and documentation).
I never released the code, but if you need it I'll give it to you with a MIT or ZLib license (open & free).