MD5 in pattern library?

[xymox12]

Hi - This is a great piece of software, and I am (very, very slowly) getting my head around the pattern language.
I have a file with a checksum (first 4 bytes) that needs recalculating and reapplying if data in the rest of the file is changed. It happens to be based on md5 with a bit of post-processing to reduce to 4 bytes. However, md5 doesn't appear to be in the std::hash library.

1. Can I access ImHex functions, such as md5, directly from the pattern library?
2. If I modify a value identified by the pattern library elsewhere in the data, can I use the pattern code to apply a new checksum before I save the file? Or is that expecting too much of what the pattern library is designed to do?

Regarding md5: I can probably use an api as a workaround e.g. as a POC 'std::print("{0}", hex::http::get("api.hashify.net/hash/md5/hex?value=helloWorld"));', but that seems a bit clunky considering the inbuilt md5 function.