I wrote a data validation utility to use with files transferred by modem and tending to have errors in them, had to read the header to determine data type, validate each field by type, handle crashes gracefully, etc

SLOW doesn't even begin to describe this! But it did work! The validation methods could easily use a table lookup rather than code, so that would compare files well enough

Wouldn't want to run it on LIVE data, though!

A more reasonable concept was a checksum of the text fields, plus a table sum of the numerics. It solved most of the problems in about 1/20 the time!