OFX is a painful spec; hard to know what is and is not used by various banks. I spent a bit of time writing a simple streaming OFXv1 (SGML) parser in Rust, but

OFX is a painful spec; hard to know what is and is not used by various banks. I spent a bit of time writing a simple streaming OFXv1 (SGML) parser in Rust, but I'm too ashamed to open-source it. The idea behind it was you read the OFX file byte by byte, using Nom to parse out tokens, and emit events when you hit SGML tags and element content (SAX-parser style). Then you have something over the top of that that accumulates state until it has a complete OFX data element, and then emits that. Advantage: Very low memory usage. Disadvantage: Probably overkill, since OFX files probably wouldn't be megabytes or gigabytes. It works for my bank feed, but who knows how many other banks! If you have any ideas on how to support this well in a non-hacky way that doesn't involve relying on a scripting language (all other existing implementations seem to be some form of scripting language :().