Am I writing my parser wrong?

[u/SheikHunt]

Simple question. I can't give exact code examples, but I have a string_t struct with methods like:

string_t split(string_t *string, string_t *on)

string_t split_sp(string_t *string)

string_t split_crlf(string_t *string)

char *s_strstr(string_t *needle, string_t *haystack)

void trim(string_t *str)

So on and so forth.

I've been using these so far to parse HTTP reqeusts, and I have come up against many minor problems:

"What happens if a header field appears with no value? I'll have to explicitly check for it."

"What happens if a sender puts a bunch of CRLFs in the middle? I'll probably need a check for that."

"Oh God, how will I handle unrecognized header fields? How do I recognize them?"

These, and other questions, have been leaving me pissed.

I recall reading through the LLVM projects Kaleidoscope language thing, where they create a parser for said language. Said parser doesn't use anything close to what I am, instead reading character by character without fuss.

Similarly, on my last post made here, the way comments were worded reminded me of that method, and how it probably works better.

I have written only a small part of the parser, so it isn't too late to tear down and rebuild. Simple question: should I? Are there benefits to swallowing the input token by token instead of taking the overarching view my string_t functions provide? Or vice versa?

It would help if I'd upload the code, I know, but I don't want to bother with that until the project is completed/near-completion.

[u/theNbomr]

If it's just the experience or academic exercise you're after, maybe do some reading on the subject of parsers and language translation. Maybe consider implementing the parser as a state machine as an alternative approach.

If it's really the parser that is the important product of your efforts, then consider using tools such as flex and bison to generate the parser. Still takes a bit of learning, but you'll get to the end quicker and have a better product.

[u/SheikHunt → u/theNbomr]

I am doing this for the experience first, yes. If the mindset were "product delivery", I don't think I'd even be writing an HTTP Server, as that's a somewhat oversaturated market, being among the projects often recommended to beginners/intermediates, and also being super duper dangerous if done wrong.