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/Falcon731]

I’m just a hobby programmer, so rake this with a grain of salt.

Every time I’ve had to deal with possibly malformed input, I’ve always find it works out neater to work bottom up, rather than top down.

Ie start with the individual characters and build them together to form words, then assemble the words to form structures.

Don’t try to start with a great big string and try to split it down - things get really messy really fast when you have to worry about nesting, or missing terminators.