How to read everything until a parser succeeds

[PNys]

Hi there,

I have been stuck with this issues for a few days now and I can't seem to figure it out on my own:

So basically the title, I want to ready everything until a parser succeeds. So essentially the terminated combinator. Here is a snippet:

let parser = make_parser(); // placeholder for brevity
let (input, text) = terminated(read_all, parser).parse(input)?;

My issues is the first argument of terminated read_all. I seem to have tried everything, but nothing works, either it stop too early and throws an error because the terminating parser is invalid or it just reads all the way through to the end and throws an error because it is eof.

The annoying part it seems is, that the text I am trying to read basically contains all types of characters and it can even contain parts of what the terminator parses. Is there a way to make terminated check the terminator before reading every character or a complete alternative to achieve this?

I think just realized the text could even exactly contain the terminator, but I need the very last one, is there a way to parse from the end of the input?

[PNys]

I was able to put something together with fold which does deliver me the result I want. However, now I have the problem that afaik with fold you can only build owned types (String in my case) and I need to pass the parsed value into another parser after this, but I can't borrow the value to the parser because I am referencing a local variable.

Is there no take_until which takes a parser instead of a tag?

[marcdejonge]

So you just want the parser to run and then some other parser after that? A tuple of parsers is also a parser in itself, so you should be able to run:

(make_parser(), read_all).parse(input)?

[PNys]

I have now come up with a solution, which does what I want. It just is a little inefficient.

I use fold step through a each character of the input. For each character I check if I have reached the terminator I am looking for. If that fails I simply read one char and increment a counter by 1. I do that until I have found the terminator (fold still runs through the entire input, because I couldn't figure out how to end it prematurely). Fold will give me the number of characters I need to read.
This let's then simply call terminate(take(<fold_result>), parser) to get what I want.

If anyone knows a better way to do this without having to iterate over the input twice, please let me now, but now it works.