Better way to find regexp in emacs buffer

Question

I'm trying to make a function to read a whole buffer and find lines that match with regexp, I think to read the whole buffer and save to list of strings but I read that it's very inefficient. Whats the better form of do this?

Answer 1

It is really unclear what you want to do, but if you are looking for an "end in itself" interactive use, then you are probably covered by one of occur et al: e.g., M-x occur RET TODO RET.

If this is a step in a long processing chain, you should start with the sources for the above commands and ask a separate, more specific question.