tail

[Marco Sulla]

On Sat, 23 Apr 2022 at 23:18, Chris Angelico <rosuav at gmail.com> wrote:

> Ah. Well, then, THAT is why it's inefficient: you're seeking back one
> single byte at a time, then reading forwards. That is NOT going to
> play nicely with file systems or buffers.
>
> Compare reading line by line over the file with readlines() and you'll
> see how abysmal this is.
>
> If you really only need one line (which isn't what your original post
> suggested), I would recommend starting with a chunk that is likely to
> include a full line, and expanding the chunk until you have that
> newline. Much more efficient than one byte at a time.
>

Well, I would like to have a sort of tail, so to generalise to more than 1
line. But I think that once you have a good algorithm for one line, you can
repeat it N times.

I understand that you can read a chunk instead of a single byte, so when
the newline is found you can return all the cached chunks concatenated. But
will this make the search of the start of the line faster? I suppose you
have always to read byte by byte (or more, if you're using urf16 etc) and
see if there's a newline.