Rename `try_fill` or `fill_bytes`?

[dhardy]

I'm not going to break out regexxer yet because I'm not convinced either way yet, but we should probably resolve this.

[pitdicker]

An other thought: for try_fill it may make sense to return the number of filled bytes. In case of an error, maybe there is still part of the result ready.

fn try_fill(&mut self, dest: &mut [u8]) -> Result<usize, Error>;

If we go this route, fill_bytes should return the number of filled bytes too. If we were to make this change, it seems ok to me to also change the name to fill.

fn fill(&mut self, dest: &mut [u8]) -> usize;

[newpavlov]

I personally prefer fill more, as bytes part should be clear from the type signature. Also try_fill_bytes feels a bit clunky. But I can live with the old name as well.

[dhardy]

But @pitdicker try_fill should fill the buffer unless it fails, so it only makes sense to return a usize on error — unless this becomes like typical read functions which may succeed with less data than requested, but this significantly complicates usability.

[pitdicker]

Hm yes I messed up. If you return Result<usize, Error> it will give either a usize or an Error, not both. Then there is no argument in that for renaming.

There is no other simple way to say a slice is only partially filled, is there?

I don't have a preference for fill vs try_fill. Well, I like fill more, but do not al that much given the breakage.

It is not completely clear to me how much breakage we have until now. Is it only a little, or so much one more change does not really make it worse?

[dhardy]

I don't know; I guess there are a fair few users of rand by now, but no idea how many use fill_bytes.

[dhardy]

We merged try_fill_bytes: rust-random#225