Change UnexpectedEnd to include the expected size

[aviramha]

Right now the enum variant of ErrorKind UnexpectedEnd is void. I suggest changing it to UnexpectedEnd(usize) so the caller will be able to know how much data it is missing for success.

This will allow development of stream protocols to be more efficient by reserving buffers & calling the decode only when data is complete.

More specifically, I'm now developing a actix-codec Encoder/Decoder and I'd wish to reserve the additional missing data before returning.

Thoughts?

[VictorKoenders]

#[derive(Decode)]
struct Foo {
    a: u64, 
    b: u64
}

Because bincode does not have a look ahead system, if you feed this struct only 1 byte, it would report a UnexpectedEnd(7) as u64 needs 8 bytes. Not the 15 bytes it actually needs. Would this be good enough for your case?

[aviramha]

Yes.