Idiomatic

[chris-ha458]

a85c5fe is worth looking at.

This would only be a problem when the file size is around usize::MAX which is around 2^64 bytes.

[chris-ha458]

something like this would be idiomatic,
but if 2^64 input is fed in there, I honestly think something would have gone wrong before this point

remaining = remaining.checked_add_signed(err.upto).ok_or_else(|| {
                        CodecError {
                            upto: remaining as isize,
                            cause: Cow::from("Integer overflow occurred"),
                        }
                    })?;