[pbs-devel] [RFC v2 pxar 04/36] decoder: add optional payload input stream

[Christian Ebner]

> On 11.03.2024 14:21 CET Fabian Grünbichler <f.gruenbichler at proxmox.com> wrote:
> 
>  
> 
> same question as for the encoder - do we want to prevent misuse here and
> check/ensure that no payload_input has already been set before?
>

Also for the decoder I will opt for the suggestion by Dietmar and lock this
down for possible misuse by adding the optional parameter to the `new` method
instead.

> 
> style: these two could be combined into
> 
> if let Some(payload_input) = self.payload_input.as_mut() {
>     if seq_read_position(payload_input).await.transpose()?.is_none() {
>        // Skip payload padding for injected chunks in sync decoder
>        let to_skip = payload_ref.offset - self.payload_consumed;
>        self.skip_payload(to_skip).await?;
>     }
> }
>

Good, this will come in handy as Dietmar also suggested to add a header for
all the payloads stored in the separated payload archive. I plan on using the
existing PXAR_PAYLOAD header for this, also encoding the payload size. I will
therefore add a check for the header here and compare the sizes as found in
the payload input and metadata archives.

> 
> nit: this could also share the "skip" part with `skip_entry`, and take the
> input and length as parameter?

I opted against that, since `skip_entry` operates only on the metadata
archive, the `skip_payload` however on the `payload_input`. I could however
factor this out into a function which takes the input as parameter, making
thereby sure to have the correct input to skip bytes.

> 
> nit: casting to usize at the start would make the code easier to parse
> IMHO
>

Okay, I can send that as independent patch already I guess.