Re: [pbs-devel] [PATCH pxar] decoder: sync: remove needless wrapper around `decoder::Contents`

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

sorry for the late reply

NAK

On Fri, Aug 11, 2023 at 11:56:00AM +0200, Max Carrara wrote:
> Similarly to the `impl` for `tokio::io::AsyncRead` in `decoder::aio`,
> this implements the `std::io::Read` trait on `decoder::Contents`
> directly while removing the wrapper.
> 
> This allows `decoder::Contents` to be used in both synchronous
> and asynchronous contexts.
> 
> Signed-off-by: Max Carrara <m.carrara@proxmox.com>
> ---
>  src/decoder/sync.rs | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/src/decoder/sync.rs b/src/decoder/sync.rs
> index 5597a03..be576f8 100644
> --- a/src/decoder/sync.rs
> +++ b/src/decoder/sync.rs
> @@ -5,7 +5,7 @@ use std::path::Path;
>  use std::pin::Pin;
>  use std::task::{Context, Poll};
> 
> -use crate::decoder::{self, SeqRead};
> +use crate::decoder::{self, Contents, SeqRead};
>  use crate::util::poll_result_once;
>  use crate::Entry;
> 
> @@ -69,7 +69,7 @@ impl<T: SeqRead> Decoder<T> {
> 
>      /// Get a reader for the contents of the current entry, if the entry has contents.
>      pub fn contents(&mut self) -> Option<Contents<T>> {
> -        self.inner.content_reader().map(|inner| Contents { inner })
> +        self.inner.content_reader()
>      }
> 
>      /// Get the size of the current contents, if the entry has contents.
> @@ -118,13 +118,8 @@ impl<T: io::Read> SeqRead for StandardReader<T> {
>      }
>  }
> 
> -/// Reader for file contents inside a pxar archive.
> -pub struct Contents<'a, T: SeqRead> {
> -    inner: decoder::Contents<'a, T>,
> -}
> -
> -impl<'a, T: SeqRead> io::Read for Contents<'a, T> {
> +impl<'a, T: SeqRead> io::Read for decoder::Contents<'a, T> {

`Read` is a sync interface and `poll_result_once()` *requires* it to
actually return `Ready`, and panics otherwise. This is only allowed (and
therefore "guaranteed" to work) when coming from the `sync` submodule,
so only *its* readers should implement it.

If anything, I'd go the other way round, take `pxar::decoder::Contents`
private and have one in `aio` (or just ... reexport it there :P)

>      fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
> -        poll_result_once(super::seq_read(&mut self.inner, buf))
> +        poll_result_once(super::seq_read(self.input, buf))
>      }
>  }
> --
> 2.39.2