feat(tvix/store/blobservice): implement seek r/6434

For memory and sled, it's trivial, as we already have a Cursor<Vec<u8>>.
For gRPC, we simply reject going backwards, and skip n bytes for now.

Once the gRPC protocol gets support for offsets and verified streaming,
this can be improved.

Change-Id: I734066a514aed287ea3db64bfb1680911ac1eeb0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8885
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

1 files changed, 2 insertions, 2 deletions

diff --git a/tvix/store/src/blobservice/sled.rs b/tvix/store/src/blobservice/sled.rs
index bff50ff3eb4a..67897cb94a24 100644
--- a/tvix/store/src/blobservice/sled.rs
+++ b/tvix/store/src/blobservice/sled.rs
@@ -1,4 +1,4 @@
-use super::{BlobService, BlobWriter};
+use super::{BlobReader, BlobService, BlobWriter};
 use crate::{B3Digest, Error};
 use std::{
     io::{self, Cursor},
@@ -65,7 +65,7 @@ impl BlobService for SledBlobService {
     }
 
     #[instrument(skip(self), fields(blob.digest=%digest))]
-    fn open_read(&self, digest: &B3Digest) -> Result<Option<Box<dyn io::Read + Send>>, Error> {
+    fn open_read(&self, digest: &B3Digest) -> Result<Option<Box<dyn BlobReader>>, Error> {
         match self.db.get(digest.to_vec()) {
             Ok(None) => Ok(None),
             Ok(Some(data)) => Ok(Some(Box::new(Cursor::new(data[..].to_vec())))),