refactor(users/edef/weave): simplify OwningRef handling r/8843

We switch to working with the underlying Arc<Bytes<u8>> type, since
Buffer<u8> is already essentially an OwningRef-esque subslice.

Because we're now working with an exposed Arc directly, we don't need
to have our own `unsafe impl StableAddress` any more.

Change-Id: I9ce2edc6899177145e15b72aa5380f708a62173c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12668
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

2 files changed, 12 insertions, 32 deletions

diff --git a/users/edef/weave/src/bytes.rs b/users/edef/weave/src/bytes.rs
deleted file mode 100644
index 689b8fdfc0c8..000000000000
--- a/users/edef/weave/src/bytes.rs
+++ /dev/null
@@ -1,27 +0,0 @@
-use owning_ref::{OwningRef, StableAddress};
-use polars::export::arrow::buffer::Buffer;
-use std::ops::Deref;
-
-/// An shared `[[u8; N]]` backed by a Polars [Buffer].
-pub type FixedBytes<const N: usize> = OwningRef<'static, Bytes, [[u8; N]]>;
-
-/// Wrapper struct to make [Buffer] implement [StableAddress].
-/// TODO(edef): upstream the `impl`
-pub struct Bytes(pub Buffer<u8>);
-
-/// SAFETY: [Buffer] is always an Arc+Vec indirection.
-unsafe impl StableAddress for Bytes {}
-
-impl Bytes {
-    pub fn map<U: ?Sized>(self, f: impl FnOnce(&[u8]) -> &U) -> OwningRef<'static, Self, U> {
-        OwningRef::new(self).map(f)
-    }
-}
-
-impl Deref for Bytes {
-    type Target = [u8];
-
-    fn deref(&self) -> &Self::Target {
-        &*self.0
-    }
-}
diff --git a/users/edef/weave/src/lib.rs b/users/edef/weave/src/lib.rs
index 8d365a4c40f1..db3d07e7de07 100644
--- a/users/edef/weave/src/lib.rs
+++ b/users/edef/weave/src/lib.rs
@@ -1,4 +1,5 @@
 use anyhow::Result;
+use owning_ref::ArcRef;
 use rayon::prelude::*;
 use std::{fs::File, ops::Range, slice};
 
@@ -8,8 +9,9 @@ use polars::{
     prelude::{ParquetReader, SerReader},
 };
 
-pub use crate::bytes::*;
-mod bytes;
+/// An shared `[[u8; N]]` backed by a Polars [Buffer].
+pub type FixedBytes<const N: usize> =
+    ArcRef<'static, polars::export::arrow::buffer::Bytes<u8>, [[u8; N]]>;
 
 pub const INDEX_NULL: u32 = !0;
 pub const DONE: &str = "\u{2714}";
@@ -60,10 +62,15 @@ fn into_fixed_binary_rechunk<const N: usize>(chunked: &BinaryChunked) -> FixedBy
     let chunked = chunked.rechunk();
     let mut iter = chunked.downcast_iter();
     let array = iter.next().unwrap();
+    assert!(iter.next().is_none());
 
-    let range = assert_fixed_dense::<N>(array);
-    Bytes(array.values().clone().sliced(range.start, range.len()))
-        .map(|buf| exact_chunks(buf).unwrap())
+    let (buf, off, len) = {
+        let range = assert_fixed_dense::<N>(array);
+        array.values().clone().sliced(range.start, range.len())
+    }
+    .into_inner();
+
+    ArcRef::new(buf).map(|bytes| exact_chunks(&bytes[off..off + len]).unwrap())
 }
 
 /// Ensures that the supplied Arrow array consists of densely packed bytestrings of length `N`.