Add primitive pipelined integrity stage

yama/src/pile/integrity.rs

@@ -120,6 +120,19 @@ impl<RP: RawPile> RawPile for RawPileIntegrityChecker<RP> {
         settings: StoragePipelineSettings,
         controller_send: Sender<ControllerMessage>,
     ) -> anyhow::Result<Sender<(ChunkId, Vec<u8>)>> {
-        todo!()
+        // TODO primitive implementation but good enough for now.
+        // May want metrics later?
+        let next_stage = self.underlying.build_storage_pipeline(settings, controller_send)?;
+        let (input, receiver) = crossbeam_channel::bounded::<(ChunkId, Vec<u8>)>(64);
+        std::thread::spawn(move || {
+            while let Ok((chunk_id, mut chunk)) = receiver.recv() {
+                let mut hasher = twox_hash::XxHash64::with_seed(XXH64_SEED);
+                hasher.write(&chunk);
+                let computed_hash = hasher.finish().to_be_bytes();
+                chunk.extend_from_slice(&computed_hash);
+                next_stage.send((chunk_id, chunk)).unwrap();
+            }
+        });
+        Ok(input)
     }
 }