refactor(tvix/nix-compat): make NixHash an enum with fixed-len bytes r/6807

Less Vec<u8> passed around.

Change-Id: Ie153a6bfaa084d7490ffa38634efdf5f3c31a768
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9722
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

1 files changed, 3 insertions, 7 deletions

diff --git a/tvix/nix-compat/src/derivation/mod.rs b/tvix/nix-compat/src/derivation/mod.rs
index 0e98e24f43dd..3c08d61831ba 100644
--- a/tvix/nix-compat/src/derivation/mod.rs
+++ b/tvix/nix-compat/src/derivation/mod.rs
@@ -168,7 +168,8 @@ impl Derivation {
             // This is not the [NixHash::to_nix_hash_string], but without the sha256: prefix).
             for (drv_path, output_names) in &self.input_derivations {
                 replaced_input_derivations.insert(
-                    data_encoding::HEXLOWER.encode(&fn_get_derivation_or_fod_hash(drv_path).digest),
+                    data_encoding::HEXLOWER
+                        .encode(fn_get_derivation_or_fod_hash(drv_path).digest_as_bytes()),
                     output_names.clone(),
                 );
             }
@@ -186,12 +187,7 @@ impl Derivation {
             hasher.finalize().to_vec()
         });
 
-        // We populate the struct directly, as we know the sha256 digest has the
-        // right size.
-        NixHash {
-            algo: crate::nixhash::HashAlgo::Sha256,
-            digest: digest.to_vec(),
-        }
+        NixHash::Sha256(digest.try_into().unwrap())
     }
 
     /// This calculates all output paths of a Derivation and updates the struct.