From 733bfcf6fa2e17dbc94487fb1b9eb4f896e53845 Mon Sep 17 00:00:00 2001
From: Valentin Popov <valentin@popov.link>
Date: Sat, 18 Jul 2026 15:15:29 +0400
Subject: perf(assets): reuse archives during mission loads

---
 crates/fparkan-resource/src/lib.rs | 45 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

(limited to 'crates/fparkan-resource')

diff --git a/crates/fparkan-resource/src/lib.rs b/crates/fparkan-resource/src/lib.rs
index 8fbd62e..f996a71 100644
--- a/crates/fparkan-resource/src/lib.rs
+++ b/crates/fparkan-resource/src/lib.rs
@@ -258,6 +258,21 @@ pub trait ResourceRepository {
     /// Returns [`ResourceError`] when the archive is missing, unsupported, or
     /// malformed.
     fn open_archive(&self, path: &NormalizedPath) -> Result<ArchiveId, ResourceError>;
+    /// Opens an archive known to remain unchanged for the caller's bounded
+    /// loading transaction.
+    ///
+    /// Implementations may reuse an already decoded archive without a second
+    /// content-fingerprint pass. Callers must use this only while their asset
+    /// source is immutable; the default preserves [`Self::open_archive`]'s
+    /// strict invalidation behavior.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`ResourceError`] when the archive is missing, unsupported, or
+    /// malformed.
+    fn open_archive_unchanged(&self, path: &NormalizedPath) -> Result<ArchiveId, ResourceError> {
+        self.open_archive(path)
+    }
     /// Finds entry.
     ///
     /// # Errors
@@ -524,6 +539,19 @@ impl ResourceRepository for CachedResourceRepository {
         }
     }
 
+    fn open_archive_unchanged(&self, path: &NormalizedPath) -> Result<ArchiveId, ResourceError> {
+        let key = path.identity_bytes().to_vec();
+        let mut state = self.state.lock().map_err(|_| ResourceError::Poisoned)?;
+        if let Some(id) = state.paths.get(&key).copied() {
+            if state.archive(id)?.document.is_some() {
+                state.touch_archive(id)?;
+                return Ok(id);
+            }
+        }
+        drop(state);
+        self.open_archive(path)
+    }
+
     fn find(
         &self,
         archive: ArchiveId,
@@ -1101,6 +1129,23 @@ mod tests {
         assert_eq!(vfs.metadata_reads.load(Ordering::Relaxed), 1);
     }
 
+    #[test]
+    fn unchanged_transaction_reuses_decoded_archive_without_rereading() {
+        let path = archive_path(b"archives/test.lib").expect("path");
+        let bytes = Arc::from(build_nres(&[("one", b"payload")]).into_boxed_slice());
+        let vfs = Arc::new(CountingVfs::new(bytes));
+        let repo = CachedResourceRepository::new(Arc::clone(&vfs) as Arc<dyn Vfs>);
+
+        let first = repo.open_archive_unchanged(&path).expect("first open");
+        let second = repo
+            .open_archive_unchanged(&path)
+            .expect("transactional cached open");
+
+        assert_eq!(first, second);
+        assert_eq!(vfs.reads.load(Ordering::Relaxed), 1);
+        assert_eq!(vfs.metadata_reads.load(Ordering::Relaxed), 1);
+    }
+
     #[test]
     fn concurrent_same_archive_open_reuses_archive_id() {
         let path = archive_path(b"archives/test.lib").expect("path");
-- 
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