1 files changed, 39 insertions, 0 deletions
diff --git a/objectstore/packed/delta_base.go b/objectstore/packed/delta_base.go
new file mode 100644
index 00000000..fd9b96d5
--- /dev/null
+++ b/objectstore/packed/delta_base.go
@@ -0,0 +1,39 @@
+package packed
+
+import (
+	"fmt"
+
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+// deltaResolveBase materializes the base object body for one delta plan.
+func (store *Store) deltaResolveBase(plan deltaPlan) (objecttype.Type, []byte, error) {
+	cacheKey := deltaBaseKey{
+		packName: plan.baseLoc.packName,
+		offset:   plan.baseLoc.offset,
+	}
+
+	store.cacheMu.RLock()
+	if ty, content, ok := store.deltaCache.get(cacheKey); ok {
+		store.cacheMu.RUnlock()
+		return ty, content, nil
+	}
+	store.cacheMu.RUnlock()
+
+	pack, meta, err := store.entryMetaAt(plan.baseLoc)
+	if err != nil {
+		return objecttype.TypeInvalid, nil, err
+	}
+	if !isBaseObjectType(meta.ty) {
+		return objecttype.TypeInvalid, nil, fmt.Errorf("objectstore/packed: delta plan base is not a base object")
+	}
+	base, err := inflateAt(pack, meta.dataOffset, meta.size)
+	if err != nil {
+		return objecttype.TypeInvalid, nil, err
+	}
+
+	store.cacheMu.Lock()
+	store.deltaCache.add(cacheKey, meta.ty, base)
+	store.cacheMu.Unlock()
+	return meta.ty, base, nil
+}