[BugFix] fix multimodal hasher hash collision risk when ndarray shape or dtype differs

fastdeploy/multimodal/hasher.py

@@ -25,5 +25,9 @@ class MultimodalHasher:
     @classmethod
     def hash_features(cls, obj: object) -> str:
         if isinstance(obj, np.ndarray):
-            return hashlib.sha256((obj.tobytes())).hexdigest()
+            # Encode shape and dtype into the hash to avoid collisions between
+            # arrays that share the same raw bytes but differ in layout, e.g.
+            # a (6,4) vs (4,6) array, or float32 vs uint8 reinterpretation.
+            header = f"{obj.shape}|{obj.dtype}|".encode()
+            return hashlib.sha256(header + obj.tobytes()).hexdigest()
         return hashlib.sha256((pickle.dumps(obj))).hexdigest()

tests/multimodal/test_hasher.py

@@ -26,9 +26,23 @@ def test_hash_features_ndarray(self):
         """Test hash features with numpy ndarray"""
         arr = np.random.randint(low=0, high=255, size=(28, 28), dtype=np.uint8)
         arr_hash = MultimodalHasher.hash_features(arr)
-        target_hash = hashlib.sha256((arr.tobytes())).hexdigest()
+        header = f"{arr.shape}|{arr.dtype}|".encode()
+        target_hash = hashlib.sha256(header + arr.tobytes()).hexdigest()
         assert arr_hash == target_hash, f"Ndarray hash mismatch: {arr_hash} != {target_hash}"
 
+    def test_hash_features_ndarray_shape_sensitivity(self):
+        """Arrays with same bytes but different shapes must produce different hashes"""
+        base = np.arange(24, dtype=np.float32)
+        a = base.reshape(6, 4)
+        b = base.reshape(4, 6)
+        assert MultimodalHasher.hash_features(a) != MultimodalHasher.hash_features(b)
+
+    def test_hash_features_ndarray_dtype_sensitivity(self):
+        """Arrays with same shape but different dtypes must produce different hashes"""
+        a = np.zeros((4, 4), dtype=np.float32)
+        b = np.zeros((4, 4), dtype=np.float64)
+        assert MultimodalHasher.hash_features(a) != MultimodalHasher.hash_features(b)
+
     def test_hash_features_object(self):
         """Test hash features with unsupported object type"""
         obj = {"key": "value"}