fix: DictSupplementaryFileContainer increment refcount in _assign_unique_name (#513)

`DictSupplementaryFileContainer_store_refcount` is designed to track how many `_name_map` entries reference the same content hash, so `delete_file()` can free the underlying bytes only when the last reference is removed. The refcount is never incremented, so files are never freed.

Previously, because `_assign_unique_name()` never increments `_store_refcount`, the count stays at 0 after any `add_file()`. Every `delete_file()` decrements to -1 and the equality check `== 0` is never true, so `_store[hash]` and `_store_refcount[hash]` are never cleaned up. Every file ever added leaks indefinitely.

This fixes this bug by incrementing `_store_refcount[sha] += 1` inside `_assign_unique_name()` when a new `_name_map` entry is created (the first branch of the `while True` loop). Also decrement it (and skip the increment) inside the second branch when a duplicate name already maps to the same hash.

Fixes #495

Author: zrgt

sdk/basyx/aas/adapter/aasx.py

@@ -880,6 +880,7 @@ def rename_file(self, old_name: str, new_name: str) -> str:
         if new_name == old_name:
             return new_name
         file_hash, file_content_type = self._name_map[old_name]
+        self._store_refcount[file_hash] -= 1
         del self._name_map[old_name]
         return self._assign_unique_name(new_name, file_hash, file_content_type)
 
@@ -889,6 +890,7 @@ def _assign_unique_name(self, name: str, sha: bytes, content_type: str) -> str:
         while True:
             if new_name not in self._name_map:
                 self._name_map[new_name] = (sha, content_type)
+                self._store_refcount[sha] += 1
                 return new_name
             elif self._name_map[new_name] == (sha, content_type):
                 return new_name

sdk/test/adapter/aasx/test_aasx.py

@@ -89,6 +89,24 @@ def test_supplementary_file_container(self) -> None:
         with self.assertRaises(KeyError):
             container.write_file(duplicate_file, file_content)
 
+    def test_supplementary_file_container_refcount(self) -> None:
+        container = aasx.DictSupplementaryFileContainer()
+        data = b"test content"
+        name1 = container.add_file("/file1.bin", io.BytesIO(data), "application/octet-stream")
+        name2 = container.add_file("/file2.bin", io.BytesIO(data), "application/octet-stream")
+        content_hash = container.get_sha256(name1)
+
+        # Both names point to same content — backing store must be present
+        self.assertIn(content_hash, container._store)
+
+        # Deleting one reference must NOT free the backing store
+        container.delete_file(name1)
+        self.assertIn(content_hash, container._store)
+
+        # Deleting the last reference must free the backing store
+        container.delete_file(name2)
+        self.assertNotIn(content_hash, container._store)
+
 
 class AASXWriterTest(unittest.TestCase):
     def test_write_missing_aas_objects(self):