Temporarily unpacking a .b2z file defaults now to the same dir as the file

Author: FrancescAlted

src/blosc2/dict_store.py

@@ -58,7 +58,8 @@ class DictStore:
         and only when ``mode="r"``. Default is None.
     tmpdir : str or None, optional
         Temporary directory to use when working with ".b2z" files. If None,
-        a system temporary directory will be managed. Default is None.
+        a temporary directory is created in the same directory as the ".b2z"
+        file, so that unpacked data stays on the same filesystem. Default is None.
     cparams : dict or None, optional
         Compression parameters for the internal embed store.
         If None, the default Blosc2 parameters are used.
@@ -165,7 +166,8 @@ def _setup_paths_and_dirs(self, tmpdir: str | None):
             self.is_zip_store = False
         if self.is_zip_store:
             if tmpdir is None:
-                self._temp_dir_obj = tempfile.TemporaryDirectory()
+                b2z_parent = os.path.dirname(os.path.abspath(self.localpath))
+                self._temp_dir_obj = tempfile.TemporaryDirectory(dir=b2z_parent)
                 self.working_dir = self._temp_dir_obj.name
             else:
                 self.working_dir = tmpdir

src/blosc2/tree_store.py

@@ -105,7 +105,8 @@ class TreeStore(DictStore):
         File mode ('r', 'w', 'a'). Default is 'a'.
     tmpdir : str or None, optional
         Temporary directory to use when working with `.b2z` files. If None,
-        a system temporary directory will be managed. Default is None.
+        a temporary directory is created in the same directory as the `.b2z`
+        file, so that unpacked data stays on the same filesystem. Default is None.
     cparams : dict or None, optional
         Compression parameters for the internal embed store.
         If None, the default Blosc2 parameters are used.