Use etils iterdir and in-memory filtering instead of glob in _glob_step_paths

PiperOrigin-RevId: 842606621

Author: mridul-sahu

checkpoint/orbax/checkpoint/_src/path/step.py

@@ -69,6 +69,12 @@
 ]
 
 
+def _is_valid_base_path(base_path: epath.PathLike) -> bool:
+  """Validates base_path and returns it as an epath.Path."""
+  base_path = epath.Path(base_path)
+  return base_path.exists() and base_path.is_dir()
+
+
 @dataclasses.dataclass(frozen=True)
 class Metadata:
   """Metadata of a step.
@@ -396,11 +402,8 @@ def _glob_step_paths(self, base_path: epath.PathLike) -> list[epath.Path]:
           if folder.startswith(os.path.join(path_prefix, self.step_prefix))
       ]
     else:
-      return list(
-          epath.Path(base_path).glob(
-              f'{step_prefix_with_underscore(self.step_prefix)}*'
-          )
-      )
+      prefix = step_prefix_with_underscore(self.step_prefix)
+      return [x for x in base_path.iterdir() if x.name.startswith(prefix)]
 
   def _get_step_paths_and_total_steps(
       self, base_path: epath.PathLike, is_primary_host: bool
@@ -526,6 +529,8 @@ def _find_all_with_single_host_load_and_broadcast(
 
   def find_all(self, base_path: epath.PathLike) -> Iterator[Metadata]:
     """Returns metadata of all steps matching with name_format attributes."""
+    if not _is_valid_base_path(base_path):
+      return iter([])
     # Note: the order of conjuncts is important here; we should not call
     # `multihost.process_count()` when `single_host_load_and_broadcast` is False
     # as this has the possible side effect of initializing the jax backend. See
@@ -539,6 +544,11 @@ def find_all(self, base_path: epath.PathLike) -> Iterator[Metadata]:
 
   def find_step(self, base_path: epath.PathLike, step: int) -> Metadata:
     """Returns the metadata for `step` or raises ValueError."""
+    if not _is_valid_base_path(base_path):
+      raise ValueError(
+          f'Invalid base_path: {base_path} does not exist or is not a'
+          ' directory.'
+      )
     step_path = build_step_path(base_path, self, step)
     metadata = self._build_metadata(step_path, step=step)
     if metadata is not None: