implement memoryfs save() and load()

fsspec/implementations/memory.py

@@ -5,7 +5,7 @@
 from errno import ENOTEMPTY
 from io import BytesIO
 from pathlib import PurePath, PureWindowsPath
-from typing import Any, ClassVar
+from typing import Any, ClassVar, BinaryIO
 
 from fsspec import AbstractFileSystem
 from fsspec.implementations.local import LocalFileSystem
@@ -265,6 +265,17 @@ def rm(self, path, recursive=False, maxdepth=None):
                 self.rm_file(p)
             else:
                 self.rmdir(p)
+
+    def save(self, file: BinaryIO):
+        import pickle
+        pickle.dump({"store": self.store, "pseudo_dirs": self.pseudo_dirs}, file)
+
+    def load(self, file: BinaryIO):
+        import pickle
+        _internal = pickle.load(file)
+        self.store = _internal["store"]
+        self.pseudo_dirs = _internal["pseudo_dirs"]
+
 
 
 class MemoryFile(BytesIO):

fsspec/implementations/tests/test_memory.py

@@ -380,3 +380,20 @@ def test_open_path_windows(m):
         f.write(b"some\nlines\nof\ntext")
 
     assert m.read_text(path) == "some\nlines\nof\ntext"
+
+def test_save_and_load(m):
+    from io import BytesIO    
+    internal = BytesIO()
+    with m.open("/foo/bar/file", "wb") as f:
+        f.write(b"some\nlines\nof\ntext")
+    with m.open("/foo/file", "wb") as f:
+        f.write(b"some\nlines\nof\ntext")
+    m.makedirs("/foo/foo")
+    m.save(internal)
+    m.store = None
+    m.pseudo_dirs = None
+    internal.seek(0)
+    m.load(internal)
+    assert m.cat("/foo/file") == b"some\nlines\nof\ntext"
+    assert m.ls("/", False) == ["/foo"]
+    assert sorted(m.ls("/foo", False)) == sorted(["/foo/foo", "/foo/bar", "/foo/file"])