API to check if a filesystem is an FAT filesystem on windows

src/calibre/db/backend.py

@@ -16,7 +16,7 @@ import shutil
 import sys
 import time
 import uuid
-from contextlib import suppress, closing
+from contextlib import closing, suppress
 from functools import partial
 
 from calibre import as_unicode, force_unicode, isbytestring, prints
@@ -40,8 +40,8 @@ from calibre.utils.config import from_json, prefs, to_json, tweaks
 from calibre.utils.date import EPOCH, parse_date, utcfromtimestamp, utcnow
 from calibre.utils.filenames import (
     WindowsAtomicFolderMove, ascii_filename, atomic_rename, copyfile_using_links,
-    copytree_using_links, hardlink_file, is_case_sensitive, remove_dir_if_empty,
-    samefile
+    copytree_using_links, hardlink_file, is_case_sensitive, is_fat_filesystem,
+    remove_dir_if_empty, samefile
 )
 from calibre.utils.formatter_functions import (
     compile_user_template_functions, formatter_functions,
@@ -470,6 +470,7 @@ class DB:
         if not os.path.exists(self.library_path):
             os.makedirs(self.library_path)
         self.is_case_sensitive = is_case_sensitive(self.library_path)
+        self.is_fat_filesystem = is_fat_filesystem(self.library_path)
 
         SchemaUpgrade(self, self.library_path, self.field_metadata)
 

src/calibre/db/cache.py

@@ -189,6 +189,10 @@ class Cache:
     def dbpath(self):
         return self.backend.dbpath
 
+    @property
+    def is_fat_filesystem(self):
+        return self.backend.is_fat_filesystem
+
     @property
     def safe_read_lock(self):
         ''' A safe read lock is a lock that does nothing if the thread already

src/calibre/utils/filenames.py

@@ -604,6 +604,25 @@ if iswindows:
         if len(path) > 200 and os.path.isabs(path) and not path.startswith(long_path_prefix):
             path = long_path_prefix + os.path.normpath(path)
         return path
+
+    def is_fat_filesystem(path):
+        try:
+            from calibre_extensions.winutil import filesystem_type_name
+        except ImportError:
+            return False
+        if not path:
+            return False
+        drive = os.path.abspath(path)[0].upper()
+        try:
+            tn = filesystem_type_name(f'{drive}:\\')
+        except OSError:
+            return False
+        # Values I have seen: FAT32, exFAT, NTFS
+        return tn.upper().startswith('FAT')
 else:
     def make_long_path_useable(path):
         return path
+
+    def is_fat_filesystem(path):
+        # TODO: Implement for Linux and macOS
+        return False