libfatx: Allow 42-character file names

libfatx/fatx_dir.c

@@ -470,7 +470,7 @@ int fatx_create_dirent(struct fatx_fs *fs, char const *path, struct fatx_dir *di
 
     /* Check basename is not too long */
     path_basename = fatx_basename(path);
-    if (strlen(path_basename) >= FATX_MAX_FILENAME_LEN)
+    if (strlen(path_basename) > FATX_MAX_FILENAME_LEN)
     {
         free(path_basename);
         fatx_error(fs, "filename is too long\n");

libfatx/fatx_file.c

@@ -427,15 +427,15 @@ int fatx_rename(struct fatx_fs *fs, char const *from, char const *to, bool excha
 
     /* Check that the new filename is not too long */
     to_basename = fatx_basename(to);
-    if (strlen(to_basename) >= FATX_MAX_FILENAME_LEN)
+    if (strlen(to_basename) > FATX_MAX_FILENAME_LEN)
     {
         fatx_error(fs, "destination name too long\n");
         status = FATX_STATUS_ERROR;
         goto done;
     }
 
     from_basename = fatx_basename(from);
-    if (strlen(from_basename) >= FATX_MAX_FILENAME_LEN)
+    if (strlen(from_basename) > FATX_MAX_FILENAME_LEN)
     {
         fatx_error(fs, "source name too long\n");
         status = FATX_STATUS_ERROR;

pyfatx/tests/test.py

@@ -446,5 +446,31 @@ def test_rename_no_replace_with_nonexistent_destination_works(self, path):
 		assert d2 == b1
 
 
+	@with_formatted_disk
+	def test_filename_max_length(self, path):
+		fs = Fatx(path)
+
+		# 42 characters is the longest name a FATX directory entry holds
+		name42 = '/' + 'a' * 38 + '.bin'
+		fs.write(name42, b'42')
+		assert fs.read(name42) == b'42'
+		assert [a.filename for a in fs.listdir('/')] == [name42[1:]]
+
+		renamed42 = '/' + 'b' * 38 + '.bin'
+		fs.rename(name42, renamed42)
+		assert fs.read(renamed42) == b'42'
+
+		name43 = '/' + 'c' * 39 + '.bin'
+		created = False
+		try:
+			fs.write(name43, b'43')
+			created = True
+		except AssertionError:
+			pass
+		assert not created
+
+		fs.unlink(renamed42)
+
+
 if __name__ == '__main__':
 	unittest.main()