From 2365936f52a35f0ac27ebdb2c71a5910f966b0d1 Mon Sep 17 00:00:00 2001
From: xmutantson <kameron.markham@gmail.com>
Date: Sun, 18 Oct 2026 17:57:50 -0700
Subject: [PATCH] libfatx: Allow 42-character file names

A FATX directory entry holds names of up to 42 bytes (FATX_MAX_FILENAME_LEN),
and retail games ship files with names of exactly that length. The length
checks in fatx_create_dirent() and fatx_rename() used >=, so those names
were rejected and copying such a file failed with EPERM.

The in-memory name buffers are FATX_MAX_FILENAME_LEN+1 bytes and the
on-disk field is FATX_MAX_FILENAME_LEN bytes with the length stored
separately, so a 42-character name already fits everywhere it is copied.
---
 libfatx/fatx_dir.c   |  2 +-
 libfatx/fatx_file.c  |  4 ++--
 pyfatx/tests/test.py | 26 ++++++++++++++++++++++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/libfatx/fatx_dir.c b/libfatx/fatx_dir.c
index a5f55a9..d7cf5f2 100644
--- a/libfatx/fatx_dir.c
+++ b/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");
diff --git a/libfatx/fatx_file.c b/libfatx/fatx_file.c
index 51a1769..f496eea 100644
--- a/libfatx/fatx_file.c
+++ b/libfatx/fatx_file.c
@@ -427,7 +427,7 @@ 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;
@@ -435,7 +435,7 @@ int fatx_rename(struct fatx_fs *fs, char const *from, char const *to, bool excha
     }
 
     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;
diff --git a/pyfatx/tests/test.py b/pyfatx/tests/test.py
index a139798..72e32c4 100755
--- a/pyfatx/tests/test.py
+++ b/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()