From cde45dc7c19bf0c14336a084ed188c160de4251e Mon Sep 17 00:00:00 2001
From: Philipp Wolfer <ph.wolfer@gmail.com>
Date: Tue, 8 Mar 2022 08:12:13 +0100
Subject: [PATCH] PICARD-2076: path node length limit on Windows is 255

---
 picard/util/__init__.py   | 13 +++++++------
 picard/util/filenaming.py | 12 ++++++++----
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/picard/util/__init__.py b/picard/util/__init__.py
index 57752c392..ba863cdfb 100644
--- a/picard/util/__init__.py
+++ b/picard/util/__init__.py
@@ -75,13 +75,14 @@ from picard.const.sys import (
 if IS_WIN:
     import winreg
 
-# Windows path length constraints:
-# the entire path's length
+# Windows path length constraints
+# See https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
+# the entire path's length (260 - 1 null character)
 WIN_MAX_FILEPATH_LEN = 259
-# the entire parent directory path's length, *excluding* the final separator
-WIN_MAX_DIRPATH_LEN = 247
-# a single node's length (this seems to be the case for older NTFS)
-WIN_MAX_NODE_LEN = 226
+# the entire parent directory path's length must leave room for a 8.3 filename
+WIN_MAX_DIRPATH_LEN = WIN_MAX_FILEPATH_LEN - 12
+# a single node's (directory or file) length
+WIN_MAX_NODE_LEN = 255
 # Prefix for long paths in Windows API
 WIN_LONGPATH_PREFIX = '\\\\?\\'
 
diff --git a/picard/util/filenaming.py b/picard/util/filenaming.py
index a35ff4d4b..b149b7eb1 100644
--- a/picard/util/filenaming.py
+++ b/picard/util/filenaming.py
@@ -213,7 +213,11 @@ def _make_win_short_filename(relpath, reserved=0):
     # http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
     #
     # The MAX_PATH is 260 characters, with this possible format for a file:
-    # "X:\<244-char dir path>\<11-char filename><NUL>".
+    # "X:\<244-char dir path>\<12-char filename><NUL>".
+
+    # Use a shorter max node length then the theoretically allowed 255 characters
+    # to leave room for longer file names
+    MAX_NODE_LENGTH = WIN_MAX_NODE_LEN - 29
 
     # to make predictable directory paths we need to fit the directories in
     # WIN_MAX_DIRPATH_LEN, and truncate the filename to whatever's left
@@ -224,8 +228,8 @@ def _make_win_short_filename(relpath, reserved=0):
         return shorten_path(path, length, mode=ShortenMode.UTF16)
     xlength = _get_utf16_length
 
-    # shorten to WIN_MAX_NODE_LEN from the beginning
-    relpath = shorten(relpath, WIN_MAX_NODE_LEN)
+    # shorten to MAX_NODE_LENGTH from the beginning
+    relpath = shorten(relpath, MAX_NODE_LENGTH)
     dirpath, filename = os.path.split(relpath)
     # what if dirpath is already the right size?
     dplen = xlength(dirpath)
@@ -366,7 +370,7 @@ def make_short_filename(basedir, relpath, win_shorten_path=False, relative_to=""
                 reserved += 1
             return _make_win_short_filename(relpath, reserved)
         else:
-            return shorten_path(relpath, 255, mode=ShortenMode.UTF16)
+            return shorten_path(relpath, WIN_MAX_NODE_LEN, mode=ShortenMode.UTF16)
     # if we're being windows compatible, figure out how much
     # needs to be reserved for the basedir part
     elif win_shorten_path: