Improved error handling and cosmetics for ctypes calls on Windows.

[tahoe-lafs/tahoe-lafs.git] / src / allmydata / util / fileutil.py

diff --git a/src/allmydata/util/fileutil.py b/src/allmydata/util/fileutil.py
index 8a044dd0b090eca8668657f6f0d4c5e9a2b8f62b..185e3fa44aeafea7503ac86b0d33c71cb747a2fd 100644 (file)
--- a/src/allmydata/util/fileutil.py
+++ b/src/allmydata/util/fileutil.py
@@ -6,6 +6,11 @@ import sys, exceptions, os, stat, tempfile, time, binascii
 from collections import namedtuple
 from errno import ENOENT
 
+if sys.platform == "win32":
+    from ctypes import WINFUNCTYPE, WinError, windll, POINTER, byref, c_ulonglong, \
+        create_unicode_buffer, get_last_error
+    from ctypes.wintypes import BOOL, DWORD, LPCWSTR, LPWSTR, LPVOID, HANDLE
+
 if sys.platform == "win32":
     from ctypes import WINFUNCTYPE, WinError, windll, POINTER, byref, c_ulonglong, \
         create_unicode_buffer, get_last_error
@@ -281,17 +286,18 @@ try:
 except ImportError:
     pass
 
-def abspath_expanduser_unicode(path, base=None):
+def abspath_expanduser_unicode(path, base=None, long_path=True):
     """
     Return the absolute version of a path. If 'base' is given and 'path' is relative,
     the path will be expanded relative to 'base'.
     'path' must be a Unicode string. 'base', if given, must be a Unicode string
     corresponding to an absolute path as returned by a previous call to
     abspath_expanduser_unicode.
+    On Windows, the result will be a long path unless long_path is given as False.
     """
     if not isinstance(path, unicode):
         raise AssertionError("paths must be Unicode strings")
-    if base is not None:
+    if base is not None and long_path:
         precondition_abspath(base)
 
     path = expanduser(path)
@@ -318,7 +324,7 @@ def abspath_expanduser_unicode(path, base=None):
     # there is always at least one Unicode path component.
     path = os.path.normpath(path)
 
-    if sys.platform == "win32":
+    if sys.platform == "win32" and long_path:
         path = to_windows_long_path(path)
 
     return path
@@ -519,11 +525,11 @@ def get_available_space(whichdir, reserved_space):
 
 
 if sys.platform == "win32":
-    from ctypes.wintypes import BOOL, HANDLE, DWORD, LPCWSTR, LPVOID, WinError, get_last_error
-
     # <http://msdn.microsoft.com/en-us/library/aa363858%28v=vs.85%29.aspx>
-    CreateFileW = WINFUNCTYPE(HANDLE, LPCWSTR, DWORD, DWORD, LPVOID, DWORD, DWORD, HANDLE) \
-                      (("CreateFileW", windll.kernel32))
+    CreateFileW = WINFUNCTYPE(
+        HANDLE,  LPCWSTR, DWORD, DWORD, LPVOID, DWORD, DWORD, HANDLE,
+        use_last_error=True
+    )(("CreateFileW", windll.kernel32))
 
     GENERIC_WRITE        = 0x40000000
     FILE_SHARE_READ      = 0x00000001
@@ -532,15 +538,25 @@ if sys.platform == "win32":
     INVALID_HANDLE_VALUE = 0xFFFFFFFF
 
     # <http://msdn.microsoft.com/en-us/library/aa364439%28v=vs.85%29.aspx>
-    FlushFileBuffers = WINFUNCTYPE(BOOL, HANDLE)(("FlushFileBuffers", windll.kernel32))
+    FlushFileBuffers = WINFUNCTYPE(
+        BOOL,  HANDLE,
+        use_last_error=True
+    )(("FlushFileBuffers", windll.kernel32))
 
     # <http://msdn.microsoft.com/en-us/library/ms724211%28v=vs.85%29.aspx>
-    CloseHandle = WINFUNCTYPE(BOOL, HANDLE)(("CloseHandle", windll.kernel32))
+    CloseHandle = WINFUNCTYPE(
+        BOOL,  HANDLE,
+        use_last_error=True
+    )(("CloseHandle", windll.kernel32))
 
     # <http://social.msdn.microsoft.com/forums/en-US/netfxbcl/thread/4465cafb-f4ed-434f-89d8-c85ced6ffaa8/>
     def flush_volume(path):
-        drive = os.path.splitdrive(os.path.realpath(path))[0]
+        abspath = os.path.realpath(path)
+        if abspath.startswith("\\\\?\\"):
+            abspath = abspath[4 :]
+        drive = os.path.splitdrive(abspath)[0]
 
+        print "flushing %r" % (drive,)
         hVolume = CreateFileW(u"\\\\.\\" + drive,
                               GENERIC_WRITE,
                               FILE_SHARE_READ | FILE_SHARE_WRITE,
@@ -550,10 +566,10 @@ if sys.platform == "win32":
                               None
                              )
         if hVolume == INVALID_HANDLE_VALUE:
-            raise WinError()
+            raise WinError(get_last_error())
 
         if FlushFileBuffers(hVolume) == 0:
-            raise WinError()
+            raise WinError(get_last_error())
 
         CloseHandle(hVolume)
 else:
@@ -574,18 +590,17 @@ def reraise(wrapper):
     raise wrapper_exc.__class__, wrapper_exc, tb
 
 if sys.platform == "win32":
-    from ctypes import WINFUNCTYPE, windll, WinError, get_last_error
-    from ctypes.wintypes import BOOL, DWORD, LPCWSTR, LPVOID
-
     # <https://msdn.microsoft.com/en-us/library/windows/desktop/aa365512%28v=vs.85%29.aspx>
     ReplaceFileW = WINFUNCTYPE(
-        BOOL,
-          LPCWSTR, LPCWSTR, LPCWSTR, DWORD, LPVOID, LPVOID,
+        BOOL,  LPCWSTR, LPCWSTR, LPCWSTR, DWORD, LPVOID, LPVOID,
         use_last_error=True
-      )(("ReplaceFileW", windll.kernel32))
+    )(("ReplaceFileW", windll.kernel32))
 
     REPLACEFILE_IGNORE_MERGE_ERRORS = 0x00000002
 
+    # <https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382%28v=vs.85%29.aspx>
+    ERROR_FILE_NOT_FOUND = 2
+
     def rename_no_overwrite(source_path, dest_path):
         os.rename(source_path, dest_path)
 
@@ -600,7 +615,13 @@ if sys.platform == "win32":
             # The UnableToUnlinkReplacementError case does not happen on Windows;
             # all errors should be treated as signalling a conflict.
             err = get_last_error()
-            raise ConflictError("WinError: %s" % (WinError(err)))
+            if err != ERROR_FILE_NOT_FOUND:
+                raise ConflictError("WinError: %s" % (WinError(err),))
+
+            try:
+                rename_no_overwrite(replacement_path, replaced_path)
+            except EnvironmentError:
+                reraise(ConflictError)
 else:
     def rename_no_overwrite(source_path, dest_path):
         # link will fail with EEXIST if there is already something at dest_path.