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 2315202610a70a223fbb94af61272509a84dd5b1..185e3fa44aeafea7503ac86b0d33c71cb747a2fd 100644 (file)
--- a/src/allmydata/util/fileutil.py
+++ b/src/allmydata/util/fileutil.py
@@ -11,6 +11,11 @@ if sys.platform == "win32":
         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
+    from ctypes.wintypes import BOOL, DWORD, LPCWSTR, LPWSTR
+
 from twisted.python import log
 
 from pycryptopp.cipher.aes import AES
@@ -521,8 +526,10 @@ def get_available_space(whichdir, reserved_space):
 
 if sys.platform == "win32":
     # <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
@@ -531,15 +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,
@@ -549,10 +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:
@@ -575,13 +592,15 @@ def reraise(wrapper):
 if sys.platform == "win32":
     # <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)
 
@@ -596,7 +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.