Refactor creation of hardlinks on windows

After creating the hardlink, open and close the file, to ensure that
the directory entry for the file contains the correct file size, see
http://blogs.msdn.com/b/oldnewthing/archive/2011/12/26/10251026.aspx

src/calibre/utils/filenames.py

@@ -70,9 +70,11 @@ def shorten_components_to(length, components, more_to_take=0):
         else:
             if x is components[-1]:
                 b, e = os.path.splitext(x)
-                if e == '.': e = ''
+                if e == '.':
+                    e = ''
                 r = shorten_component(b, delta)+e
-                if r.startswith('.'): r = x[0]+r
+                if r.startswith('.'):
+                    r = x[0]+r
             else:
                 r = shorten_component(x, delta)
             r = r.strip()
@@ -115,7 +117,7 @@ def is_case_sensitive(path):
         os.remove(f1)
     return is_case_sensitive
 
-def case_preserving_open_file(path, mode='wb', mkdir_mode=0777):
+def case_preserving_open_file(path, mode='wb', mkdir_mode=0o777):
     '''
     Open the file pointed to by path with the specified mode. If any
     directories in path do not exist, they are created. Returns the
@@ -211,7 +213,8 @@ def samefile_windows(src, dst):
     handles = []
 
     def get_fileid(x):
-        if isbytestring(x): x = x.decode(filesystem_encoding)
+        if isbytestring(x):
+            x = x.decode(filesystem_encoding)
         try:
             h = win32file.CreateFile(x, 0, 0, None, win32file.OPEN_EXISTING,
                     win32file.FILE_FLAG_BACKUP_SEMANTICS, 0)
@@ -254,6 +257,24 @@ def samefile(src, dst):
             os.path.normcase(os.path.abspath(dst)))
     return samestring
 
+def windows_hardlink(src, dest):
+    import win32file, pywintypes
+    msg = u'Creating hardlink from %s to %s failed: %%s' % (src, dest)
+    try:
+        win32file.CreateHardLink(dest, src)
+    except pywintypes.error as e:
+        raise Exception(msg % e)
+    # We open and close dest, to ensure its directory entry is updated
+    # see http://blogs.msdn.com/b/oldnewthing/archive/2011/12/26/10251026.aspx
+    h = win32file.CreateFile(
+        dest, 0, win32file.FILE_SHARE_READ | win32file.FILE_SHARE_WRITE | win32file.FILE_SHARE_DELETE,
+        None, win32file.OPEN_EXISTING, 0, None)
+    sz = win32file.GetFileSize(h)
+    win32file.CloseHandle(h)
+
+    if sz != os.path.getsize(src):
+        raise Exception(msg % ('hardlink size: %d not the same as source size' % sz))
+
 class WindowsAtomicFolderMove(object):
 
     '''
@@ -270,14 +291,16 @@ class WindowsAtomicFolderMove(object):
         import win32file, winerror
         from pywintypes import error
 
-        if isbytestring(path): path = path.decode(filesystem_encoding)
+        if isbytestring(path):
+            path = path.decode(filesystem_encoding)
 
         if not os.path.exists(path):
             return
 
         for x in os.listdir(path):
             f = os.path.normcase(os.path.abspath(os.path.join(path, x)))
-            if not os.path.isfile(f): continue
+            if not os.path.isfile(f):
+                continue
             try:
                 # Ensure the file is not read-only
                 win32file.SetFileAttributes(f, win32file.FILE_ATTRIBUTE_NORMAL)
@@ -315,9 +338,7 @@ class WindowsAtomicFolderMove(object):
             else:
                 raise ValueError(u'The file %r does not exist'%path)
         try:
-            win32file.CreateHardLink(dest, path)
+            windows_hardlink(path, dest)
-            if os.path.getsize(dest) != os.path.getsize(path):
-                raise Exception('This apparently can happen on network shares. Sigh.')
             return
         except:
             pass
@@ -355,10 +376,8 @@ class WindowsAtomicFolderMove(object):
 
 def hardlink_file(src, dest):
     if iswindows:
-        import win32file
+        windows_hardlink(src, dest)
-        win32file.CreateHardLink(dest, src)
-        if os.path.getsize(dest) != os.path.getsize(src):
-            raise Exception('This apparently can happen on network shares. Sigh.')
         return
     os.link(src, dest)
 
+