Speed up most calls to 'stat' and 'lstat' on MS-Windows.

src/w32.c (stat_worker): If w32_stat_get_owner_group is zero, do not
 try to get accurate owner and group information from NT file
 security APIs.  This is to make most callers of 'stat' and
 'lstat', which don't need that information, much faster.
 src/dired.c (Ffile_attributes) [WINDOWSNT]: Set
 w32_stat_get_owner_group to a non-zero value, to request accurate
 owner and group information from 'lstat'.

 nt/inc/sys/stat.h: Declare w32_stat_get_owner_group.

nt/ChangeLog

@@ -1,3 +1,7 @@
+2012-12-14  Eli Zaretskii  <eliz@gnu.org>
+
+	* inc/sys/stat.h: Declare w32_stat_get_owner_group.
+
 2012-12-13  Juanma Barranquero  <lekktu@gmail.com>
 
 	* config.nt: Sync with autogen/config.in.

nt/inc/sys/stat.h

@@ -98,6 +98,10 @@ struct stat {
   char		   st_gname[260];
 };
 
+/* Internal variable for asking 'stat'/'lstat' to produce accurate
+   info about owner and group of files. */
+extern int w32_stat_get_owner_group;
+
 /* Prevent redefinition by other headers, e.g. wchar.h.  */
 #define _STAT_DEFINED
 

src/ChangeLog

@@ -1,3 +1,14 @@
+2012-12-14  Eli Zaretskii  <eliz@gnu.org>
+
+	* w32.c (stat_worker): If w32_stat_get_owner_group is zero, do not
+	try to get accurate owner and group information from NT file
+	security APIs.  This is to make most callers of 'stat' and
+	'lstat', which don't need that information, much faster.
+
+	* dired.c (Ffile_attributes) [WINDOWSNT]: Set
+	w32_stat_get_owner_group to a non-zero value, to request accurate
+	owner and group information from 'lstat'.
+
 2012-12-13  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* fileio.c (Finsert_file_contents): Don't put tail into head area,

src/dired.c

@@ -895,6 +895,7 @@ so last access time will always be midnight of that day.  */)
   Lisp_Object dirname;
   struct stat sdir;
 #endif /* BSD4_2 */
+  int lstat_result;
 
   /* An array to hold the mode string generated by filemodestring,
      including its terminating space and null byte.  */
@@ -922,7 +923,21 @@ so last access time will always be midnight of that day.  */)
   encoded = ENCODE_FILE (filename);
   UNGCPRO;
 
-  if (lstat (SSDATA (encoded), &s) < 0)
+#ifdef WINDOWSNT
+  /* We usually don't request accurate owner and group info, because
+     it can be very expensive on Windows to get that, and most callers
+     of 'lstat' don't need that.  But here we do want that information
+     to be accurate.  */
+  w32_stat_get_owner_group = 1;
+#endif
+
+  lstat_result = lstat (SSDATA (encoded), &s);
+
+#ifdef WINDOWSNT
+  w32_stat_get_owner_group = 0;
+#endif
+
+  if (lstat_result < 0)
     return Qnil;
 
   values[0] = (S_ISLNK (s.st_mode) ? Ffile_symlink_p (filename)

src/w32.c

@@ -3537,6 +3537,10 @@ is_slow_fs (const char *name)
   return !(devtype == DRIVE_FIXED || devtype == DRIVE_RAMDISK);
 }
 
+/* If this is non-zero, the caller wants accurate information about
+   file's owner and group, which could be expensive to get.  */
+int w32_stat_get_owner_group;
+
 /* MSVC stat function can't cope with UNC names and has other bugs, so
    replace it with our own.  This also allows us to calculate consistent
    inode values and owner/group without hacks in the main Emacs code. */
@@ -3708,6 +3712,7 @@ stat_worker (const char * path, struct stat * buf, int follow_symlinks)
       /* We produce the fallback owner and group data, based on the
 	 current user that runs Emacs, in the following cases:
 
+	  . caller didn't request owner and group info
 	  . this is Windows 9X
 	  . getting security by handle failed, and we need to produce
 	    information for the target of a symlink (this is better
@@ -3716,23 +3721,25 @@ stat_worker (const char * path, struct stat * buf, int follow_symlinks)
 
 	 If getting security by handle fails, and we don't need to
 	 resolve symlinks, we try getting security by name.  */
-      if (is_windows_9x () != TRUE)
-	psd = get_file_security_desc_by_handle (fh);
-      if (psd)
-	{
-	  get_file_owner_and_group (psd, name, buf);
-	  LocalFree (psd);
-	}
-      else if (is_windows_9x () == TRUE)
+      if (!w32_stat_get_owner_group || is_windows_9x () == TRUE)
 	get_file_owner_and_group (NULL, name, buf);
-      else if (!(is_a_symlink && follow_symlinks))
-	{
-	  psd = get_file_security_desc_by_name (name);
-	  get_file_owner_and_group (psd, name, buf);
-	  xfree (psd);
-	}
       else
-	get_file_owner_and_group (NULL, name, buf);
+	{
+	  psd = get_file_security_desc_by_handle (fh);
+	  if (psd)
+	    {
+	      get_file_owner_and_group (psd, name, buf);
+	      LocalFree (psd);
+	    }
+	  else if (!(is_a_symlink && follow_symlinks))
+	    {
+	      psd = get_file_security_desc_by_name (name);
+	      get_file_owner_and_group (psd, name, buf);
+	      xfree (psd);
+	    }
+	  else
+	    get_file_owner_and_group (NULL, name, buf);
+	}
       CloseHandle (fh);
     }
   else
@@ -6849,6 +6856,9 @@ globals_of_w32 (void)
 
   /* "None" is the default group name on standalone workstations.  */
   strcpy (dflt_group_name, "None");
+
+  /* Reset, in case it has some value inherited from dump time.  */
+  w32_stat_get_owner_group = 0;
 }
 
 /* For make-serial-process  */