2 files changed, 21 insertions, 11 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index e69e04dd552..9d618fe0c5b 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,6 +1,8 @@
 2001-09-16  Eli Zaretskii  <eliz@is.elta.co.il>
 
-        * dos-fns.el (original-make-auto-save-file-name): New.
+        * dos-fns.el (convert-standard-filename): Replace invalid
+        characters only after converting dash/underscore to a period.
+        (original-make-auto-save-file-name): New.
         (make-auto-save-file-name): New function, overrides the definition
         on files.el and calls the original function via
         original-make-auto-save-file-name.
diff --git a/lisp/dos-fns.el b/lisp/dos-fns.el
index 3751cc76d24..4b91cdf7a1b 100644
--- a/lisp/dos-fns.el
+++ b/lisp/dos-fns.el
@@ -74,18 +74,25 @@ with a definition that really does change some file names."
             ;; Change a leading period to a leading underscore.
             (if (= (aref string 0) ?.)
                 (aset string 0 ?_))
+            ;; If the name is longer than 8 chars, and doesn't have a
+            ;; period, and we have a dash or underscore that isn't too
+            ;; close to the beginning, change that to a period.  This
+            ;; is so we could salvage more characters of the original
+            ;; name by pushing them into the extension.
+            (if (and (not (string-match "\\." string))
+                     (> (length string) 8)
+                     ;; We don't gain anything if we put the period closer
+                     ;; than 5 chars from the beginning (5 + 3 = 8).
+                     (setq i (string-match "[-_]" string 5)))
+                (aset string i ?\.))
             ;; Get rid of invalid characters.
             (while (setq i (string-match
                             "[^-a-zA-Z0-9_.%~^$!#&{}@`'()\200-\376]"
                             string))
               (aset string i ?_))
-            ;; If we don't have a period,
-            ;; and we have a dash or underscore that isn't the first char,
-            ;; change that to a period.
-            (if (and (not (string-match "\\." string))
-                     (setq i (string-match "[-_]" string 1)))
-                (aset string i ?\.))
             ;; If we don't have a period in the first 8 chars, insert one.
+            ;; This enables to have 3 more characters from the original
+            ;; name in the extension.
             (if (> (or (string-match "\\." string) (length string))
                    8)
                 (setq string
@@ -98,13 +105,14 @@ with a definition that really does change some file names."
             (if (> (length string) (+ firstdot 4))
                 (setq string (substring string 0 (+ firstdot 4))))
             ;; Change all periods except the first one into underscores.
+            ;; (DOS doesn't allow more than one period.)
             (while (string-match "\\." string (1+ firstdot))
               (setq i (string-match "\\." string (1+ firstdot)))
               (aset string i ?_))
-            ;; If the last character of the original filename was `~',
-            ;; make sure the munged name ends with it also.  This is so
-            ;; a backup file retains its final `~'.
-            (if (equal lastchar ?~)
+            ;; If the last character of the original filename was `~' or `#',
+            ;; make sure the munged name ends with it also.  This is so that
+            ;; backup and auto-save files retain their telltale form.
+            (if (memq lastchar '(?~ ?#))
                 (aset string (1- (length string)) lastchar))))
           (concat (if (and (stringp dir)
                            (memq (aref dir dlen-m-1) '(?/ ?\\)))