time values

[Luc Teirlinck]

At Richard's request, I plan to soon change the return values of
`visited-file-modtime' and `calendar-time-from-absolute' to the form
(HIGH LOW) instead of (HIGH . LOW).  Grepping shows that these are the
last two functions that still return time values in this obsolete
form.  The return value of `visited-file-modtime' is also inconsistent
with that of `file-attributes'.

The change to `visited-file-modtime' requires supporting changes in
dired.el and tramp.el.   I do not know how tramp.el has to be handled
since there is also a standalone version.

I do not believe that changes in `lisp/gnus/nnfolder.el' or
`lisp/fast-lock.el' are needed, but I use neither, so I do not feel
100% confident about that.  Anyway, any problems I missed should be
easy to correct by simple changes like replacing cdr by cadr or the
like.

Diffs:
 
===File ~/fileio.c-diff=====================================
*** fileio.c    04 Jul 2004 21:04:39 -0500      1.506
--- fileio.c    10 Jul 2004 09:18:18 -0500      
***************
*** 5628,5640 ****
  DEFUN ("visited-file-modtime", Fvisited_file_modtime,
         Svisited_file_modtime, 0, 0, 0,
         doc: /* Return the current buffer's recorded visited file modification 
time.
! The value is a list of the form (HIGH . LOW), like the time values
  that `file-attributes' returns.  If the current buffer has no recorded
  file modification time, this function returns 0.
  See Info node `(elisp)Modification Time' for more details.  */)
       ()
  {
!   return long_to_cons ((unsigned long) current_buffer->modtime);
  }
  
  DEFUN ("set-visited-file-modtime", Fset_visited_file_modtime,
--- 5628,5644 ----
  DEFUN ("visited-file-modtime", Fvisited_file_modtime,
         Svisited_file_modtime, 0, 0, 0,
         doc: /* Return the current buffer's recorded visited file modification 
time.
! The value is a list of the form (HIGH LOW), like the time values
  that `file-attributes' returns.  If the current buffer has no recorded
  file modification time, this function returns 0.
  See Info node `(elisp)Modification Time' for more details.  */)
       ()
  {
!   Lisp_Object tcons;
!   tcons = long_to_cons ((unsigned long) current_buffer->modtime);
!   if (CONSP (tcons))
!     return list2 (XCAR (tcons), XCDR (tcons));
!   return tcons;
  }
  
  DEFUN ("set-visited-file-modtime", Fset_visited_file_modtime,
============================================================

===File ~/cal-dst.el-diff===================================
*** cal-dst.el  02 Sep 2003 07:40:04 -0500      1.20
--- cal-dst.el  09 Jul 2004 20:37:09 -0500      
***************
*** 70,83 ****
  (defun calendar-time-from-absolute (abs-date s)
    "Time of absolute date ABS-DATE, S seconds after midnight.
  
! Returns the pair (HIGH . LOW) where HIGH and LOW are the high and low
  16 bits, respectively, of the number of seconds 1970-01-01 00:00:00 UTC,
  ignoring leap seconds, that is the equivalent moment to S seconds after
  midnight UTC on absolute date ABS-DATE."
    (let* ((a (- abs-date calendar-system-time-basis))
           (u (+ (* 163 (mod a 512)) (floor s 128))))
      ;; Overflow is a terrible thing!
!     (cons
       ;; floor((60*60*24*a + s) / 2^16)
       (+ a (* 163 (floor a 512)) (floor u 512))
       ;; (60*60*24*a + s) mod 2^16
--- 70,83 ----
  (defun calendar-time-from-absolute (abs-date s)
    "Time of absolute date ABS-DATE, S seconds after midnight.
  
! Returns the list (HIGH LOW) where HIGH and LOW are the high and low
  16 bits, respectively, of the number of seconds 1970-01-01 00:00:00 UTC,
  ignoring leap seconds, that is the equivalent moment to S seconds after
  midnight UTC on absolute date ABS-DATE."
    (let* ((a (- abs-date calendar-system-time-basis))
           (u (+ (* 163 (mod a 512)) (floor s 128))))
      ;; Overflow is a terrible thing!
!     (list
       ;; floor((60*60*24*a + s) / 2^16)
       (+ a (* 163 (floor a 512)) (floor u 512))
       ;; (60*60*24*a + s) mod 2^16
============================================================

===File ~/dired.el-diff=====================================
*** dired.el    11 Jun 2004 16:28:02 -0500      1.291
--- dired.el    09 Jul 2004 22:00:40 -0500      
***************
*** 620,627 ****
             (modtime (visited-file-modtime)))
         (or (eq modtime 0)
             (not (eq (car attributes) t))
!            (and (= (car (nth 5 attributes)) (car modtime))
!                 (= (nth 1 (nth 5 attributes)) (cdr modtime)))))))
  
  (defun dired-buffer-stale-p (&optional noconfirm)
    "Return non-nil if current dired buffer needs updating.
--- 620,626 ----
             (modtime (visited-file-modtime)))
         (or (eq modtime 0)
             (not (eq (car attributes) t))
!            (equal (nth 5 attributes) modtime)))))
  
  (defun dired-buffer-stale-p (&optional noconfirm)
    "Return non-nil if current dired buffer needs updating.
============================================================

===File ~/tramp.el-diff=====================================
*** tramp.el    26 Jun 2004 16:46:18 -0500      1.46
--- tramp.el    10 Jul 2004 15:10:30 -0500      
***************
*** 2338,2349 ****
        (let* ((attr (file-attributes f))
               (modtime (nth 5 attr)))
          (cond ((and attr (not (equal modtime '(0 0))))
-                ;; Why does `file-attributes' return a list (HIGH
-                ;; LOW), but `visited-file-modtime' returns a cons
-                ;; (HIGH . LOW)?
                 (let ((mt (visited-file-modtime)))
                   (< (abs (tramp-time-diff
!                           modtime (list (car mt) (cdr mt)))) 2)))
                (attr
                 (save-excursion
                   (tramp-send-command
--- 2338,2346 ----
        (let* ((attr (file-attributes f))
               (modtime (nth 5 attr)))
          (cond ((and attr (not (equal modtime '(0 0))))
                 (let ((mt (visited-file-modtime)))
                   (< (abs (tramp-time-diff
!                           modtime mt)) 2)))
                (attr
                 (save-excursion
                   (tramp-send-command
============================================================

===File ~/buffers.texi-diff=================================
*** buffers.texi        23 Jun 2004 10:21:06 -0500      1.37
--- buffers.texi        10 Jul 2004 18:48:30 -0500      
***************
*** 625,633 ****
  @c Emacs 19 feature
  @defun visited-file-modtime
  This function returns the current buffer's recorded last file
! modification time, as a list of the form @code{(@var{high} .
! @var{low})}.  (This is the same format that @code{file-attributes}
! uses to return time values; see @ref{File Attributes}.)
  
  The function returns zero if the buffer has no recorded last
  modification time, which can happen, for instance, if the record has
--- 625,633 ----
  @c Emacs 19 feature
  @defun visited-file-modtime
  This function returns the current buffer's recorded last file
! modification time, as a list of the form @code{(@var{high} @var{low})}.
! (This is the same format that @code{file-attributes} uses to return
! time values; see @ref{File Attributes}.)
  
  The function returns zero if the buffer has no recorded last
  modification time, which can happen, for instance, if the record has
============================================================