Improve time stamp handling, and be more consistent about it.

This implements a suggestion made in:
http://lists.gnu.org/archive/html/emacs-devel/2014-10/msg00587.html
Among other things, this means timer.el no longer needs to
autoload the time-date module.
* doc/lispref/os.texi (Time of Day, Time Conversion, Time Parsing)
(Processor Run Time, Time Calculations):
Document the new behavior, plus be clearer about the old behavior.
(Idle Timers): Take advantage of new functionality.
* etc/NEWS: Document the changes.
* lisp/allout-widgets.el (allout-elapsed-time-seconds): Doc fix.
* lisp/arc-mode.el (archive-ar-summarize):
* lisp/calendar/time-date.el (seconds-to-time, days-to-time, time-since):
* lisp/emacs-lisp/timer.el (timer-relative-time, timer-event-handler)
(run-at-time, with-timeout-suspend, with-timeout-unsuspend):
* lisp/net/tramp.el (tramp-time-less-p, tramp-time-subtract):
* lisp/proced.el (proced-time-lessp):
* lisp/timezone.el (timezone-time-from-absolute):
* lisp/type-break.el (type-break-schedule, type-break-time-sum):
Simplify by using new functionality.
* lisp/calendar/cal-dst.el (calendar-next-time-zone-transition):
Do not return time values in obsolete and undocumented (HI . LO)
format; use (HI LO) instead.
* lisp/calendar/time-date.el (with-decoded-time-value):
Treat 'nil' as current time.  This is mostly for XEmacs.
(encode-time-value, with-decoded-time-value): Obsolete.
(time-add, time-subtract, time-less-p): Use no-op autoloads, for
XEmacs.  Define only if XEmacs, as they're now C builtins in Emacs.
* lisp/ldefs-boot.el: Update to match new time-date.el
* lisp/proced.el: Do not require time-date.
* src/editfns.c (invalid_time): New function.
Use it instead of 'error ("Invalid time specification")'.
(time_add, time_subtract, time_arith, Ftime_add, Ftime_less_p)
(decode_float_time, lisp_to_timespec, lisp_time_struct):
New functions.
(make_time_tail, make_time): Remove.  All uses changed to use
new functions or plain list4i.
(disassemble_lisp_time): Return effective length if successful.
Check that LOW is an integer, if it's combined with other components.
(decode_time_components): Decode into struct lisp_time, not
struct timespec, so that we can support a wide set of times
regardless of whether time_t is signed.  Decode plain numbers
as seconds since the Epoch, and nil as the current time.
(lisp_time_argument, lisp_seconds_argument, Ffloat_time):
Reimplement in terms of new functions.
(Fencode_time): Just use list2i.
(syms_of_editfns): Add time-add, time-subtract, time-less-p.
* src/keyboard.c (decode_timer): Don't allow the new formats (floating
point or nil) in timers.
* src/systime.h (LO_TIME_BITS): New constant.  Use it everywhere in
place of the magic number '16'.
(struct lisp_time): New type.
(decode_time_components): Use it.
(lisp_to_timespec): New decl.

2 files changed, 24 insertions, 0 deletions

diff --git a/etc/ChangeLog b/etc/ChangeLog
index 983fcaa28eb..ed8c345eef5 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,8 @@
+2014-11-17  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Improve time stamp handling, and be more consistent about it.
+        * NEWS: Document the changes.
+
 2014-11-14  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
         * NEWS: Mention the new `M-s M-s' keystroke.
diff --git a/etc/NEWS b/etc/NEWS
index b0e08d46819..cb34e9b4613 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -377,6 +377,25 @@ optional repeat-count argument.
 *** New macros `thread-first' and `thread-last' allow threading a form
     as the first or last argument of subsequent forms.
 
++++
+** Time-related changes:
+
+*** Time-related functions now consistently accept numbers
+(representing seconds since the epoch) and nil (representing the
+current time) as well as the usual list-of-integer representation.
+Affected functions include `current-time-string', `current-time-zone',
+`decode-time', `float-time', `format-time-string', `seconds-to-time',
+`time-add', `time-less-p', `time-subtract', `time-to-day-in-year',
+`time-to-days', and `time-to-seconds'.
+
+*** The `encode-time-value' and `with-decoded-time-value' macros have
+been obsoleted.
+
+*** `calendar-next-time-zone-transition', `time-add', and
+`time-subtract' no longer return time values in the obsolete and
+undocumented integer-pair format.  Instead, they return a list of two
+integers.
+
 
 * Changes in Frames and Windows Code in Emacs 25.1