New (TICKS . HZ) timestamp format

This follows on a suggestion by Stefan Monnier in:
https://lists.gnu.org/r/emacs-devel/2018-08/msg00991.html
(Bug#32902).
* doc/lispref/buffers.texi (Modification Time):
* doc/lispref/os.texi (Processor Run Time, Time Calculations)
* doc/lispref/processes.texi (System Processes):
* doc/lispref/text.texi (Undo):
Let the "Time of Day" section cover timestamp format details.
* doc/lispref/os.texi (Time of Day):
Say that timestamp internal format should not be assumed.
Document new (ticks . hz) format.  Omit mention of seconds-to-time
since it is now just an alias for encode-time.
(Time Conversion): Document encode-time extension.
* etc/NEWS: Mention changes.
* lisp/calendar/cal-dst.el (calendar-system-time-basis): Now const.
* lisp/calendar/cal-dst.el (calendar-absolute-from-time)
(calendar-time-from-absolute)
(calendar-next-time-zone-transition):
* lisp/emacs-lisp/timer.el (timer-next-integral-multiple-of-time):
Simplify by using bignums, (TICKS . HZ), and new encode-time.
* lisp/emacs-lisp/timer.el (timer-next-integral-multiple-of-time):
Simplify by using bignums and new encode-time.
* lisp/calendar/parse-time.el (parse-iso8601-time-string):
Handle DST more accurately, by using new encode-time.
* lisp/calendar/time-date.el (seconds-to-time):
* lisp/calendar/timeclock.el (timeclock-seconds-to-time):
Now just an alias for encode-time.
* lisp/calendar/time-date.el (days-to-time):
* lisp/emacs-lisp/timer.el (timer--time-setter):
* lisp/net/ntlm.el (ntlm-compute-timestamp):
* lisp/obsolete/vc-arch.el (vc-arch-add-tagline):
* lisp/org/org-id.el (org-id-uuid, org-id-time-to-b36):
* lisp/tar-mode (tar-octal-time):
Don't assume timestamps default to list form.
* lisp/tar-mode.el (tar-parse-octal-long-integer):
Now an obsolete alias for tar-parse-octal-integer.
* src/keyboard.c (decode_timer): Adjust to changes to
time decoding functions elsewhere.
* src/timefns.c: Include bignum.h, limits.h.
(FASTER_TIMEFNS): New macro.
(WARN_OBSOLETE_TIMESTAMPS, CURRENT_TIME_LIST)
(timespec_hz, trillion, ztrillion):
New constants.
(make_timeval): Use TIME_T_MAX instead of its definiens.
(check_time_validity, time_add, time_subtract):
Remove.  All uses removed.
(disassemble_lisp_time): Remove; old code now folded into
decode_lisp_time.  All callers changed.
(invalid_hz, s_ns_to_double, ticks_hz_list4, mpz_set_time)
(timespec_mpz, timespec_ticks, time_hz_ticks)
(lisp_time_hz_ticks, lisp_time_seconds)
(time_form_stamp, lisp_time_form_stamp, decode_ticks_hz)
(decode_lisp_time, mpz_time, list4_to_timespec):
New functions.
(decode_float_time, decode_time_components, lisp_to_timespec):
Adjust to new struct lisp_time, which does not lose
information like the old one did.
(enum timeform): New enum.
(decode_time_components): New arg FORM.  All callers changed.
RESULT and DRESULT are now mutually exclusive; no callers need
to change because of this.
(decode_time_components, lisp_time_struct)
(lisp_seconds_argument, time_arith, make_lisp_time, Ffloat_time)
(Fencode_time):
Add support for (TICKS . HZ) form.
(DECODE_SECS_ONLY): New constant.
(lisp_time_struct): 2nd arg is now enum timeform, not int.
All callers changed.
(check_tm_member): Support bignums.m
(Fencode_time): Add new two-arg functionality.
* src/systime.h (struct lisp_time): Now ticks+hz rather than
hi+lo+us+ps, since ticks+hz does not lose info.
* test/src/systime-tests.el (time-equal-p-nil-nil):
New test.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/systime.h b/src/systime.h
index f2f51b009e2..0bc1e90fb05 100644
--- a/src/systime.h
+++ b/src/systime.h
@@ -75,19 +75,22 @@ extern void set_waiting_for_input (struct timespec *);
    (HI << LO_TIME_BITS) + LO + US / 1e6 + PS / 1e12.  */
 enum { LO_TIME_BITS = 16 };
 
-/* A Lisp time (HI LO US PS), sans the cons cells.  */
+/* Components of a new-format Lisp timestamp.  */
 struct lisp_time
 {
-  EMACS_INT hi;
-  int lo, us, ps;
+  /* Clock count as a Lisp integer.  */
+  Lisp_Object ticks;
+
+  /* Clock frequency (ticks per second) as a positive Lisp integer.
+     (TICKS . HZ) is a valid Lisp timestamp unless HZ < 65536.  */
+  Lisp_Object hz;
 };
 
 /* defined in timefns.c */
 extern struct timeval make_timeval (struct timespec) ATTRIBUTE_CONST;
 extern Lisp_Object make_lisp_time (struct timespec);
-extern int decode_time_components (Lisp_Object, Lisp_Object, Lisp_Object,
-				   Lisp_Object, struct lisp_time *, double *);
-extern struct timespec lisp_to_timespec (struct lisp_time);
+extern bool list4_to_timespec (Lisp_Object, Lisp_Object, Lisp_Object,
+			       Lisp_Object, struct timespec *);
 extern struct timespec lisp_time_argument (Lisp_Object);
 extern _Noreturn void time_overflow (void);
 extern void init_timefns (bool);