bug#71573: Related functions from ts.el

[Adam Porter <adam@alphapapa.net>]

Hi all,

FWIW, my ts.el timestamp library has the related functions
`ts-human-duration' and `ts-human-format-duration'.  See 
<https://github.com/alphapapa/ts.el/blob/552936017cfdec89f7fc20c254ae6b37c3f22c5b/ts.el#L440-L491> 
and code below.

They work a bit differently, but I've found them very useful in my other
Elisp projects, and my profiling has shown that they perform very well 
relative to, e.g. the existing `format-seconds' function in terms of 
runtime and GC (see benchmarks in source comments).

If any of the code in ts.el would be helpful, I'd be glad to contribute
it to Emacs (some discussion about upstreaming parts of ts.el has also 
been going on in other, Org-related contexts).

--Adam

Elisp follows:

(defun ts-human-duration (seconds)
   "Return plist describing duration SECONDS.
List includes years, days, hours, minutes, and seconds.  This is
a simple calculation that does not account for leap years, leap
seconds, etc."
   ;; TODO: Add weeks.
   (cl-macrolet ((dividef (place divisor)
                          ;; Divide PLACE by DIVISOR, set PLACE to the 
remainder, and return the quotient.
                          `(prog1 (/ ,place ,divisor)
                             (setf ,place (% ,place ,divisor)))))
     (let* ((seconds (floor seconds))
            (years (dividef seconds 31536000))
            (days (dividef seconds 86400))
            (hours (dividef seconds 3600))
            (minutes (dividef seconds 60)))
       (list :years years :days days :hours hours :minutes minutes 
:seconds seconds))))

;; See also the built-in function `format-seconds', which I seem to have
;; overlooked before writing this.  However, a quick benchmark, run
;; 100,000 times, shows that, when controllable formatting is not needed,
;; `ts-human-format-duration' is much faster and generates less garbage:

;; | Form                     | x faster than next | Total runtime | # 
of GCs | Total GC runtime |
;; 
|--------------------------+--------------------+---------------+----------+------------------|
;; | ts-human-format-duration | 5.82               |      0.832945 | 
    3 |         0.574929 |
;; | format-seconds           | slowest            |      4.848253 | 
   17 |         3.288799 |

(cl-defun ts-human-format-duration (seconds &optional abbreviate)
   "Return human-formatted string describing duration SECONDS.
If SECONDS is less than 1, returns \"0 seconds\".  If ABBREVIATE
is non-nil, return a shorter version, without spaces.  This is a
simple calculation that does not account for leap years, leap
seconds, etc."
   ;; FIXME: Doesn't work with negative values, even though 
`ts-human-duration' does.
   (if (< seconds 1)
       (if abbreviate "0s" "0 seconds")
     (cl-macrolet ((format> (place)
                            ;; When PLACE is greater than 0, return 
formatted string using its symbol name.
                            `(when (> ,place 0)
                               (format "%d%s%s" ,place
                                       (if abbreviate "" " ")
                                       (if abbreviate
                                           ,(substring (symbol-name 
place) 0 1)
                                         ,(symbol-name place)))))
                   (join-places (&rest places)
                                ;; Return string joining the names and 
values of PLACES.
                                `(->> (list ,@(cl-loop for place in places
                                                       collect `(format> 
,place)))
                                      -non-nil
                                      (s-join (if abbreviate "" ", ")))))
       (-let* (((&plist :years :days :hours :minutes :seconds) 
(ts-human-duration seconds)))
         (join-places years days hours minutes seconds)))))