Add support for sub-second ISO8601 strings

* lisp/calendar/iso8601.el (iso8601--decimalize): New function.
(iso8601-parse-time): Support sub-second ISO8601 times.

1 files changed, 29 insertions, 6 deletions

diff --git a/lisp/calendar/iso8601.el b/lisp/calendar/iso8601.el
index f8949914f78..66446dafb96 100644
--- a/lisp/calendar/iso8601.el
+++ b/lisp/calendar/iso8601.el
@@ -112,12 +112,16 @@
          iso8601--duration-combined-match)))
 
 (defun iso8601-parse (string)
-  "Parse an ISO 8601 date/time string and return a `decoded-time' structure.
+  "Parse an ISO 8601 date/time string and return a `decode-time' structure.
 
 The ISO 8601 date/time strings look like \"2008-03-02T13:47:30\",
 but shorter, incomplete strings like \"2008-03-02\" are valid, as
 well as variants like \"2008W32\" (week number) and
-\"2008-234\" (ordinal day number)."
+\"2008-234\" (ordinal day number).
+
+The `decode-time' value returned will have the same precision as
+STRING, so if a sub-second STRING is passed in, the `decode-time'
+seconds field will be on the (SECONDS . HZ) format."
   (if (not (iso8601-valid-p string))
       (signal 'wrong-type-argument string)
     (let* ((date-string (match-string 1 string))
@@ -138,7 +142,7 @@ well as variants like \"2008W32\" (week number) and
       date)))
 
 (defun iso8601-parse-date (string)
-  "Parse STRING (in ISO 8601 format) and return a decoded time value."
+  "Parse STRING (in ISO 8601 format) and return a `decode-time' value."
   (cond
    ;; Just a year: [-+]YYYY.
    ((iso8601--match iso8601--year-match string)
@@ -218,7 +222,9 @@ well as variants like \"2008W32\" (week number) and
         year))))
 
 (defun iso8601-parse-time (string)
-  "Parse STRING, which should be an ISO 8601 time string, and return a time value."
+  "Parse STRING, which should be an ISO 8601 time string.
+The return value will be a `decode-time' structure with just the
+hour/minute/seconds/zone fields filled in."
   (if (not (iso8601--match iso8601--full-time-match string))
       (signal 'wrong-type-argument string)
     (let ((time (match-string 1 string))
@@ -230,9 +236,22 @@ well as variants like \"2008W32\" (week number) and
                            (string-to-number (match-string 2 time))))
               (second (and (match-string 3 time)
                            (string-to-number (match-string 3 time))))
-              ;; Hm...
-              (_millisecond (and (match-string 4 time)
+              (fraction (and (match-string 4 time)
                              (string-to-number (match-string 4 time)))))
+          (when fraction
+            (cond
+             ;; Sub-second time.
+             (second
+              (let ((digits (1+ (truncate (log fraction 10)))))
+                (setq second (cons (+ (* second (expt 10 digits))
+                                      fraction)
+                                   (expt 10 digits)))))
+             ;; Fractional minute.
+             (minute
+              (setq second (iso8601--decimalize fraction 60)))
+             (hour
+              ;; Fractional hour.
+              (setq minute (iso8601--decimalize fraction 60)))))
           (iso8601--decoded-time :hour hour
                                  :minute (or minute 0)
                                  :second (or second 0)
@@ -240,6 +259,10 @@ well as variants like \"2008W32\" (week number) and
                                             (* 60 (iso8601-parse-zone
                                                    zone)))))))))
 
+(defun iso8601--decimalize (fraction base)
+  (round (* base (/ (float fraction)
+                    (expt 10 (1+ (truncate (log fraction 10))))))))
+
 (defun iso8601-parse-zone (string)
   "Parse STRING, which should be an ISO 8601 time zone.
 Return the number of minutes."