Consistently handle time zone specification.

* editfns.c (decode_time_zone): New function, refactored out from ...
(Fencode_time): ... adjusted user.
(Fset_time_zone_rule): Use decode_time_zone.

src/ChangeLog

@@ -16,6 +16,11 @@
 	* callproc.c (encode_current_directory, call_process):
 	* process.c (Fstart_process): Use it.
+	Consistently handle time zone specification.
+	* editfns.c (decode_time_zone): New function, refactored out from ...
+	(Fencode_time): ... adjusted user.
+	(Fset_time_zone_rule): Use decode_time_zone.
+
 2015-01-14  Paul Eggert  <eggert@cs.ucla.edu>
 	Use bool for boolean in xmenu.c, xml.c

src/editfns.c

@@ -2063,6 +2063,33 @@ check_tm_member (Lisp_Object obj, int offset)
   return n - offset;
 }
 
+/* Decode ZONE as a time zone specification.  */
+
+static const char *
+decode_time_zone (Lisp_Object zone)
+{
+  const char *tzstring = NULL;
+
+  if (EQ (zone, Qt))
+    tzstring = "UTC0";
+  else if (STRINGP (zone))
+    tzstring = SSDATA (zone);
+  else if (INTEGERP (zone))
+    {
+      static char const tzbuf_format[] = "XXX%s%"pI"d:%02d:%02d";
+      char tzbuf[sizeof tzbuf_format + INT_STRLEN_BOUND (EMACS_INT)];
+      EMACS_INT abszone = eabs (XINT (zone)), zone_hr = abszone / (60 * 60);
+      int zone_min = (abszone / 60) % 60, zone_sec = abszone % 60;
+
+      sprintf (tzbuf, tzbuf_format, &"-"[XINT (zone) < 0],
+	       zone_hr, zone_min, zone_sec);
+      tzstring = tzbuf;
+    }
+  else
+    xsignal2 (Qerror, build_string ("Invalid time zone specification"), zone);
+  return tzstring;
+}
+
 DEFUN ("encode-time", Fencode_time, Sencode_time, 6, MANY, 0,
        doc: /* Convert SECOND, MINUTE, HOUR, DAY, MONTH, YEAR and ZONE to internal time.
 This is the reverse operation of `decode-time', which see.
@@ -2105,30 +2132,7 @@ usage: (encode-time SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)  */)
     value = mktime (&tm);
   else
     {
-      static char const tzbuf_format[] = "XXX%s%"pI"d:%02d:%02d";
-      char tzbuf[sizeof tzbuf_format + INT_STRLEN_BOUND (EMACS_INT)];
-      const char *tzstring;
-
-      if (EQ (zone, Qt))
-	tzstring = "UTC0";
-      else if (STRINGP (zone))
-	tzstring = SSDATA (zone);
-      else if (INTEGERP (zone))
-	{
-	  EMACS_INT abszone = eabs (XINT (zone));
-	  EMACS_INT zone_hr = abszone / (60*60);
-	  int zone_min = (abszone/60) % 60;
-	  int zone_sec = abszone % 60;
-	  sprintf (tzbuf, tzbuf_format, &"-"[XINT (zone) < 0],
-		   zone_hr, zone_min, zone_sec);
-	  tzstring = tzbuf;
-	}
-      else
-	tzstring = 0;
-
-      timezone_t tz = tzstring ? tzalloc (tzstring) : 0;
-      if (! tz)
-	error ("Invalid time zone specification");
+      timezone_t tz = tzalloc (decode_time_zone (zone));
       value = mktime_z (tz, &tm);
       tzfree (tz);
     }
@@ -2265,7 +2269,8 @@ the data it can't find.  */)
 DEFUN ("set-time-zone-rule", Fset_time_zone_rule, Sset_time_zone_rule, 1, 1, 0,
        doc: /* Set the local time zone using TZ, a string specifying a time zone rule.
 If TZ is nil, use implementation-defined default time zone information.
-If TZ is t, use Universal Time.
+If TZ is t, use Universal Time.  If TZ is an integer, it is treated as in
+`encode-time'.
 
 Instead of calling this function, you typically want (setenv "TZ" TZ).
 That changes both the environment of the Emacs process and the
@@ -2273,17 +2278,7 @@ variable `process-environment', whereas `set-time-zone-rule' affects
 only the former.  */)
   (Lisp_Object tz)
 {
-  const char *tzstring;
-
-  if (! (NILP (tz) || EQ (tz, Qt)))
-    CHECK_STRING (tz);
-
-  if (NILP (tz))
-    tzstring = initial_tz;
-  else if (EQ (tz, Qt))
-    tzstring = "UTC0";
-  else
-    tzstring = SSDATA (tz);
+  const char *tzstring = NILP (tz) ? initial_tz : decode_time_zone (tz);
 
   block_input ();
   set_time_zone_rule (tzstring);