Some time-handling patches from Paul Eggert:

	* editfns.c (Fcurrent_time_zone): Take an optional argument specifying
	what (absolute) time should be used to determine the current time zone.
	Yield just offset and name of time zone, including DST correction.
	Yield time zone offset in seconds, not minutes.
	(lisp_time_argument, difftm): New functions.
	(Fcurrent_time_string): Use lisp_time_argument.
	* systime.h (EMACS_CURRENT_TIME_ZONE, EMACS_GET_TZ_OFFSET,
	EMACS_GET_TZ_NAMES): Remove.
	* config.h.in: Add HAVE_TM_ZONE.

1 files changed, 91 insertions, 45 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 86d292f2976..c3fdce29a5d 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -541,6 +541,27 @@ resolution finer than a second.")
 }
 
 
+static int
+lisp_time_argument (specified_time, result)
+     Lisp_Object specified_time;
+     time_t *result;
+{
+  if (NILP (specified_time))
+    return time (result) != -1;
+  else
+    {
+      Lisp_Object high, low;
+      high = Fcar (specified_time);
+      CHECK_NUMBER (high, 0);
+      low = Fcdr (specified_time);
+      if (XTYPE (low) == Lisp_Cons)
+	low = Fcar (low);
+      CHECK_NUMBER (low, 0);
+      *result = (XINT (high) << 16) + (XINT (low) & 0xffff);
+      return *result >> 16 == XINT (high);
+    }
+}
+
 DEFUN ("current-time-string", Fcurrent_time_string, Scurrent_time_string, 0, 1, 0,
   "Return the current time, as a human-readable string.\n\
 Programs can use this function to decode a time,\n\
@@ -556,24 +577,12 @@ and from `file-attributes'.")
   (specified_time)
      Lisp_Object specified_time;
 {
-  long value;
+  time_t value;
   char buf[30];
   register char *tem;
 
-  if (NILP (specified_time))
-    value = time ((long *) 0);
-  else
-    {
-      Lisp_Object high, low;
-      high = Fcar (specified_time);
-      CHECK_NUMBER (high, 0);
-      low = Fcdr (specified_time);
-      if (XTYPE (low) == Lisp_Cons)
-	low = Fcar (low);
-      CHECK_NUMBER (low, 0);
-      value = ((XINT (high) << 16) + (XINT (low) & 0xffff));
-    }
-
+  if (! lisp_time_argument (specified_time, &value))
+    value = -1;
   tem = (char *) ctime (&value);
 
   strncpy (buf, tem, 24);
@@ -582,42 +591,79 @@ and from `file-attributes'.")
   return build_string (buf);
 }
 
-DEFUN ("current-time-zone", Fcurrent_time_zone, Scurrent_time_zone, 0, 0, 0,
-  "Return the offset, savings state, and names for the current time zone.\n\
-This returns a list of the form (OFFSET SAVINGS-FLAG STANDARD SAVINGS).\n\
-OFFSET is an integer specifying how many minutes east of Greenwich the\n\
-    current time zone is located.  A negative value means west of\n\
-    Greenwich.  Note that this describes the standard time; if daylight\n\
-    savings time is in effect, it does not affect this value.\n\
-SAVINGS-FLAG is non-nil iff daylight savings time or some other sort\n\
-    of seasonal time adjustment is in effect.\n\
-STANDARD is a string giving the name of the time zone when no seasonal\n\
-    time adjustment is in effect.\n\
-SAVINGS is a string giving the name of the time zone when there is a\n\
-    seasonal time adjustment in effect.\n\
-If the local area does not use a seasonal time adjustment,\n\
-SAVINGS-FLAG is always nil, and STANDARD and SAVINGS are equal.\n\
+#define TM_YEAR_ORIGIN 1900
+
+/* Yield A - B, measured in seconds.  */
+static long
+difftm(a, b)
+     struct tm *a, *b;
+{
+  int ay = a->tm_year + (TM_YEAR_ORIGIN - 1);
+  int by = b->tm_year + (TM_YEAR_ORIGIN - 1);
+  return
+    (
+     (
+      (
+       /* difference in day of year */
+       a->tm_yday - b->tm_yday
+       /* + intervening leap days */
+       +  ((ay >> 2) - (by >> 2))
+       -  (ay/100 - by/100)
+       +  ((ay/100 >> 2) - (by/100 >> 2))
+       /* + difference in years * 365 */
+       +  (long)(ay-by) * 365
+       )*24 + (a->tm_hour - b->tm_hour)
+      )*60 + (a->tm_min - b->tm_min)
+     )*60 + (a->tm_sec - b->tm_sec);
+}
+
+DEFUN ("current-time-zone", Fcurrent_time_zone, Scurrent_time_zone, 0, 1, 0,
+  "Return the offset and name for the local time zone.\n\
+This returns a list of the form (OFFSET NAME).\n\
+OFFSET is an integer number of seconds ahead of UTC (east of Greenwich).\n\
+    A negative value means west of Greenwich.\n\
+NAME is a string giving the name of the time zone.\n\
+If an argument is given, it specifies when the time zone offset is determined\n\
+instead of using the current time.  The argument should have the form:\n\
+  (HIGH . LOW)\n\
+or the form:\n\
+  (HIGH LOW . IGNORED).\n\
+Thus, you can use times obtained from `current-time'\n\
+and from `file-attributes'.\n\
 \n\
 Some operating systems cannot provide all this information to Emacs;\n\
 in this case, current-time-zone will return a list containing nil for\n\
 the data it can't find.")
-  ()
+  (specified_time)
+     Lisp_Object specified_time;
 {
-#ifdef EMACS_CURRENT_TIME_ZONE
-  int offset, savings_flag;
-  char standard[11];
-  char savings[11];
-
-  EMACS_CURRENT_TIME_ZONE (&offset, &savings_flag, standard, savings);
-
-  return Fcons (make_number (offset),
-		Fcons ((savings_flag ? Qt : Qnil),
-		       Fcons (build_string (standard),
-			      Fcons (build_string (savings),
-				     Qnil))));
-#else
-  return Fmake_list (4, Qnil);
+  time_t value;
+  struct tm *t;
+
+  if (lisp_time_argument (specified_time, &value)
+      && (t = gmtime(&value)) != 0)
+    {
+      struct tm gmt = *t;  /* Make a copy, in case localtime modifies *t.  */
+      long offset;
+      char *s, buf[6];
+      t = localtime(&value);
+      offset = difftm(t, &gmt);
+      s = 0;
+#ifdef HAVE_TM_ZONE
+      if (t->tm_zone)
+	s = t->tm_zone;
 #endif
+      if (!s)
+	{
+	  /* No local time zone name is available; use "+-NNNN" instead.  */
+	  long am = (offset < 0 ? -offset : offset) / 60;
+	  sprintf (buf, "%c%02d%02d", (offset < 0 ? '-' : '+'), am/60, am%60);
+	  s = buf;
+	}
+      return Fcons (make_number (offset), Fcons (build_string (s), Qnil));
+    }
+  else
+    return Fmake_list (2, Qnil);
 }