Support gmtoff and zone in time struct.

* lib.c (gmtoff_s, zone_s): New symbol variables.
(tm_to_time_struct): Copy tm_gmtoff and tm_zone into
Lisp struct from struct tm, if the platform has these.
(time_fields_to_tm): Zero/null-out the tm_gmtoff
and tm_zone fields of the target structure, if the
platform has them.
(time_init): Intern the gmtoff and zone symbols,
initializing the gmtoff_s and zone_s variables.
Add the gmtoff and zone slots to the time struct.

* txr.1: Documented new slots.

2 files changed, 52 insertions, 4 deletions

diff --git a/lib.c b/lib.c
index 8676f9e2..834d137f 100644
--- a/lib.c
+++ b/lib.c
@@ -117,7 +117,7 @@ val list_f, less_f, greater_f;
 val prog_string;
 
 val time_s, time_local_s, time_utc_s, time_string_s, time_parse_s;
-val year_s, month_s, day_s, hour_s, min_s, sec_s, dst_s;
+val year_s, month_s, day_s, hour_s, min_s, sec_s, dst_s, gmtoff_s, zone_s;
 
 static val env_list;
 static val recycled_conses;
@@ -9397,6 +9397,12 @@ static void tm_to_time_struct(val time_struct, struct tm *ptm)
   slotset(time_struct, min_s, num_fast(ptm->tm_min));
   slotset(time_struct, sec_s, num_fast(ptm->tm_sec));
   slotset(time_struct, dst_s, tnil(ptm->tm_isdst));
+#if HAVE_TM_GMTOFF
+  slotset(time_struct, gmtoff_s, num_fast(ptm->TM_GMTOFF));
+#endif
+#if HAVE_TM_ZONE
+  slotset(time_struct, zone_s, if2(ptm->TM_ZONE, string_utf8(ptm->TM_ZONE)));
+#endif
 }
 
 static val broken_time_struct(struct tm *tms)
@@ -9471,6 +9477,13 @@ static void time_fields_to_tm(struct tm *ptm,
     ptm->tm_isdst = -1;
   else
     ptm->tm_isdst = 1;
+
+#if HAVE_TM_GMTOFF
+  ptm->TM_GMTOFF = 0;
+#endif
+#if HAVE_TM_ZONE
+  ptm->TM_ZONE = 0;
+#endif
 }
 
 static void time_struct_to_tm(struct tm *ptm, val time_struct, val strict)
@@ -9667,12 +9680,15 @@ static void time_init(void)
   min_s = intern(lit("min"), user_package);
   sec_s = intern(lit("sec"), user_package);
   dst_s = intern(lit("dst"), user_package);
+  gmtoff_s = intern(lit("gmtoff"), user_package);
+  zone_s = intern(lit("zone"), user_package);
 
   time_st = make_struct_type(time_s, nil,
                              list(time_local_s, time_utc_s,
                                   time_string_s, time_parse_s, nao),
                              list(year_s, month_s, day_s,
-                                  hour_s, min_s, sec_s, dst_s, nao),
+                                  hour_s, min_s, sec_s, dst_s,
+                                  gmtoff_s, zone_s, nao),
                              nil, nil, nil, nil);
 
   static_slot_set(time_st, time_local_s, func_f1(nil, time_meth));
diff --git a/txr.1 b/txr.1
index c7f53a6f..095fa482 100644
--- a/txr.1
+++ b/txr.1
@@ -38352,7 +38352,8 @@ function.
 .coNP Structure @ time
 .synb
   (defstruct time nil
-    year month day hour min sec dst)
+    year month day hour min sec dst
+    gmtoff zone)
 .syne
 .desc
 The
@@ -38377,7 +38378,7 @@ January, whereas the C member
 .code tm_mon
 uses a zero-based month.  The
 .code dst
-slot is a \*(TL Boolean value. The remaining slots
+slot is a \*(TL Boolean value. The slots
 .codn hour ,
 .codn min ,
 and
@@ -38388,6 +38389,37 @@ correspond directly to
 and
 .codn tm_sec .
 
+The slot
+.code gmtoff
+represents the number of seconds east of UTC, and
+.code zone
+holds a string giving the abbreviated time zone name.
+On platform where the C type
+.code "struct tm"
+has fields corresponding to these slots, values for
+these slots are calculated and stored into them by the
+.code time-struct-local
+and
+.code time-struct-utc
+functions, and also the related
+.code time-local
+and
+.code time-utc
+methods. On platform where the corresponding fields are not
+present in the C language
+.codn "struct tm" ,
+these slots are unaffected by those functions,
+retaining the default initial value
+.code nil
+or a previously stored value, if applicable.
+Lastly, the values of
+.code gmtoff
+and
+.code zone
+are not ignored by functions which accept a
+.code time
+structure as a source of input values.
+
 .coNP Functions @ time-struct-local and @ time-struct-utc
 .synb
 .mets (time-struct-local << time )