(struct ttinfo): New member `isgmt'. (__tzfile_read): Read isgmt flag…

…s for each type. (__tzfile_default): When using TZDEFRULES DST rules, adjust transition times according to the isstd and isgmt flags for the types of each transition, and adjust each transition to point to type index either 0 or 1. Reset type indices 0 and 1 to describe the user's settings.

time/tzfile.c

@@ -1,4 +1,4 @@
-/* Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc.
+/* Copyright (C) 1991, 1992, 1993, 1995 Free Software Foundation, Inc.
 This file is part of the GNU C Library.
 
 The GNU C Library is free software; you can redistribute it and/or
@@ -26,20 +26,15 @@ Cambridge, MA 02139, USA.  */
 #define	NOID
 #include <tzfile.h>
 
-#ifndef	HAVE_GNU_LD
-#define	__tzname	tzname
-#define	__daylight	daylight
-#define	__timezone	timezone
-#endif
-
 int __use_tzfile = 0;
 
 struct ttinfo
   {
     long int offset;		/* Seconds east of GMT.  */
     unsigned char isdst;	/* Used to set tm_isdst.  */
     unsigned char idx;		/* Index into `zone_names'.  */
-    unsigned char isstd;	/* Transition times are standard time.  */
+    unsigned char isstd;	/* Transition times are in standard time.  */
+    unsigned char isgmt;	/* Transition times are in GMT.  */
   };
 
 struct leap
@@ -67,7 +62,7 @@ static struct leap *leaps = NULL;
 void
 DEFUN(__tzfile_read, (file), CONST char *file)
 {
-  size_t num_isstd;
+  size_t num_isstd, num_isgmt;
   register FILE *f;
   struct tzhead tzhead;
   size_t chars;
@@ -113,10 +108,11 @@ DEFUN(__tzfile_read, (file), CONST char *file)
     goto lose;
 
   num_transitions = (size_t) uc2ul(tzhead.tzh_timecnt);
-  num_types = (size_t) uc2ul(tzhead.tzh_typecnt);
-  chars = (size_t) uc2ul(tzhead.tzh_charcnt);
-  num_leaps = (size_t) uc2ul(tzhead.tzh_leapcnt);
-  num_isstd = (size_t) uc2ul(tzhead.tzh_ttisstdcnt);
+  num_types = (size_t) uc2ul (tzhead.tzh_typecnt);
+  chars = (size_t) uc2ul (tzhead.tzh_charcnt);
+  num_leaps = (size_t) uc2ul (tzhead.tzh_leapcnt);
+  num_isstd = (size_t) uc2ul (tzhead.tzh_ttisstdcnt);
+  num_isgmt = (size_t) uc2ul (tzhead.tzh_ttisgmtcnt);
 
   if (num_transitions > 0)
     {
@@ -188,6 +184,16 @@ DEFUN(__tzfile_read, (file), CONST char *file)
   while (i < num_types)
     types[i++].isstd = 0;
 
+  for (i = 0; i < num_isgmt; ++i)
+    {
+      char c = getc(f);
+      if (c == EOF)
+	goto lose;
+      types[i].isgmt = c != 0;
+    }
+  while (i < num_types)
+    types[i++].isgmt = 0;
+
   (void) fclose(f);
 
   compute_tzname_max (chars);
@@ -199,12 +205,18 @@ DEFUN(__tzfile_read, (file), CONST char *file)
   (void) fclose(f);
 }
 
+/* The user specified a hand-made timezone, but not its DST rules.
+   We will use the names and offsets from the user, and the rules
+   from the TZDEFRULES file.  */
+
 void
 DEFUN(__tzfile_default, (std, dst, stdoff, dstoff),
       char *std AND char *dst AND
       long int stdoff AND long int dstoff)
 {
   size_t stdlen, dstlen, i;
+  long int rule_offset, rule_stdoff, rule_dstoff;
+  int isdst;
 
   __tzfile_read (TZDEFRULES);
   if (!__use_tzfile)
@@ -216,8 +228,10 @@ DEFUN(__tzfile_default, (std, dst, stdoff, dstoff),
       return;
     }
 
+  /* Ignore the zone names read from the file.  */
   free (zone_names);
 
+  /* Use the names the user specified.  */
   stdlen = strlen (std) + 1;
   dstlen = strlen (dst) + 1;
   zone_names = malloc (stdlen + dstlen);
@@ -229,19 +243,60 @@ DEFUN(__tzfile_default, (std, dst, stdoff, dstoff),
   memcpy (zone_names, std, stdlen);
   memcpy (&zone_names[stdlen], dst, dstlen);
 
-  for (i = 0; i < num_types; ++i)
-    if (types[i].isdst)
-      {
-	types[i].idx = stdlen;
-	if (dst[0] != '\0')
-	  types[i].offset = dstoff;
-      }
-    else
-      {
-	types[i].idx = 0;
-	if (dst[0] != '\0')
-	  types[i].offset = stdoff;
-      }
+  /* Find the standard and daylight time offsets used by the rule file.
+     We choose the offsets in the types of each flavor that are
+     transitioned to earliest in time.  */
+  rule_dstoff = 0;
+  for (i = 0; i < num_transitions; ++i)
+    {
+      if (!rule_stdoff && !types[type_idxs[i]].isdst)
+	rule_stdoff = types[type_idxs[i]].offset;
+      if (!rule_dstoff && types[type_idxs[i]].isdst)
+	rule_dstoff = types[type_idxs[i]].offset;
+      if (rule_stdoff && rule_dstoff)
+	break;
+    }
+
+  /* Now correct the transition times for the user-specified standard and
+     daylight offsets from GMT.  */
+  isdst = 0;
+  rule_offset = rule_offset;
+  for (i = 0; i < num_transitions; ++i)
+    {
+      struct ttinfo *trans_type = &types[type_idxs[i]];
+
+      /* We will use only types 0 (standard) and 1 (daylight).
+	 Fix up this transition to point to whichever matches
+	 the flavor of its original type.  */
+      type_idxs[i] = trans_type->isdst;
+
+      if (trans_type->isgmt)
+	/* The transition time is in GMT.  No correction to apply.  */ ;
+      else if (isdst && !trans_type->isstd)
+	/* The type says this transition is in "local wall clock time", and
+	   wall clock time as of the previous transition was DST.  Correct
+	   for the difference between the rule's DST offset and the user's
+	   DST offset.  */
+	transitions[i] += dstoff - rule_dstoff;
+      else
+	/* This transition is in "local wall clock time", and wall clock
+	   time as of this iteration is non-DST.  Correct for the
+	   difference between the rule's standard offset and the user's
+	   standard offset.  */
+	transitions[i] += stdoff - rule_stdoff;
+
+      /* The DST state of "local wall clock time" for the next iteration is
+	 as specified by this transition.  */
+      isdst = trans_type->isdst;
+    }
+
+  /* Reset types 0 and 1 to describe the user's settings.  */
+  types[0].idx = 0;
+  types[0].offset = stdoff;
+  types[0].isdst = 0;
+  types[1].idx = stdlen;
+  types[1].offset = dstoff;
+  types[1].isdst = 1;
 
   compute_tzname_max (stdlen + dstlen);
 }