RE: [Gpsbabel-code] patch for calculating GMT

[Martin F. <fo...@fo...>]

Time is one of those things people can never agree on. My own preference is
to have data storage in GMT and a GMT/Local option for display and use. That
way there's less confusion when you cross time zones.

The patched version is a cleaner implementation than my inline version.


-----Original Message-----
From: gps...@li...
[mailto:gps...@li...]On Behalf Of Robert
Lipe
Sent: Monday, January 06, 2003 9:30 PM
To: Martin Fouts
Cc: gpsbabel
Subject: Re: [Gpsbabel-code] patch for calculating GMT



I took your idea and moved it to a function of its own (since the logic may
be needed by other formats.

This exercise did make me realize we probably shoudl standardize what's
in the struct wpt itself.  Is "creation time" local or GMT?

Martin, Ron, does this patch work for you?

Index: gpx.c
===================================================================
RCS file: /cvsroot/gpsbabel/gpsbabel/gpx.c,v
retrieving revision 1.26
diff -p -u -r1.26 gpx.c
--- gpx.c	2 Jan 2003 04:07:24 -0000	1.26
+++ gpx.c	7 Jan 2003 05:25:35 -0000
@@ -388,19 +388,7 @@ gpx_end(void *data, const char *el)
 			tm.tm_mon -= 1;
 			tm.tm_year -= 1900;
 			tm.tm_isdst = 1;
-			wpt_tmp->creation_time = mktime(&tm);
-#if 0
-			/* mktime assumes local time, and Z is gmtime */
-			/* localtime will initialize timezone and daylight */
-			/* 12/31/02 - RJL - unfortunately, this fix relies
-			 * on non-ANSI extensions, so I've turned this off
-			 * and reverted to the old way.
-			 */
-			localtime( &wpt_tmp->creation_time );
-			wpt_tmp->creation_time -= timezone - (daylight?3600:0);
-#else
-                        wpt_tmp->creation_time = mktime(&tm);
-#endif
+                        wpt_tmp->creation_time = mktime(&tm) +
get_tz_offset();
 		}
 		if (in_wpt && in_gs_type && !in_gs_log) {
 			wpt_tmp->gc_data.type = gs_mktype(cdatastr);
Index: util.c
===================================================================
RCS file: /cvsroot/gpsbabel/gpsbabel/util.c,v
retrieving revision 1.13
diff -p -u -r1.13 util.c
--- util.c	6 Jan 2003 23:58:53 -0000	1.13
+++ util.c	7 Jan 2003 05:25:35 -0000
@@ -109,6 +109,7 @@ fprintdms(FILE *file, const coord *c, in
 	}
 	fprintf(file, "%c%f\t", d, fabs(c->degrees));
 }
+
 void
 fatal(const char *fmt, ...)
 {
@@ -196,5 +197,22 @@ si_round( double d )
 	}
 	else {
 		return (signed int)(d+0.5);
+	}
+}
+
+/*
+ *  Return a time_t suitable for adding to a time_t that is in GMT to
+ *  make it a local time.
+ */
+signed int
+get_tz_offset(void)
+{
+	time_t now = time(0);
+	time_t later = mktime(gmtime(&now));
+
+	if (later == -1) {
+		return 0;
+	} else {
+		return (signed int) difftime(now, later);
 	}
 }
Index: defs.h
===================================================================
RCS file: /cvsroot/gpsbabel/gpsbabel/defs.h,v
retrieving revision 1.25
diff -p -u -r1.25 defs.h
--- defs.h	6 Jan 2003 23:33:13 -0000	1.25
+++ defs.h	7 Jan 2003 05:25:35 -0000
@@ -212,6 +212,7 @@ void *xcalloc(size_t nmemb, size_t size)
 void *xmalloc(size_t size);
 char *xstrdup(const char *s);
 void *rtrim(char *s);
+signed int get_tz_offset(void);

 /*
  * PalmOS records like fixed-point numbers, which should be rounded


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