From 73c1d137e51ec6f2fe03cb619335f1f8c4c16973 Mon Sep 17 00:00:00 2001
From: oliskoli <oliskoli>
Date: Sun, 30 Jul 2006 17:38:41 +0000
Subject: [PATCH] Add new function 'mklocaltime'. Define new consts
 'unknown_speed' and 'unknown_course'.

---
 defs.h |  6 ++++--
 util.c | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/defs.h b/defs.h
index bae98af0f..5a3400054 100644
--- a/defs.h
+++ b/defs.h
@@ -677,6 +677,7 @@ int xasprintf(char **strp, const char *fmt, ...);
 char *strupper(char *src);
 char *strlower(char *src);
 signed int get_tz_offset(void);
+time_t mklocaltime(struct tm *t);
 time_t mkgmtime(struct tm *t);
 time_t current_time(void);
 signed int month_lookup(const char *m);
@@ -798,8 +799,9 @@ int color_to_bbggrr(char *cname);
  * A constant for unknown altitude.   It's tempting to just use zero
  * but that's not very nice for the folks near sea level.
  */
-#define unknown_alt -99999999.0
-
+#define unknown_alt 	-99999999.0
+#define unknown_course 	     -999.0
+#define unknown_speed	     -999.0
 /*
  * textfile: buffered OS independent (CRLF,NL,CR) text reader
  */
diff --git a/util.c b/util.c
index b61a12cc0..282ed20c2 100644
--- a/util.c
+++ b/util.c
@@ -25,6 +25,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <stdarg.h>
+#include <time.h>
 
 static int i_am_little_endian = -1;
 static int doswap(void);
@@ -702,6 +703,26 @@ mkgmtime(struct tm *t)
 	return(result);
 }
 
+/*
+ * mklocaltime: same as mktime, but try to recover the "Summer time flag",
+ *              which is evaluated by mktime
+ */
+time_t
+mklocaltime(struct tm *t)
+{
+	time_t result;
+	struct tm check = *t;
+	
+	check.tm_isdst = 0;
+	result = mktime(&check);
+	check = *localtime(&result);
+	if (check.tm_isdst == 1) {	/* DST is in effect */
+		check = *t;
+		check.tm_isdst = 1;
+		result = mktime(&check);
+	}
+	return result;
+}
 
 /*
  * A wrapper for time(2) that allows us to "freeze" time for testing.
-- 
2.30.2