[PATCH] osmo-msc[master]: 04.08: find a portable way to obtain the timezone offset

[Neels Hofmeyr]

Review at  https://gerrit.osmocom.org/3612

04.08: find a portable way to obtain the timezone offset

Portable GMT offset calculation to display correct
time on GSM.

Change-Id: I673f17af2550c9708c4771e4ea4eafbbfafbb824
---
M src/libmsc/gsm_04_08.c
1 file changed, 10 insertions(+), 3 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-msc refs/changes/12/3612/1

diff --git a/src/libmsc/gsm_04_08.c b/src/libmsc/gsm_04_08.c
index 3f3f905..a4e16fb 100644
--- a/src/libmsc/gsm_04_08.c
+++ b/src/libmsc/gsm_04_08.c
@@ -496,12 +496,19 @@
 	else {
 		/* Need to get GSM offset and convert into 15 min units */
 		/* This probably breaks if gmtoff returns a value not evenly divisible by 15? */
-		local_time = localtime(&cur_t);
 #ifdef HAVE_TM_GMTOFF_IN_TM
+		local_time = localtime(&cur_t);
 		tzunits = (local_time->tm_gmtoff/60)/15;
 #else
-#warning find a portable way to obtain the timezone offset
-		tzunits = 0;
+		/* find timezone offset */
+		time_t utc;
+		double offsetFromUTC;
+		utc = mktime(gmt_time);
+		local_time = localtime(&cur_t);
+		offsetFromUTC = difftime(cur_t, utc);
+		if (local_time->tm_isdst)
+			offsetFromUTC += 3600.0;
+		tzunits = ((int)offsetFromUTC) / 60 / 15;
 #endif
 		if (tzunits < 0) {
 			tzunits = tzunits/-1;

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I673f17af2550c9708c4771e4ea4eafbbfafbb824
Gerrit-PatchSet: 1
Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-Owner: Neels Hofmeyr <nhofmeyr at sysmocom.de>