[PATCH 3/4] gsm0411_utils: Fix timezone offs calculation in gsm340_gen_scts()

[Daniel Willmann]

The current code uses gmtime which returns the time in UTC. This is not
the intended behaviour (otherwise the offset could always be set to
zero).

Iinstead of relying on tm_gmtoff this patch uses the (portable)
gmtoffset_from_ts() function to determine the current time offset.

Update the test with the expected result
---
 src/gsm/gsm0411_utils.c | 33 +++++++++++++++++----------------
 tests/sms/sms_test.ok   | 12 ------------
 2 files changed, 17 insertions(+), 28 deletions(-)

diff --git a/src/gsm/gsm0411_utils.c b/src/gsm/gsm0411_utils.c
index d857e41..c6d68bd 100644
--- a/src/gsm/gsm0411_utils.c
+++ b/src/gsm/gsm0411_utils.c
@@ -93,23 +93,24 @@ static time_t gmtoffset_from_ts(time_t time)
 /* Generate 03.40 TP-SCTS */
 void gsm340_gen_scts(uint8_t *scts, time_t time)
 {
-	struct tm *tm = gmtime(&time);
-
-	*scts++ = gsm411_bcdify(tm->tm_year % 100);
-	*scts++ = gsm411_bcdify(tm->tm_mon + 1);
-	*scts++ = gsm411_bcdify(tm->tm_mday);
-	*scts++ = gsm411_bcdify(tm->tm_hour);
-	*scts++ = gsm411_bcdify(tm->tm_min);
-	*scts++ = gsm411_bcdify(tm->tm_sec);
-#ifdef HAVE_TM_GMTOFF_IN_TM
-	if (tm->tm_gmtoff >= 0)
-		*scts++ = gsm411_bcdify(tm->tm_gmtoff/(60*15));
+	struct tm tm;
+	time_t gmtoffset;
+
+	localtime_r(&time, &tm);
+
+	*scts++ = gsm411_bcdify(tm.tm_year % 100);
+	*scts++ = gsm411_bcdify(tm.tm_mon + 1);
+	*scts++ = gsm411_bcdify(tm.tm_mday);
+	*scts++ = gsm411_bcdify(tm.tm_hour);
+	*scts++ = gsm411_bcdify(tm.tm_min);
+	*scts++ = gsm411_bcdify(tm.tm_sec);
+
+	gmtoffset = gmtoffset_from_ts(time);
+
+	if (gmtoffset >= 0)
+		*scts++ = gsm411_bcdify(gmtoffset/(60*15));
 	else
-		*scts++ = gsm411_bcdify(-tm->tm_gmtoff/(60*15)) | 0x08;
-#else
-#warning find a portable way to obtain timezone offset
-	*scts++ = 0;
-#endif
+		*scts++ = gsm411_bcdify(-gmtoffset/(60*15)) | 0x08;
 }
 
 /* Decode 03.40 TP-SCTS (into utc/gmt timestamp) */
diff --git a/tests/sms/sms_test.ok b/tests/sms/sms_test.ok
index a3d816c..a779f12 100644
--- a/tests/sms/sms_test.ok
+++ b/tests/sms/sms_test.ok
@@ -28,22 +28,10 @@ Result: len(9) data(0e d0 4f 78 d9 2d 9c 0e 01 )
 Result: len(12) data(14 d0 4f 78 d9 2d 9c 0e c3 e2 31 19 )
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ UTC
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ Europe/London
-1364691600 -> 31301310000000 -> 1364695200
-Timezone Europe/London failed at ts 1364691600
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ Europe/Berlin
-1364695200 -> 31301320000000 -> 1364698800
-Timezone Europe/Berlin failed at ts 1364695200
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ Europe/Athens
-1364698800 -> 31301330000000 -> 1364702400
-Timezone Europe/Athens failed at ts 1364698800
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ Europe/Moscow
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ Canada/Central
-1362880800 -> 31300120000000 -> 1362884400
-Timezone Canada/Central failed at ts 1362880800
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ America/New_York
-1362880800 -> 31300120000000 -> 1362884400
-Timezone America/New_York failed at ts 1362880800
 Testing gsm340_scts(gsm340_gen_scts(ts)) == ts for TZ America/Los_Angeles
-1362880800 -> 31300120000000 -> 1362884400
-Timezone America/Los_Angeles failed at ts 1362880800
 OK
-- 
1.8.4.2