@GENE, @Alain,
Thank you for your suggestion.
I thought the same as you at first.
I checked with the following debug code.
LOGF_DEBUG("### OnStep ltm.tm_isdst: %i", ltm.tm_isdst);
double offset = 0;
if (getUTFOffset(&offset))
{
char utcStr[8] = {0};
snprintf(utcStr, 8, "%.2f", offset);
IUSaveText(&TimeT[1], utcStr);
}
else
{
LOG_WARN("Could not obtain UTC offset from mount!");
return false;
}
if (getLocalTime(ctime) == false)
{
LOG_WARN("Could not obtain local time from mount!");
return false;
}
if (getLocalDate(cdate) == false)
{
LOG_WARN("Could not obtain local date from mount!");
return false;
}
// To ISO 8601 format in LOCAL TIME!
char datetime[MAXINDINAME] = {0};
snprintf(datetime, MAXINDINAME, "%sT%s", cdate, ctime);
LOGF_DEBUG("### OnStep Local DateTime: %s", datetime);
// Now that date+time are combined, let's get tm representation of it.
if (strptime(datetime, "%FT%T", <m) == nullptr)
{
LOGF_WARN("Could not process mount date and time: %s", datetime);
return false;
}
LOGF_DEBUG("### OnStep after strptime ltm date: %i-%i-%i", ltm.tm_year, ltm.tm_mon, ltm.tm_mday);
LOGF_DEBUG("### OnStep after strptime ltm time: %i:%i:%i", ltm.tm_hour, ltm.tm_min, ltm.tm_sec);
LOGF_DEBUG("### OnStep after strptime ltm.tm_isdst: %i", ltm.tm_isdst);
// Get local time epoch in UNIX seconds
time_epoch = mktime(<m);
LOGF_DEBUG("OnStep Local DateTime time_epoch: %i", time_epoch);
// LOCAL to UTC by subtracting offset.
time_epoch -= static_cast<int>(offset * 3600.0);
The log when ltm is not initialized is as follows.
LX200 OnStep : "[DEBUG] ### OnStep ltm.tm_isdst: 1074791425 " <<<< wrong value
LX200 OnStep : "[SCOPE] CMD <:GG#> "
LX200 OnStep : "[SCOPE] RES <+09> "
LX200 OnStep : "[SCOPE] VAL [9] "
LX200 OnStep : "[SCOPE] CMD <:GL#> "
LX200 OnStep : "[SCOPE] RES <04:08:07> "
LX200 OnStep : "[SCOPE] VAL [4.13528] "
LX200 OnStep : "[SCOPE] <getCalendarDate> "
LX200 OnStep : "[SCOPE] CMD <:GC#> "
LX200 OnStep : "[SCOPE] RES <03/23/22> "
LX200 OnStep : "[DEBUG] ### OnStep Local DateTime: 2022-03-23T04:08:07 " <<<< OnStep Local
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm date: 122-2-23 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm time: 4:8:7 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm.tm_isdst: 1074791425 " <<<< wrong value
LX200 OnStep : "[DEBUG] OnStep Local DateTime time_epoch: -1 " <<<< Error
LX200 OnStep : "[DEBUG] Mount controller UTC Time: 1970-01-01T17:59:59 " <<<< failed
LX200 OnStep : "[DEBUG] Mount controller UTC Offset: -9.00 "
Setting UTC time from device: "LX200 OnStep" "木 1月 1 17:59:59 1970 GMT" <<<< failed
->>>>>> snprintf(datetime, MAXINDINAME, "%sT%s", cdate, ctime);
LX200 OnStep : "[DEBUG] ### OnStep Local DateTime: 2022-03-23T04:08:07 " <<<< OnStep Local
snprintf returns the correct value "2022-03-23T04: 08: 07".
->>>>>> if (strptime(datetime, "%FT%T", <m) == nullptr)
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm date: 122-2-23 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm time: 4:8:7 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm.tm_isdst: 1074791425 " <<<< wrong value
LX200 OnStep : "[DEBUG] OnStep Local DateTime time_epoch: -1 " <<<< Error
The date and time split by strptime is also done correctly, but time_epoch is an error (-1).
strptime doesn't seem to recalculate ltm.tm_isdst.
tm_isdst remains an uninitialized wrong value, and processing result of mktime returns an error.
When ltm is initialized, it is as follows.
LX200 OnStep : "[DEBUG] ### OnStep ltm.tm_isdst: 0 " <<<< initialized value
LX200 OnStep : "[SCOPE] CMD <:GG#> "
LX200 OnStep : "[SCOPE] RES <+09> "
LX200 OnStep : "[SCOPE] VAL [9] "
LX200 OnStep : "[SCOPE] CMD <:GL#> "
LX200 OnStep : "[SCOPE] RES <04:11:37> "
LX200 OnStep : "[SCOPE] VAL [4.19361] "
LX200 OnStep : "[SCOPE] <getCalendarDate> "
LX200 OnStep : "[SCOPE] CMD <:GC#> "
LX200 OnStep : "[SCOPE] RES <03/23/22> "
LX200 OnStep : "[DEBUG] ### OnStep Local DateTime: 2022-03-23T04:11:37 " <<<< OnStep Local
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm date: 122-2-23 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm time: 4:11:37 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm.tm_isdst: 0 " <<<< initialized value
LX200 OnStep : "[DEBUG] OnStep Local DateTime time_epoch: 1647976297 " <<<< OK
LX200 OnStep : "[DEBUG] Mount controller UTC Time: 2022-03-23T13:11:37 " <<<< OK
LX200 OnStep : "[DEBUG] Mount controller UTC Offset: -9.00 "
Setting UTC time from device: "LX200 OnStep" "水 3月 23 13:11:37 2022 GMT" <<<< OK
->>>>>> snprintf(datetime, MAXINDINAME, "%sT%s", cdate, ctime);
LX200 OnStep : "[DEBUG] ### OnStep Local DateTime: 2022-03-23T04:11:37 " <<<< OnStep Local
snprintf returns the correct value "2022-03-23T04:11:37".
->>>>>> if (strptime(datetime, "%FT%T", <m) == nullptr)
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm date: 122-2-23 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm time: 4:11:37 " <<<< OK
LX200 OnStep : "[DEBUG] ### OnStep after strptime ltm.tm_isdst: 0 " <<<< initialized value
LX200 OnStep : "[DEBUG] OnStep Local DateTime time_epoch: 1647976297 " <<<< OK
LX200 OnStep : "[DEBUG] Mount controller UTC Time: 2022-03-23T13:11:37 " <<<< OK
The date and time decomposition by strptime is also done correctly, and time_epoch is the correct value.
I think how mktime handles wrong tm_isdst depends on the implementation system (H / W, OS, lib, etc).
strptime manpage NOTES also describes the initialization of the tm structure.
man7.org/linux/man-pages/man3/strptime.3.html
Because of these, I think that ltm should be initialized.
You can try set the wrong value in ltm.tm_isdst.
Is there any other way to check?
