Method SetTimeZone

xmpsdk/src/XMPUtils.cpp:1944–2036

class static */

// to do all the right stuff, as long as we call them properly!

/* class static */ void
XMPUtils::SetTimeZone ( XMP_DateTime * xmpTime )
{
	XMP_Assert ( xmpTime != 0 );	// ! Enforced by wrapper.

	if ( (xmpTime->tzSign != 0) || (xmpTime->tzHour != 0) || (xmpTime->tzMinute != 0) ) {
		XMP_Throw ( "SetTimeZone can only be used on \"zoneless\" times", kXMPErr_BadParam );
	}

	// Create ansi_tt form of the input time. Need the ansi_tm form to make the ansi_tt form.

	ansi_tt ttTime;
	ansi_tm tmLocal, tmUTC;

	if ( (xmpTime->year == 0) && (xmpTime->month == 0) && (xmpTime->day == 0) ) {
		ansi_tt now = ansi_time(0);
		if ( now == -1 ) XMP_Throw ( "Failure from ANSI C time function", kXMPErr_ExternalFailure );
		ansi_localtime ( &now, &tmLocal );
	} else {
		if (xmpTime->year < std::numeric_limits<decltype(tmLocal.tm_year)>::min() + 1900) {
			XMP_Throw ( "Invalid year", kXMPErr_BadParam);
		} else if (xmpTime->year > std::numeric_limits<decltype(tmLocal.tm_year)>::max()) {
			XMP_Throw ( "Invalid year", kXMPErr_BadParam);
		} else {
			tmLocal.tm_year = xmpTime->year - 1900;
		}
		tmLocal.tm_mon	 = xmpTime->month - 1;
		tmLocal.tm_mday	 = xmpTime->day;
	}

	tmLocal.tm_hour = xmpTime->hour;
	tmLocal.tm_min = xmpTime->minute;
	tmLocal.tm_sec = xmpTime->second;
	tmLocal.tm_isdst = -1;	// Don't know if daylight time is in effect.

	ttTime = ansi_mktime ( &tmLocal );
	if ( ttTime == -1 ) XMP_Throw ( "Failure from ANSI C mktime function", kXMPErr_ExternalFailure );

	// Convert back to a localized ansi_tm time and get the corresponding UTC ansi_tm time.

	ansi_localtime ( &ttTime, &tmLocal );
	ansi_gmtime ( &ttTime, &tmUTC );

	// Get the offset direction and amount.

	ansi_tm tmx = tmLocal;	// ! Note that mktime updates the ansi_tm parameter, messing up difftime!
	ansi_tm tmy = tmUTC;
	tmx.tm_isdst = tmy.tm_isdst = 0;
	ansi_tt ttx = ansi_mktime ( &tmx );
	ansi_tt tty = ansi_mktime ( &tmy );
	double diffSecs;

	if ( (ttx != -1) && (tty != -1) ) {
		diffSecs = ansi_difftime ( ttx, tty );
	} else {
		#if XMP_MacBuild
			// Looks like Apple's mktime is buggy - see W1140533. But the offset is visible.
			diffSecs = tmLocal.tm_gmtoff;