これが __getzone() の私の実装です。したがって、システムのタイムベースは UTC になります。ユーザーがシステムを構成するときに、タイム ソースが UTC を提供していない場合、ローカル タイムを尋ねます。次に、彼らが私のシステムに時刻同期を提供すると、彼らが提供する時刻は MKTIME への呼び出しによって UTC に変換されます (DST ルールが考慮されます)。次に、時間がユーザーにレンダリングされると、 localtime() の呼び出しによって行われます。
これを実装するプロセスで学んだもう 1 つのことは、IAR の MKTIME() の実装は __getzone() を呼び出すが、tm_isdst を「-1」に設定しない限り、DST 規則は考慮されないということです。-1 は、ルールに基づいて DST を適用するかどうかを判断する MKTIME() への呼び出しを行います。
/*!
* \brief Overrides default library function __getzone to support different time
* zones and DST rules.
* \returns Pointer to a const string containing the timezone + dst rules
*
* This function supports all time zones and DST rules for the U.S. and Canada.
*
* \par IAR Notes
* The return value should be a string on the following form:
* \code
* :[XXX[:YYY[:NNN[:DST[:DST ...]]]]]
* \endcode
* \par
* Where \b XXX is the standard time-zone name, \b YYY is the daylight
* savings time-zone name, \b NNN is the time zone offset, and the DSTs
* are the daylight savings time rules. Daylight savings time will add
* one hour to the normal time.
* \par
* The time zone offset \b NNN is specified as a number relative to UTC,
* possibly negative (east is positive), on the format HHMM, where HH
* is hours and MM is minutes.
* \par
* The DSTs specifes a set of rules for how daylight savings time is
* applied. The rules must be sorted in increasing date order starting
* from the earliest date. The first rule for a specific year will
* enable DST, the next will disable it, and so on. Each rule is on
* the following form:
* \code
* [(YYYY)]MMDD[HH][-W|+W]
* \endcode
*
* * \b (YYYY) is the first year the daylight savings rule was applied.
* It is optional. If not specified it will default to the same
* year as the previous rule or zero if no previous rule.
* * \b MM is the month number (1-12).
* * \b DD is the day of the month (1-31).
* * \b HH is the hour number in a 24-hour day (optional, defaults to 0).
* * \b +/-W specifies the day of the week the rule takes effect (where
* Sunday = 0, Monday = 1, etc). +W means that the rule applies
* to the first such day on or after the specified date and -W
* strictly before the date. If this is not specified, the rule
* will take effect on the exact date, regardless of the day of
* the week.
*
* \par Example
* U.S. Eastern Standard time is UTC -5. Eastern Daylight time is UTC -4.
* Daylight time goes into affect on the second sunday of March at 2:00AM local
* time. Daylight time ends on the first sunday of November at 2:00AM local
* time. The law that defines this went into affect in 2007.
* Therefore here is how the DST string is constructed:
* | \| | STD Time | \| | DST Time | \| | UTC Offset | \| | DST Rule Year | Month DST Starts | Day DST Starts | Hour DST Starts | Day of Week | \| | Month DST Ends | Day DST Ends | Hour DST Ends | Day of Week |
* |----|----------|----|----------|----|------------|----|---------------|------------------|----------------|-----------------|-------------|----|----------------|--------------|---------------|-------------|
* | : | XXX | : | YYY | : | NNN | : | (YYYY) | MM | DD* | HH | +/-W** | : | MM | DD | HH | +/-W |
* | : | GMT-5 | : | GMT-4 | : | -0500 | : | (2007) | 03 | 08 | 02 | +0 | : | 11 | 01 | 02 | +0 |
* - * An 8 for the day means that DST will start around the 8th day of the
* month. Or that the +/-W parameter is relative to the 8th day of the month.
* - ** A + here means that the DST rule will start \b on or \b after the
* previously specified day (the 8th). 0 means that it should happen on a
* sunday. Therefore if the 8th is a sunday (and the 8th cannot be the first
* sunday of the month) then the rule will take affect on that day - or it
* will happen on the very next sunday.
* \par
* Result:
* \code
* :GMT-5:GMT-4:-0500:(2007)030802+0:110102+0
* \endcode
*
* \sa
* - time_zones - Supported time zones
*/
const char8_t * __getzone(void)
{
const char8_t *current_zone = NULL;
static const char8_t dst_time_zones[][50] =
{
// UTC time
":GMT+0:GMT+0:0000:0",
// Newfoundland Standard Time UTC – 3:30
":GMT-3:GMT-2:-0330:(2007)030802+0:110102+0",
// Atlantic Standard Time, UTC – 4
":GMT-4:GMT-3:-0400:(2007)030802+0:110102+0",
// Eastern Standard Time, UTC – 5
":GMT-5:GMT-4:-0500:(2007)030802+0:110102+0",
// Central Standard Time, UTC – 6
":GMT-6:GMT-5:-0600:(2007)030802+0:110102+0",
// Mountain Standard Time, UTC – 7
":GMT-7:GMT-6:-0700:(2007)030802+0:110102+0",
// Pacific Standard Time, UTC – 8
":GMT-8:GMT-7:-0800:(2007)030802+0:110102+0",
// Alaska Standard Time, UTC – 9
":GMT-9:GMT-8:-0900:(2007)030802+0:110102+0",
// Hawaii-Aleutian Standard Time, UTC – 10
":GMT-10:GMT-9:-1000:(2007)030802+0:110102+0"
};
static const char8_t std_time_zones[][20] =
{
// UTC time
":GMT+0:GMT+0:0000",
// Newfoundland Standard Time UTC – 3:30
":GMT-3:GMT-2:-0330",
// Atlantic Standard Time, UTC – 4
":GMT-4:GMT-3:-0400",
// Eastern Standard Time, UTC – 5
":GMT-5:GMT-4:-0500",
// Central Standard Time, UTC – 6
":GMT-6:GMT-5:-0600",
// Mountain Standard Time, UTC – 7
":GMT-7:GMT-6:-0700",
// Pacific Standard Time, UTC – 8
":GMT-8:GMT-7:-0800",
// Alaska Standard Time, UTC – 9
":GMT-9:GMT-8:-0900",
// Hawaii-Aleutian Standard Time, UTC – 10
":GMT-10:GMT-9:-1000"
};
switch(get_config()->time_zone)
{
case NST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[NST];
}
else
{
current_zone = std_time_zones[NST];
}
}
break;
case AST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[AST];
}
else
{
current_zone = std_time_zones[AST];
}
}
break;
case EST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[EST];
}
else
{
current_zone = std_time_zones[EST];
}
}
break;
case CST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[CST];
}
else
{
current_zone = std_time_zones[CST];
}
}
break;
case MST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[MST];
}
else
{
current_zone = std_time_zones[MST];
}
}
break;
case PST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[PST];
}
else
{
current_zone = std_time_zones[PST];
}
}
break;
case AKST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[AKST];
}
else
{
current_zone = std_time_zones[AKST];
}
}
break;
case HAST:
{
if(get_config()->b_dst)
{
current_zone = dst_time_zones[HAST];
}
else
{
current_zone = std_time_zones[HAST];
}
}
break;
case UTC:
default:
current_zone = std_time_zones[UTC];
break;
}
return current_zone;
}