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LibUnicode: Implement TR-35's localized GMT offset formatting

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This adds an API to use LibTimeZone to convert a time zone such as
"America/New_York" to a GMT offset string like "GMT-5" (short form) or
"GMT-05:00" (long form).
This commit is contained in:
Timothy Flynn 2022-01-11 11:35:50 -05:00 • committed by Linus Groh
parent 6409900a5b
commit 8d35563f28
5 changed files with 238 additions and 20 deletions
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80
Userland/Libraries/LibUnicode/DateTimeFormat.cpp
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@ -6,8 +6,11 @@
#include <AK/Array.h>
#include <AK/StringBuilder.h>
#include <LibTimeZone/TimeZone.h>
#include <LibUnicode/DateTimeFormat.h>
#include <LibUnicode/Locale.h>
#include <LibUnicode/NumberFormat.h>
#include <stdlib.h>
namespace Unicode {
@ -191,6 +194,83 @@ Optional<StringView> __attribute__((weak)) get_calendar_month_symbol(StringView,
Optional<StringView> __attribute__((weak)) get_calendar_weekday_symbol(StringView, StringView, CalendarPatternStyle, Weekday) { return {}; }
Optional<StringView> __attribute__((weak)) get_calendar_day_period_symbol(StringView, StringView, CalendarPatternStyle, DayPeriod) { return {}; }
Optional<StringView> __attribute__((weak)) get_calendar_day_period_symbol_for_hour(StringView, StringView, CalendarPatternStyle, u8) { return {}; }
Optional<StringView> __attribute__((weak)) get_time_zone_name(StringView, StringView, CalendarPatternStyle) { return {}; }
Optional<TimeZoneFormat> __attribute__((weak)) get_time_zone_format(StringView) { return {}; }
static Optional<String> format_time_zone_offset(StringView locale, StringView time_zone, CalendarPatternStyle style, AK::Time time)
{
auto formats = get_time_zone_format(locale);
if (!formats.has_value())
return {};
auto number_system = get_default_number_system(locale);
if (!number_system.has_value())
return {};
auto offset_seconds = TimeZone::get_time_zone_offset(time_zone, time);
if (!offset_seconds.has_value())
return {};
if (*offset_seconds == 0)
return formats->gmt_zero_format;
auto sign = *offset_seconds > 0 ? formats->symbol_ahead_sign : formats->symbol_behind_sign;
auto separator = *offset_seconds > 0 ? formats->symbol_ahead_separator : formats->symbol_behind_separator;
*offset_seconds = llabs(*offset_seconds);
auto offset_hours = *offset_seconds / 3'600;
*offset_seconds %= 3'600;
auto offset_minutes = *offset_seconds / 60;
*offset_seconds %= 60;
StringBuilder builder;
builder.append(sign);
switch (style) {
// The long format always uses 2-digit hours field and minutes field, with optional 2-digit seconds field.
case CalendarPatternStyle::LongOffset:
builder.appendff("{:02}{}{:02}", offset_hours, separator, offset_minutes);
if (*offset_seconds > 0)
builder.appendff("{}{:02}", separator, *offset_seconds);
break;
// The short format is intended for the shortest representation and uses hour fields without leading zero, with optional 2-digit minutes and seconds fields.
case CalendarPatternStyle::ShortOffset:
builder.appendff("{}", offset_hours);
if (offset_minutes > 0) {
builder.appendff("{}{:02}", separator, offset_minutes);
if (*offset_seconds > 0)
builder.appendff("{}{:02}", separator, *offset_seconds);
}
break;
default:
VERIFY_NOT_REACHED();
}
// The digits used for hours, minutes and seconds fields in this format are the locale's default decimal digits.
auto offset = replace_digits_for_number_system(*number_system, builder.build());
return formats->gmt_format.replace("{0}"sv, offset);
}
// https://unicode.org/reports/tr35/tr35-dates.html#Time_Zone_Format_Terminology
String format_time_zone(StringView locale, StringView time_zone, CalendarPatternStyle style, AK::Time time)
{
switch (style) {
case CalendarPatternStyle::Short:
case CalendarPatternStyle::Long:
case CalendarPatternStyle::ShortGeneric:
case CalendarPatternStyle::LongGeneric:
return get_time_zone_name(locale, time_zone, style).value_or(time_zone);
case CalendarPatternStyle::ShortOffset:
case CalendarPatternStyle::LongOffset:
return format_time_zone_offset(locale, time_zone, style, time).value_or(time_zone);
default:
VERIFY_NOT_REACHED();
}
}
}