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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
namespace System.Globalization
{
/// <remarks>
/// Rules for the Hijri calendar:
/// - The Hijri calendar is a strictly Lunar calendar.
/// - Days begin at sunset.
/// - Islamic Year 1 (Muharram 1, 1 A.H.) is equivalent to absolute date
/// 227015 (Friday, July 16, 622 C.E. - Julian).
/// - Leap Years occur in the 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, & 29th
/// years of a 30-year cycle. Year = leap iff ((11y+14) mod 30 < 11).
/// - There are 12 months which contain alternately 30 and 29 days.
/// - The 12th month, Dhu al-Hijjah, contains 30 days instead of 29 days
/// in a leap year.
/// - Common years have 354 days. Leap years have 355 days.
/// - There are 10,631 days in a 30-year cycle.
/// - The Islamic months are:
/// 1. Muharram (30 days) 7. Rajab (30 days)
/// 2. Safar (29 days) 8. Sha'ban (29 days)
/// 3. Rabi I (30 days) 9. Ramadan (30 days)
/// 4. Rabi II (29 days) 10. Shawwal (29 days)
/// 5. Jumada I (30 days) 11. Dhu al-Qada (30 days)
/// 6. Jumada II (29 days) 12. Dhu al-Hijjah (29 days) {30}
///
/// NOTENOTE
/// The calculation of the HijriCalendar is based on the absolute date. And the
/// absolute date means the number of days from January 1st, 1 A.D.
/// Therefore, we do not support the days before the January 1st, 1 A.D.
///
/// Calendar support range:
/// Calendar Minimum Maximum
/// ========== ========== ==========
/// Gregorian 0622/07/18 9999/12/31
/// Hijri 0001/01/01 9666/04/03
/// </remarks>
public partial class HijriCalendar : Calendar
{
public static readonly int HijriEra = 1;
private const int DatePartYear = 0;
private const int DatePartDayOfYear = 1;
private const int DatePartMonth = 2;
private const int DatePartDay = 3;
private const int MinAdvancedHijri = -2;
private const int MaxAdvancedHijri = 2;
private static ReadOnlySpan<int> HijriMonthDays => [0, 30, 59, 89, 118, 148, 177, 207, 236, 266, 295, 325, 355];
private int _hijriAdvance = int.MinValue;
// DateTime.MaxValue = Hijri calendar (year:9666, month: 4, day: 3).
private const int MaxCalendarYear = 9666;
private const int MaxCalendarMonth = 4;
// Hijri calendar (year: 1, month: 1, day:1 ) = Gregorian (year: 622, month: 7, day: 18)
// This is the minimal Gregorian date that we support in the HijriCalendar.
private static readonly DateTime s_calendarMinValue = new DateTime(622, 7, 18);
private static readonly DateTime s_calendarMaxValue = DateTime.MaxValue;
public override DateTime MinSupportedDateTime => s_calendarMinValue;
public override DateTime MaxSupportedDateTime => s_calendarMaxValue;
public override CalendarAlgorithmType AlgorithmType => CalendarAlgorithmType.LunarCalendar;
public HijriCalendar()
{
}
internal override CalendarId ID => CalendarId.HIJRI;
protected override int DaysInYearBeforeMinSupportedYear =>
// the year before the 1st year of the cycle would have been the 30th year
// of the previous cycle which is not a leap year. Common years have 354 days.
354;
private long GetAbsoluteDateHijri(int y, int m, int d)
{
return (long)(DaysUpToHijriYear(y) + HijriMonthDays[m - 1] + d - 1 - HijriAdjustment);
}
private long DaysUpToHijriYear(int HijriYear)
{
// Compute the number of years up to the current 30 year cycle.
int numYear30 = ((HijriYear - 1) / 30) * 30;
// Compute the number of years left. This is the number of years
// into the 30 year cycle for the given year.
int numYearsLeft = HijriYear - numYear30 - 1;
// Compute the number of absolute days up to the given year.
long numDays = ((numYear30 * 10631L) / 30L) + 227013L;
while (numYearsLeft > 0)
{
// Common year is 354 days, and leap year is 355 days.
numDays += 354 + (IsLeapYear(numYearsLeft, CurrentEra) ? 1 : 0);
numYearsLeft--;
}
return numDays;
}
public int HijriAdjustment
{
get
{
if (_hijriAdvance == int.MinValue)
{
// Never been set before. Use the system value from registry.
_hijriAdvance = GetHijriDateAdjustment();
}
return _hijriAdvance;
}
set
{
if (value < MinAdvancedHijri || value > MaxAdvancedHijri)
{
throw new ArgumentOutOfRangeException(
nameof(value),
value,
SR.Format(SR.ArgumentOutOfRange_Bounds_Lower_Upper, MinAdvancedHijri, MaxAdvancedHijri));
}
VerifyWritable();
_hijriAdvance = value;
}
}
internal static void CheckTicksRange(long ticks)
{
if (ticks < s_calendarMinValue.Ticks || ticks > s_calendarMaxValue.Ticks)
{
throw new ArgumentOutOfRangeException(
"time",
ticks,
SR.Format(
CultureInfo.InvariantCulture,
SR.ArgumentOutOfRange_CalendarRange,
s_calendarMinValue,
s_calendarMaxValue));
}
}
internal static void CheckEraRange(int era)
{
if (era != CurrentEra && era != HijriEra)
{
throw new ArgumentOutOfRangeException(nameof(era), era, SR.ArgumentOutOfRange_InvalidEraValue);
}
}
internal static void CheckYearRange(int year, int era)
{
CheckEraRange(era);
if (year < 1 || year > MaxCalendarYear)
{
throw new ArgumentOutOfRangeException(
nameof(year),
SR.Format(SR.ArgumentOutOfRange_Range, 1, MaxCalendarYear));
}
}
internal static void CheckYearMonthRange(int year, int month, int era)
{
CheckYearRange(year, era);
if (year == MaxCalendarYear)
{
if (month > MaxCalendarMonth)
{
throw new ArgumentOutOfRangeException(
nameof(month),
month,
SR.Format(SR.ArgumentOutOfRange_Range, 1, MaxCalendarMonth));
}
}
if (month < 1 || month > 12)
{
ThrowHelper.ThrowArgumentOutOfRange_Month(month);
}
}
/// <summary>
/// First, we get the absolute date (the number of days from January 1st, 1 A.C) for the given ticks.
/// Use the formula (((AbsoluteDate - 227013) * 30) / 10631) + 1, we can a rough value for the Hijri year.
/// In order to get the exact Hijri year, we compare the exact absolute date for HijriYear and (HijriYear + 1).
/// From here, we can get the correct Hijri year.
/// </summary>
private int GetDatePart(long ticks, int part)
{
CheckTicksRange(ticks);
// Get the absolute date. The absolute date is the number of days from January 1st, 1 A.D.
// 1/1/0001 is absolute date 1.
long numDays = ticks / TimeSpan.TicksPerDay + 1;
// See how much we need to backup or advance
numDays += HijriAdjustment;
// Calculate the appromixate Hijri Year from this magic formula.
int hijriYear = (int)(((numDays - 227013) * 30) / 10631) + 1;
long daysToHijriYear = DaysUpToHijriYear(hijriYear); // The absolute date for HijriYear
long daysOfHijriYear = GetDaysInYear(hijriYear, CurrentEra); // The number of days for (HijriYear+1) year.
if (numDays < daysToHijriYear)
{
daysToHijriYear -= daysOfHijriYear;
hijriYear--;
}
else if (numDays == daysToHijriYear)
{
hijriYear--;
daysToHijriYear -= GetDaysInYear(hijriYear, CurrentEra);
}
else
{
if (numDays > daysToHijriYear + daysOfHijriYear)
{
daysToHijriYear += daysOfHijriYear;
hijriYear++;
}
}
if (part == DatePartYear)
{
return hijriYear;
}
// Calculate the Hijri Month.
int hijriMonth = 1;
numDays -= daysToHijriYear;
if (part == DatePartDayOfYear)
{
return (int)numDays;
}
while ((hijriMonth <= 12) && (numDays > HijriMonthDays[hijriMonth - 1]))
{
hijriMonth++;
}
hijriMonth--;
if (part == DatePartMonth)
{
return hijriMonth;
}
// Calculate the Hijri Day.
int hijriDay = (int)(numDays - HijriMonthDays[hijriMonth - 1]);
if (part == DatePartDay)
{
return hijriDay;
}
// Incorrect part value.
throw new InvalidOperationException(SR.InvalidOperation_DateTimeParsing);
}
public override DateTime AddMonths(DateTime time, int months)
{
if (months < -120000 || months > 120000)
{
throw new ArgumentOutOfRangeException(
nameof(months),
months,
SR.Format(SR.ArgumentOutOfRange_Range, -120000, 120000));
}
// Get the date in Hijri calendar.
int y = GetDatePart(time.Ticks, DatePartYear);
int m = GetDatePart(time.Ticks, DatePartMonth);
int d = GetDatePart(time.Ticks, DatePartDay);
int i = m - 1 + months;
if (i >= 0)
{
m = i % 12 + 1;
y += i / 12;
}
else
{
m = 12 + (i + 1) % 12;
y += (i - 11) / 12;
}
int days = GetDaysInMonth(y, m);
if (d > days)
{
d = days;
}
long ticks = GetAbsoluteDateHijri(y, m, d) * TimeSpan.TicksPerDay + (time.Ticks % TimeSpan.TicksPerDay);
CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
return new DateTime(ticks);
}
public override DateTime AddYears(DateTime time, int years)
{
return AddMonths(time, years * 12);
}
public override int GetDayOfMonth(DateTime time)
{
return GetDatePart(time.Ticks, DatePartDay);
}
public override DayOfWeek GetDayOfWeek(DateTime time) => time.DayOfWeek;
public override int GetDayOfYear(DateTime time)
{
return GetDatePart(time.Ticks, DatePartDayOfYear);
}
public override int GetDaysInMonth(int year, int month, int era)
{
CheckYearMonthRange(year, month, era);
if (month == 12)
{
// For the 12th month, leap year has 30 days, and common year has 29 days.
return IsLeapYear(year, CurrentEra) ? 30 : 29;
}
// Other months contain 30 and 29 days alternatively. The 1st month has 30 days.
return ((month % 2) == 1) ? 30 : 29;
}
public override int GetDaysInYear(int year, int era)
{
CheckYearRange(year, era);
// Common years have 354 days. Leap years have 355 days.
return IsLeapYear(year, CurrentEra) ? 355 : 354;
}
public override int GetEra(DateTime time)
{
CheckTicksRange(time.Ticks);
return HijriEra;
}
public override int[] Eras => [HijriEra];
public override int GetMonth(DateTime time)
{
return GetDatePart(time.Ticks, DatePartMonth);
}
public override int GetMonthsInYear(int year, int era)
{
CheckYearRange(year, era);
return 12;
}
public override int GetYear(DateTime time)
{
return GetDatePart(time.Ticks, DatePartYear);
}
public override bool IsLeapDay(int year, int month, int day, int era)
{
// The year/month/era value checking is done in GetDaysInMonth().
int daysInMonth = GetDaysInMonth(year, month, era);
if (day < 1 || day > daysInMonth)
{
throw new ArgumentOutOfRangeException(
nameof(day),
day,
SR.Format(SR.ArgumentOutOfRange_Day, daysInMonth, month));
}
return IsLeapYear(year, era) && month == 12 && day == 30;
}
public override int GetLeapMonth(int year, int era)
{
CheckYearRange(year, era);
return 0;
}
public override bool IsLeapMonth(int year, int month, int era)
{
CheckYearMonthRange(year, month, era);
return false;
}
public override bool IsLeapYear(int year, int era)
{
CheckYearRange(year, era);
return (((year * 11) + 14) % 30) < 11;
}
public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
{
// The year/month/era checking is done in GetDaysInMonth().
int daysInMonth = GetDaysInMonth(year, month, era);
if (day < 1 || day > daysInMonth)
{
throw new ArgumentOutOfRangeException(
nameof(day),
day,
SR.Format(SR.ArgumentOutOfRange_Day, daysInMonth, month));
}
long lDate = GetAbsoluteDateHijri(year, month, day);
if (lDate < 0)
{
throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
}
return new DateTime(lDate * TimeSpan.TicksPerDay + TimeToTicks(hour, minute, second, millisecond));
}
private const int DefaultTwoDigitYearMax = 1451;
public override int TwoDigitYearMax
{
get
{
if (_twoDigitYearMax == -1)
{
_twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DefaultTwoDigitYearMax);
}
return _twoDigitYearMax;
}
set
{
VerifyWritable();
if (value < 99 || value > MaxCalendarYear)
{
throw new ArgumentOutOfRangeException(
nameof(value),
value,
SR.Format(SR.ArgumentOutOfRange_Range, 99, MaxCalendarYear));
}
_twoDigitYearMax = value;
}
}
public override int ToFourDigitYear(int year)
{
ArgumentOutOfRangeException.ThrowIfNegative(year);
if (year < 100)
{
return base.ToFourDigitYear(year);
}
if (year > MaxCalendarYear)
{
throw new ArgumentOutOfRangeException(
nameof(year),
year,
SR.Format(SR.ArgumentOutOfRange_Range, 1, MaxCalendarYear));
}
return year;
}
}
}
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