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167 lines
6.0 KiB
167 lines
6.0 KiB
// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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/*
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**********************************************************************
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* Copyright (c) 2003-2008, International Business Machines
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* Corporation and others. All Rights Reserved.
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**********************************************************************
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* Author: Alan Liu
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* Created: September 2 2003
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* Since: ICU 2.8
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**********************************************************************
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*/
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#include "gregoimp.h"
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#if !UCONFIG_NO_FORMATTING
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#include "unicode/ucal.h"
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#include "uresimp.h"
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#include "cstring.h"
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#include "uassert.h"
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U_NAMESPACE_BEGIN
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int32_t ClockMath::floorDivide(int32_t numerator, int32_t denominator) {
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return (numerator >= 0) ?
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numerator / denominator : ((numerator + 1) / denominator) - 1;
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}
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int64_t ClockMath::floorDivide(int64_t numerator, int64_t denominator) {
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return (numerator >= 0) ?
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numerator / denominator : ((numerator + 1) / denominator) - 1;
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}
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int32_t ClockMath::floorDivide(double numerator, int32_t denominator,
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int32_t& remainder) {
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double quotient;
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quotient = uprv_floor(numerator / denominator);
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remainder = (int32_t) (numerator - (quotient * denominator));
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return (int32_t) quotient;
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}
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double ClockMath::floorDivide(double dividend, double divisor,
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double& remainder) {
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// Only designed to work for positive divisors
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U_ASSERT(divisor > 0);
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double quotient = floorDivide(dividend, divisor);
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remainder = dividend - (quotient * divisor);
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// N.B. For certain large dividends, on certain platforms, there
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// is a bug such that the quotient is off by one. If you doubt
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// this to be true, set a breakpoint below and run cintltst.
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if (remainder < 0 || remainder >= divisor) {
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// E.g. 6.7317038241449352e+022 / 86400000.0 is wrong on my
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// machine (too high by one). 4.1792057231752762e+024 /
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// 86400000.0 is wrong the other way (too low).
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double q = quotient;
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quotient += (remainder < 0) ? -1 : +1;
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if (q == quotient) {
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// For quotients > ~2^53, we won't be able to add or
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// subtract one, since the LSB of the mantissa will be >
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// 2^0; that is, the exponent (base 2) will be larger than
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// the length, in bits, of the mantissa. In that case, we
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// can't give a correct answer, so we set the remainder to
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// zero. This has the desired effect of making extreme
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// values give back an approximate answer rather than
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// crashing. For example, UDate values above a ~10^25
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// might all have a time of midnight.
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remainder = 0;
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} else {
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remainder = dividend - (quotient * divisor);
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}
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}
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U_ASSERT(0 <= remainder && remainder < divisor);
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return quotient;
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}
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const int32_t JULIAN_1_CE = 1721426; // January 1, 1 CE Gregorian
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const int32_t JULIAN_1970_CE = 2440588; // January 1, 1970 CE Gregorian
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const int16_t Grego::DAYS_BEFORE[24] =
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{0,31,59,90,120,151,181,212,243,273,304,334,
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0,31,60,91,121,152,182,213,244,274,305,335};
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const int8_t Grego::MONTH_LENGTH[24] =
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{31,28,31,30,31,30,31,31,30,31,30,31,
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31,29,31,30,31,30,31,31,30,31,30,31};
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double Grego::fieldsToDay(int32_t year, int32_t month, int32_t dom) {
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int32_t y = year - 1;
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double julian = 365 * y + ClockMath::floorDivide(y, 4) + (JULIAN_1_CE - 3) + // Julian cal
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ClockMath::floorDivide(y, 400) - ClockMath::floorDivide(y, 100) + 2 + // => Gregorian cal
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DAYS_BEFORE[month + (isLeapYear(year) ? 12 : 0)] + dom; // => month/dom
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return julian - JULIAN_1970_CE; // JD => epoch day
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}
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void Grego::dayToFields(double day, int32_t& year, int32_t& month,
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int32_t& dom, int32_t& dow, int32_t& doy) {
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// Convert from 1970 CE epoch to 1 CE epoch (Gregorian calendar)
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day += JULIAN_1970_CE - JULIAN_1_CE;
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// Convert from the day number to the multiple radix
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// representation. We use 400-year, 100-year, and 4-year cycles.
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// For example, the 4-year cycle has 4 years + 1 leap day; giving
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// 1461 == 365*4 + 1 days.
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int32_t n400 = ClockMath::floorDivide(day, 146097, doy); // 400-year cycle length
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int32_t n100 = ClockMath::floorDivide(doy, 36524, doy); // 100-year cycle length
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int32_t n4 = ClockMath::floorDivide(doy, 1461, doy); // 4-year cycle length
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int32_t n1 = ClockMath::floorDivide(doy, 365, doy);
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year = 400*n400 + 100*n100 + 4*n4 + n1;
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if (n100 == 4 || n1 == 4) {
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doy = 365; // Dec 31 at end of 4- or 400-year cycle
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} else {
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++year;
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}
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UBool isLeap = isLeapYear(year);
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// Gregorian day zero is a Monday.
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dow = (int32_t) uprv_fmod(day + 1, 7);
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dow += (dow < 0) ? (UCAL_SUNDAY + 7) : UCAL_SUNDAY;
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// Common Julian/Gregorian calculation
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int32_t correction = 0;
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int32_t march1 = isLeap ? 60 : 59; // zero-based DOY for March 1
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if (doy >= march1) {
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correction = isLeap ? 1 : 2;
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}
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month = (12 * (doy + correction) + 6) / 367; // zero-based month
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dom = doy - DAYS_BEFORE[month + (isLeap ? 12 : 0)] + 1; // one-based DOM
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doy++; // one-based doy
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}
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void Grego::timeToFields(UDate time, int32_t& year, int32_t& month,
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int32_t& dom, int32_t& dow, int32_t& doy, int32_t& mid) {
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double millisInDay;
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double day = ClockMath::floorDivide((double)time, (double)U_MILLIS_PER_DAY, millisInDay);
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mid = (int32_t)millisInDay;
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dayToFields(day, year, month, dom, dow, doy);
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}
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int32_t Grego::dayOfWeek(double day) {
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int32_t dow;
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ClockMath::floorDivide(day + UCAL_THURSDAY, 7, dow);
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return (dow == 0) ? UCAL_SATURDAY : dow;
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}
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int32_t Grego::dayOfWeekInMonth(int32_t year, int32_t month, int32_t dom) {
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int32_t weekInMonth = (dom + 6)/7;
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if (weekInMonth == 4) {
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if (dom + 7 > monthLength(year, month)) {
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weekInMonth = -1;
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}
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} else if (weekInMonth == 5) {
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weekInMonth = -1;
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}
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return weekInMonth;
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}
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U_NAMESPACE_END
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#endif
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//eof
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