230 lines
7.8 KiB
C++
230 lines
7.8 KiB
C++
/*
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**********************************************************************
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* Copyright (c) 2003, 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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#ifndef GREGOIMP_H
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#define GREGOIMP_H
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#if !UCONFIG_NO_FORMATTING
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#include "unicode/utypes.h"
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U_NAMESPACE_BEGIN
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/**
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* A utility class providing mathematical functions used by time zone
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* and calendar code. Do not instantiate.
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*/
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class U_I18N_API Math {
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public:
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/**
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* Divide two integers, returning the floor of the quotient.
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* Unlike the built-in division, this is mathematically
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* well-behaved. E.g., <code>-1/4</code> => 0 but
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* <code>floorDivide(-1,4)</code> => -1.
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* @param numerator the numerator
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* @param denominator a divisor which must be != 0
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* @return the floor of the quotient
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*/
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static int32_t floorDivide(int32_t numerator, int32_t denominator);
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/**
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* Divide two numbers, returning the floor of the quotient.
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* Unlike the built-in division, this is mathematically
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* well-behaved. E.g., <code>-1/4</code> => 0 but
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* <code>floorDivide(-1,4)</code> => -1.
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* @param numerator the numerator
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* @param denominator a divisor which must be != 0
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* @return the floor of the quotient
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*/
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static inline double floorDivide(double numerator, double denominator);
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/**
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* Divide two numbers, returning the floor of the quotient and
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* the modulus remainder. Unlike the built-in division, this is
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* mathematically well-behaved. E.g., <code>-1/4</code> => 0 and
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* <code>-1%4</code> => -1, but <code>floorDivide(-1,4)</code> =>
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* -1 with <code>remainder</code> => 3. NOTE: If numerator is
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* too large, the returned quotient may overflow.
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* @param numerator the numerator
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* @param denominator a divisor which must be != 0
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* @param remainder output parameter to receive the
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* remainder. Unlike <code>numerator % denominator</code>, this
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* will always be non-negative, in the half-open range <code>[0,
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* |denominator|)</code>.
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* @return the floor of the quotient
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*/
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static int32_t floorDivide(double numerator, int32_t denominator,
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int32_t& remainder);
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};
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// Useful millisecond constants
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#define kOneDay (1.0 * U_MILLIS_PER_DAY) // 86,400,000
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#define kOneHour (60*60*1000)
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#define kOneMinute 60000
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#define kOneSecond 1000
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#define kOneMillisecond 1
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#define kOneWeek (7.0 * kOneDay) // 604,800,000
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// Epoch constants
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#define kJan1_1JulianDay 1721426 // January 1, year 1 (Gregorian)
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#define kEpochStartAsJulianDay 2440588 // January 1, 1970 (Gregorian)
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#define kEpochYear 1970
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#define kEarliestViableMillis -185331720384000000.0 // minimum representable by julian day -1e17
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#define kLatestViableMillis 185753453990400000.0 // max representable by julian day +1e17
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/**
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* A utility class providing proleptic Gregorian calendar functions
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* used by time zone and calendar code. Do not instantiate.
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*
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* Note: Unlike GregorianCalendar, all computations performed by this
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* class occur in the pure proleptic GregorianCalendar.
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*/
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class U_I18N_API Grego {
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public:
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/**
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* Return TRUE if the given year is a leap year.
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* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
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* @return TRUE if the year is a leap year
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*/
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static inline UBool isLeapYear(int32_t year);
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/**
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* Return the number of days in the given month.
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* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
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* @param month 0-based month, with 0==Jan
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* @return the number of days in the given month
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*/
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static inline int8_t monthLength(int32_t year, int32_t month);
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/**
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* Return the length of a previous month of the Gregorian calendar.
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* @param y the extended year
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* @param m the 0-based month number
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* @return the number of days in the month previous to the given month
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*/
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static inline int8_t previousMonthLength(int y, int m);
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/**
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* Convert a year, month, and day-of-month, given in the proleptic
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* Gregorian calendar, to 1970 epoch days.
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* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
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* @param month 0-based month, with 0==Jan
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* @param dom 1-based day of month
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* @return the day number, with day 0 == Jan 1 1970
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*/
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static double fieldsToDay(int32_t year, int32_t month, int32_t dom);
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/**
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* Convert a 1970-epoch day number to proleptic Gregorian year,
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* month, day-of-month, and day-of-week.
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* @param day 1970-epoch day (integral value)
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* @param year output parameter to receive year
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* @param month output parameter to receive month (0-based, 0==Jan)
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* @param dom output parameter to receive day-of-month (1-based)
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* @param dow output parameter to receive day-of-week (1-based, 1==Sun)
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* @param doy output parameter to receive day-of-year (1-based)
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*/
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static void 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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/**
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* Convert a 1970-epoch day number to proleptic Gregorian year,
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* month, day-of-month, and day-of-week.
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* @param day 1970-epoch day (integral value)
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* @param year output parameter to receive year
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* @param month output parameter to receive month (0-based, 0==Jan)
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* @param dom output parameter to receive day-of-month (1-based)
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* @param dow output parameter to receive day-of-week (1-based, 1==Sun)
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*/
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static inline void dayToFields(double day, int32_t& year, int32_t& month,
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int32_t& dom, int32_t& dow);
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/**
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* Converts Julian day to time as milliseconds.
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* @param julian the given Julian day number.
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* @return time as milliseconds.
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* @internal
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*/
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static inline double julianDayToMillis(int32_t julian);
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/**
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* Converts time as milliseconds to Julian day.
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* @param millis the given milliseconds.
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* @return the Julian day number.
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* @internal
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*/
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static inline int32_t millisToJulianDay(double millis);
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/**
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* Calculates the Gregorian day shift value for an extended year.
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* @param eyear Extended year
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* @returns number of days to ADD to Julian in order to convert from J->G
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*/
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static inline int32_t gregorianShift(int32_t eyear);
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private:
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static const int16_t DAYS_BEFORE[24];
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static const int8_t MONTH_LENGTH[24];
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};
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inline double Math::floorDivide(double numerator, double denominator) {
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return uprv_floor(numerator / denominator);
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}
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inline UBool Grego::isLeapYear(int32_t year) {
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// year&0x3 == year%4
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return ((year&0x3) == 0) && ((year%100 != 0) || (year%400 == 0));
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}
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inline int8_t
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Grego::monthLength(int32_t year, int32_t month) {
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return MONTH_LENGTH[month + isLeapYear(year)?12:0];
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}
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inline int8_t
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Grego::previousMonthLength(int y, int m) {
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return (m > 0) ? monthLength(y, m-1) : 31;
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}
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inline void Grego::dayToFields(double day, int32_t& year, int32_t& month,
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int32_t& dom, int32_t& dow) {
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int32_t doy_unused;
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dayToFields(day,year,month,dom,dow,doy_unused);
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}
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inline double Grego::julianDayToMillis(int32_t julian)
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{
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return (julian - kEpochStartAsJulianDay) * kOneDay;
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}
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inline int32_t Grego::millisToJulianDay(double millis) {
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return (int32_t) (kEpochStartAsJulianDay + Math::floorDivide(millis, (double)kOneDay));
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}
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inline int32_t Grego::gregorianShift(int32_t eyear) {
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int32_t y = eyear-1;
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int32_t gregShift = Math::floorDivide(y, 400) - Math::floorDivide(y, 100) + 2;
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return gregShift;
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}
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U_NAMESPACE_END
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#endif // !UCONFIG_NO_FORMATTING
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#endif // GREGOIMP_H
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//eof
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