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Diffstat (limited to 'intl/icu/source/i18n/gregoimp.cpp')
| -rw-r--r-- | intl/icu/source/i18n/gregoimp.cpp | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/intl/icu/source/i18n/gregoimp.cpp b/intl/icu/source/i18n/gregoimp.cpp new file mode 100644 index 000000000..1b313602d --- /dev/null +++ b/intl/icu/source/i18n/gregoimp.cpp @@ -0,0 +1,161 @@ +// Copyright (C) 2016 and later: Unicode, Inc. and others. +// License & terms of use: http://www.unicode.org/copyright.html +/* + ********************************************************************** + * Copyright (c) 2003-2008, International Business Machines + * Corporation and others. All Rights Reserved. + ********************************************************************** + * Author: Alan Liu + * Created: September 2 2003 + * Since: ICU 2.8 + ********************************************************************** + */ + +#include "gregoimp.h" + +#if !UCONFIG_NO_FORMATTING + +#include "unicode/ucal.h" +#include "uresimp.h" +#include "cstring.h" +#include "uassert.h" + +U_NAMESPACE_BEGIN + +int32_t ClockMath::floorDivide(int32_t numerator, int32_t denominator) { + return (numerator >= 0) ? + numerator / denominator : ((numerator + 1) / denominator) - 1; +} + +int32_t ClockMath::floorDivide(double numerator, int32_t denominator, + int32_t& remainder) { + double quotient; + quotient = uprv_floor(numerator / denominator); + remainder = (int32_t) (numerator - (quotient * denominator)); + return (int32_t) quotient; +} + +double ClockMath::floorDivide(double dividend, double divisor, + double& remainder) { + // Only designed to work for positive divisors + U_ASSERT(divisor > 0); + double quotient = floorDivide(dividend, divisor); + remainder = dividend - (quotient * divisor); + // N.B. For certain large dividends, on certain platforms, there + // is a bug such that the quotient is off by one. If you doubt + // this to be true, set a breakpoint below and run cintltst. + if (remainder < 0 || remainder >= divisor) { + // E.g. 6.7317038241449352e+022 / 86400000.0 is wrong on my + // machine (too high by one). 4.1792057231752762e+024 / + // 86400000.0 is wrong the other way (too low). + double q = quotient; + quotient += (remainder < 0) ? -1 : +1; + if (q == quotient) { + // For quotients > ~2^53, we won't be able to add or + // subtract one, since the LSB of the mantissa will be > + // 2^0; that is, the exponent (base 2) will be larger than + // the length, in bits, of the mantissa. In that case, we + // can't give a correct answer, so we set the remainder to + // zero. This has the desired effect of making extreme + // values give back an approximate answer rather than + // crashing. For example, UDate values above a ~10^25 + // might all have a time of midnight. + remainder = 0; + } else { + remainder = dividend - (quotient * divisor); + } + } + U_ASSERT(0 <= remainder && remainder < divisor); + return quotient; +} + +const int32_t JULIAN_1_CE = 1721426; // January 1, 1 CE Gregorian +const int32_t JULIAN_1970_CE = 2440588; // January 1, 1970 CE Gregorian + +const int16_t Grego::DAYS_BEFORE[24] = + {0,31,59,90,120,151,181,212,243,273,304,334, + 0,31,60,91,121,152,182,213,244,274,305,335}; + +const int8_t Grego::MONTH_LENGTH[24] = + {31,28,31,30,31,30,31,31,30,31,30,31, + 31,29,31,30,31,30,31,31,30,31,30,31}; + +double Grego::fieldsToDay(int32_t year, int32_t month, int32_t dom) { + + int32_t y = year - 1; + + double julian = 365 * y + ClockMath::floorDivide(y, 4) + (JULIAN_1_CE - 3) + // Julian cal + ClockMath::floorDivide(y, 400) - ClockMath::floorDivide(y, 100) + 2 + // => Gregorian cal + DAYS_BEFORE[month + (isLeapYear(year) ? 12 : 0)] + dom; // => month/dom + + return julian - JULIAN_1970_CE; // JD => epoch day +} + +void Grego::dayToFields(double day, int32_t& year, int32_t& month, + int32_t& dom, int32_t& dow, int32_t& doy) { + + // Convert from 1970 CE epoch to 1 CE epoch (Gregorian calendar) + day += JULIAN_1970_CE - JULIAN_1_CE; + + // Convert from the day number to the multiple radix + // representation. We use 400-year, 100-year, and 4-year cycles. + // For example, the 4-year cycle has 4 years + 1 leap day; giving + // 1461 == 365*4 + 1 days. + int32_t n400 = ClockMath::floorDivide(day, 146097, doy); // 400-year cycle length + int32_t n100 = ClockMath::floorDivide(doy, 36524, doy); // 100-year cycle length + int32_t n4 = ClockMath::floorDivide(doy, 1461, doy); // 4-year cycle length + int32_t n1 = ClockMath::floorDivide(doy, 365, doy); + year = 400*n400 + 100*n100 + 4*n4 + n1; + if (n100 == 4 || n1 == 4) { + doy = 365; // Dec 31 at end of 4- or 400-year cycle + } else { + ++year; + } + + UBool isLeap = isLeapYear(year); + + // Gregorian day zero is a Monday. + dow = (int32_t) uprv_fmod(day + 1, 7); + dow += (dow < 0) ? (UCAL_SUNDAY + 7) : UCAL_SUNDAY; + + // Common Julian/Gregorian calculation + int32_t correction = 0; + int32_t march1 = isLeap ? 60 : 59; // zero-based DOY for March 1 + if (doy >= march1) { + correction = isLeap ? 1 : 2; + } + month = (12 * (doy + correction) + 6) / 367; // zero-based month + dom = doy - DAYS_BEFORE[month + (isLeap ? 12 : 0)] + 1; // one-based DOM + doy++; // one-based doy +} + +void Grego::timeToFields(UDate time, int32_t& year, int32_t& month, + int32_t& dom, int32_t& dow, int32_t& doy, int32_t& mid) { + double millisInDay; + double day = ClockMath::floorDivide((double)time, (double)U_MILLIS_PER_DAY, millisInDay); + mid = (int32_t)millisInDay; + dayToFields(day, year, month, dom, dow, doy); +} + +int32_t Grego::dayOfWeek(double day) { + int32_t dow; + ClockMath::floorDivide(day + UCAL_THURSDAY, 7, dow); + return (dow == 0) ? UCAL_SATURDAY : dow; +} + +int32_t Grego::dayOfWeekInMonth(int32_t year, int32_t month, int32_t dom) { + int32_t weekInMonth = (dom + 6)/7; + if (weekInMonth == 4) { + if (dom + 7 > monthLength(year, month)) { + weekInMonth = -1; + } + } else if (weekInMonth == 5) { + weekInMonth = -1; + } + return weekInMonth; +} + +U_NAMESPACE_END + +#endif +//eof |