1// © 2016 and later: Unicode, Inc. and others.
2// License & terms of use: http://www.unicode.org/copyright.html
3/*
4 **********************************************************************
5 * Copyright (c) 2003-2008, International Business Machines
6 * Corporation and others. All Rights Reserved.
7 **********************************************************************
8 * Author: Alan Liu
9 * Created: September 2 2003
10 * Since: ICU 2.8
11 **********************************************************************
12 */
13
14#include "gregoimp.h"
15
16#if !UCONFIG_NO_FORMATTING
17
18#include "unicode/ucal.h"
19#include "uresimp.h"
20#include "cstring.h"
21#include "uassert.h"
22
23U_NAMESPACE_BEGIN
24
25int32_t ClockMath::floorDivide(int32_t numerator, int32_t denominator) {
26 return (numerator >= 0) ?
27 numerator / denominator : ((numerator + 1) / denominator) - 1;
28}
29
30int64_t ClockMath::floorDivide(int64_t numerator, int64_t denominator) {
31 return (numerator >= 0) ?
32 numerator / denominator : ((numerator + 1) / denominator) - 1;
33}
34
35int32_t ClockMath::floorDivide(double numerator, int32_t denominator,
36 int32_t& remainder) {
37 double quotient;
38 quotient = uprv_floor(numerator / denominator);
39 remainder = (int32_t) (numerator - (quotient * denominator));
40 return (int32_t) quotient;
41}
42
43double ClockMath::floorDivide(double dividend, double divisor,
44 double& remainder) {
45 // Only designed to work for positive divisors
46 U_ASSERT(divisor > 0);
47 double quotient = floorDivide(dividend, divisor);
48 remainder = dividend - (quotient * divisor);
49 // N.B. For certain large dividends, on certain platforms, there
50 // is a bug such that the quotient is off by one. If you doubt
51 // this to be true, set a breakpoint below and run cintltst.
52 if (remainder < 0 || remainder >= divisor) {
53 // E.g. 6.7317038241449352e+022 / 86400000.0 is wrong on my
54 // machine (too high by one). 4.1792057231752762e+024 /
55 // 86400000.0 is wrong the other way (too low).
56 double q = quotient;
57 quotient += (remainder < 0) ? -1 : +1;
58 if (q == quotient) {
59 // For quotients > ~2^53, we won't be able to add or
60 // subtract one, since the LSB of the mantissa will be >
61 // 2^0; that is, the exponent (base 2) will be larger than
62 // the length, in bits, of the mantissa. In that case, we
63 // can't give a correct answer, so we set the remainder to
64 // zero. This has the desired effect of making extreme
65 // values give back an approximate answer rather than
66 // crashing. For example, UDate values above a ~10^25
67 // might all have a time of midnight.
68 remainder = 0;
69 } else {
70 remainder = dividend - (quotient * divisor);
71 }
72 }
73 U_ASSERT(0 <= remainder && remainder < divisor);
74 return quotient;
75}
76
77const int32_t JULIAN_1_CE = 1721426; // January 1, 1 CE Gregorian
78const int32_t JULIAN_1970_CE = 2440588; // January 1, 1970 CE Gregorian
79
80const int16_t Grego::DAYS_BEFORE[24] =
81 {0,31,59,90,120,151,181,212,243,273,304,334,
82 0,31,60,91,121,152,182,213,244,274,305,335};
83
84const int8_t Grego::MONTH_LENGTH[24] =
85 {31,28,31,30,31,30,31,31,30,31,30,31,
86 31,29,31,30,31,30,31,31,30,31,30,31};
87
88double Grego::fieldsToDay(int32_t year, int32_t month, int32_t dom) {
89
90 int32_t y = year - 1;
91
92 double julian = 365 * y + ClockMath::floorDivide(y, 4) + (JULIAN_1_CE - 3) + // Julian cal
93 ClockMath::floorDivide(y, 400) - ClockMath::floorDivide(y, 100) + 2 + // => Gregorian cal
94 DAYS_BEFORE[month + (isLeapYear(year) ? 12 : 0)] + dom; // => month/dom
95
96 return julian - JULIAN_1970_CE; // JD => epoch day
97}
98
99void Grego::dayToFields(double day, int32_t& year, int32_t& month,
100 int32_t& dom, int32_t& dow, int32_t& doy) {
101
102 // Convert from 1970 CE epoch to 1 CE epoch (Gregorian calendar)
103 day += JULIAN_1970_CE - JULIAN_1_CE;
104
105 // Convert from the day number to the multiple radix
106 // representation. We use 400-year, 100-year, and 4-year cycles.
107 // For example, the 4-year cycle has 4 years + 1 leap day; giving
108 // 1461 == 365*4 + 1 days.
109 int32_t n400 = ClockMath::floorDivide(day, 146097, doy); // 400-year cycle length
110 int32_t n100 = ClockMath::floorDivide(doy, 36524, doy); // 100-year cycle length
111 int32_t n4 = ClockMath::floorDivide(doy, 1461, doy); // 4-year cycle length
112 int32_t n1 = ClockMath::floorDivide(doy, 365, doy);
113 year = 400*n400 + 100*n100 + 4*n4 + n1;
114 if (n100 == 4 || n1 == 4) {
115 doy = 365; // Dec 31 at end of 4- or 400-year cycle
116 } else {
117 ++year;
118 }
119
120 UBool isLeap = isLeapYear(year);
121
122 // Gregorian day zero is a Monday.
123 dow = (int32_t) uprv_fmod(day + 1, 7);
124 dow += (dow < 0) ? (UCAL_SUNDAY + 7) : UCAL_SUNDAY;
125
126 // Common Julian/Gregorian calculation
127 int32_t correction = 0;
128 int32_t march1 = isLeap ? 60 : 59; // zero-based DOY for March 1
129 if (doy >= march1) {
130 correction = isLeap ? 1 : 2;
131 }
132 month = (12 * (doy + correction) + 6) / 367; // zero-based month
133 dom = doy - DAYS_BEFORE[month + (isLeap ? 12 : 0)] + 1; // one-based DOM
134 doy++; // one-based doy
135}
136
137void Grego::timeToFields(UDate time, int32_t& year, int32_t& month,
138 int32_t& dom, int32_t& dow, int32_t& doy, int32_t& mid) {
139 double millisInDay;
140 double day = ClockMath::floorDivide((double)time, (double)U_MILLIS_PER_DAY, millisInDay);
141 mid = (int32_t)millisInDay;
142 dayToFields(day, year, month, dom, dow, doy);
143}
144
145int32_t Grego::dayOfWeek(double day) {
146 int32_t dow;
147 ClockMath::floorDivide(day + UCAL_THURSDAY, 7, dow);
148 return (dow == 0) ? UCAL_SATURDAY : dow;
149}
150
151int32_t Grego::dayOfWeekInMonth(int32_t year, int32_t month, int32_t dom) {
152 int32_t weekInMonth = (dom + 6)/7;
153 if (weekInMonth == 4) {
154 if (dom + 7 > monthLength(year, month)) {
155 weekInMonth = -1;
156 }
157 } else if (weekInMonth == 5) {
158 weekInMonth = -1;
159 }
160 return weekInMonth;
161}
162
163U_NAMESPACE_END
164
165#endif
166//eof
167