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