• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
floorDivide(int32_t numerator,int32_t denominator)25 int32_t ClockMath::floorDivide(int32_t numerator, int32_t denominator) {
26     return (numerator >= 0) ?
27         numerator / denominator : ((numerator + 1) / denominator) - 1;
28 }
29 
floorDivide(int64_t numerator,int64_t denominator)30 int64_t ClockMath::floorDivide(int64_t numerator, int64_t denominator) {
31     return (numerator >= 0) ?
32         numerator / denominator : ((numerator + 1) / denominator) - 1;
33 }
34 
floorDivide(double numerator,int32_t denominator,int32_t & remainder)35 int32_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 
floorDivide(double dividend,double divisor,double & remainder)43 double 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 
77 const int32_t JULIAN_1_CE    = 1721426; // January 1, 1 CE Gregorian
78 const int32_t JULIAN_1970_CE = 2440588; // January 1, 1970 CE Gregorian
79 
80 const 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 
84 const 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 
fieldsToDay(int32_t year,int32_t month,int32_t dom)88 double 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 
dayToFields(double day,int32_t & year,int32_t & month,int32_t & dom,int32_t & dow,int32_t & doy)99 void 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 
timeToFields(UDate time,int32_t & year,int32_t & month,int32_t & dom,int32_t & dow,int32_t & doy,int32_t & mid)137 void 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 
dayOfWeek(double day)145 int32_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 
dayOfWeekInMonth(int32_t year,int32_t month,int32_t dom)151 int32_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 
163 U_NAMESPACE_END
164 
165 #endif
166 //eof
167