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tcalcalcs.h (10069B)
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1 /*
2 The CalCalcs routines, a set of C-language routines to perform
3 calendar calculations.
4
5 Version 1.0, released 7 January 2010
6
7 Copyright (C) 2010 David W. Pierce, dpierce@ucsd.edu
8
9 This program is free software: you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation, either version 3 of the License, or
12 (at your option) any later version.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 */
22
23 #ifdef __cplusplus
24 extern "C" {
25 #endif
26
27 #define CALCALCS_VERSION_NUMBER 1.0
28
29 struct cccalendar {
30 int sig;
31 char *name;
32 int ndays_reg, ndays_leap;
33
34 int (*c_isleap) ( int, int * );
35 int (*c_date2jday) ( int, int, int, int * );
36 int (*c_jday2date) ( int, int *, int *, int * );
37 int (*c_dpm) ( int, int, int * );
38
39 /* The following implement "mixed" calendars, for example, our standard
40 * civil calendar, which converts from Julian to Gregorian, with the
41 * last day of the Julian calendar being 4 Oct 1582 and the first day
42 * of the Gregorian calendar being 15 Oct 1582
43 */
44 int mixed;
45 struct cccalendar *early_cal, *late_cal;
46 int year_x, month_x, day_x; /* These are the transition Y,M,D, i.e., the FIRST DATE the LATER CAL is used */
47 int year_px, month_px, day_px; /* These are the DAY BEFORE the transition Y,M,D, i.e., the last date the earlier cal is used */
48 int jday_x; /* Julian day of the transition date */
49 };
50
51 /* A "country code", which holds the 2-letter code (abbreviation) for the country or region,
52 * its long name, and the Y/M/D date that it transitioned from the Julian to Gregorian calendar
53 */
54 struct ccs_ccode {
55 char *code, *longname;
56 int year, month, day;
57 };
58
59 typedef struct cccalendar calcalcs_cal;
60 typedef struct ccs_ccode ccs_country_code;
61
62 /* =====================================================================================
63 * Here are all the services this library supplies
64 *
65 * -------------------------------------------------------------------------
66 * ccs_init_calendar : initialize a calendar. Valid passed arguments are
67 * one of the following strings:
68 * Standard, proleptic_Gregorian, proleptic_Julian, noleap (aka 365_day and no_leap), 360_day
69 *
70 * The "Standard" calendar transitions from the Julian to the Gregorian calendar,
71 * with the last day of the Julian calender being 1582-10-04 and the next day being
72 * the first day of the Gregorian calendar, with the date 1582-10-15. This "transition date"
73 * can be set to be the value used by various countries, or set to any arbitrary
74 * date, using routine "set_cal_xition_date", below.
75 */
76 calcalcs_cal *ccs_init_calendar( const char *calname );
77
78 /*------------------------------------------------------------------------------
79 * Frees the storage previously allocated by ccs_init_calendar()
80 */
81 void ccs_free_calendar( calcalcs_cal *calendar );
82
83 /*--------------------------------------------------------------------------
84 * ccs_date2jday: turn a Y/M/D date into a (true) Julian day number. Note that
85 * a Julian day is not the day number of the year, but rather
86 * the integer day number starting from 1 on the day that would
87 * have been 1 Jan 4713 BC if the Julian calendar went back
88 * to that time.
89 */
90 int ccs_date2jday( calcalcs_cal *calendar, int year, int month, int day, int *jday );
91
92 /*--------------------------------------------------------------------------
93 * ccs_jday2date: turn a (true) Julian day number into a calendar date.
94 */
95 int ccs_jday2date( calcalcs_cal *calendar, int jday, int *year, int *month, int *day );
96
97 /*--------------------------------------------------------------------------
98 * ccs_isleap: determine if the specified year is a leap year in
99 * the specified calendar
100 */
101 int ccs_isleap( calcalcs_cal *calendar, int year, int *leap );
102
103 /*--------------------------------------------------------------------------
104 * ccs_dpm: returns the days per month for the given year/month.
105 * Note that during the month that transitions from a Julian to a
106 * Gregorian calendar, this might be a strange number of days.
107 */
108 int ccs_dpm( calcalcs_cal *calendar, int year, int month, int *dpm );
109
110 /*--------------------------------------------------------------------------
111 * ccs_date2doy: given a Y/M/D date, calculates the day number of the year, starting at 1 for
112 * January 1st.
113 */
114 int ccs_date2doy( calcalcs_cal *calendar, int year, int month, int day, int *doy );
115
116 /*--------------------------------------------------------------------------
117 * ccs_doy2date: given a year and a day number in that year (with counting starting at 1 for
118 * Jan 1st), this returns the month and day of the month that the doy refers to.
119 */
120 int ccs_doy2date( calcalcs_cal *calendar, int year, int doy, int *month, int *day );
121
122 /*--------------------------------------------------------------------------
123 * ccs_dayssince: Given a Y/M/D date in a specified calendar, and the number of days since
124 * that date, this returns the new Y/M/D date in a (possibly different) calendar.
125 *
126 * Note that specifying "zero" days since, and giving different calendars as the original
127 * and new calendars, essentially converts dates between calendars.
128 */
129 int ccs_dayssince( calcalcs_cal *calendar_orig, int year_orig, int month_orig, int day_orig,
130 int ndays_since, calcalcs_cal *calendar_new, int *year_new, int *month_new, int *day_new );
131
132 /*--------------------------------------------------------------------------
133 * get/set_cal_xition_date: these routines set the transition date for a Standard
134 * calendar, which is the date that the Gregorian calendar was first used.
135 * Before that, it is assumed that the Julian calendar was used.
136 *
137 * Historically, this transition date varies by country and region. The
138 * variation can be extreme, and over the centuries country boundaries have
139 * changed, so this should be considered only the grossest approximation. For
140 * that matter, for several countries, different districts/regions converted
141 * at different times anyway, so actually doing a good job at this task is
142 * far beyond this library's capability. Nevertheless, this does give some
143 * basic simplified capabilities in this regard. And you can always set
144 * the routines to use an arbitrary transition date of your own calculation.
145 *
146 * How to use these routines:
147 *
148 * If you know the transition date you want to impose, simply call
149 * set_cal_xition_date with the specified transition date. The date
150 * specified is the FIRST date that the new (Gregorian) calendar was
151 * used. For exaple, in Italy, the Gregorian calendar was first used
152 * on 15 October 1582.
153 *
154 * If you don't know what transition date to use, there is a brief
155 * database with some APPROXIMATE dates of transition that can be accessed
156 * by calling get_cal_xition_date with a two-letter country code, corresponding
157 * to the internet suffix for the country. (As a special case, "US" is used
158 * for the United States of America.) If the routine returns 0, then the
159 * country code is recognized and the approximate transition date is returned
160 * in the passed parameters year, month, day. These should then be given to
161 * routine set_cal_xition_date to make that calendar use the specified
162 * transition date. If the get_cal_xition_date routine does not return 0,
163 * then there is no information on that country in the database.
164 *
165 * routine set_cal_xition_date returns 0 on success, and something other than
166 * 0 on an error. Errors include trying to set the transition date to an
167 * invalid date, or trying to set the transition date for any calendar
168 * other than the "Standard" calendar.
169 *
170 * The following country/region codes are recognized: AK (Alaska) 1867/10/18;
171 * AL (Albania) 1912/12/1; AT (Austria) 1583/10/16; BE (Belgium) 1582/12/25;
172 * BG (Bulgaria) 1916/4/1; CN (China) 1929/1/1; CZ (Czechoslovakia) 1584/1/17;
173 * DK (Denmark) 1700/3/1; NO (Norway) 1700/3/1; EG (Egypt) 1875/1/1;
174 * EE (Estonia) 1918/1/1; FI (Finland) 1753/3/1; FR (France) 1582/12/20;
175 * DE (Germany, note different states actually used different dates between
176 * 1583 and 1700!) 1583/11/22; UK (Great Britain and Dominions) 1752/9/14;
177 * GR (Greece) 1924/3/23; HU (Hungary) 1587/11/1; IT (Italy) 1582/10/15;
178 * JP (Japan) 1918/1/1; LV (Latvia) 1915/1/1; LT (Lithuania) 1915/1/1;
179 * LU (Luxemburg) 1582/12/15; NL (Netherlands, note Catholic regions
180 * transitioned in various dates of 1582/83, while Protestant regions
181 * transitioned in various dates of 1700/01) 1582/10/15; NO (Norway) 1700/3/1;
182 * PL (Poland) 1582/10/15; PT (Portugal) 1582/10/15; RO (Romania) 1919/4/14;
183 * ES (Spain) 1582/10/15; SE (Sweden) 1753/3/1; CH (Switzerland, note,
184 * varied bewteen 1584 and 1701 by Canton) 1584/1/22; TR (Turkey)
185 * 1927/1/1; YU (Yugoslavia) 1919/1/1; UK (Great Britain and Dominions) 1752/9/14;
186 * US (United States) 1752/9/14; SU (former Soviet Union) 1918/2/1;
187 * RU (Russia) 1918/2/1.
188 */
189 int ccs_set_xition_date( calcalcs_cal *calendar, int year, int month, int day );
190 int ccs_get_xition_date( const char *country_code, int *year, int *month, int *day );
191
192 /*--------------------------------------------------------------------------
193 * calcalcs_err_str: return a static char * to an error string, given the error nmmber
194 */
195 char *ccs_err_str( int errno );
196
197 #define CALCALCS_ERR_NO_YEAR_ZERO -10
198 #define CALCALCS_ERR_DATE_NOT_IN_CALENDAR -11
199 #define CALCALCS_ERR_INVALID_DAY_OF_YEAR -12
200 #define CALCALCS_ERR_NOT_A_MIXED_CALENDAR -13
201 #define CALCALCS_ERR_UNKNOWN_COUNTRY_CODE -14
202 #define CALCALCS_ERR_OUT_OF_RANGE -15
203 #define CALCALCS_ERR_NULL_CALENDAR -16
204 #define CALCALCS_ERR_INVALID_CALENDAR -17
205
206 #ifdef __cplusplus
207 }
208 #endif