xref: /titanic_51/usr/src/lib/libast/common/tm/tmweek.c (revision 835ee2195df075073d2670eb95a6eab413d6c789)
1 /***********************************************************************
2 *                                                                      *
3 *               This software is part of the ast package               *
4 *          Copyright (c) 1985-2009 AT&T Intellectual Property          *
5 *                      and is licensed under the                       *
6 *                  Common Public License, Version 1.0                  *
7 *                    by AT&T Intellectual Property                     *
8 *                                                                      *
9 *                A copy of the License is available at                 *
10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
12 *                                                                      *
13 *              Information and Software Systems Research               *
14 *                            AT&T Research                             *
15 *                           Florham Park NJ                            *
16 *                                                                      *
17 *                 Glenn Fowler <gsf@research.att.com>                  *
18 *                  David Korn <dgk@research.att.com>                   *
19 *                   Phong Vo <kpv@research.att.com>                    *
20 *                                                                      *
21 ***********************************************************************/
22 #pragma prototyped
23 /*
24  * Glenn Fowler
25  * AT&T Research
26  *
27  * Time_t conversion support
28  */
29 
30 #include <tmx.h>
31 
32 static unsigned char	offset[7][3] =
33 {
34 	{ 7, 6, 6 },
35 	{ 1, 7, 7 },
36 	{ 2, 1, 8 },
37 	{ 3, 2, 9 },
38 	{ 4, 3, 10},
39 	{ 5, 4, 4 },
40 	{ 6, 5, 5 },
41 };
42 
43 /*
44  * type is week type
45  *	0 sunday first day of week
46  *	1 monday first day of week
47  *	2 monday first day of iso week
48  * if week<0 then return week for tm
49  * if day<0 then set tm to first day of week
50  * otherwise set tm to day in week
51  * and return tm->tm_yday
52  */
53 
54 int
55 tmweek(Tm_t* tm, int type, int week, int day)
56 {
57 	int	d;
58 
59 	if (week < 0)
60 	{
61 		if ((day = tm->tm_wday - tm->tm_yday % 7) < 0)
62 			day += 7;
63 		week = (tm->tm_yday + offset[day][type]) / 7;
64 		if (type == 2)
65 		{
66 			if (!week)
67 				week = (day > 0 && day < 6 || tmisleapyear(tm->tm_year - 1)) ? 53 : 52;
68 			else if (week == 53 && (tm->tm_wday + (31 - tm->tm_mday)) < 4)
69 				week = 1;
70 		}
71 		return week;
72 	}
73 	if (day < 0)
74 		day = type != 0;
75 	tm->tm_mon = 0;
76 	tm->tm_mday = 1;
77 	tmfix(tm);
78 	d = tm->tm_wday;
79 	tm->tm_mday = week * 7 - offset[d][type] + ((day || type != 2) ? day : 7);
80 	tmfix(tm);
81 	if (d = tm->tm_wday - day)
82 	{
83 		tm->tm_mday -= d;
84 		tmfix(tm);
85 	}
86 	return tm->tm_yday;
87 }
88