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28f540f4 RM |
1 | /* Copyright (C) 1991, 1993 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. | |
3 | ||
4 | The GNU C Library is free software; you can redistribute it and/or | |
5 | modify it under the terms of the GNU Library General Public License as | |
6 | published by the Free Software Foundation; either version 2 of the | |
7 | License, or (at your option) any later version. | |
8 | ||
9 | The GNU C Library is distributed in the hope that it will be useful, | |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | Library General Public License for more details. | |
13 | ||
14 | You should have received a copy of the GNU Library General Public | |
15 | License along with the GNU C Library; see the file COPYING.LIB. If | |
16 | not, write to the Free Software Foundation, Inc., 675 Mass Ave, | |
17 | Cambridge, MA 02139, USA. */ | |
18 | ||
19 | #include <ansidecl.h> | |
20 | #include <time.h> | |
21 | ||
22 | ||
23 | /* Defined in mktime.c. */ | |
24 | extern CONST unsigned short int __mon_lengths[2][12]; | |
25 | ||
26 | #define SECS_PER_HOUR (60 * 60) | |
27 | #define SECS_PER_DAY (SECS_PER_HOUR * 24) | |
28 | ||
c2216480 RM |
29 | /* Compute the `struct tm' representation of *T, |
30 | offset OFFSET seconds east of UTC, | |
31 | and store year, yday, mon, mday, wday, hour, min, sec into *TP. */ | |
32 | void | |
33 | DEFUN(__offtime, (t, offset, tp), | |
34 | CONST time_t *t AND long int offset AND struct tm *tp) | |
28f540f4 | 35 | { |
28f540f4 RM |
36 | register long int days, rem; |
37 | register int y; | |
38 | register CONST unsigned short int *ip; | |
39 | ||
28f540f4 RM |
40 | days = *t / SECS_PER_DAY; |
41 | rem = *t % SECS_PER_DAY; | |
42 | rem += offset; | |
43 | while (rem < 0) | |
44 | { | |
45 | rem += SECS_PER_DAY; | |
46 | --days; | |
47 | } | |
48 | while (rem >= SECS_PER_DAY) | |
49 | { | |
50 | rem -= SECS_PER_DAY; | |
51 | ++days; | |
52 | } | |
c2216480 | 53 | tp->tm_hour = rem / SECS_PER_HOUR; |
28f540f4 | 54 | rem %= SECS_PER_HOUR; |
c2216480 RM |
55 | tp->tm_min = rem / 60; |
56 | tp->tm_sec = rem % 60; | |
28f540f4 | 57 | /* January 1, 1970 was a Thursday. */ |
c2216480 RM |
58 | tp->tm_wday = (4 + days) % 7; |
59 | if (tp->tm_wday < 0) | |
60 | tp->tm_wday += 7; | |
28f540f4 RM |
61 | y = 1970; |
62 | while (days >= (rem = __isleap(y) ? 366 : 365)) | |
63 | { | |
64 | ++y; | |
65 | days -= rem; | |
66 | } | |
67 | while (days < 0) | |
68 | { | |
69 | --y; | |
70 | days += __isleap(y) ? 366 : 365; | |
71 | } | |
c2216480 RM |
72 | tp->tm_year = y - 1900; |
73 | tp->tm_yday = days; | |
28f540f4 RM |
74 | ip = __mon_lengths[__isleap(y)]; |
75 | for (y = 0; days >= ip[y]; ++y) | |
76 | days -= ip[y]; | |
c2216480 RM |
77 | tp->tm_mon = y; |
78 | tp->tm_mday = days + 1; | |
79 | tp->tm_isdst = -1; | |
28f540f4 | 80 | } |