1 /*
2 * Copyright (c) 1990 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that: (1) source code distributions
7 * retain the above copyright notice and this paragraph in its entirety, (2)
8 * distributions including binary code include the above copyright notice and
9 * this paragraph in its entirety in the documentation or other materials
10 * provided with the distribution, and (3) all advertising materials mentioning
11 * features or use of this software display the following acknowledgement:
12 * ``This product includes software developed by the University of California,
13 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
14 * the University nor the names of its contributors may be used to endorse
15 * or promote products derived from this software without specific prior
16 * written permission.
17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20 */
21 #ifndef lint
22 static char rcsid[] =
23 "@(#)$Header: /usr/staff/martinh/tcpview/RCS/gwtm2secs.c,v 1.1 1993/04/22 20:22:12 martinh Exp $ (LBL)";
24 #endif
25
26 /*
27 * gwtm2secs.c - convert "tm" structs for Greenwich time to Unix timestamp
28 */
29
30 #include <stdio.h>
31 #include <sys/types.h>
32 #include <time.h>
33
34 static int days_in_month[] =
35 /* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
36 { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
37
38 #define IS_LEAP_YEAR(year) \
39 (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))
40
gwtm2secs(tm)41 time_t gwtm2secs( tm )
42 struct tm *tm;
43 {
44 int i, days, year;
45
46 year = tm->tm_year;
47
48 /* Allow for year being specified with either 2 digits or 4 digits.
49 * 2-digit years are either 19xx or 20xx - a simple heuristic
50 * distinguishes them, since we can't represent any time < 1970.
51 */
52 if ( year < 100 )
53 if ( year >= 70 )
54 year += 1900;
55 else
56 year += 2000;
57
58 days = 0;
59 for ( i = 1970; i < year; ++i )
60 {
61 days += 365;
62 if ( IS_LEAP_YEAR(i) )
63 ++days;
64 }
65
66 for ( i = 0; i < tm->tm_mon; ++i )
67 days += days_in_month[i];
68
69 if ( IS_LEAP_YEAR(year) && tm->tm_mon > 1 ) /* 1 is February */
70 ++days;
71
72 days += tm->tm_mday - 1; /* -1 since days are numbered starting at 1 */
73
74 return days * 86400 + tm->tm_hour * 3600 + tm->tm_min * 60 + tm->tm_sec;
75 }
76