timezone.c revision 9935 
1/*
2 * Copyright (c) 1987, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#if defined(LIBC_SCCS) && !defined(lint)
35static char sccsid[] = "@(#)timezone.c	8.1 (Berkeley) 6/4/93";
36#endif /* LIBC_SCCS and not lint */
37
38#include <sys/types.h>
39#include <sys/time.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#define TZ_MAX_CHARS 255
44
45char *_tztab();
46
47/*
48 * timezone --
49 *	The arguments are the number of minutes of time you are westward
50 *	from Greenwich and whether DST is in effect.  It returns a string
51 *	giving the name of the local timezone.  Should be replaced, in the
52 *	application code, by a call to localtime.
53 */
54
55static char	czone[TZ_MAX_CHARS];		/* space for zone name */
56
57char *
58timezone(zone, dst)
59	int	zone,
60		dst;
61{
62	register char	*beg,
63			*end;
64
65	if (beg = getenv("TZNAME")) {		/* set in environment */
66		if (end = index(beg, ',')) {	/* "PST,PDT" */
67			if (dst)
68				return(++end);
69			*end = '\0';
70			(void)strncpy(czone,beg,sizeof(czone) - 1);
71			czone[sizeof(czone) - 1] = '\0';
72			*end = ',';
73			return(czone);
74		}
75		return(beg);
76	}
77	return(_tztab(zone,dst));	/* default: table or created zone */
78}
79
80static struct zone {
81	int	offset;
82	char	*stdzone;
83	char	*dlzone;
84} zonetab[] = {
85	-1*60,	"MET",	"MET DST",	/* Middle European */
86	-2*60,	"EET",	"EET DST",	/* Eastern European */
87	4*60,	"AST",	"ADT",		/* Atlantic */
88	5*60,	"EST",	"EDT",		/* Eastern */
89	6*60,	"CST",	"CDT",		/* Central */
90	7*60,	"MST",	"MDT",		/* Mountain */
91	8*60,	"PST",	"PDT",		/* Pacific */
92#ifdef notdef
93	/* there's no way to distinguish this from WET */
94	0,	"GMT",	0,		/* Greenwich */
95#endif
96	0*60,	"WET",	"WET DST",	/* Western European */
97	-10*60,	"EST",	"EST",		/* Aust: Eastern */
98     -10*60+30,	"CST",	"CST",		/* Aust: Central */
99	-8*60,	"WST",	0,		/* Aust: Western */
100	-1
101};
102
103/*
104 * _tztab --
105 *	check static tables or create a new zone name; broken out so that
106 *	we can make a guess as to what the zone is if the standard tables
107 *	aren't in place in /etc.  DO NOT USE THIS ROUTINE OUTSIDE OF THE
108 *	STANDARD LIBRARY.
109 */
110char *
111_tztab(zone,dst)
112	register int	zone;
113	int	dst;
114{
115	register struct zone	*zp;
116	register char	sign;
117
118	for (zp = zonetab; zp->offset != -1;++zp)	/* static tables */
119		if (zp->offset == zone) {
120			if (dst && zp->dlzone)
121				return(zp->dlzone);
122			if (!dst && zp->stdzone)
123				return(zp->stdzone);
124		}
125
126	if (zone < 0) {					/* create one */
127		zone = -zone;
128		sign = '+';
129	}
130	else
131		sign = '-';
132	(void)sprintf(czone,"GMT%c%d:%02d",sign,zone / 60,zone % 60);
133	return(czone);
134}
135