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