lib/libc/gen/timezone.c

   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  * @(#)timezone.c       8.1 (Berkeley) 6/4/93
  34  * $DragonFly: src/lib/libc/gen/timezone.c,v 1.5 2005/11/19 22:32:53 swildner Exp $
  35  */
  36
  37 #include <sys/types.h>
  38 #include <sys/time.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #define TZ_MAX_CHARS 255
  43
  44 char *_tztab(int, int);
  45
  46 /*
  47  * timezone --
  48  *      The arguments are the number of minutes of time you are westward
  49  *      from Greenwich and whether DST is in effect.  It returns a string
  50  *      giving the name of the local timezone.  Should be replaced, in the
  51  *      application code, by a call to localtime.
  52  */
  53
  54 static char     czone[TZ_MAX_CHARS];            /* space for zone name */
  55
  56 char *
  57 timezone(int zone, int dst)
  58 {
  59         char    *beg,
  60                         *end;
  61
  62         if ( (beg = getenv("TZNAME")) ) {       /* set in environment */
  63                 if ( (end = index(beg, ',')) ) {/* "PST,PDT" */
  64                         if (dst)
  65                                 return(++end);
  66                         *end = '\0';
  67                         strncpy(czone,beg,sizeof(czone) - 1);
  68                         czone[sizeof(czone) - 1] = '\0';
  69                         *end = ',';
  70                         return(czone);
  71                 }
  72                 return(beg);
  73         }
  74         return(_tztab(zone,dst));       /* default: table or created zone */
  75 }
  76
  77 static struct zone {
  78         int     offset;
  79         char    *stdzone;
  80         char    *dlzone;
  81 } zonetab[] = {
  82         {-1*60, "MET",  "MET DST"},     /* Middle European */
  83         {-2*60, "EET",  "EET DST"},     /* Eastern European */
  84         {4*60,  "AST",  "ADT"},         /* Atlantic */
  85         {5*60,  "EST",  "EDT"},         /* Eastern */
  86         {6*60,  "CST",  "CDT"},         /* Central */
  87         {7*60,  "MST",  "MDT"},         /* Mountain */
  88         {8*60,  "PST",  "PDT"},         /* Pacific */
  89 #ifdef notdef
  90         /* there's no way to distinguish this from WET */
  91         {0,     "GMT",  0},             /* Greenwich */
  92 #endif
  93         {0*60,  "WET",  "WET DST"},     /* Western European */
  94         {-10*60,"EST",  "EST"},         /* Aust: Eastern */
  95      {-10*60+30,"CST",  "CST"},         /* Aust: Central */
  96         {-8*60, "WST",  0},             /* Aust: Western */
  97         {-1,     NULL,  NULL}
  98 };
  99
 100 /*
 101  * _tztab --
 102  *      check static tables or create a new zone name; broken out so that
 103  *      we can make a guess as to what the zone is if the standard tables
 104  *      aren't in place in /etc.  DO NOT USE THIS ROUTINE OUTSIDE OF THE
 105  *      STANDARD LIBRARY.
 106  */
 107 char *
 108 _tztab(int zone, int dst)
 109 {
 110         struct zone     *zp;
 111         char    sign;
 112
 113         for (zp = zonetab; zp->offset != -1;++zp)       /* static tables */
 114                 if (zp->offset == zone) {
 115                         if (dst && zp->dlzone)
 116                                 return(zp->dlzone);
 117                         if (!dst && zp->stdzone)
 118                                 return(zp->stdzone);
 119                 }
 120
 121         if (zone < 0) {                                 /* create one */
 122                 zone = -zone;
 123                 sign = '+';
 124         }
 125         else
 126                 sign = '-';
 127         snprintf(czone, sizeof(czone),
 128             "GMT%c%d:%02d",sign,zone / 60,zone % 60);
 129         return(czone);
 130 }