BSD 4_4 release

[unix-history] / usr / src / lib / libc / gen / timezone.c

/*
* Copyright (c) 1987, 1993
*      The Regents of the University of California.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)timezone.c  8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tzfile.h>

char *_tztab();

/*
* timezone --
*      The arguments are the number of minutes of time you are westward
*      from Greenwich and whether DST is in effect.  It returns a string
*      giving the name of the local timezone.  Should be replaced, in the
*      application code, by a call to localtime.
*/

static char     czone[TZ_MAX_CHARS];            /* space for zone name */

char *
timezone(zone, dst)
       int     zone,
               dst;
{
       register char   *beg,
                       *end;

       if (beg = getenv("TZNAME")) {           /* set in environment */
               if (end = index(beg, ',')) {    /* "PST,PDT" */
                       if (dst)
                               return(++end);
                       *end = '\0';
                       (void)strncpy(czone,beg,sizeof(czone) - 1);
                       czone[sizeof(czone) - 1] = '\0';
                       *end = ',';
                       return(czone);
               }
               return(beg);
       }
       return(_tztab(zone,dst));       /* default: table or created zone */
}

static struct zone {
       int     offset;
       char    *stdzone;
       char    *dlzone;
} zonetab[] = {
       -1*60,  "MET",  "MET DST",      /* Middle European */
       -2*60,  "EET",  "EET DST",      /* Eastern European */
       4*60,   "AST",  "ADT",          /* Atlantic */
       5*60,   "EST",  "EDT",          /* Eastern */
       6*60,   "CST",  "CDT",          /* Central */
       7*60,   "MST",  "MDT",          /* Mountain */
       8*60,   "PST",  "PDT",          /* Pacific */
#ifdef notdef
       /* there's no way to distinguish this from WET */
       0,      "GMT",  0,              /* Greenwich */
#endif
       0*60,   "WET",  "WET DST",      /* Western European */
       -10*60, "EST",  "EST",          /* Aust: Eastern */
    -10*60+30, "CST",  "CST",          /* Aust: Central */
       -8*60,  "WST",  0,              /* Aust: Western */
       -1
};

/*
* _tztab --
*      check static tables or create a new zone name; broken out so that
*      we can make a guess as to what the zone is if the standard tables
*      aren't in place in /etc.  DO NOT USE THIS ROUTINE OUTSIDE OF THE
*      STANDARD LIBRARY.
*/
char *
_tztab(zone,dst)
       register int    zone;
       int     dst;
{
       register struct zone    *zp;
       register char   sign;

       for (zp = zonetab; zp->offset != -1;++zp)       /* static tables */
               if (zp->offset == zone) {
                       if (dst && zp->dlzone)
                               return(zp->dlzone);
                       if (!dst && zp->stdzone)
                               return(zp->stdzone);
               }

       if (zone < 0) {                                 /* create one */
               zone = -zone;
               sign = '+';
       }
       else
               sign = '-';
       (void)sprintf(czone,"GMT%c%d:%02d",sign,zone / 60,zone % 60);
       return(czone);
}