add Berkeley specific header

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

/*
* Copyright (c) 1987 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that this notice is preserved and that due credit is given
* to the University of California at Berkeley. The name of the University
* may not be used to endorse or promote products derived from this
* software without specific written prior permission. This software
* is provided ``as is'' without express or implied warranty.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)timezone.c  5.7 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

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

/*
* 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;
       char    *getenv(), *index(), *strncpy(), *_tztab();

       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);
}