lowleveltime.h

/* -*- Mode: C++ -*- *****************************************************
 * lowleveltime.h
 * Written by various people (I"ll look up the exact credits later)
 * Modified by Durk Talsma, July 1999 for use in FlightGear
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 **************************************************************************/

/********************************************************************
 * This file redefines some low-level Unix-like time functions for  *
 * use with FlightGear. Most notably, localtime() is adapted to use *
 * a custom timezone, in order to get the 'local' time for a given  *
 * aircraft's position, and not only for the current location of the*
 * computer running the sim.                                        *
 *                                                                  *
 * Software adapted from glibc functions, by Durk Talsma. Started   *
 * July, 17, 1999.                                                  *
 ********************************************************************/

#ifndef _LOWLEVELTIME_H_
#define _LOWLEVELTIME_H_

#include <time.h>

/* adapted from zdump.c */
void show (const char *zone, time_t t, int v);

/* adapted from <time.h> */
struct tm * fgLocaltime (const time_t *t, const char *tzName);

/* Prototype for the internal function to get information based on TZ.  */
extern struct tm *fgtz_convert (const time_t *t, int use_localtime,
                                     struct tm *tp, const char *tzName);

/* This structure contains all the information about a
   timezone given in the POSIX standard TZ envariable.  */
typedef struct
  {
    const char *name;

    /* When to change.  */
    enum { J0, J1, M } type;    /* Interpretation of:  */
    unsigned short int m, n, d; /* Month, week, day.  */
    unsigned int secs;          /* Time of day.  */

    long int offset;            /* Seconds east of GMT (west if < 0).  */

    /* We cache the computed time of change for a
       given year so we don't have to recompute it.  */
    time_t change;      /* When to change to this zone.  */
    int computed_for;   /* Year above is computed for.  */
  } fgtz_rule;

struct tzhead {
        char    tzh_magic[4];           /* TZ_MAGIC */
        char    tzh_reserved[16];       /* reserved for future use */
        char    tzh_ttisgmtcnt[4];      /* coded number of trans. time flags */
        char    tzh_ttisstdcnt[4];      /* coded number of trans. time flags */
        char    tzh_leapcnt[4];         /* coded number of leap seconds */
        char    tzh_timecnt[4];         /* coded number of transition times */
        char    tzh_typecnt[4];         /* coded number of local time types */
        char    tzh_charcnt[4];         /* coded number of abbr. chars */
};


/* Defined in mktime.c.  */
extern const unsigned short int mon_yday[2][13];

#ifndef TZDIR
#define TZDIR   "/usr/local/etc/zoneinfo" /* Time zone object file directory */
#endif /* !defined TZDIR */



#ifndef TZDEFAULT
#define TZDEFAULT       "localtime"
#endif /* !defined TZDEFAULT */

#define SECSPERMIN      60
#define MINSPERHOUR     60
#define HOURSPERDAY     24
#define DAYSPERWEEK     7
#define DAYSPERNYEAR    365
#define DAYSPERLYEAR    366
#define SECSPERHOUR     (SECSPERMIN * MINSPERHOUR)
#define SECSPERDAY      ((long) SECSPERHOUR * HOURSPERDAY)
#define MONSPERYEAR     12

#define TM_SUNDAY       0
#define TM_MONDAY       1
#define TM_TUESDAY      2
#define TM_WEDNESDAY    3
#define TM_THURSDAY     4
#define TM_FRIDAY       5
#define TM_SATURDAY     6

#define TM_JANUARY      0
#define TM_FEBRUARY     1
#define TM_MARCH        2
#define TM_APRIL        3
#define TM_MAY          4
#define TM_JUNE         5
#define TM_JULY         6
#define TM_AUGUST       7
#define TM_SEPTEMBER    8
#define TM_OCTOBER      9
#define TM_NOVEMBER     10
#define TM_DECEMBER     11

#define TM_YEAR_BASE    1900

#define EPOCH_YEAR      1970
#define EPOCH_WDAY      TM_THURSDAY

#endif 

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