/* <TITLE> VMS time -> unix time_t conversion </TITLE> */
/* Author: Joseph Huber  huber @ mppmu.mpg.de */

#include stddef
#include stdlib
#include time
#include starlet
#include unixlib

#ifndef __vax
void vmstime_to_time_t(__int64 *vmstime, time_t *epoch)
#else
/*to make it working even on older Vax systems*/
void vmstime_to_time_t(void *vmstime, time_t *epoch)
#endif
/* vmstime: pointer to VMS quadword time (absolute time)
   epoch:   pointer to store epoch time 

No attempt is made to handle error cases: invalid VMS time inputs or
times before Unix epoch.
*/
{
 struct tm tm;
 unsigned short numtim[8];  
 *epoch = time(0);

#ifdef DECCFIX
 /* use decc$fix_time */
/*
  looks like the easiest, but:
  treats the VMS quad time as GMT, not local time.
  The result epoch time is then added the GMT offset when printing!
*/
  *epoch = decc$fix_time(vmstime);
#else /* before I learned about decc$fix-time ;-) */
 (void)localtime_r(epoch, &tm); /* preset fields like GMT offset*/
                               /* not sure if the DST flag is o.k.*/
                              /* but we don't know it from vmstime anyway */
 (void) sys$numtim(numtim,vmstime);
  tm.tm_year = numtim[0] - 1900;
  tm.tm_mon = numtim[1] - 1;
  tm.tm_mday = numtim[2];
  tm.tm_hour = numtim[3];
  tm.tm_min = numtim[4];
  tm.tm_sec = numtim[5];
  tm.tm_wday = tm.tm_yday = 0;
  *epoch = mktime(&tm);
#endif
}

#ifdef TEST
#include stdio

int main() {
 time_t unixtime;
#ifndef __vax
  __int64 datenow;

 (void) sys$gettim(&datenow);
 vmstime_to_time_t(&datenow,&unixtime);
#else
  long datenow[2];

 (void) sys$gettim(datenow);
 vmstime_to_time_t(datenow,&unixtime);
#endif
 printf("Time is: %s\n",ctime(&unixtime));
 return 0;
}
#endif