text: /*** dt-core-tz-glue.c -- gluing date/times and tzs
   *
   * Copyright (C) 2012-2019 Sebastian Freundt
   *
   * Author:  Sebastian Freundt <freundt@ga-group.nl>
   *
   * This file is part of dateutils.
   *
   * 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. Neither the name of the author nor the names of any contributors
   *    may be used to endorse or promote products derived from this
   *    software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR "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.
   *
   **/
  /* dt-core-tz-glue.h implementation */
  #if !defined INCLUDED_dt_core_tz_glue_c_
  #define INCLUDED_dt_core_tz_glue_c_
  
  #if defined HAVE_CONFIG_H
  # include "config.h"
  #endif	/* HAVE_CONFIG_H */
  #include "nifty.h"
  #include "dt-core-tz-glue.h"
  
  #if !defined DEFUN
  # define DEFUN
  #endif	/* !DEFUN */
  
  
  /**
   * Return a dt object that forgot about DT's zone and uses ZONE instead. */
  DEFUN struct dt_dt_s
  dtz_forgetz(struct dt_dt_s d, zif_t zone)
  {
  	dt_ssexy_t d_unix;
  	dt_ssexy_t d_locl;
  	int32_t zdiff;
  
  	if (dt_unk_p(d) || dt_sandwich_only_d_p(d)) {
  		/* we need date/times to do the conversion */
  		return d;
  	} else if (d.znfxd) {
  		/* already forgotten about */
  		return d;
  	} else if (zone == NULL) {
  		/* convert from UTC, great idea */
  		return d;
  	}
  
  	/* convert date/time part to unix stamp */
  	d_locl = dt_to_unix_epoch(d);
  	d_unix = zif_utc_time(zone, d_locl);
  	if (LIKELY((zdiff = d_unix - d_locl))) {
  		/* let dt_dtadd() do the magic */
  #if defined HAVE_ANON_STRUCTS_INIT
  		d = dt_dtadd(d, (struct dt_dtdur_s){DT_DURS, .dv = zdiff});
  #else
  		{
  			struct dt_dtdur_s tmp = {DT_DURS};
  			tmp.dv = zdiff;
  			d = dt_dtadd(d, tmp);
  		}
  #endif
  		d.znfxd = 1;
  		if (zdiff > 0) {
  			d.neg = 1;
  			d.zdiff = (uint16_t)(zdiff / ZDIFF_RES);
  		} else if (zdiff < 0) {
  			d.zdiff = (uint16_t)(-zdiff / ZDIFF_RES);
  		}
  	}
  	return d;
  }
  
  /**
   * Return a dt object from a UTC'd DT that uses ZONE. */
  DEFUN struct dt_dt_s
  dtz_enrichz(struct dt_dt_s d, zif_t zone)
  {
  	dt_ssexy_t d_unix;
  	dt_ssexy_t d_locl;
  	int32_t zdiff;
  
  	if (dt_sandwich_only_d_p(d)) {
  		/* nah, we need a date/time for this */
  		return d;
  	} else if (zone == NULL) {
  		/* UTC -> UTC? */
  		return d;
  	}
  
  	/* convert date/time part to unix stamp */
  	d_unix = dt_to_unix_epoch(d);
  	d_locl = zif_local_time(zone, d_unix);
  	if (LIKELY((zdiff = d_locl - d_unix))) {
  		/* let dt_dtadd() do the magic */
  #if defined HAVE_ANON_STRUCTS_INIT
  		d = dt_dtadd(d, (struct dt_dtdur_s){DT_DURS, .dv = zdiff});
  #else
  		{
  			struct dt_dtdur_s tmp = {DT_DURS};
  			tmp.dv = zdiff;
  			d = dt_dtadd(d, tmp);
  		}
  #endif
  		if (zdiff > 0) {
  			d.zdiff = (uint16_t)(zdiff / ZDIFF_RES);
  		} else if (zdiff < 0) {
  			d.neg = 1;
  			d.zdiff = (uint16_t)(-zdiff / ZDIFF_RES);
  		}
  	} else {
  		/* no difference to UTC means the offset is +00:00 */
  		d.zdiff = 0U;
  		d.neg = 0U;
  	}
  	return d;
  }
  
  #endif	/* INCLUDED_dt_core_tz_glue_c_ */
  /* dt-core-tz-glue.c ends here */
  