localtime.c

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				}
			}
			theirdstoffset = 0;
			for (i = 0; i < sp->timecnt; ++i) {
				j = sp->types[i];
				if (sp->ttis[j].tt_isdst) {
					theirdstoffset =
						-sp->ttis[j].tt_gmtoff;
					break;
				}
			}
			/*
			** Initially we're assumed to be in standard time.
			*/
			isdst = FALSE;
			theiroffset = theirstdoffset;
			/*
			** Now juggle transition times and types
			** tracking offsets as you do.
			*/
			for (i = 0; i < sp->timecnt; ++i) {
				j = sp->types[i];
				sp->types[i] = sp->ttis[j].tt_isdst;
				if (sp->ttis[j].tt_ttisgmt) {
					/* No adjustment to transition time */
				} else {
					/*
					** If summer time is in effect, and the
					** transition time was not specified as
					** standard time, add the summer time
					** offset to the transition time;
					** otherwise, add the standard time
					** offset to the transition time.
					*/
					/*
					** Transitions from DST to DDST
					** will effectively disappear since
					** POSIX provides for only one DST
					** offset.
					*/
					if (isdst && !sp->ttis[j].tt_ttisstd) {
						sp->ats[i] += dstoffset -
							theirdstoffset;
					} else {
						sp->ats[i] += stdoffset -
							theirstdoffset;
					}
				}
				theiroffset = -sp->ttis[j].tt_gmtoff;
				if (sp->ttis[j].tt_isdst)
					theirdstoffset = theiroffset;
				else	theirstdoffset = theiroffset;
			}
			/*
			** Finally, fill in ttis.
			** ttisstd and ttisgmt need not be handled.
			*/
			sp->ttis[0].tt_gmtoff = -stdoffset;
			sp->ttis[0].tt_isdst = FALSE;
			sp->ttis[0].tt_abbrind = 0;
			sp->ttis[1].tt_gmtoff = -dstoffset;
			sp->ttis[1].tt_isdst = TRUE;
			sp->ttis[1].tt_abbrind = stdlen + 1;
			sp->typecnt = 2;
		}
	} else {
		dstlen = 0;
		sp->typecnt = 1;		/* only standard time */
		sp->timecnt = 0;
		sp->ttis[0].tt_gmtoff = -stdoffset;
		sp->ttis[0].tt_isdst = 0;
		sp->ttis[0].tt_abbrind = 0;
	}
	sp->charcnt = stdlen + 1;
	if (dstlen != 0)
		sp->charcnt += dstlen + 1;
	if ((size_t) sp->charcnt > sizeof sp->chars)
		return -1;
	cp = sp->chars;
	(void) strncpy(cp, stdname, stdlen);
	cp += stdlen;
	*cp++ = '\0';
	if (dstlen != 0) {
		(void) strncpy(cp, dstname, dstlen);
		*(cp + dstlen) = '\0';
	}
	return 0;
}

static int gmtload(struct state *sp)
{
	if (tzload(gmt, sp, TRUE) != 0)
		return tzparse(gmt, sp, TRUE);
	else
		return -1;
}

static const struct state *ast_tzset(const char *zone)
{
	struct state *sp;

	if (ast_strlen_zero(zone))
		zone = "/etc/localtime";

	AST_LIST_LOCK(&zonelist);
	AST_LIST_TRAVERSE(&zonelist, sp, list) {
		if (!strcmp(sp->name, zone)) {
			AST_LIST_UNLOCK(&zonelist);
			return sp;
		}
	}
	AST_LIST_UNLOCK(&zonelist);

	if (!(sp = ast_calloc(1, sizeof *sp)))
		return NULL;

	if (tzload(zone, sp, TRUE) != 0) {
		if (zone[0] == ':' || tzparse(zone, sp, FALSE) != 0)
			(void) gmtload(sp);
	}
	ast_copy_string(sp->name, zone, sizeof(sp->name));
	AST_LIST_LOCK(&zonelist);
	AST_LIST_INSERT_TAIL(&zonelist, sp, list);
	AST_LIST_UNLOCK(&zonelist);
	return sp;
}

/*! \note
** The easy way to behave "as if no library function calls" localtime
** is to not call it--so we drop its guts into "localsub", which can be
** freely called. (And no, the PANS doesn't require the above behavior--
** but it *is* desirable.)
**
** The unused offset argument is for the benefit of mktime variants.
*/

static struct ast_tm *localsub(const struct timeval *timep, const long offset, struct ast_tm *tmp, const struct state *sp)
{
	const struct ttinfo *	ttisp;
	int			i;
	struct ast_tm *		result;
	struct timeval	t;
	memcpy(&t, timep, sizeof(t));

	if (sp == NULL)
		return gmtsub(timep, offset, tmp);
	if ((sp->goback && t.tv_sec < sp->ats[0]) ||
		(sp->goahead && t.tv_sec > sp->ats[sp->timecnt - 1])) {
			struct timeval	newt = t;
			time_t		seconds;
			time_t		tcycles;
			int_fast64_t	icycles;

			if (t.tv_sec < sp->ats[0])
				seconds = sp->ats[0] - t.tv_sec;
			else	seconds = t.tv_sec - sp->ats[sp->timecnt - 1];
			--seconds;
			tcycles = seconds / YEARSPERREPEAT / AVGSECSPERYEAR;
			++tcycles;
			icycles = tcycles;
			if (tcycles - icycles >= 1 || icycles - tcycles >= 1)
				return NULL;
			seconds = icycles;
			seconds *= YEARSPERREPEAT;
			seconds *= AVGSECSPERYEAR;
			if (t.tv_sec < sp->ats[0])
				newt.tv_sec += seconds;
			else	newt.tv_sec -= seconds;
			if (newt.tv_sec < sp->ats[0] ||
				newt.tv_sec > sp->ats[sp->timecnt - 1])
					return NULL;	/* "cannot happen" */
			result = localsub(&newt, offset, tmp, sp);
			if (result == tmp) {
				time_t	newy;

				newy = tmp->tm_year;
				if (t.tv_sec < sp->ats[0])
					newy -= icycles * YEARSPERREPEAT;
				else
					newy += icycles * YEARSPERREPEAT;
				tmp->tm_year = newy;
				if (tmp->tm_year != newy)
					return NULL;
			}
			return result;
	}
	if (sp->timecnt == 0 || t.tv_sec < sp->ats[0]) {
		i = 0;
		while (sp->ttis[i].tt_isdst) {
			if (++i >= sp->typecnt) {
				i = 0;
				break;
			}
		}
	} else {
		int	lo = 1;
		int	hi = sp->timecnt;

		while (lo < hi) {
			int	mid = (lo + hi) >> 1;

			if (t.tv_sec < sp->ats[mid])
				hi = mid;
			else
				lo = mid + 1;
		}
		i = (int) sp->types[lo - 1];
	}
	ttisp = &sp->ttis[i];
	/*
	** To get (wrong) behavior that's compatible with System V Release 2.0
	** you'd replace the statement below with
	**	t += ttisp->tt_gmtoff;
	**	timesub(&t, 0L, sp, tmp);
	*/
	result = timesub(&t, ttisp->tt_gmtoff, sp, tmp);
	tmp->tm_isdst = ttisp->tt_isdst;
#ifndef SOLARIS /* Solaris doesn't have this element */
	tmp->tm_gmtoff = ttisp->tt_gmtoff;
#endif
#ifdef TM_ZONE
	tmp->TM_ZONE = &sp->chars[ttisp->tt_abbrind];
#endif /* defined TM_ZONE */
	tmp->tm_usec = timep->tv_usec;
	return result;
}

struct ast_tm *ast_localtime(const struct timeval *timep, struct ast_tm *tmp, const char *zone)
{
	const struct state *sp = ast_tzset(zone);
	memset(tmp, 0, sizeof(*tmp));
	return sp ? localsub(timep, 0L, tmp, sp) : NULL;
}

/*
** This function provides informaton about daylight savings time 
** for the given timezone.  This includes whether it can determine 
** if daylight savings is used for this timezone, the UTC times for 
** when daylight savings transitions, and the offset in seconds from 
** UTC. 
*/

void ast_get_dst_info(const time_t * const timep, int *dst_enabled, time_t *dst_start, time_t *dst_end, int *gmt_off, const char * const zone)
{
	int i;	
	int transition1 = -1;
	int transition2 = -1;
	time_t		seconds;
	int  bounds_exceeded = 0;
	time_t  t = *timep;
	const struct state *sp;
	
	if (NULL == dst_enabled)
		return;
	*dst_enabled = 0;

	if (NULL == dst_start || NULL == dst_end || NULL == gmt_off)
		return;

	*gmt_off = 0; 
	
	sp = ast_tzset(zone);
	if (NULL == sp) 
		return;
	
	/* If the desired time exceeds the bounds of the defined time transitions  
	* then give give up on determining DST info and simply look for gmt offset 
	* This requires that I adjust the given time using increments of Gregorian 
	* repeats to place the time within the defined time transitions in the 
	* timezone structure.  
	*/
	if ((sp->goback && t < sp->ats[0]) ||
			(sp->goahead && t > sp->ats[sp->timecnt - 1])) {
		time_t		tcycles;
		int_fast64_t	icycles;

		if (t < sp->ats[0])
			seconds = sp->ats[0] - t;
		else	seconds = t - sp->ats[sp->timecnt - 1];
		--seconds;
		tcycles = seconds / YEARSPERREPEAT / AVGSECSPERYEAR;
		++tcycles;
		icycles = tcycles;
		if (tcycles - icycles >= 1 || icycles - tcycles >= 1)
			return;
		seconds = icycles;
		seconds *= YEARSPERREPEAT;
		seconds *= AVGSECSPERYEAR;
		if (t < sp->ats[0])
			t += seconds;
		else
			t -= seconds;
		
		if (t < sp->ats[0] || t > sp->ats[sp->timecnt - 1])
			return;	/* "cannot happen" */

		bounds_exceeded = 1;
	}

	if (sp->timecnt == 0 || t < sp->ats[0]) {
		/* I have no transition times or I'm before time */
		*dst_enabled = 0;
		/* Find where I can get gmtoff */
		i = 0;
		while (sp->ttis[i].tt_isdst)
			if (++i >= sp->typecnt) {
			i = 0;
			break;
			}
			*gmt_off = sp->ttis[i].tt_gmtoff;
			return;
	} 

	for (i = 1; i < sp->timecnt; ++i) {
		if (t < sp->ats[i]) {
			transition1 = sp->types[i - 1];
			transition2 = sp->types[i];
			break;
		} 
	}
	/* if I found transition times that do not bounded the given time and these correspond to 
		or the bounding zones do not reflect a changes in day light savings, then I do not have dst active */
	if (i >= sp->timecnt || 0 > transition1 || 0 > transition2 ||
			(sp->ttis[transition1].tt_isdst == sp->ttis[transition2].tt_isdst)) {
		*dst_enabled = 0;
		*gmt_off 	 = sp->ttis[sp->types[sp->timecnt -1]].tt_gmtoff;
	} else {
		/* I have valid daylight savings information. */
		if(sp->ttis[transition2].tt_isdst) 
			*gmt_off = sp->ttis[transition1].tt_gmtoff;
		else 
			*gmt_off = sp->ttis[transition2].tt_gmtoff;

		/* If I adjusted the time earlier, indicate that the dst is invalid */
		if (!bounds_exceeded) {
			*dst_enabled = 1;
			/* Determine which of the bounds is the start of daylight savings and which is the end */
			if(sp->ttis[transition2].tt_isdst) {
				*dst_start = sp->ats[i];
				*dst_end = sp->ats[i -1];
			} else {
				*dst_start = sp->ats[i -1];
				*dst_end = sp->ats[i];
			}
		}
	}	
	return;
}

/*
** gmtsub is to gmtime as localsub is to localtime.
*/

static struct ast_tm *gmtsub(const struct timeval *timep, const long offset, struct ast_tm *tmp)
{
	struct ast_tm *	result;
	struct state *sp;

	AST_LIST_LOCK(&zonelist);
	AST_LIST_TRAVERSE(&zonelist, sp, list) {
		if (!strcmp(sp->name, "UTC"))
			break;
	}

	if (!sp) {
		if (!(sp = (struct state *) ast_calloc(1, sizeof *sp)))
			return NULL;
		gmtload(sp);
		AST_LIST_INSERT_TAIL(&zonelist, sp, list);
	}
	AST_LIST_UNLOCK(&zonelist);

	result = timesub(timep, offset, sp, tmp);
#ifdef TM_ZONE
	/*
	** Could get fancy here and deliver something such as
	** "UTC+xxxx" or "UTC-xxxx" if offset is non-zero,
	** but this is no time for a treasure hunt.
	*/
	if (offset != 0)
		tmp->TM_ZONE = "    ";
	else
		tmp->TM_ZONE = sp->chars;
#endif /* defined TM_ZONE */
	return result;
}

/*! \brief
** Return the number of leap years through the end of the given year
** where, to make the math easy, the answer for year zero is defined as zero.
*/

static int leaps_thru_end_of(const int y)
{
	return (y >= 0) ? (y / 4 - y / 100 + y / 400) :
		-(leaps_thru_end_of(-(y + 1)) + 1);
}

static struct ast_tm *timesub(const struct timeval *timep, const long offset, const struct state *sp, struct ast_tm *tmp)
{
	const struct lsinfo *	lp;
	time_t			tdays;
	int			idays;	/* unsigned would be so 2003 */
	long			rem;
	int				y;
	const int *		ip;
	long			corr;
	int			hit;
	int			i;
	long	seconds;


	corr = 0;
	hit = 0;
	i = (sp == NULL) ? 0 : sp->leapcnt;
	while (--i >= 0) {
		lp = &sp->lsis[i];
		if (timep->tv_sec >= lp->ls_trans) {
			if (timep->tv_sec == lp->ls_trans) {
				hit = ((i == 0 && lp->ls_corr > 0) ||
					lp->ls_corr > sp->lsis[i - 1].ls_corr);
				if (hit)
					while (i > 0 &&
						sp->lsis[i].ls_trans ==
						sp->lsis[i - 1].ls_trans + 1 &&
						sp->lsis[i].ls_corr ==
						sp->lsis[i - 1].ls_corr + 1) {
							++hit;
							--i;
					}
			}
			corr = lp->ls_corr;
			break;
		}
	}
	y = EPOCH_YEAR;
	tdays = timep->tv_sec / SECSPERDAY;
	rem = timep->tv_sec - tdays * SECSPERDAY;
	while (tdays < 0 || tdays >= year_lengths[isleap(y)]) {
		int		newy;
		time_t	tdelta;
		int	idelta;
		int	leapdays;

		tdelta = tdays / DAYSPERLYEAR;
		idelta = tdelta;
		if (tdelta - idelta >= 1 || idelta - tdelta >= 1)
			return NULL;
		if (idelta == 0)
			idelta = (tdays < 0) ? -1 : 1;
		newy = y;
		if (increment_overflow(&newy, idelta))
			return NULL;
		leapdays = leaps_thru_end_of(newy - 1) -
			leaps_thru_end_of(y - 1);
		tdays -= ((time_t) newy - y) * DAYSPERNYEAR;