1/*	$NetBSD: maketime.c,v 1.1.1.1 2016/01/14 03:05:06 christos Exp $	*/
2
3/* Convert struct partime into time_t.  */
4
5/* Copyright 1992, 1993, 1994, 1995 Paul Eggert
6   Distributed under license by the Free Software Foundation, Inc.
7
8This file is part of RCS.
9
10RCS is free software; you can redistribute it and/or modify
11it under the terms of the GNU General Public License as published by
12the Free Software Foundation; either version 2, or (at your option)
13any later version.
14
15RCS is distributed in the hope that it will be useful,
16but WITHOUT ANY WARRANTY; without even the implied warranty of
17MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18GNU General Public License for more details.
19
20You should have received a copy of the GNU General Public License
21along with RCS; see the file COPYING.
22If not, write to the Free Software Foundation,
2359 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24
25Report problems and direct all questions to:
26
27    rcs-bugs@cs.purdue.edu
28
29*/
30
31#if has_conf_h
32#	include "conf.h"
33#else
34#	ifdef __STDC__
35#		define P(x) x
36#	else
37#		define const
38#		define P(x) ()
39#	endif
40#	include <stdlib.h>
41#	include <time.h>
42#endif
43
44#include "partime.h"
45#include "maketime.h"
46
47char const maketId[]
48  = "Id: maketime.c,v 5.11 1995/06/16 06:19:24 eggert Exp ";
49
50static int isleap P((int));
51static int month_days P((struct tm const*));
52static time_t maketime P((struct partime const*,time_t));
53
54/*
55* For maximum portability, use only localtime and gmtime.
56* Make no assumptions about the time_t epoch or the range of time_t values.
57* Avoid mktime because it's not universal and because there's no easy,
58* portable way for mktime to yield the inverse of gmtime.
59*/
60
61#define TM_YEAR_ORIGIN 1900
62
63	static int
64isleap(y)
65	int y;
66{
67	return (y&3) == 0  &&  (y%100 != 0 || y%400 == 0);
68}
69
70static int const month_yday[] = {
71	/* days in year before start of months 0-12 */
72	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
73};
74
75/* Yield the number of days in TM's month.  */
76	static int
77month_days(tm)
78	struct tm const *tm;
79{
80	int m = tm->tm_mon;
81	return month_yday[m+1] - month_yday[m]
82		+ (m==1 && isleap(tm->tm_year + TM_YEAR_ORIGIN));
83}
84
85/*
86* Convert UNIXTIME to struct tm form.
87* Use gmtime if available and if !LOCALZONE, localtime otherwise.
88*/
89	struct tm *
90time2tm(unixtime, localzone)
91	time_t unixtime;
92	int localzone;
93{
94	struct tm *tm;
95#	if TZ_must_be_set
96		static char const *TZ;
97		if (!TZ  &&  !(TZ = getenv("TZ")))
98			faterror("The TZ environment variable is not set; please set it to your timezone");
99#	endif
100	if (localzone  ||  !(tm = gmtime(&unixtime)))
101		tm = localtime(&unixtime);
102	return tm;
103}
104
105/* Yield A - B, measured in seconds.  */
106	time_t
107difftm(a, b)
108	struct tm const *a, *b;
109{
110	int ay = a->tm_year + (TM_YEAR_ORIGIN - 1);
111	int by = b->tm_year + (TM_YEAR_ORIGIN - 1);
112	int difference_in_day_of_year = a->tm_yday - b->tm_yday;
113	int intervening_leap_days = (
114		((ay >> 2) - (by >> 2))
115		- (ay/100 - by/100)
116		+ ((ay/100 >> 2) - (by/100 >> 2))
117	);
118	time_t difference_in_years = ay - by;
119	time_t difference_in_days = (
120		difference_in_years*365
121		+ (intervening_leap_days + difference_in_day_of_year)
122	);
123	return
124		(
125			(
126				24*difference_in_days
127				+ (a->tm_hour - b->tm_hour)
128			)*60 + (a->tm_min - b->tm_min)
129		)*60 + (a->tm_sec - b->tm_sec);
130}
131
132/*
133* Adjust time T by adding SECONDS.  SECONDS must be at most 24 hours' worth.
134* Adjust only T's year, mon, mday, hour, min and sec members;
135* plus adjust wday if it is defined.
136*/
137	void
138adjzone(t, seconds)
139	register struct tm *t;
140	long seconds;
141{
142	/*
143	* This code can be off by a second if SECONDS is not a multiple of 60,
144	* if T is local time, and if a leap second happens during this minute.
145	* But this bug has never occurred, and most likely will not ever occur.
146	* Liberia, the last country for which SECONDS % 60 was nonzero,
147	* switched to UTC in May 1972; the first leap second was in June 1972.
148	*/
149	int leap_second = t->tm_sec == 60;
150	long sec = seconds + (t->tm_sec - leap_second);
151	if (sec < 0) {
152	    if ((t->tm_min -= (59-sec)/60) < 0) {
153		if ((t->tm_hour -= (59-t->tm_min)/60) < 0) {
154		    t->tm_hour += 24;
155		    if (TM_DEFINED(t->tm_wday)  &&  --t->tm_wday < 0)
156			t->tm_wday = 6;
157		    if (--t->tm_mday <= 0) {
158			if (--t->tm_mon < 0) {
159			    --t->tm_year;
160			    t->tm_mon = 11;
161			}
162			t->tm_mday = month_days(t);
163		    }
164		}
165		t->tm_min += 24 * 60;
166	    }
167	    sec += 24L * 60 * 60;
168	} else
169	    if (60 <= (t->tm_min += sec/60))
170		if (24 <= (t->tm_hour += t->tm_min/60)) {
171		    t->tm_hour -= 24;
172		    if (TM_DEFINED(t->tm_wday)  &&  ++t->tm_wday == 7)
173			t->tm_wday = 0;
174		    if (month_days(t) < ++t->tm_mday) {
175			if (11 < ++t->tm_mon) {
176			    ++t->tm_year;
177			    t->tm_mon = 0;
178			}
179			t->tm_mday = 1;
180		    }
181		}
182	t->tm_min %= 60;
183	t->tm_sec = (int) (sec%60) + leap_second;
184}
185
186/*
187* Convert TM to time_t, using localtime if LOCALZONE and gmtime otherwise.
188* Use only TM's year, mon, mday, hour, min, and sec members.
189* Ignore TM's old tm_yday and tm_wday, but fill in their correct values.
190* Yield -1 on failure (e.g. a member out of range).
191* Posix 1003.1-1990 doesn't allow leap seconds, but some implementations
192* have them anyway, so allow them if localtime/gmtime does.
193*/
194	time_t
195tm2time(tm, localzone)
196	struct tm *tm;
197	int localzone;
198{
199	/* Cache the most recent t,tm pairs; 1 for gmtime, 1 for localtime.  */
200	static time_t t_cache[2];
201	static struct tm tm_cache[2];
202
203	time_t d, gt;
204	struct tm const *gtm;
205	/*
206	* The maximum number of iterations should be enough to handle any
207	* combinations of leap seconds, time zone rule changes, and solar time.
208	* 4 is probably enough; we use a bigger number just to be safe.
209	*/
210	int remaining_tries = 8;
211
212	/* Avoid subscript errors.  */
213	if (12 <= (unsigned)tm->tm_mon)
214	    return -1;
215
216	tm->tm_yday = month_yday[tm->tm_mon] + tm->tm_mday
217		-  (tm->tm_mon<2  ||  ! isleap(tm->tm_year + TM_YEAR_ORIGIN));
218
219	/* Make a first guess.  */
220	gt = t_cache[localzone];
221	gtm = gt ? &tm_cache[localzone] : time2tm(gt,localzone);
222
223	/* Repeatedly use the error from the guess to improve the guess.  */
224	while ((d = difftm(tm, gtm)) != 0) {
225		if (--remaining_tries == 0)
226			return -1;
227		gt += d;
228		gtm = time2tm(gt,localzone);
229	}
230	t_cache[localzone] = gt;
231	tm_cache[localzone] = *gtm;
232
233	/*
234	* Check that the guess actually matches;
235	* overflow can cause difftm to yield 0 even on differing times,
236	* or tm may have members out of range (e.g. bad leap seconds).
237	*/
238	if (   (tm->tm_year ^ gtm->tm_year)
239	    |  (tm->tm_mon  ^ gtm->tm_mon)
240	    |  (tm->tm_mday ^ gtm->tm_mday)
241	    |  (tm->tm_hour ^ gtm->tm_hour)
242	    |  (tm->tm_min  ^ gtm->tm_min)
243	    |  (tm->tm_sec  ^ gtm->tm_sec))
244		return -1;
245
246	tm->tm_wday = gtm->tm_wday;
247	return gt;
248}
249
250/*
251* Check *PT and convert it to time_t.
252* If it is incompletely specified, use DEFAULT_TIME to fill it out.
253* Use localtime if PT->zone is the special value TM_LOCAL_ZONE.
254* Yield -1 on failure.
255* ISO 8601 day-of-year and week numbers are not yet supported.
256*/
257	static time_t
258maketime(pt, default_time)
259	struct partime const *pt;
260	time_t default_time;
261{
262	int localzone, wday;
263	struct tm tm;
264	struct tm *tm0 = 0;
265	time_t r;
266
267	tm0 = 0; /* Keep gcc -Wall happy.  */
268	localzone = pt->zone==TM_LOCAL_ZONE;
269
270	tm = pt->tm;
271
272	if (TM_DEFINED(pt->ymodulus) || !TM_DEFINED(tm.tm_year)) {
273	    /* Get tm corresponding to current time.  */
274	    tm0 = time2tm(default_time, localzone);
275	    if (!localzone)
276		adjzone(tm0, pt->zone);
277	}
278
279	if (TM_DEFINED(pt->ymodulus))
280	    tm.tm_year +=
281		(tm0->tm_year + TM_YEAR_ORIGIN)/pt->ymodulus * pt->ymodulus;
282	else if (!TM_DEFINED(tm.tm_year)) {
283	    /* Set default year, month, day from current time.  */
284	    tm.tm_year = tm0->tm_year + TM_YEAR_ORIGIN;
285	    if (!TM_DEFINED(tm.tm_mon)) {
286		tm.tm_mon = tm0->tm_mon;
287		if (!TM_DEFINED(tm.tm_mday))
288		    tm.tm_mday = tm0->tm_mday;
289	    }
290	}
291
292	/* Convert from partime year (Gregorian) to Posix year.  */
293	tm.tm_year -= TM_YEAR_ORIGIN;
294
295	/* Set remaining default fields to be their minimum values.  */
296	if (!TM_DEFINED(tm.tm_mon)) tm.tm_mon = 0;
297	if (!TM_DEFINED(tm.tm_mday)) tm.tm_mday = 1;
298	if (!TM_DEFINED(tm.tm_hour)) tm.tm_hour = 0;
299	if (!TM_DEFINED(tm.tm_min)) tm.tm_min = 0;
300	if (!TM_DEFINED(tm.tm_sec)) tm.tm_sec = 0;
301
302	if (!localzone)
303	    adjzone(&tm, -pt->zone);
304	wday = tm.tm_wday;
305
306	/* Convert and fill in the rest of the tm.  */
307	r = tm2time(&tm, localzone);
308
309	/* Check weekday.  */
310	if (r != -1  &&  TM_DEFINED(wday)  &&  wday != tm.tm_wday)
311		return -1;
312
313	return r;
314}
315
316/* Parse a free-format date in SOURCE, yielding a Unix format time.  */
317	time_t
318str2time(source, default_time, default_zone)
319	char const *source;
320	time_t default_time;
321	long default_zone;
322{
323	struct partime pt;
324
325	if (*partime(source, &pt))
326	    return -1;
327	if (pt.zone == TM_UNDEFINED_ZONE)
328	    pt.zone = default_zone;
329	return maketime(&pt, default_time);
330}
331
332#if TEST
333#include <stdio.h>
334	int
335main(argc, argv) int argc; char **argv;
336{
337	time_t default_time = time((time_t *)0);
338	long default_zone = argv[1] ? atol(argv[1]) : 0;
339	char buf[1000];
340	while (gets(buf)) {
341		time_t t = str2time(buf, default_time, default_zone);
342		printf("%s", asctime(gmtime(&t)));
343	}
344	return 0;
345}
346#endif
347