xref: /dragonfly/gnu/usr.bin/rcs/lib/maketime.c (revision b40e316c) 
1 /* Convert struct partime into time_t.  */
2 
3 /* Copyright 1992, 1993, 1994, 1995 Paul Eggert
4    Distributed under license by the Free Software Foundation, Inc.
5 
6 This file is part of RCS.
7 
8 RCS is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
11 any later version.
12 
13 RCS is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16 GNU General Public License for more details.
17 
18 You should have received a copy of the GNU General Public License
19 along with RCS; see the file COPYING.
20 If not, write to the Free Software Foundation,
21 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
22 
23 Report problems and direct all questions to:
24 
25     rcs-bugs@cs.purdue.edu
26 */
27 
28 /*
29  * $FreeBSD: src/gnu/usr.bin/rcs/lib/maketime.c,v 1.7 1999/08/27 23:36:43 peter Exp $
30  * $DragonFly: src/gnu/usr.bin/rcs/lib/maketime.c,v 1.2 2003/06/17 04:25:47 dillon Exp $
31  */
32 
33 #if has_conf_h
34 #	include "conf.h"
35 #else
36 #	ifdef __STDC__
37 #		define P(x) x
38 #	else
39 #		define const
40 #		define P(x) ()
41 #	endif
42 #	include <stdlib.h>
43 #	include <time.h>
44 #endif
45 
46 #include "partime.h"
47 #include "maketime.h"
48 
49 static int isleap P((int));
50 static int month_days P((struct tm const*));
51 static time_t maketime P((struct partime const*,time_t));
52 
53 /*
54 * For maximum portability, use only localtime and gmtime.
55 * Make no assumptions about the time_t epoch or the range of time_t values.
56 * Avoid mktime because it's not universal and because there's no easy,
57 * portable way for mktime to yield the inverse of gmtime.
58 */
59 
60 #define TM_YEAR_ORIGIN 1900
61 
62 	static int
63 isleap(y)
64 	int y;
65 {
66 	return (y&3) == 0  &&  (y%100 != 0 || y%400 == 0);
67 }
68 
69 static int const month_yday[] = {
70 	/* days in year before start of months 0-12 */
71 	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
72 };
73 
74 /* Yield the number of days in TM's month.  */
75 	static int
76 month_days(tm)
77 	struct tm const *tm;
78 {
79 	int m = tm->tm_mon;
80 	return month_yday[m+1] - month_yday[m]
81 		+ (m==1 && isleap(tm->tm_year + TM_YEAR_ORIGIN));
82 }
83 
84 /*
85 * Convert UNIXTIME to struct tm form.
86 * Use gmtime if available and if !LOCALZONE, localtime otherwise.
87 */
88 	struct tm *
89 time2tm(unixtime, localzone)
90 	time_t unixtime;
91 	int localzone;
92 {
93 	struct tm *tm;
94 #	if TZ_must_be_set
95 		static char const *TZ;
96 		if (!TZ  &&  !(TZ = getenv("TZ")))
97 			faterror("The TZ environment variable is not set; please set it to your timezone");
98 #	endif
99 	if (localzone  ||  !(tm = gmtime(&unixtime)))
100 		tm = localtime(&unixtime);
101 	return tm;
102 }
103 
104 /* Yield A - B, measured in seconds.  */
105 	time_t
106 difftm(a, b)
107 	struct tm const *a, *b;
108 {
109 	int ay = a->tm_year + (TM_YEAR_ORIGIN - 1);
110 	int by = b->tm_year + (TM_YEAR_ORIGIN - 1);
111 	int difference_in_day_of_year = a->tm_yday - b->tm_yday;
112 	int intervening_leap_days = (
113 		((ay >> 2) - (by >> 2))
114 		- (ay/100 - by/100)
115 		+ ((ay/100 >> 2) - (by/100 >> 2))
116 	);
117 	time_t difference_in_years = ay - by;
118 	time_t difference_in_days = (
119 		difference_in_years*365
120 		+ (intervening_leap_days + difference_in_day_of_year)
121 	);
122 	return
123 		(
124 			(
125 				24*difference_in_days
126 				+ (a->tm_hour - b->tm_hour)
127 			)*60 + (a->tm_min - b->tm_min)
128 		)*60 + (a->tm_sec - b->tm_sec);
129 }
130 
131 /*
132 * Adjust time T by adding SECONDS.  SECONDS must be at most 24 hours' worth.
133 * Adjust only T's year, mon, mday, hour, min and sec members;
134 * plus adjust wday if it is defined.
135 */
136 	void
137 adjzone(t, seconds)
138 	register struct tm *t;
139 	long seconds;
140 {
141 	/*
142 	* This code can be off by a second if SECONDS is not a multiple of 60,
143 	* if T is local time, and if a leap second happens during this minute.
144 	* But this bug has never occurred, and most likely will not ever occur.
145 	* Liberia, the last country for which SECONDS % 60 was nonzero,
146 	* switched to UTC in May 1972; the first leap second was in June 1972.
147 	*/
148 	int leap_second = t->tm_sec == 60;
149 	long sec = seconds + (t->tm_sec - leap_second);
150 	if (sec < 0) {
151 	    if ((t->tm_min -= (59-sec)/60) < 0) {
152 		if ((t->tm_hour -= (59-t->tm_min)/60) < 0) {
153 		    t->tm_hour += 24;
154 		    if (TM_DEFINED(t->tm_wday)  &&  --t->tm_wday < 0)
155 			t->tm_wday = 6;
156 		    if (--t->tm_mday <= 0) {
157 			if (--t->tm_mon < 0) {
158 			    --t->tm_year;
159 			    t->tm_mon = 11;
160 			}
161 			t->tm_mday = month_days(t);
162 		    }
163 		}
164 		t->tm_min += 24 * 60;
165 	    }
166 	    sec += 24L * 60 * 60;
167 	} else
168 	    if (60 <= (t->tm_min += sec/60))
169 		if (24 <= (t->tm_hour += t->tm_min/60)) {
170 		    t->tm_hour -= 24;
171 		    if (TM_DEFINED(t->tm_wday)  &&  ++t->tm_wday == 7)
172 			t->tm_wday = 0;
173 		    if (month_days(t) < ++t->tm_mday) {
174 			if (11 < ++t->tm_mon) {
175 			    ++t->tm_year;
176 			    t->tm_mon = 0;
177 			}
178 			t->tm_mday = 1;
179 		    }
180 		}
181 	t->tm_min %= 60;
182 	t->tm_sec = (int) (sec%60) + leap_second;
183 }
184 
185 /*
186 * Convert TM to time_t, using localtime if LOCALZONE and gmtime otherwise.
187 * Use only TM's year, mon, mday, hour, min, and sec members.
188 * Ignore TM's old tm_yday and tm_wday, but fill in their correct values.
189 * Yield -1 on failure (e.g. a member out of range).
190 * Posix 1003.1-1990 doesn't allow leap seconds, but some implementations
191 * have them anyway, so allow them if localtime/gmtime does.
192 */
193 	time_t
194 tm2time(tm, localzone)
195 	struct tm *tm;
196 	int localzone;
197 {
198 	/* Cache the most recent t,tm pairs; 1 for gmtime, 1 for localtime.  */
199 	static time_t t_cache[2];
200 	static struct tm tm_cache[2];
201 
202 	time_t d, gt;
203 	struct tm const *gtm;
204 	/*
205 	* The maximum number of iterations should be enough to handle any
206 	* combinations of leap seconds, time zone rule changes, and solar time.
207 	* 4 is probably enough; we use a bigger number just to be safe.
208 	*/
209 	int remaining_tries = 8;
210 
211 	/* Avoid subscript errors.  */
212 	if (12 <= (unsigned)tm->tm_mon)
213 	    return -1;
214 
215 	tm->tm_yday = month_yday[tm->tm_mon] + tm->tm_mday
216 		-  (tm->tm_mon<2  ||  ! isleap(tm->tm_year + TM_YEAR_ORIGIN));
217 
218 	/* Make a first guess.  */
219 	gt = t_cache[localzone];
220 	gtm = gt ? &tm_cache[localzone] : time2tm(gt,localzone);
221 
222 	/* Repeatedly use the error from the guess to improve the guess.  */
223 	while ((d = difftm(tm, gtm)) != 0) {
224 		if (--remaining_tries == 0)
225 			return -1;
226 		gt += d;
227 		gtm = time2tm(gt,localzone);
228 	}
229 	t_cache[localzone] = gt;
230 	tm_cache[localzone] = *gtm;
231 
232 	/*
233 	* Check that the guess actually matches;
234 	* overflow can cause difftm to yield 0 even on differing times,
235 	* or tm may have members out of range (e.g. bad leap seconds).
236 	*/
237 	if (   (tm->tm_year ^ gtm->tm_year)
238 	    |  (tm->tm_mon  ^ gtm->tm_mon)
239 	    |  (tm->tm_mday ^ gtm->tm_mday)
240 	    |  (tm->tm_hour ^ gtm->tm_hour)
241 	    |  (tm->tm_min  ^ gtm->tm_min)
242 	    |  (tm->tm_sec  ^ gtm->tm_sec))
243 		return -1;
244 
245 	tm->tm_wday = gtm->tm_wday;
246 	return gt;
247 }
248 
249 /*
250 * Check *PT and convert it to time_t.
251 * If it is incompletely specified, use DEFAULT_TIME to fill it out.
252 * Use localtime if PT->zone is the special value TM_LOCAL_ZONE.
253 * Yield -1 on failure.
254 * ISO 8601 day-of-year and week numbers are not yet supported.
255 */
256 	static time_t
257 maketime(pt, default_time)
258 	struct partime const *pt;
259 	time_t default_time;
260 {
261 	int localzone, wday;
262 	struct tm tm;
263 	struct tm *tm0 = 0;
264 	time_t r;
265 
266 	tm0 = 0; /* Keep gcc -Wall happy.  */
267 	localzone = pt->zone==TM_LOCAL_ZONE;
268 
269 	tm = pt->tm;
270 
271 	if (TM_DEFINED(pt->ymodulus) || !TM_DEFINED(tm.tm_year)) {
272 	    /* Get tm corresponding to current time.  */
273 	    tm0 = time2tm(default_time, localzone);
274 	    if (!localzone)
275 		adjzone(tm0, pt->zone);
276 	}
277 
278 	if (TM_DEFINED(pt->ymodulus))
279 	    tm.tm_year +=
280 		(tm0->tm_year + TM_YEAR_ORIGIN)/pt->ymodulus * pt->ymodulus;
281 	else if (!TM_DEFINED(tm.tm_year)) {
282 	    /* Set default year, month, day from current time.  */
283 	    tm.tm_year = tm0->tm_year + TM_YEAR_ORIGIN;
284 	    if (!TM_DEFINED(tm.tm_mon)) {
285 		tm.tm_mon = tm0->tm_mon;
286 		if (!TM_DEFINED(tm.tm_mday))
287 		    tm.tm_mday = tm0->tm_mday;
288 	    }
289 	}
290 
291 	/* Convert from partime year (Gregorian) to Posix year.  */
292 	tm.tm_year -= TM_YEAR_ORIGIN;
293 
294 	/* Set remaining default fields to be their minimum values.  */
295 	if (!TM_DEFINED(tm.tm_mon)) tm.tm_mon = 0;
296 	if (!TM_DEFINED(tm.tm_mday)) tm.tm_mday = 1;
297 	if (!TM_DEFINED(tm.tm_hour)) tm.tm_hour = 0;
298 	if (!TM_DEFINED(tm.tm_min)) tm.tm_min = 0;
299 	if (!TM_DEFINED(tm.tm_sec)) tm.tm_sec = 0;
300 
301 	if (!localzone)
302 	    adjzone(&tm, -pt->zone);
303 	wday = tm.tm_wday;
304 
305 	/* Convert and fill in the rest of the tm.  */
306 	r = tm2time(&tm, localzone);
307 
308 	/* Check weekday.  */
309 	if (r != -1  &&  TM_DEFINED(wday)  &&  wday != tm.tm_wday)
310 		return -1;
311 
312 	return r;
313 }
314 
315 /* Parse a free-format date in SOURCE, yielding a Unix format time.  */
316 	time_t
317 str2time(source, default_time, default_zone)
318 	char const *source;
319 	time_t default_time;
320 	long default_zone;
321 {
322 	struct partime pt;
323 
324 	if (*partime(source, &pt))
325 	    return -1;
326 	if (pt.zone == TM_UNDEFINED_ZONE)
327 	    pt.zone = default_zone;
328 	return maketime(&pt, default_time);
329 }
330 
331 #if TEST
332 #include <stdio.h>
333 	int
334 main(argc, argv) int argc; char **argv;
335 {
336 	time_t default_time = time((time_t *)0);
337 	long default_zone = argv[1] ? atol(argv[1]) : 0;
338 	char buf[1000];
339 	while (fgets(buf, 1000, stdin)) {
340 		time_t t = str2time(buf, default_time, default_zone);
341 		printf("%s", asctime(gmtime(&t)));
342 	}
343 	return 0;
344 }
345 #endif
346