gnu/usr.bin/rcs/lib/maketime.c

   1 /*      $NetBSD: maketime.c,v 1.1.1.2 1996/10/13 21:57:09 veego 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
   8 This file is part of RCS.
   9
  10 RCS is free software; you can redistribute it and/or modify
  11 it under the terms of the GNU General Public License as published by
  12 the Free Software Foundation; either version 2, or (at your option)
  13 any later version.
  14
  15 RCS is distributed in the hope that it will be useful,
  16 but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 GNU General Public License for more details.
  19
  20 You should have received a copy of the GNU General Public License
  21 along with RCS; see the file COPYING.
  22 If not, write to the Free Software Foundation,
  23 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  24
  25 Report 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
  47 char const maketId[]
  48   = "Id: maketime.c,v 5.11 1995/06/16 06:19:24 eggert Exp";
  49
  50 static int isleap P((int));
  51 static int month_days P((struct tm const*));
  52 static 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
  64 isleap(y)
  65         int y;
  66 {
  67         return (y&3) == 0  &&  (y%100 != 0 || y%400 == 0);
  68 }
  69
  70 static 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
  77 month_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 *
  90 time2tm(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
 107 difftm(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
 138 adjzone(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
 195 tm2time(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
 258 maketime(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
 318 str2time(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
 335 main(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 (fgets(buf, 1000, stdin)) {
 341                 time_t t = str2time(buf, default_time, default_zone);
 342                 printf("%s", asctime(gmtime(&t)));
 343         }
 344         return 0;
 345 }
 346 #endif