jcs.org
mutt stable branch with some hacks
1/*
2 * Copyright (C) 1996-2000 Michael R. Elkins <me@mutt.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
17 */
18
19#if HAVE_CONFIG_H
20# include "config.h"
21#endif
22
23#include "mutt.h"
24#include <string.h>
25
26/* returns the seconds east of UTC given `g' and its corresponding gmtime()
27 representation */
28static time_t compute_tz (time_t g, struct tm *utc)
29{
30 struct tm *lt = localtime (&g);
31 time_t t;
32 int yday;
33
34 t = (((lt->tm_hour - utc->tm_hour) * 60) + (lt->tm_min - utc->tm_min)) * 60;
35
36 if ((yday = (lt->tm_yday - utc->tm_yday)))
37 {
38 /* This code is optimized to negative timezones (West of Greenwich) */
39 if (yday == -1 || /* UTC passed midnight before localtime */
40 yday > 1) /* UTC passed new year before localtime */
41 t -= 24 * 60 * 60;
42 else
43 t += 24 * 60 * 60;
44 }
45
46 return t;
47}
48
49/* Returns the local timezone in seconds east of UTC for the time t,
50 * or for the current time if t is zero.
51 */
52time_t mutt_local_tz (time_t t)
53{
54 struct tm *ptm;
55 struct tm utc;
56
57 if (!t)
58 t = time (NULL);
59 ptm = gmtime (&t);
60 /* need to make a copy because gmtime/localtime return a pointer to
61 static memory (grr!) */
62 memcpy (&utc, ptm, sizeof (utc));
63 return (compute_tz (t, &utc));
64}
65
66/* theoretically time_t can be float but it is integer on most (if not all) systems */
67#define TIME_T_MAX ((((time_t) 1 << (sizeof(time_t) * 8 - 2)) - 1) * 2 + 1)
68#define TM_YEAR_MAX (1970 + (((((TIME_T_MAX - 59) / 60) - 59) / 60) - 23) / 24 / 366)
69
70/* converts struct tm to time_t, but does not take the local timezone into
71 account unless ``local'' is nonzero */
72time_t mutt_mktime (struct tm *t, int local)
73{
74 time_t g;
75 int year;
76
77 static const int AccumDaysPerMonth[12] = {
78 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
79 };
80
81 /* Large years, even those that are less than INT_MAX, seem to give
82 * gmtime() and localtime() indigestion. Cap the year at 9999 to
83 * prevent those from returning NULL. */
84 year = (t->tm_year > 9999-1900) ? 9999-1900 : t->tm_year;
85
86 /* Prevent an integer overflow for 32-bit time_t platforms.
87 * The time_t cast is an attempt to silence a clang range warning. */
88 if ((time_t)year > TM_YEAR_MAX)
89 return TIME_T_MAX;
90
91 /* Compute the number of days since January 1 in the same year */
92 g = AccumDaysPerMonth [t->tm_mon % 12];
93
94 /* The leap years are 1972 and every 4. year until 2096,
95 * but this algorithm will fail after year 2099 */
96 g += t->tm_mday;
97 if ((year % 4) || t->tm_mon < 2)
98 g--;
99 t->tm_yday = g;
100
101 /* Compute the number of days since January 1, 1970 */
102 g += (year - 70) * (time_t)365;
103 g += (year - 69) / 4;
104
105 /* Compute the number of hours */
106 g *= 24;
107 g += t->tm_hour;
108
109 /* Compute the number of minutes */
110 g *= 60;
111 g += t->tm_min;
112
113 /* Compute the number of seconds */
114 g *= 60;
115 g += t->tm_sec;
116
117 if (local)
118 g -= compute_tz (g, t);
119
120 return (g);
121}
122
123/* Safely add a timeout to a given time_t value, truncating instead of
124 * overflowing. */
125time_t mutt_add_timeout (time_t now, long timeout)
126{
127 if (timeout < 0)
128 return now;
129
130 if (TIME_T_MAX - now < timeout)
131 return TIME_T_MAX;
132
133 return now + timeout;
134}
135
136/* Return 1 if month is February of leap year, else 0 */
137static int isLeapYearFeb (struct tm *tm)
138{
139 if (tm->tm_mon == 1)
140 {
141 int y = tm->tm_year + 1900;
142 return (((y & 3) == 0) && (((y % 100) != 0) || ((y % 400) == 0)));
143 }
144 return (0);
145}
146
147void mutt_normalize_time (struct tm *tm)
148{
149 static const char DaysPerMonth[12] = {
150 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
151 };
152 int nLeap;
153
154 while (tm->tm_sec < 0)
155 {
156 tm->tm_sec += 60;
157 tm->tm_min--;
158 }
159 while (tm->tm_sec >= 60)
160 {
161 tm->tm_sec -= 60;
162 tm->tm_min++;
163 }
164 while (tm->tm_min < 0)
165 {
166 tm->tm_min += 60;
167 tm->tm_hour--;
168 }
169 while (tm->tm_min >= 60)
170 {
171 tm->tm_min -= 60;
172 tm->tm_hour++;
173 }
174 while (tm->tm_hour < 0)
175 {
176 tm->tm_hour += 24;
177 tm->tm_mday--;
178 }
179 while (tm->tm_hour >= 24)
180 {
181 tm->tm_hour -= 24;
182 tm->tm_mday++;
183 }
184 /* use loops on NNNdwmy user input values? */
185 while (tm->tm_mon < 0)
186 {
187 tm->tm_mon += 12;
188 tm->tm_year--;
189 }
190 while (tm->tm_mon >= 12)
191 {
192 tm->tm_mon -= 12;
193 tm->tm_year++;
194 }
195 while (tm->tm_mday <= 0)
196 {
197 if (tm->tm_mon)
198 tm->tm_mon--;
199 else
200 {
201 tm->tm_mon = 11;
202 tm->tm_year--;
203 }
204 tm->tm_mday += DaysPerMonth[tm->tm_mon] + isLeapYearFeb (tm);
205 }
206 while (tm->tm_mday > (DaysPerMonth[tm->tm_mon] +
207 (nLeap = isLeapYearFeb (tm))))
208 {
209 tm->tm_mday -= DaysPerMonth[tm->tm_mon] + nLeap;
210 if (tm->tm_mon < 11)
211 tm->tm_mon++;
212 else
213 {
214 tm->tm_mon = 0;
215 tm->tm_year++;
216 }
217 }
218}