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
76 static const int AccumDaysPerMonth[12] = {
77 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
78 };
79
80 /* Prevent an integer overflow.
81 * The time_t cast is an attempt to silence a clang range warning. */
82 if ((time_t)t->tm_year > TM_YEAR_MAX)
83 return TIME_T_MAX;
84
85 /* Compute the number of days since January 1 in the same year */
86 g = AccumDaysPerMonth [t->tm_mon % 12];
87
88 /* The leap years are 1972 and every 4. year until 2096,
89 * but this algorithm will fail after year 2099 */
90 g += t->tm_mday;
91 if ((t->tm_year % 4) || t->tm_mon < 2)
92 g--;
93 t->tm_yday = g;
94
95 /* Compute the number of days since January 1, 1970 */
96 g += (t->tm_year - 70) * (time_t)365;
97 g += (t->tm_year - 69) / 4;
98
99 /* Compute the number of hours */
100 g *= 24;
101 g += t->tm_hour;
102
103 /* Compute the number of minutes */
104 g *= 60;
105 g += t->tm_min;
106
107 /* Compute the number of seconds */
108 g *= 60;
109 g += t->tm_sec;
110
111 if (local)
112 g -= compute_tz (g, t);
113
114 return (g);
115}
116
117/* Return 1 if month is February of leap year, else 0 */
118static int isLeapYearFeb (struct tm *tm)
119{
120 if (tm->tm_mon == 1)
121 {
122 int y = tm->tm_year + 1900;
123 return (((y & 3) == 0) && (((y % 100) != 0) || ((y % 400) == 0)));
124 }
125 return (0);
126}
127
128void mutt_normalize_time (struct tm *tm)
129{
130 static const char DaysPerMonth[12] = {
131 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
132 };
133 int nLeap;
134
135 while (tm->tm_sec < 0)
136 {
137 tm->tm_sec += 60;
138 tm->tm_min--;
139 }
140 while (tm->tm_sec >= 60)
141 {
142 tm->tm_sec -= 60;
143 tm->tm_min++;
144 }
145 while (tm->tm_min < 0)
146 {
147 tm->tm_min += 60;
148 tm->tm_hour--;
149 }
150 while (tm->tm_min >= 60)
151 {
152 tm->tm_min -= 60;
153 tm->tm_hour++;
154 }
155 while (tm->tm_hour < 0)
156 {
157 tm->tm_hour += 24;
158 tm->tm_mday--;
159 }
160 while (tm->tm_hour >= 24)
161 {
162 tm->tm_hour -= 24;
163 tm->tm_mday++;
164 }
165 /* use loops on NNNdwmy user input values? */
166 while (tm->tm_mon < 0)
167 {
168 tm->tm_mon += 12;
169 tm->tm_year--;
170 }
171 while (tm->tm_mon >= 12)
172 {
173 tm->tm_mon -= 12;
174 tm->tm_year++;
175 }
176 while (tm->tm_mday <= 0)
177 {
178 if (tm->tm_mon)
179 tm->tm_mon--;
180 else
181 {
182 tm->tm_mon = 11;
183 tm->tm_year--;
184 }
185 tm->tm_mday += DaysPerMonth[tm->tm_mon] + isLeapYearFeb (tm);
186 }
187 while (tm->tm_mday > (DaysPerMonth[tm->tm_mon] +
188 (nLeap = isLeapYearFeb (tm))))
189 {
190 tm->tm_mday -= DaysPerMonth[tm->tm_mon] + nLeap;
191 if (tm->tm_mon < 11)
192 tm->tm_mon++;
193 else
194 {
195 tm->tm_mon = 0;
196 tm->tm_year++;
197 }
198 }
199}