[efi] Include installed protocol list in unknown handle names
[ipxe.git] / src / core / time.c
1 /*
2 * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * 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
17 * 02110-1301, USA.
18 *
19 * You can also choose to distribute this program under the terms of
20 * the Unmodified Binary Distribution Licence (as given in the file
21 * COPYING.UBDL), provided that you have satisfied its requirements.
22 */
23
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25
26 #include <time.h>
27
28 /** @file
29 *
30 * Date and time
31 *
32 * POSIX:2008 section 4.15 defines "seconds since the Epoch" as an
33 * abstract measure approximating the number of seconds that have
34 * elapsed since the Epoch, excluding leap seconds. The formula given
35 * is
36 *
37 * tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
38 * (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
39 * ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400
40 *
41 * This calculation assumes that leap years occur in each year that is
42 * either divisible by 4 but not divisible by 100, or is divisible by
43 * 400.
44 */
45
46 /** Days of week (for debugging) */
47 static const char *weekdays[] = {
48 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
49 };
50
51 /**
52 * Determine whether or not year is a leap year
53 *
54 * @v tm_year Years since 1900
55 * @v is_leap_year Year is a leap year
56 */
57 static int is_leap_year ( int tm_year ) {
58 int leap_year = 0;
59
60 if ( ( tm_year % 4 ) == 0 )
61 leap_year = 1;
62 if ( ( tm_year % 100 ) == 0 )
63 leap_year = 0;
64 if ( ( tm_year % 400 ) == 100 )
65 leap_year = 1;
66
67 return leap_year;
68 }
69
70 /**
71 * Calculate number of leap years since 1900
72 *
73 * @v tm_year Years since 1900
74 * @v num_leap_years Number of leap years
75 */
76 static int leap_years_to_end ( int tm_year ) {
77 int leap_years = 0;
78
79 leap_years += ( tm_year / 4 );
80 leap_years -= ( tm_year / 100 );
81 leap_years += ( ( tm_year + 300 ) / 400 );
82
83 return leap_years;
84 }
85
86 /**
87 * Calculate day of week
88 *
89 * @v tm_year Years since 1900
90 * @v tm_mon Month of year [0,11]
91 * @v tm_day Day of month [1,31]
92 */
93 static int day_of_week ( int tm_year, int tm_mon, int tm_mday ) {
94 static const uint8_t offset[12] =
95 { 1, 4, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5 };
96 int pseudo_year = tm_year;
97
98 if ( tm_mon < 2 )
99 pseudo_year--;
100 return ( ( pseudo_year + leap_years_to_end ( pseudo_year ) +
101 offset[tm_mon] + tm_mday ) % 7 );
102 }
103
104 /** Days from start of year until start of months (in non-leap years) */
105 static const uint16_t days_to_month_start[] =
106 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
107
108 /**
109 * Calculate seconds since the Epoch
110 *
111 * @v tm Broken-down time
112 * @ret time Seconds since the Epoch
113 */
114 time_t mktime ( struct tm *tm ) {
115 int days_since_epoch;
116 int seconds_since_day;
117 time_t seconds;
118
119 /* Calculate day of year */
120 tm->tm_yday = ( ( tm->tm_mday - 1 ) +
121 days_to_month_start[ tm->tm_mon ] );
122 if ( ( tm->tm_mon >= 2 ) && is_leap_year ( tm->tm_year ) )
123 tm->tm_yday++;
124
125 /* Calculate day of week */
126 tm->tm_wday = day_of_week ( tm->tm_year, tm->tm_mon, tm->tm_mday );
127
128 /* Calculate seconds since the Epoch */
129 days_since_epoch = ( tm->tm_yday + ( 365 * tm->tm_year ) - 25567 +
130 leap_years_to_end ( tm->tm_year - 1 ) );
131 seconds_since_day =
132 ( ( ( ( tm->tm_hour * 60 ) + tm->tm_min ) * 60 ) + tm->tm_sec );
133 seconds = ( ( ( ( time_t ) days_since_epoch ) * ( ( time_t ) 86400 ) ) +
134 seconds_since_day );
135
136 DBGC ( &weekdays, "TIME %04d-%02d-%02d %02d:%02d:%02d => %lld (%s, "
137 "day %d)\n", ( tm->tm_year + 1900 ), ( tm->tm_mon + 1 ),
138 tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec, seconds,
139 weekdays[ tm->tm_wday ], tm->tm_yday );
140
141 return seconds;
142 }