lib/clock.c

   1 /*
   2  * (C) Copyright 2007-2010  Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
   3  *
   4  * This file is released under the GPLv2.  See the COPYING file for more
   5  * details.
   6  */
   7
   8 #include <clock.h>
   9
  10 #define LS_NONE                 0x00    /* non-leap second entry */
  11 #define LS_LS                   0x10    /* previous second was leap */
  12
  13 #define LS_MASK                 (LS_LS)
  14
  15 #define LS_YM2DATE(y, m, f)     ((y) << 8 | (f) | (m))
  16 #define LS_DATE2Y(d)            ((d) >> 8)
  17 #define LS_DATE2M(d)            ((d) & 0xf)
  18 #define LS_DATE2F(d)            ((d) & LS_MASK)
  19
  20 struct leap_sec_info {
  21         u64 tod;
  22         u32 date;
  23 };
  24
  25 /*
  26  * List of TOD clocks for each of the leap seconds
  27  */
  28 static struct leap_sec_info leap_secs[] = {
  29         { 0xC3870CB9BB600000ULL, LS_YM2DATE(2009, 1, LS_LS  ), },
  30         { 0xBE251097973C0000ULL, LS_YM2DATE(2006, 1, LS_LS  ), },
  31         { 0xB1962F9305180000ULL, LS_YM2DATE(1999, 1, LS_LS  ), },
  32         { 0xAEE3EFA402F40000ULL, LS_YM2DATE(1997, 7, LS_LS  ), },
  33         { 0xAC34336FECD00000ULL, LS_YM2DATE(1996, 1, LS_LS  ), },
  34         { 0xA981F380EAAC0000ULL, LS_YM2DATE(1994, 7, LS_LS  ), },
  35         { 0xA7B70ABEB8880000ULL, LS_YM2DATE(1993, 7, LS_LS  ), },
  36         { 0xA5EC21FC86640000ULL, LS_YM2DATE(1992, 7, LS_LS  ), },
  37         { 0xA33C65C870400000ULL, LS_YM2DATE(1991, 1, LS_LS  ), },
  38         { 0xA1717D063E1C0000ULL, LS_YM2DATE(1990, 1, LS_LS  ), },
  39         { 0x9DDA69A557F80000ULL, LS_YM2DATE(1988, 1, LS_LS  ), },
  40         { 0x995D40F517D40000ULL, LS_YM2DATE(1985, 7, LS_LS  ), },
  41         { 0x95C62D9431B00000ULL, LS_YM2DATE(1983, 7, LS_LS  ), },
  42         { 0x93FB44D1FF8C0000ULL, LS_YM2DATE(1982, 7, LS_LS  ), },
  43         { 0x92305C0FCD680000ULL, LS_YM2DATE(1981, 7, LS_LS  ), },
  44         { 0x8F809FDBB7440000ULL, LS_YM2DATE(1980, 1, LS_LS  ), },
  45         { 0x8DB5B71985200000ULL, LS_YM2DATE(1979, 1, LS_LS  ), },
  46         { 0x8BEACE5752FC0000ULL, LS_YM2DATE(1978, 1, LS_LS  ), },
  47         { 0x8A1FE59520D80000ULL, LS_YM2DATE(1977, 1, LS_LS  ), },
  48         { 0x8853BAF578B40000ULL, LS_YM2DATE(1976, 1, LS_LS  ), },
  49         { 0x8688D23346900000ULL, LS_YM2DATE(1975, 1, LS_LS  ), },
  50         { 0x84BDE971146C0000ULL, LS_YM2DATE(1974, 1, LS_LS  ), },
  51         { 0x82F300AEE2480000ULL, LS_YM2DATE(1973, 1, LS_LS  ), },
  52         { 0x820BA9811E240000ULL, LS_YM2DATE(1972, 7, LS_LS  ), },
  53         { 0x8126D60E46000000ULL, LS_YM2DATE(1972, 1, LS_NONE), }, /* UTC begins */
  54         { 0x0000000000000000ULL, LS_YM2DATE(1900, 1, LS_NONE), }, /* TOD begins */
  55 };
  56
  57 /*
  58  * Number of days passed since the beginning of the year
  59  */
  60 static const short int month_offsets[2][12] = {
  61         /* J    F    M    A    M    J    J    A    S    O    N    D */
  62         {   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334},
  63         {   0,  31,  60,  91, 121, 152, 182, 213, 244, 274, 305, 335},
  64 };
  65
  66 struct datetime *parse_tod(struct datetime *dt, u64 tod)
  67 {
  68         int add_sec;
  69         int leap;
  70         int done;
  71         int i,j;
  72
  73         /*
  74          * find the most recent info for this tod (i), as well as for one
  75          * that's one second ahead (j)
  76          */
  77         for (i=0; leap_secs[i].tod > tod; i++)
  78                 ;
  79         for (j=0; leap_secs[j].tod > (tod + CLK_SEC); j++)
  80                 ;
  81
  82         tod -= leap_secs[i].tod;
  83
  84         dt->dy = LS_DATE2Y(leap_secs[i].date);
  85         dt->dm = LS_DATE2M(leap_secs[i].date);
  86
  87         /*
  88          * If we're in the leap second, let's pretend we're a second
  89          * earlier, and then add it back in at the end of the function
  90          */
  91         add_sec = 0;
  92
  93         if ((i != j) && (LS_DATE2F(leap_secs[j].date) == LS_LS)) {
  94                 tod -= CLK_SEC;
  95                 add_sec = 1;
  96         }
  97
  98         /* The month should be 1 or 7! */
  99         if ((dt->dm != 1) && (dt->dm != 7))
 100                 return NULL;
 101
 102         /*
 103          * At this point, we have a TOD value to add to a struct datetime.
 104          * We don't have to worry about leap seconds.  Life is good.
 105          */
 106
 107         for(;;) {
 108                 if (leap_year((dt->dm == 1) ? dt->dy : (dt->dy+1)))
 109                         done = tod < (CLK_YEAR + CLK_DAY);
 110                 else
 111                         done = tod < CLK_YEAR;
 112
 113                 if (done)
 114                         break;
 115
 116                 if ((dt->dm == 1 && leap_year(dt->dy)) ||
 117                     (dt->dm == 7 && leap_year(dt->dy+1)))
 118                         tod -= (CLK_YEAR + CLK_DAY);
 119                 else
 120                         tod -= CLK_YEAR;
 121
 122                 dt->dy++;
 123         }
 124
 125         /*
 126          * At this point, we have the year and we know the month is either Jan
 127          * or Jul; let's get an actual month
 128          */
 129
 130         dt->dd = tod / CLK_DAY;
 131         tod -= dt->dd * CLK_DAY;
 132
 133         do {
 134                 leap = leap_year(dt->dy);
 135                 i = month_offsets[leap][dt->dm - 1];
 136
 137                 while((dt->dm < 12) &&
 138                       ((i + dt->dd) >= month_offsets[leap][dt->dm]))
 139                         dt->dm++;
 140
 141                 dt->dd = dt->dd + i - month_offsets[leap][dt->dm-1];
 142
 143                 if ((dt->dm < 12) || (dt->dd < 31))
 144                         break;
 145
 146                 dt->dy++;
 147                 dt->dm = 1;
 148                 dt->dd -= 31;
 149         } while(1);
 150
 151         dt->dd++;
 152
 153         /*
 154          * At this point, we have the year, the month, and even the day;
 155          * let's get the hours, minutes and seconds
 156          */
 157
 158         dt->th = tod / CLK_HOUR;
 159         tod -= dt->th * CLK_HOUR;
 160
 161         dt->tm = tod / CLK_MIN;
 162         tod -= dt->tm * CLK_MIN;
 163
 164         dt->ts = tod / CLK_SEC;
 165         tod -= dt->ts * CLK_SEC;
 166
 167         /*
 168          * If we borrowed a second before, then add it back! (We borrow only
 169          * for leap seconds in progress.)
 170          */
 171         dt->ts += add_sec;
 172
 173         dt->tmicro = (u32) (tod >> 12);
 174
 175         return dt;
 176 }