com32/sysdump/ctime.c

   1 #include <com32.h>
   2 #include <string.h>
   3 #include "ctime.h"
   4
   5 static uint8_t frombcd(uint8_t v)
   6 {
   7     uint8_t a = v & 0x0f;
   8     uint8_t b = v >> 4;
   9
  10     return a + b*10;
  11 }
  12
  13 uint32_t posix_time(void)
  14 {
  15     /* Days from March 1 for a specific month, starting in March */
  16     static const unsigned int yday[12] =
  17         { 0, 31, 61, 92, 122, 153, 184, 214, 245, 275, 306, 337 };
  18     com32sys_t ir, d0, d1, t0;
  19     unsigned int c, y, mo, d, h, m, s;
  20     uint32_t t;
  21
  22     memset(&ir, 0, sizeof ir);
  23
  24     ir.eax.b[1] = 0x04;
  25     __intcall(0x1A, &ir, &d0);
  26
  27     ir.eax.b[1] = 0x02;
  28     __intcall(0x1A, &ir, &t0);
  29
  30     ir.eax.b[1] = 0x04;
  31     __intcall(0x1A, &ir, &d1);
  32
  33     if (t0.ecx.b[1] < 0x12)
  34         d0 = d1;
  35
  36     c  = frombcd(d0.ecx.b[1]);
  37     y  = frombcd(d0.ecx.b[0]);
  38     mo = frombcd(d0.edx.b[1]);
  39     d  = frombcd(d0.edx.b[0]);
  40
  41     h  = frombcd(t0.ecx.b[1]);
  42     m  = frombcd(t0.ecx.b[0]);
  43     s  = frombcd(t0.edx.b[1]);
  44
  45     /* We of course have no idea about the timezone, so ignore it */
  46
  47     /*
  48      * Look for impossible dates... this code was written in 2010, so
  49      * assume any century less than 20 is just broken.
  50      */
  51     if (c < 20)
  52         c = 20;
  53     y += c*100;
  54
  55     /* Consider Jan and Feb as the last months of the previous year */
  56     if (mo < 3) {
  57         y--;
  58         mo += 12;
  59     }
  60
  61     /*
  62      * Just in case: if the month is nonsense, don't read off the end
  63      * of the table...
  64      */
  65     if (mo-3 > 11)
  66         return 0;
  67
  68     t = y*365 + y/4 - y/100 + y/400 + yday[mo-3] + d - 719469;
  69     t *= 24;
  70     t += h;
  71     t *= 60;
  72     t += m;
  73     t *= 60;
  74     t += s;
  75
  76     return t;
  77 }