1#include <com32.h>
2#include <string.h>
3#include "ctime.h"
4
5static 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
13uint32_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    memset(&ir, 0, sizeof ir);
28    ir.eax.b[1] = 0x02;
29    __intcall(0x1A, &ir, &t0);
30
31    memset(&ir, 0, sizeof ir);
32    ir.eax.b[1] = 0x04;
33    __intcall(0x1A, &ir, &d1);
34
35    if (t0.ecx.b[1] < 0x12)
36	d0 = d1;
37
38    c  = frombcd(d0.ecx.b[1]);
39    y  = frombcd(d0.ecx.b[0]);
40    mo = frombcd(d0.edx.b[1]);
41    d  = frombcd(d0.edx.b[0]);
42
43    h  = frombcd(t0.ecx.b[1]);
44    m  = frombcd(t0.ecx.b[0]);
45    s  = frombcd(t0.edx.b[1]);
46
47    /* We of course have no idea about the timezone, so ignore it */
48
49    /*
50     * Look for impossible dates... this code was written in 2010, so
51     * assume any century less than 20 is just broken.
52     */
53    if (c < 20)
54	c = 20;
55    y += c*100;
56
57    /* Consider Jan and Feb as the last months of the previous year */
58    if (mo < 3) {
59	y--;
60	mo += 12;
61    }
62
63    /*
64     * Just in case: if the month is nonsense, don't read off the end
65     * of the table...
66     */
67    if (mo-3 > 11)
68	return 0;
69
70    t = y*365 + y/4 - y/100 + y/400 + yday[mo-3] + d - 719469;
71    t *= 24;
72    t += h;
73    t *= 60;
74    t += m;
75    t *= 60;
76    t += s;
77
78    return t;
79}
80