1 files changed, 127 insertions, 0 deletions
diff --git a/libc/bios/time.c b/libc/bios/time.c
new file mode 100644
index 0000000..9bc63e5
--- /dev/null
+++ b/libc/bios/time.c
@@ -0,0 +1,127 @@
+/*
+ * Time functions for standalone mode, on the first call to time() it tries
+ * to query the RTC, on success it sets it's own day counter an the PC's
+ * ticks since midnight clock. From the second call on it uses the day
+ * counter and ticks clock.
+ *
+ * NOTES:
+ *    DOS's midnight bug is here too, it's actually in the bios.
+ *    If there's no RTC the clock will fall to Jan 3 1970.
+ */
+
+#include <time.h>
+
+static int mdays[13] = { 0,31,31+28,31+28+31,31+28+31+30,
+	31+28+31+30+31,31+28+31+30+31+30,31+28+31+30+31+30+31,
+	31+28+31+30+31+30+31+31,31+28+31+30+31+30+31+31+30,
+	31+28+31+30+31+30+31+31+30+31,31+28+31+30+31+30+31+31+30+31+30,
+	365 };
+
+#define SECSPERHOUR	(60*60)
+#define SECSPERDAY	(SECSPERHOUR*24L)
+
+/****************************************
+ * Return the number of seconds that have elapsed since the start
+ * of 1970.
+ * Input:
+ *	timer	pointer to where to store result (or NULL)
+ * Output:
+ *	*timer = result (unless timer == NULL)
+ * Returns:
+ *	time
+ */
+
+static int xt_days = 0, ax_val, huns = 0;
+
+static long get_time(ah)
+{
+#asm
+#if !__FIRST_ARG_IN_AX__
+  mov	bx,sp
+  mov	ax,[bx+2]
+#endif
+  mov	ah,al
+  int	$1A
+  jnc	intok
+  mov	cx,#-1
+  mov	dx,cx
+intok:
+  mov	[_ax_val],ax
+  mov	ax,dx
+  mov	dx,cx
+#endasm
+}
+
+static int
+unbcd(bcdval)
+int bcdval;
+{
+   return (bcdval&0xF) + 10*((bcdval>>4)&0xF);
+}
+
+time_t time(timer)
+time_t *timer;
+{
+  unsigned day,month,year;
+  long rv;
+  time_t t;
+
+  if( xt_days ) goto XT_time;
+
+  rv = get_time(0x02);
+  if(rv == -1) goto XT_time;
+          huns = unbcd(rv & 0xFF);	/* Save for stime */
+  rv >>= 8; t =  unbcd(rv & 0xFF);
+  rv >>= 8; t += unbcd(rv & 0xFF)*60;
+  rv >>= 8; t += unbcd(rv & 0xFF)*3600;
+
+  rv = get_time(0x04);
+  if(rv == -1) goto XT_time;
+            day   = unbcd(rv & 0xFF);
+  rv >>= 8; month = unbcd(rv & 0xFF) -1;
+  rv >>= 8; year  = unbcd(rv & 0xFF);
+  rv >>= 8; year += unbcd(rv & 0xFF)*100;
+            year -= 1970;
+  if( year < 1950 && year >= 1900 )
+     year += 100;		/* Century is not updated on RTC */
+
+  if (month <= 1 || year & 3)	/* if before Feb or not a leap year	*/
+	day--;			/* don't add day for leap year		*/
+  day += mdays[month];		/* day in year				*/
+  day += (year + 3) >> 2;	/* add a day for each leap year		*/
+  t += ((year * 365L) + day) * SECSPERDAY;
+
+  stime(t);
+
+  if(0)
+  {
+XT_time:
+     rv = get_time(0);
+     xt_days += (ax_val&0xFF);
+     rv = xt_days*SECSPERDAY + rv * 1080 / 19663;
+  }
+
+  if (timer)
+	*timer = t;
+  return t;
+}
+
+static long ticks;
+
+stime(timer)
+time_t timer;
+{
+   xt_days = (timer/SECSPERDAY);
+
+   ticks = ((timer%SECSPERDAY) * 19663L + huns*196) / 1080;
+   huns = 0;
+
+#asm
+   mov	cx,[_ticks+2]
+   mov	dx,[_ticks]
+   mov	ah,#1
+   int	$1A
+#endasm
+
+   return 0;
+}