/****************************************************************/
/*                                                              */
/*                           sysclk.c                           */
/*                                                              */
/*                     System Clock Driver                      */
/*                                                              */
/*                      Copyright (c) 1995                      */
/*                      Pasquale J. Villani                     */
/*                      All Rights Reserved                     */
/*                                                              */
/* This file is part of DOS-C.                                  */
/*                                                              */
/* DOS-C is free software; you can redistribute it and/or       */
/* modify it under the terms of the GNU General Public License  */
/* as published by the Free Software Foundation; either version */
/* 2, or (at your option) any later version.                    */
/*                                                              */
/* DOS-C is distributed in the hope that it will be useful, but */
/* WITHOUT ANY WARRANTY; without even the implied warranty of   */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See    */
/* the GNU General Public License for more details.             */
/*                                                              */
/* You should have received a copy of the GNU General Public    */
/* License along with DOS-C; see the file COPYING.  If not,     */
/* write to the Free Software Foundation, 675 Mass Ave,         */
/* Cambridge, MA 02139, USA.                                    */
/****************************************************************/

#include "portab.h"
#include "globals.h"

#ifdef VERSION_STRINGS
static BYTE *RcsId =
    "$Id$";
#endif

#ifdef PROTO
VOID ASMCFUNC WriteATClock(BYTE *, BYTE, BYTE, BYTE);
VOID ASMCFUNC WritePCClock(ULONG);
COUNT BcdToByte(COUNT);
COUNT BcdToWord(BYTE *, UWORD *, UWORD *, UWORD *);
COUNT ByteToBcd(COUNT);
VOID DayToBcd(BYTE *, UWORD *, UWORD *, UWORD *);
#else
VOID WriteATClock();
VOID WritePCClock();
COUNT BcdToByte();
COUNT BcdToWord();
COUNT ByteToBcd();
VOID DayToBcd();
#endif

/*                                                                      */
/* WARNING - THIS DRIVER IS NON-PORTABLE!!!!                            */
/*                                                                      */
extern UWORD days[2][13];       /* this is defined by SYSTIME.C */

static struct ClockRecord clk;

/*
static BYTE bcdDays[4];
static UWORD Month,
  Day,
  Year;
static BYTE bcdMinutes;
static BYTE bcdHours;
/ ** static BYTE bcdHundredths;* /
static BYTE bcdSeconds;

static ULONG Ticks;
*/
UWORD ASM DaysSinceEpoch = 0;

BOOL ASMCFUNC ReadATClock(BYTE *, BYTE *, BYTE *, BYTE *);

STATIC COUNT BcdToByte(COUNT x)
{
  return ((((x) >> 4) & 0xf) * 10 + ((x) & 0xf));
}

WORD ASMCFUNC FAR clk_driver(rqptr rp)
{
  COUNT c;
  UWORD *pdays;
  BYTE bcd_days[4], bcd_minutes, bcd_hours, bcd_seconds;
  ULONG Ticks;
  UWORD Month, Day, Year;

  switch (rp->r_command)
  {
    case C_INIT:
      /* If AT clock exists, copy AT clock time to system clock */
      if (!ReadATClock(bcd_days, &bcd_hours, &bcd_minutes, &bcd_seconds))
      {
        DaysSinceEpoch =
            DaysFromYearMonthDay(100 * BcdToByte(bcd_days[3]) +
                                 BcdToByte(bcd_days[2]),
                                 BcdToByte(bcd_days[1]),
                                 BcdToByte(bcd_days[0]));

        /*
         * This is a rather tricky calculation. The number of timer ticks per
         * second is not exactly 18.2, but rather 0x1800b0 / 86400 = 19663 / 1080
         * (the timer interrupt updates the midnight flag when the tick count
         * reaches 0x1800b0). Fortunately, 86400 * 19663 = 1698883200 < ULONG_MAX,
         * so we can simply multiply the number of seconds by 19663 without
         * worrying about overflow. :) -- ror4
         */
        Ticks = (3600ul * BcdToByte(bcd_hours) +
                 60ul * BcdToByte(bcd_minutes) +
                 BcdToByte(bcd_seconds)) * 19663ul / 1080ul;
        WritePCClock(Ticks);
      }
      rp->r_endaddr = device_end();
      rp->r_nunits = 0;
      return S_DONE;

    case C_INPUT:
      {
        ULONG remainder, hs;
        ReadPCClock(&Ticks);
        clk.clkDays = DaysSinceEpoch;
        /*
         * Another tricky calculation (after the one in `main.c'). This time
         * we do have a problem with overflow, because we need to extract the
         * 1/100s portion too. The scaling factor is now
         * (100 x 86400) / 0x1800b0 = 108000 / 19663. -- ror4
         */
        hs = 0;
#if 0
        if (Ticks >= 64 * 19663ul)
        {
          hs += 64 * 108000ul;
          Ticks -= 64 * 19663ul;
        }
        if (Ticks >= 32 * 19663ul)
        {
          hs += 32 * 108000ul;
          Ticks -= 32 * 19663ul;
        }
        if (Ticks >= 16 * 19663ul)
        {
          hs += 16 * 108000ul;
          Ticks -= 16 * 19663ul;
        }
        if (Ticks >= 8 * 19663ul)
        {
          hs += 8 * 108000ul;
          Ticks -= 8 * 19663ul;
        }
        if (Ticks >= 4 * 19663ul)
        {
          hs += 4 * 108000ul;
          Ticks -= 4 * 19663ul;
        }
        if (Ticks >= 2 * 19663ul)
        {
          hs += 2 * 108000ul;
          Ticks -= 2 * 19663ul;
        }
        if (Ticks >= 19663ul)
        {
          hs += 108000ul;
          Ticks -= 19663ul;
        }
#else
        {
          UWORD q1 = Ticks / 19663ul;

          Ticks -= q1 * 19663ul;
          hs = q1 * 108000ul;
        }

#endif
        /*
         * Now Ticks < 19663, so Ticks * 108000 < 2123604000 < ULONG_MAX.
         * *phew* -- ror4
         */
        hs += Ticks * 108000ul / 19663ul;
        clk.clkHours = hs / 360000ul;
        remainder = hs % 360000ul;
        clk.clkMinutes = remainder / 6000ul;
        remainder %= 6000ul;
        clk.clkSeconds = remainder / 100ul;
        clk.clkHundredths = remainder % 100ul;
      }

      fmemcpy(rp->r_trans, &clk,
              min(sizeof(struct ClockRecord), rp->r_count));
      return S_DONE;

    case C_OUTPUT:
      rp->r_count = min(rp->r_count, sizeof(struct ClockRecord));
      fmemcpy(&clk, rp->r_trans, rp->r_count);

      /* Set PC Clock first                                   */
      DaysSinceEpoch = clk.clkDays;
      {
        ULONG hs;
        hs = 360000ul * clk.clkHours +
            6000ul * clk.clkMinutes +
            100ul * clk.clkSeconds + clk.clkHundredths;
        Ticks = 0;
#if 0
        if (hs >= 64 * 108000ul)
        {
          Ticks += 64 * 19663ul;
          hs -= 64 * 108000ul;
        }
        if (hs >= 32 * 108000ul)
        {
          Ticks += 32 * 19663ul;
          hs -= 32 * 108000ul;
        }
        if (hs >= 16 * 108000ul)
        {
          Ticks += 16 * 19663ul;
          hs -= 16 * 108000ul;
        }
        if (hs >= 8 * 108000ul)
        {
          Ticks += 8 * 19663ul;
          hs -= 8 * 108000ul;
        }
        if (hs >= 4 * 108000ul)
        {
          Ticks += 4 * 19663ul;
          hs -= 4 * 108000ul;
        }
        if (hs >= 2 * 108000ul)
        {
          Ticks += 2 * 19663ul;
          hs -= 2 * 108000ul;
        }
        if (hs >= 108000ul)
        {
          Ticks += 19663ul;
          hs -= 108000ul;
        }
#else
        {
          UWORD q1 = hs / 108000ul;

          hs -= q1 * 108000ul;
          Ticks = q1 * 19663ul;
        }

#endif
        Ticks += hs * 19663ul / 108000ul;
      }
      WritePCClock(Ticks);

      /* Now set AT clock                                     */
      /* Fix year by looping through each year, subtracting   */
      /* the appropriate number of days for that year.        */
      for (Year = 1980, c = clk.clkDays;;)
      {
        pdays = is_leap_year_monthdays(Year);
        if (c >= pdays[12])
        {
          ++Year;
          c -= pdays[12];
        }
        else
          break;
      }

      /* c contains the days left and count the number of     */
      /* days for that year.  Use this to index the table.    */
      for (Month = 1; Month < 13; ++Month)
      {
        if (pdays[Month] > c)
        {
          Day = c - pdays[Month - 1] + 1;
          break;
        }
      }

      DayToBcd((BYTE *) bcd_days, &Month, &Day, &Year);
      bcd_minutes = ByteToBcd(clk.clkMinutes);
      bcd_hours = ByteToBcd(clk.clkHours);
      bcd_seconds = ByteToBcd(clk.clkSeconds);
      WriteATClock(bcd_days, bcd_hours, bcd_minutes, bcd_seconds);
      return S_DONE;

    case C_OFLUSH:
    case C_IFLUSH:
      return S_DONE;

    case C_OUB:
    case C_NDREAD:
    case C_OSTAT:
    case C_ISTAT:
    default:
      return failure(E_FAILURE);        /* general failure */
  }
}

COUNT ByteToBcd(COUNT x)
{
  return ((x / 10) << 4) | (x % 10);
}

VOID DayToBcd(BYTE * x, UWORD * mon, UWORD * day, UWORD * yr)
{
  x[1] = ByteToBcd(*mon);
  x[0] = ByteToBcd(*day);
  x[3] = ByteToBcd(*yr / 100);
  x[2] = ByteToBcd(*yr % 100);
}

/*
 * Log: sysclk.c,v - for newer entries do "cvs log sysclk.c"
 *
 * Revision 1.3  2000/03/09 06:07:11  kernel
 * 2017f updates by James Tabor
 *
 * Revision 1.2  1999/04/12 03:21:17  jprice
 * more ror4 patches.  Changes for multi-block IO
 *
 * Revision 1.1.1.1  1999/03/29 15:41:33  jprice
 * New version without IPL.SYS
 *
 * Revision 1.5  1999/02/08 05:55:58  jprice
 * Added Pat's 1937 kernel patches
 *
 * Revision 1.4  1999/02/04 03:14:07  jprice
 * Formating.  Added comments.
 *
 * Revision 1.3  1999/02/01 01:48:41  jprice
 * Clean up; Now you can use hex numbers in config.sys. added config.sys screen function to change screen mode (28 or 43/50 lines)
 *
 * Revision 1.2  1999/01/22 04:13:27  jprice
 * Formating
 *
 * Revision 1.1.1.1  1999/01/20 05:51:01  jprice
 * Imported sources
 *
 *
 *    Rev 1.4   04 Jan 1998 23:15:16   patv
 * Changed Log for strip utility
 *
 *    Rev 1.3   29 May 1996 21:03:48   patv
 * bug fixes for v0.91a
 *
 *    Rev 1.2   19 Feb 1996  3:21:34   patv
 * Added NLS, int2f and config.sys processing
 *
 *    Rev 1.1   01 Sep 1995 17:54:18   patv
 * First GPL release.
 *
 *    Rev 1.0   02 Jul 1995  8:32:30   patv
 * Initial revision.
 */