Date:	Mon, 17 Feb 1997 15:39:32 +0200 (IST)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To:	Jan Hubicka <hubicka AT ta DOT jcu DOT cz>
cc:	Ian Miller <itmiller AT dra DOT hmg DOT gb>, djgpp AT delorie DOT com
Subject:	Re: Exact timming II
In-Reply-To:	<Pine.LNX.3.91.970217141522.32046C-100000@tabor.ta.jcu.cz>
Message-ID:	<Pine.SUN.3.91.970217153640.18258B-100000@is>
MIME-Version:	1.0

On Mon, 17 Feb 1997, Jan Hubicka wrote:

> please can you send me separated uclock code? (I don't want to download
> whole library sources and uncompress then to my 80MB dos partition)

Below.  Btw, you don't need to uncompress the entire lot to get a single 
source.  Just uncompress that single source and use it.  Anybody who's 
serious about DJGPP development should IMHO have djlsr at his disposal, 
if only to see what the docs forgot to mention.

/* Copyright (C) 1996 DJ Delorie, see COPYING.DJ for details */
/* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
#include <time.h>
#include <pc.h>
#include <libc/farptrgs.h>
#include <go32.h>
#include <libc/bss.h>

static int uclock_bss = -1;

/* tics = about 18.2 * 65536 (1,192,755)

   actually, it's   0x1800b0 tics/day (FAQ)
                  / 24*60*60 sec/day
                  * 65536 utics/tic
		  = 1,193,180 utics/sec */

uclock_t
uclock(void)
{
  static uclock_t base = 0;
  static unsigned long last_tics = 0;
  unsigned char lsb, msb;
  unsigned long tics, otics;
  uclock_t rv;

  if (uclock_bss != __bss_count)
  {
    /* switch the timer to mode 2 (rate generator) */
    /* rather than mode 3 (square wave), which doesn't count linearly. */

    outportb(0x43, 0x34);
    outportb(0x40, 0xff);
    outportb(0x40, 0xff);

    base = 0;
    last_tics = 0;
    uclock_bss = __bss_count;
  }

  /* Make sure the numbers we get are consistent */
  do {
    otics = _farpeekl(_dos_ds, 0x46c);
    outportb(0x43, 0x00);
    lsb = inportb(0x40);
    msb = inportb(0x40);
    tics = _farpeekl(_dos_ds, 0x46c);
  } while (otics != tics);

  /* calculate absolute time */
  msb ^= 0xff;
  lsb ^= 0xff;
  rv = ((uclock_t)tics << 16) | (msb << 8) | lsb;

  if (base == 0L)
    base = rv;

  if (last_tics > tics) /* midnight happened */
    base -= 0x1800b00000LL;

  last_tics = tics;

  /* return relative time */
  return rv - base;
}

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