From: Genady Beryozkin <c0467082 AT techst02 DOT technion DOT ac DOT il>
Newsgroups: comp.os.msdos.djgpp
Subject: A little problem with the assembler
Date: Thu, 16 Oct 1997 09:21:55 +0200
Organization: The Technion
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Hello !

Recently I've been converting a cpp file, which uses a Borland 16bit
inline assembler, into a 32bit djgpp code. Well, after carefully
converting each instruction, it still didn't work.

The module is intended to measure time with some super-high accuracy
(of 1 nanosecond) and I desparately need it to work under djgpp.

The source is at the bottom of this message.

If you could please take a look at the code (it's a really short code)
and help me converting it, I'd be much grateful.
If anybody know about any other code which compiles under gcc, and does
the same, please write me.

Thanks in advance
Genady
c0467082 AT t2 DOT technion DOT ac DOT il


// -------------  tctimer.cpp  --------------------
#define __DPMI32__
#include <dos.h>
#undef outportb

const TimerResolution=1193181.667;

void cardinal(long l,double *result)           // internal function -
works ok.
{
	*result = ((l<0)?4294967296.0 + (long)l : (long)l);
}

void elapsedtime(long start, long stop, double *result)  // works ok.
{
	double r;

	cardinal(stop - start, &r);

	*result = (1000.0 * r) / TimerResolution;
}

void initializetimer(void)			// troubles start here ....
{						// HELP !!!!!!!!!!!!!!1

  outportb(0x043,0x034);
  asm jmp short NullJump1

NullJump1:;

  outportb(0x040,0x000);
  asm jmp short NullJump2

NullJump2:;

  outportb(0x040,0x000);

}

void restoretimer(void)
{
  outportb(0x043,0x036);
  asm jmp short NullJump1

NullJump1:;

  outportb(0x040,0x000);
  asm jmp short NullJump2

NullJump2:;

  outportb(0x040,0x000);

}

long readtimer(void)				// ok - this is the most problematic code.
						// please notice the DOS memory access below (at 0040:006C)
						// also here the function returns a "long" result in DX:AX
						// (borland)
{
  asm cli             /* Disable interrupts */
  asm mov  dx,020h     /* Address PIC ocw3   */
  asm mov  al,00Ah     /* Ask to read irr    */
  asm out  dx,al
  asm mov  al,00h     /* Latch timer 0 */
  asm out  043h,al
  asm in   al,dx      /* Read irr      */
  asm mov  di,ax      /* Save it in DI */
  asm in   al,040h     /* Counter --> bx*/
  asm mov  bl,al      /* LSB in BL     */
  asm in   al,040h
  asm mov  bh,al      /* MSB in BH     */
  asm not  bx         /* Need ascending counter */
  asm in   al,021h     /* Read PIC imr  */
  asm mov  si,ax      /* Save it in SI */
  asm mov  al,00FFh    /* Mask all interrupts */
  asm out  021h,al
  asm mov  ax,040h     /* read low word of time */
  asm mov  es,ax      /* from BIOS data area   */
  asm mov  dx,es:[06Ch]
  asm mov  ax,si      /* Restore imr from SI   */
  asm out  021h,al
  asm sti             /* Enable interrupts */
  asm mov  ax,di      /* Retrieve old irr  */
  asm test al,001h     /* Counter hit 0?    */
  asm jz   done       /* Jump if not       */
  asm cmp  bx,0FFh     /* Counter > 0x0FF?    */
  asm ja   done       /* Done if so        */
  asm inc  dx         /* Else count int req. */
done:;
  asm mov ax,bx   /* set function result */
}
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