问在FreeDOS/FreeDOS应用程序中实现超时

EN

// file: tmr.c
#include <stddef.h>
#include <stdio.h>
#include <dos.h>
#include <conio.h>

#ifdef __WATCOMC__
// Define Borland C aliases:
#define getvect _dos_getvect
#define setvect _dos_setvect
#define outportb outp
#define inportb inp
#define disable _disable
#define enable _enable
#endif

typedef unsigned uint;
typedef unsigned char uchar;

void interrupt (*pOldInt1C)(void) = NULL;

volatile uint int1Ccnt = 0;

void interrupt NewInt1C(void)
{
  int1Ccnt++;
  pOldInt1C();
}

void SetPitResolutionInHz(uint ResolutionInHz)
{
  uint count;

  if (ResolutionInHz < 18 || ResolutionInHz >= 65535)
    return;

  count = (ResolutionInHz == 18) ? 0 : (uint)(1193181 / ResolutionInHz);

  disable();

  outportb(0x43, 0x34);
  outportb(0x40, (uchar)(count & 0xFF));
  outportb(0x40, (uchar)(count >> 8));

  enable();
}

int main(void)
{
  pOldInt1C = getvect(0x1C);
  setvect(0x1C, &NewInt1C);

  printf("3 seconds delay, default timer rate...\n");
  while (int1Ccnt < 18*1*3)
  {
    static uint last = 0;
    if (last != int1Ccnt)
    {
      printf("1"); fflush(stdout);
      last = int1Ccnt;
    }
  }
  printf("\n");

  SetPitResolutionInHz(18*2);
  printf("3 seconds delay, double timer rate...\n");
  int1Ccnt = 0;
  while (int1Ccnt < 18*2*3)
  {
    static uint last = 0;
    if (last != int1Ccnt)
    {
      printf("2"); fflush(stdout);
      last = int1Ccnt;
    }
  }
  printf("\n");

  SetPitResolutionInHz(18*3);
  printf("3 seconds delay, triple timer rate...\n");
  int1Ccnt = 0;
  while (int1Ccnt < 18*3*3)
  {
    static uint last = 0;
    if (last != int1Ccnt)
    {
      printf("3"); fflush(stdout);
      last = int1Ccnt;
    }
  }
  printf("\n");

  // Set default rate: 1193181 MHz / 65536 = 18.2 Hz
  SetPitResolutionInHz(18*1);
  printf("3 seconds delay, default timer rate...\n");
  int1Ccnt = 0;
  while (int1Ccnt < 18*1*3)
  {
    static uint last = 0;
    if (last != int1Ccnt)
    {
      printf("1"); fflush(stdout);
      last = int1Ccnt;
    }
  }
  printf("\n");

  setvect(0x1C, pOldInt1C);

  return 0;
}

tmTimerHandler PROC
    push ds
    mov ds,cs:tmDataSeg
    add ds:tmTicker,65536
    pop ds
    jmp cs:tmOldTimer
tmTimerHandler ENDP


tmInit PROC
    mov tmDataSeg,ds
    mov tmTicker,65536
    push es
    ; Save the old timer interrupt vector
    mov ax,3508h
    int 21h
    mov dword ptr tmOldTimer+0,ebx
    mov word ptr tmOldTimer+4,es
    pop es

    ; Install our own timer interrupt vector
    push ds
    mov ax,2508h
    push cs
    pop ds
    mov edx,OFFSET tmTimerHandler
    int 21h
    pop ds

    ; Configure the PIT to generate interrupts
    ; at the maximum rate
    mov al,34h
    out 43h,al
    xor al,al  ; zero divisor
    out 40h,al
    out 40h,al
    ret
tmInit ENDP


tmClose PROC
   push ds
   mov ax,2508h
   lds edx,tmOldTimer
   int 21h
   pop ds
   ret
tmClose ENDP


; Returns the current tick count in eax
tmGetTimer PROC
   pushf
   cli
   xor eax,eax
   out 43h,al
   in al,40h
   mov ah,al
   in al,40h
   xchg ah,al
   neg eax
   add eax,tmTicker
   popf
   ret
tmGetTimer ENDP


.data
  tmOldTimer    df 0
  tmDataSeg dw 0
  tmTicker  dd 0