miscemu/int25.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include "msdos.h"
   5 #include "ldt.h"
   6 #include "miscemu.h"
   7 #include "drive.h"
   8 #include "stddebug.h"
   9 /* #define DEBUG_INT */
  10 #include "debug.h"
  11
  12 /**********************************************************************
  13  *          INT_Int25Handler
  14  *
  15  * Handler for int 25h (absolute disk read).
  16  */
  17 void INT_Int25Handler( SIGCONTEXT *context )
  18 {
  19     BYTE *dataptr = PTR_SEG_OFF_TO_LIN( DS_reg(context), BX_reg(context) );
  20     DWORD begin, length;
  21
  22     if (!DRIVE_IsValid(AL_reg(context)))
  23     {
  24         SET_CFLAG(context);
  25         AX_reg(context) = 0x0101;        /* unknown unit */
  26         return;
  27     }
  28
  29     if (CX_reg(context) == 0xffff)
  30     {
  31         begin   = *(DWORD *)dataptr;
  32         length  = *(WORD *)(dataptr + 4);
  33         dataptr = (BYTE *)PTR_SEG_TO_LIN( *(SEGPTR *)(dataptr + 6) );
  34     }
  35     else
  36     {
  37         begin  = DX_reg(context);
  38         length = CX_reg(context);
  39     }
  40     dprintf_int( stdnimp, "int25: abs diskread, drive %d, sector %ld, "
  41                  "count %ld, buffer %d\n",
  42                  AL_reg(context), begin, length, (int) dataptr);
  43
  44     memset(dataptr, 0, length * 512);
  45
  46     if (begin == 0 && length > 1) *(dataptr + 512) = 0xf8;
  47
  48     if (begin == 1) *dataptr = 0xf8;
  49
  50     RESET_CFLAG(context);
  51 }