msdos/int25.c

   1 /*
   2  * DOS interrupt 25h handler
   3  */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <string.h>
   8 #include "msdos.h"
   9 #include "ldt.h"
  10 #include "miscemu.h"
  11 #include "drive.h"
  12 #include "stddebug.h"
  13 /* #define DEBUG_INT */
  14 #include "debug.h"
  15
  16 /**********************************************************************
  17  *          INT_Int25Handler
  18  *
  19  * Handler for int 25h (absolute disk read).
  20  */
  21 void WINAPI INT_Int25Handler( CONTEXT *context )
  22 {
  23     BYTE *dataptr = PTR_SEG_OFF_TO_LIN( DS_reg(context), BX_reg(context) );
  24     DWORD begin, length;
  25
  26     if (!DRIVE_IsValid(AL_reg(context)))
  27     {
  28         SET_CFLAG(context);
  29         AX_reg(context) = 0x0101;        /* unknown unit */
  30         return;
  31     }
  32
  33     if (CX_reg(context) == 0xffff)
  34     {
  35         begin   = *(DWORD *)dataptr;
  36         length  = *(WORD *)(dataptr + 4);
  37         dataptr = (BYTE *)PTR_SEG_TO_LIN( *(SEGPTR *)(dataptr + 6) );
  38     }
  39     else
  40     {
  41         begin  = DX_reg(context);
  42         length = CX_reg(context);
  43     }
  44     dprintf_int( stdnimp, "int25: abs diskread, drive %d, sector %ld, "
  45                  "count %ld, buffer %d\n",
  46                  AL_reg(context), begin, length, (int) dataptr);
  47
  48     memset(dataptr, 0, length * 512);
  49
  50     if (begin == 0 && length > 1) *(dataptr + 512) = 0xf8;
  51
  52     if (begin == 1) *dataptr = 0xf8;
  53
  54     RESET_CFLAG(context);
  55 }