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 <fcntl.h>
   9 #include <unistd.h>
  10 #include "msdos.h"
  11 #include "ldt.h"
  12 #include "miscemu.h"
  13 #include "drive.h"
  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     int fd;
  26
  27     if (!DRIVE_IsValid(AL_reg(context)))
  28     {
  29         SET_CFLAG(context);
  30         AX_reg(context) = 0x0101;        /* unknown unit */
  31         return;
  32     }
  33
  34     if (CX_reg(context) == 0xffff)
  35     {
  36         begin   = *(DWORD *)dataptr;
  37         length  = *(WORD *)(dataptr + 4);
  38         dataptr = (BYTE *)PTR_SEG_TO_LIN( *(SEGPTR *)(dataptr + 6) );
  39     }
  40     else
  41     {
  42         begin  = DX_reg(context);
  43         length = CX_reg(context);
  44     }
  45     TRACE(int, "int25: abs diskread, drive %d, sector %ld, "
  46                  "count %ld, buffer %d\n",
  47                  AL_reg(context), begin, length, (int) dataptr);
  48
  49     if ((fd = DRIVE_OpenDevice( AL_reg(context), O_RDONLY )) != -1)
  50     {
  51         lseek( fd, begin * 512, SEEK_SET );
  52         /* FIXME: check errors */
  53         read( fd, dataptr, length * 512 );
  54         close( fd );
  55     }
  56     else
  57     {
  58         memset(dataptr, 0, length * 512);
  59         if (begin == 0 && length > 1) *(dataptr + 512) = 0xf8;
  60         if (begin == 1) *dataptr = 0xf8;
  61     }
  62     RESET_CFLAG(context);
  63 }
  64