msdos/int25.c

   1 /*
   2  * DOS interrupt 25h handler
   3  */
   4
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <fcntl.h>
   8 #include <unistd.h>
   9 #include "msdos.h"
  10 #include "ldt.h"
  11 #include "miscemu.h"
  12 #include "drive.h"
  13 #include "debug.h"
  14
  15 /**********************************************************************
  16  *          INT_Int25Handler
  17  *
  18  * Handler for int 25h (absolute disk read).
  19  */
  20 void WINAPI INT_Int25Handler( CONTEXT *context )
  21 {
  22     BYTE *dataptr = PTR_SEG_OFF_TO_LIN( DS_reg(context), BX_reg(context) );
  23     DWORD begin, length;
  24     int fd;
  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     TRACE(int, "int25: abs diskread, drive %d, sector %ld, "
  45                  "count %ld, buffer %d\n",
  46                  AL_reg(context), begin, length, (int) dataptr);
  47
  48     if ((fd = DRIVE_OpenDevice( AL_reg(context), O_RDONLY )) != -1)
  49     {
  50         lseek( fd, begin * 512, SEEK_SET );
  51         /* FIXME: check errors */
  52         read( fd, dataptr, length * 512 );
  53         close( fd );
  54     }
  55     else
  56     {
  57         memset(dataptr, 0, length * 512);
  58         if (begin == 0 && length > 1) *(dataptr + 512) = 0xf8;
  59         if (begin == 1) *dataptr = 0xf8;
  60     }
  61     RESET_CFLAG(context);
  62 }
  63