Encapsulating the DOS IOCTL Interface

Listing 6 chandle.cpp — adds character-device specific capability to class IoctlHandle

#include <string.h>
#include "chandle.h"

struct { char *dname;
       int dtype;
       } static dcat[]= { { "COM", 1 },{ "AUX", 1 },
                       { "CON", 3 },{ "LPT", 5 },
                       { "PRN", 5 },{ 0, 0 }   };
static int getcat( const char *dname )    {
   for( int i = 0; dcat[i].dname; i++ )
      if( strnicmp( dcat[i].dname, dname, 3 ) == 0 )
             break;
   return dcat[i].dtype;
}
charHandle::charHandle( const char *device )
                    : IoctlHandle( device )    {
  _cat = getcat( device );
}
charHandle *charHandle::Init(const char *device)   {
   charHandle *obj = new charHandle( device );

   if( obj->_handle == -1 ||   //bad handle
      obj->isFile()      ||   //can't be a file
      obj->_cat == 0        )  {   //unknown device
             delete obj;
             return (charHandle *) 0;
   }
   return obj;
}
void charHandle::handle_info( int handle,
                         unsigned info )  {
  /* Set device information word  */
   _iregs.x.dx = info & 0x00ff;   //dh must be 0
   _iregs.x.bx = handle;
   int21_44h(set_handle_info);
}
unsigned charHandle::ioctl_data( ioctl_cmd fn,
                            unsigned count,
                            void *buffer )   {
  /* Send/receive I/O Control data to char device */
   _iregs.x.bx = _handle;
   _iregs.x.cx = count;     //#bytes to read/write
   _iregs.x.dx = FP_OFF( (void far *) buffer );
   _sregs.ds   = FP_SEG( (void far *) buffer );
   int21_44h(fn);          //function number (2/3)
   return _oregs.x.ax;     //#bytes xfered
}
int charHandle::char_ioctl( char_cmd minor_code,
                       void *param_block ) {
  /* Access DOS int21h/44h/0Ch for the current
   * handle and device category, generic ioctl for
   * character devices.
   */
   _iregs.x.bx = _handle;
   _iregs.h.ch = (char) _cat;
   _iregs.h.cl = (char) minor_code;
   _iregs.x.dx = FP_OFF( (void far *) param_block );
   _sregs.ds   = FP_SEG( (void far *) param_block );
   int21_44h( gen_ioctl_char );
   return_dos_error ? _oregs.x.ax: 0;
}
int charHandle::sendIoctl( unsigned *count,
                       void *data      )   {
  /* Send ioctl data to current device.  */
   *count = ioctl_data( send_ioctl_char,
                        *count, data );
   return _dos_error ? _oregs.x.ax : 0;
}
int charHandle::readIoctl( unsigned *count,
                       void *data      )   {
   *count = ioctl_data( read_ioctl_char,
                        *count, data );

   return _dos_error ? _oregs.x.ax : 0;
}
unsigned charHandle::busyCount( void )     {
  /* Return LPTx device busy count, 0 on error. */
   unsigned count_buf;
   if( _cat != 5 ) return 0;      //error
   char_itoctl ( get_iter count, (void *) &count_buf );
   return _dos_error ? 0 : count_buf;
}
unsigned charHandle::busyCount( unsigned count )   {
  /* Set LPTx device busy count. Return new count,
   * or 0 on error........      */
   if( _cat != 5 ) return 0;      //error
   char_ioctl( set_iter_count, (void *) &count);
   return busyCount();
}
int charHandle::getANSIdata( struct ANSIdata *dis) {
  /* Get config data for an ANSI display driver.   */
   if( _cat != 3 ) return -1;       //error
   dis->info = 0;
   dis->block_length = 14;
   char_ioctl( get_display_mode, (void *) dis);
   return _dos_error ? -1 : 0;
}
int charHandle::setANSIdata( struct ANSidata *dis) {
  /* Set config data for an ANSI display driver. */
   if( _cat != 3 ) return -1;       //error
   dis->info = 0;
   dis->block_length = 14;
   char_ioctl( set_display_mode, (void *) dis);
   return _dos_error ? -1 : 0;
}
// End of File