Encapsulating the DOS IOCTL Interface

Listing 1 iobase.h — IOCTL base class definition

#ifndef __IOBASE_H
#define __IOBASE_H
#include <dos.h>

class IoctlBase   {
public:
   //DOS IOCTL subfunction codes .....
   enum ioctl_cmd    {
   get_handle_info,    set_handle_info,
   read_ioctl_char,    send_ioctl_char,
   read_ioctl_block,   send_ioctl_block,
   input_status,       output_status,
   drive_removable,    drive_remote,
   handle_remote,      sharing_retry,
   gen_ioctl_char,     gen_ioctl_block,
   get_log_drivemap,   set_log_drivemap,
   query_ioctl_char,   query_ioctl_block
   };
   //Minor function codes, Generic IOCTL
   //for character devices ....
   enum char_cmd {
   set_iter_count = 0x45,     get_iter_count = 0x65,
   select_code_page = 0x4a,   start_code_page = 0x4c,
   end_code_page = 0x4d,      query_code_page = 0x6a,
   query_prepare_list = 0x6b, set_display_mode = 0x5f,
   get_display_mode = 0x7f
   };
   //Minor function codes for, Generic IOCTL
   //for block devices. ....
   enum block_cmd {
   set_params = 0x40,         write_track = 0x41,
   format_and_verify = 0x42,  set_media_id = 0x46,
   set_access_flag = 0x47,    get_params = 0x60,
   read_track = 0x61,         verify_track = 0x62,
   get_media_id = 0x66,       get_access_flag = 0x67,
   sense_media_type = 0x68
   };
   IoctlBase();
   ~IoctlBase() { }
protected:
   //switch DOS major/minor version numbers
   //for direct version comparisons .........
   struct DOS_MM { unsigned char minor, major;};
   union DOS_VERSION { int version;
                    struct DOS_MM ver; };
   union DOS_VERSION _dos;
   int _dos_error; //saved DOS error number
   union REGS _iregs, _oregs;
   struct SREGS_sregs;
   virtual void int21_44h(ioctl_cmd code );
   virtual void IoctlError( int ) { }  //error proc
};  // .... end class IoctlBase
#endif    //_IOBASE_H

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