c++.dos.32-bits - Accessing VRAM directly

"Javier Guti�rrez" <nikkho hotmail.com> Aug 28 2001

"Walter" <walter digitalmars.com> Aug 28 2001
Roland <rv ronetech.com> Aug 30 2001

"Javier Guti�rrez" <nikkho hotmail.com> Aug 31 2001

"Javier Guti�rrez" <nikkho hotmail.com> writes:

    How can I access the VRAM directly under a DOSX DMC program. The PDF
only explain it using assembler.

    In real mode it was easy, only create a pointer as:

    unsigned char far *pVram=MK_FP(0xA000, 0x0000);

    How can I do it in protected mode?

Aug 28 2001

"Walter" <walter digitalmars.com> writes:

The inline assembler ought to do the trick. -Walter

Javier Guti�rrez wrote in message <9mgsmq$1lhk$1 digitaldaemon.com>...
    How can I access the VRAM directly under a DOSX DMC program. The PDF
only explain it using assembler.

    In real mode it was easy, only create a pointer as:

    unsigned char far *pVram=MK_FP(0xA000, 0x0000);

    How can I do it in protected mode?

Aug 28 2001

Roland <rv ronetech.com> writes:

"Javier Guti�rrez" a �crit :

     How can I access the VRAM directly under a DOSX DMC program. The PDF
 only explain it using assembler.

     In real mode it was easy, only create a pointer as:

     unsigned char far *pVram=MK_FP(0xA000, 0x0000);

     How can I do it in protected mode?


use _dosptr_toptr macro below

regards

Roland

-----------------------------------------------------------------------
here some code to manipulate pointers.
compile and run for 16 bit large model and 32 bit DOSX model as well.
comes from code debugged and tested for years.
but i had to make some cut and past to make this.
i had to translate my comments to english. sorry if it is not sheakspear..
i hope i don't forget anything and it compile like that.
let me know if i forgot something

//-----------------------------------------------------------------------
#if (1==0)
written by Roland VARICHON for RONE Technologies 69100 FRANCE        //does
not hurt
#endif

#if (sizeof(int)==2)
    #define __INTSIZE 2
#else
    #define __INTSIZE 4
#endif

#if (__INTSIZE==4)
    #include <io.h>  //getDS
#endif

//-----------------------------------------------------------------------
//some definitions and declaration:


#if (__INTSIZE==2)
   #define dword unsigned long
#else
    #define dword unsigned int
#endif

#define dosptr dword        //real mode far pointer: segment:offset

#define dosptr_tooff(ptr) ( ((((unsigned)(ptr))>>12) &
~0xf)+(((unsigned)(ptr)) & 0xffff) )
//transform a dosptr to an offset based on 0000:0000 addresse

extern "C" dosptr off_todosptr(const dword s);
//transform an offset based on 0000:0000 addresse to a dosptr
//see asm code below

extern "C" dosptr dosptr_align(const dosptr ptr);
//align a dosptr: transform it so that offset <= 0xf
//see asm code below

extern "C" dosptr dosptr_add(const dosptr ptr, const dword v);
//add v to a dosptr, return an aligned dosptr
//!! v must be >=0
//see asm code below

extern "C" dosptr dosptr_seek(const dosptr ptr, const long v);
//same as dosptr_add but v can be <0
//see asm code below

//-----------------------------------------------------------------------------

//C++ code

#if (__INTSIZE==2)

#define _dosptr_toptr(ptr) ( ((void*)(ptr)) )
//nop on 16 bit lare model

#define _ptr_align(ptr) ( ((void*)dosptr_align((dosptr)(ptr))) )
//align a real mode far pointer: transform it so that offset <= 0xf

#define _ptr_add(ptr,v) ( ((void*)dosptr_add((dosptr)(ptr),v)) )
//add an offset to a real mode far pointer, return an aligned real mode far
pointer
//!! v must be >=0

#define _ptr_seek(ptr,v) ( ((void*)dosptr_seek((dosptr)(ptr),v)) )
//same as _ptr_add but v can be <0

#else
//__INTSIZE==4

//#include <dos.h> //_x386_get_abs_addresse
//commented here because in a SC++ version, if included here it didn't
compile, i don't know why

#define DGROUP MK_FP(getDS(),0)

#define _offtoptr(off) ( ((void*)(-_x386_get_abs_address(DGROUP)+off)) )
//transform an offset based on 0000:0000 addresse to a DOSX near pointer

#define _dosptr_toptr(ptr) (
((void*)(-_x386_get_abs_address(DGROUP)+dosptr_tooff(ptr))) )
//transform a real mode far pointer to a DOSX near pointer

#define _ptr_align(ptr) ( ((void*)(ptr)) )
//nop in DOSX model

#define _ptr_add(ptr,v) ( ((void*)(((byte*)(ptr))+((unsigned)(v)))) )
//add an offset to a pointer

#define _ptr_seek(ptr,v) ( ((void*)(((byte*)(ptr))+((int)(v)))) )
//same as _ptr_add but v is int

#endif    //__INTSIZE==2

//-----------------------------------------------------------------------------

//ASSEMBLY CODE
; you may have to rewrite the functions as i can't give you all the macro i
wrote for assembly
;it may be enough to be understandable
;just know that all names beginning with ' ' charactere are macros

;extern "C" dword dosptr_tooff(dosptr s);
;//
 CS
 PROC _dosptr_tooff,<_dosptr ??s>;
  enter
 movzx eax,WORD PTR P.??s
 movzx edx,WORD PTR P.??s[WORD]
 shl  edx,4
 add  eax,edx
  IF (INTG EQ 2)
 shld edx,eax,16
  ENDIF
  leave
 ENDP
 ENDS

;extern "C" dosptr off_todosptr(dword s);
;//
 CS
 PROC _off_todosptr,<_dword ??s>;
  enter
 mov  eax,P.??s
 mov  edx,eax
 shr  edx,4
 and  _ax,0fh
  IF (INTG EQ 4)
 shl  eax,16
 shrd eax,edx,16
  ENDIF
  leave
 ENDP
 ENDS

;extern "C" dosptr dosptr_align(dosptr ptr);
;//
 CS
 PROC _dosptr_align,<_dosptr ??ptr>;
  enter
 movzx eax,WORD PTR P.??ptr
 mov  edx,eax
 shr  _dx,4
 add  dx,WORD PTR P.??ptr[WORD]
 and  _ax,0fh
  IF (INTG EQ 4)
 shl eax,16
 shrd eax,edx,16
  ENDIF
  leave
 ENDP
 ENDS

;extern "C" dosptr dosptr_add(dosptr ptr, dword v);
;//
 CS
 PROC _dosptr_add,<_dosptr ??ptr, _dword ??v>;
  enter
 movzx eax,WORD PTR P.??ptr
 add  eax,P.??v
 mov  edx,eax
 shr  edx,4
 add  dx,WORD PTR P.??ptr[WORD]
 and  _ax,0fh
  IF (INTG EQ 4)
 shl eax,16
 shrd eax,edx,16
  ENDIF
  leave
 ENDP
 ENDS

;extern "C" dosptr dosptr_seek(dosptr ptr, long_short v);
;//
 CS
 PROC _dosptr_seek,<_dosptr ??ptr, _dword ??v>;
  enter
 movzx eax,WORD PTR P.??ptr
 movzx edx,WORD PTR P.??ptr[WORD]
 shl  edx,4
 add  eax,edx
 add  eax,P.??v
 mov  edx,eax
 shr  edx,4
 and  _ax,0fh
  IF (INTG EQ 4)
 shl  eax,16
 shrd eax,edx,16
  ENDIF
  leave
 ENDP
 ENDS

Aug 30 2001

"Javier Guti�rrez" <nikkho hotmail.com> writes:

    Thank you very much Roland for your sample code, I think I got the idea.

    PD: I am not from the Shackespeare's realms, so I understand your
comments qute good.

"Roland" <rv ronetech.com> escribi� en el mensaje
news:3B8DF4FF.219FB09F ronetech.com...
 "Javier Guti�rrez" a �crit :

     How can I access the VRAM directly under a DOSX DMC program. The PDF
 only explain it using assembler.

     In real mode it was easy, only create a pointer as:

     unsigned char far *pVram=MK_FP(0xA000, 0x0000);

     How can I do it in protected mode?


 use _dosptr_toptr macro below

 regards

 Roland

 -----------------------------------------------------------------------
 here some code to manipulate pointers.
 compile and run for 16 bit large model and 32 bit DOSX model as well.
 comes from code debugged and tested for years.
 but i had to make some cut and past to make this.
 i had to translate my comments to english. sorry if it is not sheakspear..
 i hope i don't forget anything and it compile like that.
 let me know if i forgot something

 //-----------------------------------------------------------------------
 #if (1==0)
 written by Roland VARICHON for RONE Technologies 69100 FRANCE


 not hurt
 #endif

 #if (sizeof(int)==2)
     #define __INTSIZE 2
 #else
     #define __INTSIZE 4
 #endif

 #if (__INTSIZE==4)
     #include <io.h>  //getDS
 #endif

 //-----------------------------------------------------------------------
 //some definitions and declaration:


 #if (__INTSIZE==2)
    #define dword unsigned long
 #else
     #define dword unsigned int
 #endif

 #define dosptr dword        //real mode far pointer: segment:offset

 #define dosptr_tooff(ptr) ( ((((unsigned)(ptr))>>12) &
 ~0xf)+(((unsigned)(ptr)) & 0xffff) )
 //transform a dosptr to an offset based on 0000:0000 addresse

 extern "C" dosptr off_todosptr(const dword s);
 //transform an offset based on 0000:0000 addresse to a dosptr
 //see asm code below

 extern "C" dosptr dosptr_align(const dosptr ptr);
 //align a dosptr: transform it so that offset <= 0xf
 //see asm code below

 extern "C" dosptr dosptr_add(const dosptr ptr, const dword v);
 //add v to a dosptr, return an aligned dosptr
 //!! v must be >=0
 //see asm code below

 extern "C" dosptr dosptr_seek(const dosptr ptr, const long v);
 //same as dosptr_add but v can be <0
 //see asm code below


---
 //C++ code

 #if (__INTSIZE==2)

 #define _dosptr_toptr(ptr) ( ((void*)(ptr)) )
 //nop on 16 bit lare model

 #define _ptr_align(ptr) ( ((void*)dosptr_align((dosptr)(ptr))) )
 //align a real mode far pointer: transform it so that offset <= 0xf

 #define _ptr_add(ptr,v) ( ((void*)dosptr_add((dosptr)(ptr),v)) )
 //add an offset to a real mode far pointer, return an aligned real mode


 pointer
 //!! v must be >=0

 #define _ptr_seek(ptr,v) ( ((void*)dosptr_seek((dosptr)(ptr),v)) )
 //same as _ptr_add but v can be <0

 #else
 //__INTSIZE==4

 //#include <dos.h> //_x386_get_abs_addresse
 //commented here because in a SC++ version, if included here it didn't
 compile, i don't know why

 #define DGROUP MK_FP(getDS(),0)

 #define _offtoptr(off) ( ((void*)(-_x386_get_abs_address(DGROUP)+off)) )
 //transform an offset based on 0000:0000 addresse to a DOSX near pointer

 #define _dosptr_toptr(ptr) (
 ((void*)(-_x386_get_abs_address(DGROUP)+dosptr_tooff(ptr))) )
 //transform a real mode far pointer to a DOSX near pointer

 #define _ptr_align(ptr) ( ((void*)(ptr)) )
 //nop in DOSX model

 #define _ptr_add(ptr,v) ( ((void*)(((byte*)(ptr))+((unsigned)(v)))) )
 //add an offset to a pointer

 #define _ptr_seek(ptr,v) ( ((void*)(((byte*)(ptr))+((int)(v)))) )
 //same as _ptr_add but v is int

 #endif    //__INTSIZE==2


---
 //ASSEMBLY CODE
 ; you may have to rewrite the functions as i can't give you all the macro


 wrote for assembly
 ;it may be enough to be understandable
 ;just know that all names beginning with ' ' charactere are macros

 ;extern "C" dword dosptr_tooff(dosptr s);
 ;//
  CS
  PROC _dosptr_tooff,<_dosptr ??s>;
   enter
  movzx eax,WORD PTR P.??s
  movzx edx,WORD PTR P.??s[WORD]
  shl  edx,4
  add  eax,edx
   IF (INTG EQ 2)
  shld edx,eax,16
   ENDIF
   leave
  ENDP
  ENDS

 ;extern "C" dosptr off_todosptr(dword s);
 ;//
  CS
  PROC _off_todosptr,<_dword ??s>;
   enter
  mov  eax,P.??s
  mov  edx,eax
  shr  edx,4
  and  _ax,0fh
   IF (INTG EQ 4)
  shl  eax,16
  shrd eax,edx,16
   ENDIF
   leave
  ENDP
  ENDS

 ;extern "C" dosptr dosptr_align(dosptr ptr);
 ;//
  CS
  PROC _dosptr_align,<_dosptr ??ptr>;
   enter
  movzx eax,WORD PTR P.??ptr
  mov  edx,eax
  shr  _dx,4
  add  dx,WORD PTR P.??ptr[WORD]
  and  _ax,0fh
   IF (INTG EQ 4)
  shl eax,16
  shrd eax,edx,16
   ENDIF
   leave
  ENDP
  ENDS

 ;extern "C" dosptr dosptr_add(dosptr ptr, dword v);
 ;//
  CS
  PROC _dosptr_add,<_dosptr ??ptr, _dword ??v>;
   enter
  movzx eax,WORD PTR P.??ptr
  add  eax,P.??v
  mov  edx,eax
  shr  edx,4
  add  dx,WORD PTR P.??ptr[WORD]
  and  _ax,0fh
   IF (INTG EQ 4)
  shl eax,16
  shrd eax,edx,16
   ENDIF
   leave
  ENDP
  ENDS

 ;extern "C" dosptr dosptr_seek(dosptr ptr, long_short v);
 ;//
  CS
  PROC _dosptr_seek,<_dosptr ??ptr, _dword ??v>;
   enter
  movzx eax,WORD PTR P.??ptr
  movzx edx,WORD PTR P.??ptr[WORD]
  shl  edx,4
  add  eax,edx
  add  eax,P.??v
  mov  edx,eax
  shr  edx,4
  and  _ax,0fh
   IF (INTG EQ 4)
  shl  eax,16
  shrd eax,edx,16
   ENDIF
   leave
  ENDP
  ENDS

Aug 31 2001

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c++.dos.32-bits - Accessing VRAM directly