New syntax for numerical expressions: with arguments

Index > Macroinstructions > New syntax for numerical expressions: with arguments

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daluca

Joined: 05 Nov 2005
Posts: 86

daluca 28 Aug 2006, 04:23

Hello:

Let's say we want to load a constant RGB value color in to some register,
eax for instance, but don't want to code:

Code:


xor eax,eax
mov ah,100   ;blue
mov al,180   ;green
shl eax,8
mov al,190   ;red

Instead we want Fasm to do the calculations and load the value directly
like:

Code:


         ;blue        green      red
mov eax,(100 shl 16)+(180 shl 8)+190

Of course we can do the calculations ourselves and then code:

Code:


mov eax,64B4BEh
 ;or in decimal:
mov eax,6599870

But what if we want to performe such mov operation with another three
values?... well, macro:

Code:


macro movRGB destination,red,green,blue 
{
mov destination,(blue shl 16)+(green shl 8)+red
}

movRGB ebx,255,0,255
movRBG edx,128,64,32
movRGB [Color1],192,192,192

But what about pushing the color,or other operation apart from mov?
we have to extend the macro:

Code:


macro RGBoperation operation,destination,red,green,blue
{
operation destination,(blue shl 16)+(green shl 8)+red
}

RGBoperation xor,eax,192,192,192
RGBoperation and,[Color2],255,0,255
RGBoperation or,ebx,128,64,32

And about defining these values in data?... another macro?
or maybe a structure?
I don't like this approach of adding more mnemonics,because what we
are doing here is just handling immediate values.
so I would like to have a way to define values based on arguments
I know this is like inline macros, and in an old topic I found:
"inlining the macros is something against the Fasm's concept"
but please, let me continue...

I'm going to jump directly to my proposal,and then give some advantages
and examples of use:

1.- A new Keyword: I will use FORMULA
2.- A name for the formula freely chosen by the coder
3.- A list of arguments that the formula will take
4.- The actual formula

Code:


FORMULA RGB red,green,blue = (blue shl 16)+( green shl 8 ) + red

Since this definition is just a constant value specified by any
numerical expression,it should take only one line.
Obviously the arguments should be immediate values too.

The invocation of the formula would be something simple like:

Code:


RGB(192,192,192)

Or maybe: (RGB,192,192,192) to indicate that this expression should be
readed as one single immediate value.(I will use the two ways)
And wherever this expresion appears
in the source will be replaced with: (192 shl 16)+(192 shl 8 ) + 192

Why should be implemented:

- More readability.

- Less typing.

- No new mnemonics,we can use the standar ones.

- They are just numbers so we can use them as parameters to macros:

Code:


mov eax,RGB(190,181,100)

xor eax,RGB(192,192,192)

cmp eax,(RGB,255,0,255)

color1 dd  RGB(128,64,32)

ColorArray dd  (RGB,255,0,255)
           dd  (RGB,190,181,100)
           dd  (RGB,128,64,32)
           dd  (RGB,80h,80h,80h)

invoke SetTextColor,[hdc],(RGB,128,32,32)

Some usages:

For seting the highword of some register or memory to
a specific decimal value:
(The low word will be zero of course)

Code:


        ;HW = HighWord
FORMULA HW value = value shl 16

mov eax,HW(1523)

mov [VAR_1],(HW,4096)

To set or compare the cursor position with the bios interrupt
10h, or to define constant positions in memory:

Code:


FORMULA Pos column,row = (row shl 8) + column

;Set cursor:
mov ah,2
mov bh,0  ;page number
mov dx,Pos(5,15)
int 10h

;Get cursor
mov ah,3
mov bh,0  ;page number
int 10h
cmp dx,(Pos,24,79)

;or:
cmp dx,[EndPos]
;...code
;...code

;...data
EndPos dw (Pos,24,79)

The formula definition can be altered to define the
positions starting from 1 instead of 0:

Code:


FORMULA Pos column,row = ((row-1) shl 8 )) + (column-1)

Code:


FORMULA Date,day,month,year =  ((year -1980) shl 9)+(month shl 5)+day

FORMULA Time,hour,minute,second = (hour shl 11)+(minute shl 5) +(second/2)

mov bx,[filehandle]
mov ah,57h
mov al,0    ;0=get time and date of file
cmp dx,Date(27,8,2006)
je some_code
cmp cx,Time(17,30,0)
jne some_other_code

;...data
date1 dw (Date,1,1,2006)
date2 dw (Date,31,12,2006)

InitTime dw Time(0,0,0)
EndTime  dw Time(12,59,59)

Why should not be implemented:

-It would be dificult to implement.

well I don't know how much dificulty would it take
but from my naive point of view it would be just text
replecement by the preprocesor,and the assembler would
do the calculations as already does.

-The same thing can be achieved with macros.

maybe, but macros can't be use as parameters.

-This is just inline macros and that goes "against the Fasm's concept".

we can see this as inline macros although we can also see it
as a new way to represent constant values,a way that would be more
flexible because the use of arguments.

-The few occasions that we need to handle constant values in
this way,doesn't justify the implementation of this new "feature".

that maybe true but; how often do you use,in your sorces,directives
like load,store or virtual? I think this directives have usage in
few specific situations as well.

Well this is just an idea that i put to your consideration.

Thank you for your time.

28 Aug 2006, 04:23

IceStudent

Joined: 19 Dec 2003
Posts: 60
Location: Ukraine

IceStudent 28 Aug 2006, 09:03

Interesting. It seems as macro function in the masm.

28 Aug 2006, 09:03

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20571
Location: In your JS exploiting you and your system

revolution 28 Aug 2006, 09:37

Perhaps the syntax can look better like this:

Code:

FORMULA Date(day,month,year) = ...

28 Aug 2006, 09:37

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 28 Aug 2006, 09:57

already discussed - search for "inline macros" or something like that. It's design problem of FASM.

(But i still believe it could be added... it there's a will)

28 Aug 2006, 09:57

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453 28 Aug 2006, 16:36

@ daluca: Some of the things you mentioned can be accomplished by rewriting the actual function your using e.g.

Code:

macro mov op1,op2,v1,v2,v3
 {
        if op2 eq RGBVal
                mov op1,((v3 shl 16) + (v2 shl 8) + v1)
        else
                mov op1,op2
        end if
 }

struc RGB r,g,b
 {
        . dd ((b shl 16) + (g shl 8) + r)
 }

use32
mov eax,RGBVal,128,128,128
mov eax,[Colour]

Colour   RGB 128,128,128

This avoids creating "new" macros and inline macros, but it does mean you have to add RGB,Pos,... options for all the operations you want to use (mov, xor, cmp, ...) and define strucs with different names Sad

but once you've written them you'll never have to do it again Wink

28 Aug 2006, 16:36

chris

Joined: 05 Jan 2006
Posts: 62
Location: China->US->China->?

chris 29 Aug 2006, 03:40

I guess this could be done by extending the 'fix' directive, so that the replacement could take arguments, like

Date(day,month,year) fix ((year -1980) shl 9)+(month shl 5)+day

but since 'fix' is introduced to adjust some language syntax, this might have some side effects.

29 Aug 2006, 03:40

Madis731

Joined: 25 Sep 2003
Posts: 2139
Location: Estonia

Madis731 29 Aug 2006, 14:48

But it which project would this be used? I think that all you described is needed only for debugging, but in real life you only use these kinds of strctures when inititalizing something. Well, actually, everything that makes use of macros does some kind of initialization Razz

. I still think that writing:

Code:

mov eax,128 shl 16+128 shl 8+128

instead of:

Code:

mov eax,RGB(128,128,128)

isn't much of a trouble and is clearer. with RGB() you don't know which value goes to which byte and weather red is actually in the place of red :S

29 Aug 2006, 14:48

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8376
Location: Kraków, Poland

Tomasz Grysztar 30 Aug 2006, 11:53

Such feature was requested and considered a few times in fasm's history, but I never decided to go into such direction, as I had a "slightly different vision" of macro processor that I made into fasm. See also http://board.flatassembler.net/topic.php?t=4795

30 Aug 2006, 11:53

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 10 Sep 2006, 14:27

My solution:

Code:

macro overload1 instr {
 macro instr op1 \{
  match =RGB red green blue, op1 \\{
   instr (red shl 16) or (green shl 8) or blue \\} \} }

macro overload2 instr {
 macro instr op1, op2 \{
  match =RGB red green blue, op2 \\{
   instr op1, (red shl 16) or (green shl 8) or blue \\} \} }

irps instruction, push {
 overload1 instruction }

irps instruction, mov xor sub add {
 overload2 instruction }


        mov     eax, RGB 192 192 192
        xor     ecx, RGB 255 255 0
        sub     edx, RGB 160 170 23

        push    dword RGB 1 1 1

10 Sep 2006, 14:27

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