About memory buffer

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AE

Joined: 07 Apr 2022
Posts: 70

AE 19 Nov 2022, 18:17

The full title of the topic should sound something like "Memory buffer as a replacement for the data section for dynamic stuff".

Code:

struct ST
    a      dq ?
    b      dt ?
    c      dt ?
ends

Do I understand correctly that this structure will not take up space in the file after compilation, and only needed to generate offsets in the code?
If I plan to allocate a memory buffer at the beginning of the code and use it as a variable store, how do I assign variable aliases to the addresses?
It is logical to assume that a structure can be used for this, but here we go back to the previous question...

Could you give some advice on this?

19 Nov 2022, 18:17

macomics

Joined: 26 Jan 2021
Posts: 1042
Location: Russia

macomics 19 Nov 2022, 18:58

I do not use the proposed struct macros, but define structures using struc. My solution for this problem

Code:

use64

struc assume base*, type& { if ~ type eq
    virtual at base
      . type
      .Length = $ - $$
    end virtual
  else
    label . at base
    .Length = 0
  end if }

struc POINT vX=0, vY=0 {
  .x  dd vX
  .y  dd vY }

struc ST {
  .a  dq ?
  .b  dt ?
  .c  dt ?
  .d  POINT ?, ? }
; ...
memory_pointer dq ? ; A pointer to the allocated memory block is stored here
; ...
memory_area     assume  rbx, ST
cursor  assume  memory_area.d, POINT ?, ?
    mov rbx, [memory_pointer]
    mov rax, [memory_area.a] ; rax = qword [rbx + 0]
    fld [memory_area.b] ; st0 = tbyte [rbx + 8]
    fbstp [memory_area.c] ; tbyte [rbx + 18] = bcd(st0)
    mov edx, [memory_area.d.x] ; edx = dword [rbx + 28]
    mov [cursor.x], eax ; dword [rbx + 28] = eax

; flat assembler  version 1.73.30  (1024 kilobytes memory)
; 1 passes, 30 bytes.

; 00000000  00 00 00 00 00 00 00 00  48 8b 1d f1 ff ff ff 48  |........H......H|
; 00000010  8b 03 db 6b 08 df 73 12  8b 53 1c 89 43 1c        |...k..s..S..C.|

Last edited by macomics on 20 Nov 2022, 09:11; edited 4 times in total

19 Nov 2022, 18:58

Roman

Joined: 21 Apr 2012
Posts: 1847

Roman 20 Nov 2022, 08:28

macomics wrote:

I do not use the proposed struct macros, but define structures using struc. My solution for this problem

Code:

struc assume base*, type& { if ~ type eq
    virtual at base
      . type
      .Length = $ - .
    end virtual
  else
    label . at base
    .Length = 0
  end if }

struc POINT vX=0, vY=0 {
  .x  dd vX
  .y  dd vY
}

struc ST {
  .a  dq ?
  .b  dt ?
  .c  dt ?
  .d POINT
}
...
memory_pointer dq ? ; A pointer to the allocated memory block is stored here
...
memory_area assume rbx, ST
cursor assume memory_area.d, POINT ?, ?
    mov rbx, [memory_pointer]
    mov rax, [memory_area.a] ; rax = qword [rbx + 0]
    fld [memory_area.b] ; st0 = tbyte [rbx + 8]
    fbstp [memory_area.c] ; tbyte [rbx + 18] = bcd(st0)
    mov edx, [memory_area.d.x] ; edx = dword [rbx + 28]
    mov [cursor.x], eax ; dword [rbx + 28] = eax

cursor assume memory_area.d, POINT 0, 0 ;error invalid macro arguments fasmw 1.73
assume cool stuff !
I changed:

Code:

 ppcursor assume memory_area.d, POINT 0, 0 ;and fasm compiled this.
...
 mov [ppcursor.x], eax

20 Nov 2022, 08:28

macomics

Joined: 26 Jan 2021
Posts: 1042
Location: Russia

macomics 20 Nov 2022, 08:53

Corrected typos.

20 Nov 2022, 08:53

AE

Joined: 07 Apr 2022
Posts: 70

AE 20 Nov 2022, 10:49

Thank you!
Is there no way to keep the variable names in their original form?
Otherwise I have to rewrite a lot of code where they are used.

20 Nov 2022, 10:49

macomics

Joined: 26 Jan 2021
Posts: 1042
Location: Russia

macomics 20 Nov 2022, 13:29

Code:

; ./test.asm
use64

macro global name& { if 0
        label name
    end if }

struc assume base*, type& { if ~ type eq
    virtual at base
      . type
      .Length = $ - $$
    end virtual
    global .
  else
    label . at base
    .Length = 0
  end if }

struc POINT vX=0, vY=0 {
  .x  dd vX
  .y  dd vY }

struc ST {
  .a  dq ?
  .b  dt ?
  .c  dt ?
  .d  POINT ?, ? }
; ...
memory_pointer dq ? ; A pointer to the allocated memory block is stored here
; ...
memory_area     assume  rbx, ST
    mov rbx, [memory_pointer]
    mov rax, [.a] ; rax = qword [rbx + 0]
    fld [.b] ; st0 = tbyte [rbx + 8]

cursor  assume  .d, POINT ?, ?

    mov [.x], eax ; dword [rbx + 28] = eax

global memory_area

    fbstp [.c] ; tbyte [rbx + 18] = bcd(st0)
    mov edx, [.d.y] ; edx = dword [rbx + 32]

; $ fasm -m 1024 ./test.asm ./test.bin
; flat assembler  version 1.73.30  (1024 kilobytes memory)
; 1 passes, 30 bytes.

; $ hexdump -C ./test.bin
; 00000000  00 00 00 00 00 00 00 00  48 8b 1d f1 ff ff ff 48  |........H......H|
; 00000010  8b 03 db 6b 08 89 43 1c  df 73 12 8b 53 20        |...k..C..s..S |

20 Nov 2022, 13:29

AE

Joined: 07 Apr 2022
Posts: 70

AE 20 Nov 2022, 13:47

Thanks!

20 Nov 2022, 13:47

AE

Joined: 07 Apr 2022
Posts: 70

AE 12 Jan 2023, 04:30

A lot of questions...

At first everything seems very convenient, but as the code is written, inconveniences begin to come to light.
It looks like this directive significantly changes how the compiler works.

Named labels in code give errors (Anonymous labels works fine)
Some types of structures give errors [Solved]

Can I use structure members without dots?
How to "turn this mode off"?

Maybe it makes sense to include 'MACRO\MASM.INC' and use 'assume reg:STRUCT' ?
What is the purpose of 'assumed' macro in MASM.INC ?

I'll try to explain again
I would like a simple way to "map" the page of allocated memory for variables in the form of a structure.
Why structure?
Of course, you can access variables by offset, but when adding or changing some of them the offsets will no longer be relevant and you will have to change a lot of places in the code.
When accessing structured data, there is no such problem.

Simple example:

Code:

    struc PMEM {
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT 
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    }

; alloc some memory
mov     [MyMem], baseaddr ; save addr
; ...
; Uncomfortable version
mov     rax, [MyMem+8]  ; get ImagePathName
; And I would like at least (or kind of)
mov     rax, [MyMem.ImagePathName]
; looks like just
mov     rax, [ImagePathName]
; requires complex code and introduces more confusion and compiler errors

A little chaotic, but I hope you understand Smile

In general, is there a simple way to do what was intended without changing the usual style of writing code and without breaking the usual behavior of the compiler?

Last edited by AE on 12 Jan 2023, 07:00; edited 2 times in total

12 Jan 2023, 04:30

macomics

Joined: 26 Jan 2021
Posts: 1042
Location: Russia

macomics 12 Jan 2023, 05:29

AE wrote:

Code:

IMEM    assume  rbx, PMEM
[45] assume [2]:
          . type
[91] PMEM [11]:
        .MonInfo                         MONITORINFO ?
error: invalid macro arguments.

Check the definition of the '.MonInfo MONITORINFO ?' structure. This line contains an extra argument for the structure (?).

The dots inside the struct macro are attached to each name for you. Just for the sake of this, I don't see the point in using this macro.

The compiler's behavior most likely violates global. Try not to use this macro all the time and inside functions, because function macros also change the names of labels.

12 Jan 2023, 05:29

AE

Joined: 07 Apr 2022
Posts: 70

AE 12 Jan 2023, 06:20

Yes tis was a typo (extra ?). Thx.

Also can't use it in invoke args, have to use lea
Like this

Code:

lea     rcx, [.wc]
invoke  RegisterClassEx, rcx

And seems like it can't handle

Code:

mov     rax, [.MonInfo.rcMonitor.right]
; processed: mov rax,[.MonInfo.rcMonitor.right]
; error: undefined symbol 'IMEM.MonInfo.rcMonitor.right'

Quote:

Try not to use this macro all the time

I just use it ones in the beginning of the code.

Maybe there is a simpler and more flexible way to "map" structure to a "memory variable"?
Let it be a little less convenient, the main thing is not to create such problems.

Something like

Code:

    struc PMEM {
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    }

  MyMem    PMEM  sizeof.PMEM

But only in runtime for allocated memory address...

12 Jan 2023, 06:20

macomics

Joined: 26 Jan 2021
Posts: 1042
Location: Russia

macomics 12 Jan 2023, 08:14

AE wrote:

Code:

mov     rax, [.MonInfo.rcMonitor.right]
; processed: mov rax,[.MonInfo.rcMonitor.right]
; error: undefined symbol 'IMEM.MonInfo.rcMonitor.right'

Show me how you have declared the MONITORINFO structure?

AE wrote:

macomics wrote:
Try not to use this macro all the time

I just use it ones in the beginning of the code.

I'm talking about the global macro. The assume macro should be used 1 time. This is more than enough to define a global description of the block.

AE wrote:

Something like

Code:

    struc PMEM {
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    }

  MyMem    PMEM  sizeof.PMEM

Instead of sizeof, the assume macro sets the .Length value.

Code:

struc assume base*, type& { if ~ type eq
    virtual at base
      . type
      .Length = $ - $$
    end virtual
  else
    label . at base
    .Length = 0
  end if }

    struc PMEM {
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    }

  MyMem    assume rbx
  mov eax, MyMem.Length

If you need to declare only one description, then you can not use the assume structure, but write everything manually.

Code:

    struc PMEM {
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    }

virtual at rbx
  MyMem PMEM
end virtual

P.S. Why do you have a parameter passed to it in the form of sizeof.PMEM when declaring MyMem? However there are no formal parameters in the PMEM declaration.

12 Jan 2023, 08:14

AE

Joined: 07 Apr 2022
Posts: 70

AE 12 Jan 2023, 08:45

macomics wrote:

Show me how you have declared the MONITORINFO structure?

Code:

    struc MONITORINFO {
        cbSize          dd ?
        rcMonitor       RECT ?
        rcWork          RECT ?
        dwFlags         dd ?
    }

Damn, again that "?" in structures types Smile

But error have nothing to do with that BTW. So the question is open.

Quote:

If you need to declare only one description

I don't quite understand that sentence. What does "one description" mean?

Quote:

P.S

Unfortunately, I didn't understand exactly what you are talking about either.

And I guess in your last example all of the structure members must be prepended with dots for it works with [MyMem.hWnd].

12 Jan 2023, 08:45

AE

Joined: 07 Apr 2022
Posts: 70

AE 12 Jan 2023, 10:43

I eventually came to avoid using macros and just do this

Code:

    struct MONITORINFO
        cbSize          dd ?
        rcMonitor       RECT
        rcWork          RECT
        dwFlags         dd ?
    ends

    struct M
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    ends


    mov     r15, [IntMem]
    ;...
    invoke MonitorFromPoint, qword [r15+M.Mouse], 2
    mov     [r15+M.MonInfo.cbSize], sizeof.MONITORINFO
    lea     rdx, [r15+M.MonInfo]
    invoke GetMonitorInfo, rax, rdx

not very pretty, but it works and there are no side effects...

Thanks anyway, learned a couple of cool tricks!

12 Jan 2023, 10:43

macomics

Joined: 26 Jan 2021
Posts: 1042
Location: Russia

macomics 12 Jan 2023, 10:48

AE wrote:

Unfortunately, I didn't understand exactly what you are talking about either.

Code:

;             v - no formal parameters
    struc PMEM {
        MajorVersion                    dd ?
        MinorVersion                    dd ?
        ImagePathName                   dq ?
        Mouse                           POINT
        ImageName                       dq ?
        wc                              WNDCLASSEX
        hWnd                            dq ?
        MonInfo                         MONITORINFO
    }
;                 v - actual parameter for PMEM
  MyMem    PMEM  sizeof.PMEM

12 Jan 2023, 10:48

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