A function that accepts a function pointer

[bf2]

It's a generic question, but how do I create a function in MASM that accepts a function pointer?

I have searched a few books (including Irvine and Pirogov) and couldn't find anything on this.

I have searched the forum and found some discussions on how to call a function using a pointer, but not how to write a function that expects a function pointer - like you do in C.

Thanks in advance.

[dedndave]

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FuncProc PROTO :DWORD
Func     PROTO

;

        .CODE

FuncProc PROC lpfnProc:DWORD

        call dword ptr lpfnProc
        ret

FuncProc ENDP

Func    PROC

        ret

Func    ENDP

;to call it

        INVOKE  FuncProc,Func

[ToutEnMasm]

Perhaps more explains ( a sample for example) could be useful.
Here is some samples

Monproc proc
...
Monproc endp

.data
pointer dd Monproc                                        ;put the adress of Monproc in pointer
.code
invoke afunction,parm1,Monproc                     ;pass the adress of Monproc to afunction

[qWord]

If you want to use INVOKE, a typedef is needed:

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MYMSG typedef proto hWnd:HWND,psz1:PCHAR,psz2:PCHAR,flg:DWORD
PMYMSG typedef ptr MYMSG

myMsg proc hWnd:HWND,psz1:PCHAR,psz2:PCHAR,flg:DWORD

invoke MessageBox,hWnd,psz1,psz2,flg
ret

myMsg endp

xyz proc pFnc:PMYMSG

invoke pFnc,0,0,0,0
; or:  invoke PMYMSG ptr ...,0,0,0,0
ret
xyz endp
...
invoke xyz,myMsg

[Farabi]

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;I translate this from syslinux
; It has a table function defined like this


PMVect struc
nSize dword 0
_lmalloc dd 0   
_lfree dd 0   
_open_file dd 0   
_read_file dd 0   
_close_file dd 0   
_opendir dd 0   
_readdir dd 0   
_closedir dd 0   
_idle dd 0   
_reset_idle dd 0   
_chdir dd 0   
_getcwd dd 0   
_jiffies dd 0   
_ms_timer dd 0
PMVect ends

PM_VEC_TABLE dd OFFSET nSize dword, OFFSET _lmalloc,OFFSET_lfree, OFFSET_open_file dd 0   ... etc. OFFSET _ms_time

GetPMVector proc

mov eax,offset _ms_time

ret
GetPMVector endp

OpenFile proc lpPointer:dword,lpName:dword

mov ecx,lpPointer
push lpname
call [ecx].PMVect._open_file
add esp,4

ret
OpenFile endp


;Here is how you used it

Invoke GetVectoreTable
invoke OpenFile,eax,CADD("MyFile.txt")


[hutch--]

its pretty easy, get the ADDRESS of the function and pass it to another function as a single DWORD value.

Now with the receiving function, it needs to be able to call the passed function, the low level way to do this is to use the PUSH / CALL technique common in MASM programming.

Pseudo code.

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called_function proc fptr:DWORD, any other args etc ...

    LOCAL retval  :DWORD

    push arg3    ; args required by the passed function
    puch arg2
    push arg1
    call fptr

    mov retval, eax  ; get its return value

  ; any other code

    ret

called_function endp