Assembly help

[Jules Marchildon]

I have not done much in the way of assembly with Win32 and I am
hoping to give myself more time in this area. One of the ways
to quickly learn is to cut and paste some existing code. I am
converting a small TASM win32 example to compile in PBDLL60. I want
to preserve as much ASM code as possible. My question is if PB allows
me to use the ASM 'call' instruction to make an API call.

For instance,

    '*GET some needed SystemMetrics
 
    ! push %SM_CXSIZEFRAME
    ! call GetSystemMetrics
 
    ! mov [SM_CX_SizeFrame], eax

    ! push %SM_CYSIZEFRAME
    ! call GetSystemMetrics

I could convert this back to an API call, but I want to preserve as
much as I can. What I think I need is the address of the function
GetSystemMetrics to use the asm call instruction. So perhaps CODEPTR()
would be the answer?

    Local lpAnyApiCall As Dword
    lpAnyApiCall = CODEPTR(GetSystemMetrics)

    ! push %SM_CXSIZEFRAME
    ! call GetSystemMetrics
 
    ! mov [SM_CX_SizeFrame], eax

    ! push %SM_CYSIZEFRAME
    ! call lpAnyApiCall

Any tips, suggestions, comments are much appreciated.

Thanks!
Regards, Jules

[Florent Heyworth]

Hi Jules

CODEPTR will only return the address of a function/label/sub in your file not in a dll.

For your purpose something like:

LOCAL hLib AS LONG
LOCAL dwCall AS DWORD
LOCAL lResult AS LONG

hLib = LoadLibrary( "user32.dll" )
IF hLib <> %NULL THEN
    dwCall = GetProcAdress( hLib, "GetSystemMetrics" )
    IF dwCall <> %NULL THEN
        ! push %SM_CXSIZEFRAME
        ! call dwCall
        ! mov lResult, eax
        
        MSGBOX STR$(lResult)
        
        ! push %SM_CXFULLSCREEN
        ! call dwCall
        ! mov lResult, eax
        
         MSBOX STR$(lResult)

would do the trick

Cheers

Florent

------------------

[Jules Marchildon]

Thanks Florent!

I think I have seen this demonstrated before? Maybe Hutch? I thought the
codeptr boundaries was limited only for labels?

In any case your solution works.

I thought that user32.dll was already loaded by the win32api.inc delares?
If so, perhaps another method to obtain the address is possible?
Just thinking of reducing 3 lines of code,

LoadLibrary
GetProcAddress
FreeLibrary

to one line. Otherwise it would now be worth just converting back to a conventional
PB function with a parameter list.

Regards, Jules

[Florent Heyworth]

hi jules

codeptr will work for functions, subs and labels which have actual "bodies" in your code - procedures in a dll are not accessible.

it's true that user32.dll is mapped in your process space - however i can't, offhand, think of any simple way to access the mapped dll without having to consider stuff like readprocessmemory and such which would significantly increase the complexity of the code and would offset any negligible advantage you might get by not calling loadlibrary, etc

a quick search on the pb site did indeed reveal some code by hutch at

as they say in french "qui cherche trouve" (he who seeks findeth)

florent


[this message has been edited by florent heyworth (edited may 26, 2000).]