wsprintf

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coconut

Joined: 02 Apr 2004
Posts: 326
Location: US

coconut 28 Mar 2005, 02:36

having trouble with this, crashes when it reaches wsprintf call:

Code:


buffer rb 10

proc wndproc ...
  ...
        call        showmsg    
endp

proc showmsg ...
        mov      ecx,[lparam]  ;structure: im interested in dword value at [ecx+4]
        lea        eax,[buffer]
        cinvoke  wsprintf,eax,"%d", dword [ecx+4]
        invoke   MessageBox,0,eax,eax,0
        return
endp

what i want to do is display in a msgbox the value of [ecx+4]. im trying to use wsprintf to convert dword to string, but i guess im calling it wrong. any help would be great

28 Mar 2005, 02:36

Tommy

Joined: 17 Jun 2003
Posts: 489
Location: Norway

Tommy 28 Mar 2005, 07:18

if "dword [ecx+4]" is a pointer to a string, use "%s" instead of "%d"... btw: have you passed the argument(s) correctly to showmsg?

28 Mar 2005, 07:18

coconut

Joined: 02 Apr 2004
Posts: 326
Location: US

coconut 28 Mar 2005, 11:37

yes it is in fact a callback function, so i can assume the parameters will always be correct. lparam holds a structure of dword values, the second member is the one i want to convert to a string and display. perhaps i can just use a dwtoa function?

28 Mar 2005, 11:37

mike.dld

Joined: 03 Oct 2003
Posts: 235
Location: Belarus, Minsk

mike.dld 28 Mar 2005, 12:26

lparam is actually an EQU like EBP+???, but when you call showmsg, ebp value is changed so [lparam] isn't what you expect. You better try to mov lparam to ecx inside wndproc Wink

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28 Mar 2005, 12:26

f0dder

Joined: 19 Feb 2004
Posts: 3175
Location: Denmark

f0dder 28 Mar 2005, 16:14

Also, remember that the return value of wsprintf is the number of characters written to the buffer, so the msgbox call on the next line will not do what you expect it to. a "dwtoa" or "itoa" function would indeed do the trick, and most likely be faster. If you want hexadecimal output, such a routine can be made very fast.

28 Mar 2005, 16:14

coconut

Joined: 02 Apr 2004
Posts: 326
Location: US

coconut 28 Mar 2005, 17:35

well actually its a standard windows hook callback, gets called whenever certain mouse/keyboard events occur so i think ebp will be ok. in this case im trying to display a messagebox of the virtual keycode pressed. the KBDLLHOOKSTRUCT.vkCode is at [lparam+4]

f0dder do you have an example of dwtoa or itoa?

28 Mar 2005, 17:35

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