Calling opcode string discussion

[Pierre Bellisle]

Calling opcode string discussion was started at https://forum.powerbasic.com/forum/user-...discussion

It is an answer To Anne on how to get and embed a function in a string and call it via "call dword"
This one show particularly how to find the end of the function code by inserting data near the end.

Code:

'follow up of https://forum.powerbasic.com/forum/user-to-user-discussions/programming/838669-calling-opcode-string-discussion

#compile exe '#Win 10.04 (D:\Dev\Pow\Bas\Jose Roca\Forum\Jose\Windows API Headers\3.1.07\uz)#
#dim all
'#register none
'%Unicode = 1
#include "Win32Api.inc"

#RESOURCE MANIFEST, 1, "XPTheme.xml"

global hDlg as dword

$AppName  = "call dword"
%Static01 = 101
%Button01 = 201

declare function myfunction(byval var1 as long ,byval var2 as long) as long 'for call dword to use
'_____________________________________________________________________________

function HexView$(sString as string) as string 'HexString
local  pByte   as byte pointer
local  sBuffer as string
local  sChar16 as string
local  Looper  as long

pByte = strptr(sString)
do
   if (Looper and 15) = 00 then                 'Like MOD 16
     sBuffer = sBuffer & hex$(Looper, 4) & ": " 'Line number:
   elseif (Looper and 07) = 00 then             'Like MOD 8
     sBuffer = sBuffer & "- "                   'Middle dash
   end if

   if Looper < len(sString) then                'Add data
     sBuffer = sBuffer & hex$(@pByte[Looper], 2) & $spc
   else
     #if %def(%pb_win32) 'A to F have bigger width
     sBuffer = sBuffer & "     "                'Windows: No more data, fill with five spaces
     #else 'Use STDOUT in console
     sBuffer = sBuffer & "   "                  'Console: No more data, fill with three spaces
     #endif
   end if

   if (Looper and 15) = 15 then                 'End of 16 bytes line
     sChar16 = mid$(sString, Looper -14, 16) 'Next line replace non visible characters with dot
     replace any chr$(0,1,7,9,10,13,27 to 31,127,129,140,141,143,144,152,157) with "..................." in sChar16
     sBuffer = sBuffer & "; " & sChar16 & $crlf 'Add ascii string and CRLF
     if Looper >= len(sString) - 1 then exit do 'Job done
   end if

   incr Looper

loop
function = "Binary data lenght is" & str$(len(sString)) & " bytes." & $crlf & sBuffer

end function
'____________________________________________________________________________

function Add2Numbers(byval var1 as long ,byval var2 as long) as long

function = var1 + var2
'function = var2

exit function
!DB &h12, &h34, &h56, &h78, &h9A, &hBC, &hDE, &hF0

end function
'_____________________________________________________________________________

callback function DlgProc
local sAsm        as string
local sTerminator as string
local pcode       as dword
local pString     as dword
local RetVal      as long
local byteVal     as byte

select case cbmsg

   case %wm_command
     select case cbctl

       case %Button01
         if cbctlmsg = %bn_clicked or cbctlmsg = 1 then
           'call original function
           sTerminator = chr$(&h12, &h34, &h56, &h78, &h9A, &hBC, &hDE, &hF0)
           pcode       = codeptr(Add2Numbers)
           RetVal      = 0
           call dword pcode using myfunction(2, 2) to RetVal
           MessageBox(hDlg, "CALL DWORD pcode result =" & str$(RetVal), $AppName, 266240)
           '-----------------------------------------------------------------------------
           'call a copy of original function using myfunction()
           sAsm = ""
           do
             sAsm &= peek$(pcode, 1) 'build sAsm byte by byte to be sure to not access out of bound memory
             incr pcode
             if instr(sAsm, sTerminator) then
                sAsm &= peek$(pcode, 16) 'get the end of function
                exit do
             end if
           loop
           RetVal = 0
           pString = strptr(sAsm)
           call dword pString using myfunction(2, 3) to RetVal
           MessageBox(hDlg, "CALL DWORD pString result =" & str$(RetVal), $AppName, 266240)
           '-------------------------------------------------------------------------------------------------
           'call a copy of original function without using myfunction()
           pString = strptr(sAsm)
           ! push 4
           ! push 2
           call dword pString 'Or you may use !call pcode
           ! mov RetVal, eax
           MessageBox(hDlg, "CALL DWORD ASM result =" & str$(RetVal), $AppName, 266240)
           '-------------------------------------------------------------------------------------------------
           'show the copy and original function code side to side
           MessageBox(hDlg, "pcode:" & $crlf & HexView$(peek$(codeptr(Add2Numbers), len(sAsm))) & $crlf & $crlf & $crlf & _
                      "pString:" & $crlf & HexView$(peek$(codeptr(Add2Numbers), len(sAsm))), $AppName, 266240)
         end if

     end select

  end select

end function
'_____________________________________________________________________________

function pbmain()

dialog font "Segoe UI", 9
dialog new %hwnd_desktop, $AppName, , , 150, 50, _
%ws_caption or %ws_minimizebox or %ws_maximizebox or %ws_sizebox or %ws_sysmenu, %ws_ex_left to hDlg

control add label, hDlg, %Static01, "codeptr() and strptr() test", 5, 10, 140, 11, %ss_center

control add button, hDlg, %Button01, "test codeptr() and strptr()", 15, 25, 120, 15

dialog show modal hDlg call DlgProc

end function
'_____________________________________________________________________________
'