Other architecture DLL in PowerBASIC

[Steve Hutchesson]

The advantage of using a true low level compiler shows when you need to
do something different from normal, where "method" based languages do
not give you the freedom to do unusual things, PowerBASIC has the low
level grunt needed to be original.

Below is the code for a different interface in a DLL, instead of having an
EXPORT for each function that is called, this design only has one which is
the despatch function which calls the required internal function and
passes back any return value to the calling EXE.

It allows very large parameter counts to be passed in a way that normal
functions find difficult to handle. This example is limited to 32 bit
return values but of course, the address of a different size parameter can
be used in the array or structure parameters for different size return
values.

It can use either an array or a structure to pass the parameters,
depending if you need different size parameters or not. The advantage of
an architecture of this type is that it does not require the operating
system to look up a large EXPORT table. A DLL of this type is also a lot
harder to hack as there is no EXPORT to look up.

There are 2 techniques used to get the parameters at the DLL function end,
the first uses inline asm to dereference the parameters, the second uses
the standard PowerBASIC pointers and is clean and easy to understand code.
This example is still a little rough around the edges and it needs to be
civilised some but it is a viable technique that can be done in the
current PowerBASIC DLL compiler.

James Fuller has a different design that is also original and that has a
number of advantages when understood, perhaps James if time allows would
make an example available as I am sure many would appreciate his design
work here.

Regards,

[email protected]

  ' Include file components
  
      TYPE IF1
        par1 as DWORD
        par2 as DWORD
        par3 as DWORD
        par4 as DWORD
      END TYPE
  
      GLOBAL RemoteMessageBoxS as DWORD
      GLOBAL RemoteMessageBoxA as DWORD
  
  ' runtime code
  
    ' --------------------------
    ' give DLL functions a name
    ' --------------------------
      RemoteMessageBoxA = 1
      RemoteMessageBoxS = 2
  
  ' call the DLL functions
  
        LOCAL if1p      as IF1
        LOCAL mbMsg     as ASCIIZ * 128
        LOCAL mbTit     as ASCIIZ * 128
  
        Case  50
  
          mbMsg = "This messagebox in displayed in iface.dll !!!"
          mbTit = "Parameters passed in structure"
  
          if1p.par1 = hWin
          if1p.par2 = VarPtr(mbMsg)
          if1p.par3 = VarPtr(mbTit)
          if1p.par4 = %MB_OK
  
          rv& = icall(RemoteMessageBoxS,VarPtr(if1p))
  
        Case  51
  
          mbMsg = "This messagebox in displayed in iface.dll !!!"
          mbTit = "Parameters passed in array"
  
          redim pars&(4)
  
          pars&(0) = hWin
          pars&(1) = VarPtr(mbMsg)
          pars&(2) = VarPtr(mbTit)
          pars&(3) = %MB_OK
          
          rv& = icall(RemoteMessageBoxA,VarPtr(pars&(0)))
  
  
      ' The basic despatch DLL interface
  
  ' ###########################################################################
  
      #COMPILE DLL
  
      #INCLUDE "d:\pb6\winapi\win32api.inc"
  
      GLOBAL hInstance as LONG    ' the DLLs instance handle
  
      DECLARE FUNCTION One(ByVal Address as LONG) as LONG
      DECLARE FUNCTION Two(ByVal Address as DWORD) as LONG
      DECLARE FUNCTION Three(ByVal Address as LONG) as LONG
      DECLARE FUNCTION Four(ByVal Address as LONG) as LONG
      DECLARE FUNCTION Five(ByVal Address as LONG) as LONG
  
  ' ###########################################################################
  
  FUNCTION LibMain(BYVAL hInst    AS LONG, _
                   BYVAL Reason   AS LONG, _
                   BYVAL Reserved AS LONG) EXPORT AS LONG
  
      LOCAL RetVal as LONG
  
      Select Case Reason
        Case %DLL_PROCESS_ATTACH
          hInstance = hInst       ' make DLL instance global
          RetVal = 1              ' needed so DLL will start
  
        ' -------------------
        ' uncomment if needed
        ' -------------------
        ' Case %DLL_PROCESS_DETACH
        
        ' Case %DLL_THREAD_ATTACH
        
        ' Case %DLL_THREAD_DETACH
        
      End Select
  
      FUNCTION = RetVal
  
  END FUNCTION
  
  ' ###########################################################################
  
  FUNCTION icall ALIAS "icall"(ByVal FuncNum as LONG, _
                               ByVal Address as LONG) EXPORT as LONG
  
      Select Case FuncNum
        Case 1
          FUNCTION = One(Address)
        Case 2
          FUNCTION = Two(Address)
        Case 3
          FUNCTION = Three(Address)
        Case 4
          FUNCTION = Four(Address)
        Case 5
          FUNCTION = Five(Address)
      End Select
  
      FUNCTION = -1   '< function not supported
  
  END FUNCTION
  
  ' ###########################################################################
  
  FUNCTION One(ByVal Address as LONG) as LONG
  
      LOCAL par1 as LONG
      LOCAL par2 as LONG
      LOCAL par3 as LONG
      LOCAL par4 as LONG
  
      ! mov eax, Address
  
      ! mov ecx, [eax]
      ! mov par1, ecx
  
      ! mov ecx, [eax + 4]
      ! mov par2, ecx
  
      ! mov ecx, [eax + 8]
      ! mov par3, ecx
  
      ! mov ecx, [eax + 12]
      ! mov par4, ecx
  
      FUNCTION = MessageBox(par1,ByVal par2,ByVal par3,par4)
  
  END FUNCTION
  
  ' ###########################################################################
  
  FUNCTION Two(ByVal Address as DWORD) as LONG
  
      LOCAL par1 as DWORD PTR
      LOCAL par2 as DWORD PTR
      LOCAL par3 as DWORD PTR
      LOCAL par4 as DWORD PTR
  
      par1 = Address
      par2 = Address + 4
      par3 = Address + 8
      par4 = Address + 12
  
      FUNCTION = MessageBox(@par1,ByVal @par2,ByVal @par3,@par4)
  
  END FUNCTION
  
  ' ###########################################################################
  
  FUNCTION Three(ByVal Address as LONG) as LONG
  
  
      FUNCTION = 0
  
  END FUNCTION
  
  ' ###########################################################################
  
  FUNCTION Four(ByVal Address as LONG) as LONG
  
  
      FUNCTION = 0
  
  END FUNCTION
  
  ' ###########################################################################
  
  FUNCTION Five(ByVal Address as LONG) as LONG
  
  
      FUNCTION = 0
  
  END FUNCTION
  
  ' ###########################################################################

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

[jcfuller]

Here is my rendition which shows two similiar methods.

Method one would be used when the dll contains many functions but the application
only uses a few functions or there are a small number of times the application calls
the functions.

Method two would be used when the application relies heavily on the functions in the dll.

James

'==============================================================================
'DLL CODE:
'------------------------------------------------------------------------------
#COMPILE DLL "MYWAY.DLL"
#REGISTER NONE
#DIM ALL

FUNCTION _
  One& ( _
    BYVAL a& _
  )
  
  MsgBox "In Dll Function One"+ $CR + "a& = " + FORMAT$(a&) 
  FUNCTION = a& * 10 
END FUNCTION    
'------------------------------------------------------------------------------
FUNCTION _
  Two& ( _
    BYVAL a&,BYVAL b& _
  )
  
    MsgBox "In Dll Function Two"+ $CR + " a& = " + FORMAT$(a&) + $CR + " b& = " + FORMAT$(b&)  
    FUNCTION = a& + b&
END FUNCTION    
'------------------------------------------------------------------------------
FUNCTION _
  Three$ ( _
    StrIn$ _
  )
  
  FUNCTION = StrIn$ + " More Characters Added" + $CR + "Another Line"
  
END FUNCTION    
'------------------------------------------------------------------------------
FUNCTION _
  Test01& ALIAS "Test01" ( _
    BYVAL Id& _
  )EXPORT

  SELECT CASE Id&
    CASE 1
    FUNCTION = CODEPTR(One&)
    CASE 2
      FUNCTION = CODEPTR(Two&) 
    CASE 3
      FUNCTION = CODEPTR(Three$) 
  END SELECT 
END FUNCTION    
'------------------------------------------------------------------------------
FUNCTION _
  Test02& ALIAS "Test02" ( _
    IdArray???() _
  )EXPORT

  IF UBOUND(IdArray???) < 3 THEN
    FUNCTION = -1
    EXIT FUNCTION
  END IF   

  IdArray???(1) = CODEPTR(One&)
  IdArray???(2) = CODEPTR(Two&)
  IdArray???(3) = CODEPTR(Three&)
END FUNCTION    
'==============================================================================

'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
'Test Code
'Method #1
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
#COMPILE EXE
#DIM ALL
#REGISTER NONE
'------------------------------------------------------------------------------
DECLARE _
  FUNCTION _
    Test  LIB "MYWAY.DLL" ALIAS "Test01" ( _
      BYVAL Id& _
    )  AS DWORD
'------------------------------------------------------------------------------
FUNCTION _
  One& ( _
    BYVAL a& _
    )
  LOCAL pAdd???
  pAdd??? = Test(1)  
  CALL DWORD pAdd USING One&(a&) 
 !mov FUNCTION,eax
END FUNCTION    
'------------------------------------------------------------------------------
FUNCTION _
  Two& ( _
    BYVAL a&, _
    BYVAL b& _
  )
  LOCAL pAdd???
  pAdd??? = Test(2)  
  CALL DWORD pAdd USING Two&(a&,b&) 
 !mov FUNCTION,eax
    
END FUNCTION  
'------------------------------------------------------------------------------
FUNCTION _
  Three$ ( _
    StrIn$ _
  )

  LOCAL pAdd???
  pAdd??? = Test(3)  
  CALL DWORD pAdd USING Three$(StrIn$)
 !mov FUNCTION,eax
  
END FUNCTION      
'------------------------------------------------------------------------------    

FUNCTION _
  PBMain ( _
  ) AS LONG
  
  LOCAL RetVal& ,Temp$
  
  RetVal& = One&(1)
  MsgBox "RetVal From One = " +FORMAT$(RetVal&)
  RetVal& = Two&(1,2)
  MsgBox "RetVal From Two = " + FORMAT$(RetVal&)
  Temp$ = Three$("some text")
  MsgBox Temp$
END FUNCTION
'==============================================================================
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
'Test Code      
'Method #2
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
#COMPILE EXE
#DIM ALL
#REGISTER NONE
'------------------------------------------------------------------------------
DECLARE _
  FUNCTION _
    Test  LIB "MYWAY.DLL" ALIAS "Test02" ( _
      IdArray???() _
    )  AS DWORD
'------------------------------------------------------------------------------
GLOBAL IdArray???()
'------------------------------------------------------------------------------
FUNCTION _
  One& ( _
    BYVAL a& _
    )
  CALL DWORD IdArray???(1) USING One&(a&) 
 !mov FUNCTION,eax
END FUNCTION    
'------------------------------------------------------------------------------
FUNCTION _
  Two& ( _
    BYVAL a&, _
    BYVAL b& _
  )

  CALL DWORD IdArray???(2) USING Two&(a&,b&) 
 !mov FUNCTION,eax
    
END FUNCTION  
'------------------------------------------------------------------------------
FUNCTION _
  Three$ ( _
    StrIn$ _
  )

  CALL DWORD IdArray???(3) USING Three$(StrIn$)
 !mov FUNCTION,eax
  
END FUNCTION      
'------------------------------------------------------------------------------    

FUNCTION _
  PBMain ( _
  ) AS LONG
  
  LOCAL RetVal& ,Temp$
  REDIM IdArray???(1:3)
  RetVal& = Test(IdArray())
  
  RetVal& = One&(1)
  MsgBox "RetVal From One = " +FORMAT$(RetVal&)
  RetVal& = Two&(1,2)
  MsgBox "RetVal From Two = " + FORMAT$(RetVal&)
  Temp$ = Three$("some text")
  MsgBox Temp$
END FUNCTION

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