Callback - Strings

[Niraj Bhatt]

My Powerbasic dll is calling a VB function sent through Addressof.
Now I am able to call the function and pass the Long values, but not the strings.
Is there any other simple way then passing the pointer of the string to VB and then reading it from there. Simpley passing the string gives me rubbish data at VB end.

Thank You

-------------
Niraj Bhatt

[Fred Oxenby]

You can try to use this in your VB-application
  
Private Declare Function lstrlenA Lib "kernel32" (ByVal PtrToString As Long) As Long
Private Declare Sub PtrToString Lib "kernel32" Alias "RtlMoveMemory" (Byval ptrTo As Any, Byval ptrFrom As Any, ByVal BytesToCopy As Long)
   
Public Function PB_Callback(ByVal lpMyString As Long) As Long
Dim MyString$
Dim StrLen As Long
'--MakeYourPointerToString-------------   
   If lpMyString Then
    StrLen = lstrlenA(lpMyString)
    If StrLen Then 
     MyString$=Space(StrLen)
     Call PtrToString(MyString$,lpMyString,StrLen)
    End If 
   End If
'--ContinueToDoYourJob-----------------
---YourCode---
---Etc     ---
End Function
   
In PB you will use callback-prototype
Declare Function PB_CallBack(lpMyString as Asciiz)as long
   
You call it like this
   
 Call DWord PBCB?? Using PB_Callback(Byval StrPtr(MyString$)) To result&

I think it works


-------------
Fred
mailto:[email protected][email protected]</A>
http://www.oxenby.se

[Niraj Bhatt]

That was exactly what I did not wanted to do. Is there not an easier way to do so.

[Fred Oxenby]

Private Declare Function lstrlenA Lib "kernel32" (ByVal PtrToString As Long) As Long
Private Declare Sub PtrToString Lib "kernel32" Alias "RtlMoveMemory" (Byval ptrTo As Any, Byval ptrFrom As Any, ByVal BytesToCopy As Long)

   
Public Function StringFromPointer(ByVal lpMyString As Long) As String
Dim MyString$
Dim StrLen As Long
   If lpMyString Then
    StrLen = lstrlenA(lpMyString)
    If StrLen Then 
     MyString$=Space(StrLen)
     Call PtrToString(MyString$,lpMyString,StrLen)
    End If 
   End If
   StringFromPointer=Mystring$
End Function

Put this in a .BAS module and now you
can resuse it as often as you wish