Neuralyst Technical Note: 14-5

Release Date:  2-December-1994


Affected Versions:  Neuralyst Run-time Library - all versions


Symptoms:  When declaring and calling Neuralyst Run-time Library DLL 
functions which specify a return type of “String” in Excel Visual Basic, a General 
Protection Failure, crash, or other errors occur.


Problem:  A DLL cannot return a simple pointer to string to Visual Basic.  Visual 
Basic expects return values of type “String” to be pointers to BSTR’s,  a more 
complex data type.

Solution: The Neuralyst DLL functions which return pointers to strings can be 
declared to return “Long”.  The conversion routine listed below will then copy the 
contents at the pointer into a Visual Basic string.

Declare Function lstrcpy Lib "KERNEL" (ByVal lpstr1 As Any, ByVal 
lpstr2 As Any) As Long

Function lptostr(lp As Long) As String
    Dim buf As String
    
    buf = Space$(256)
    lp = lstrcpy(buf, lp)
    lptostr = buf
End Function

Used as follows for the example call of SetParams:

Declare Function SetParams Lib "NEUR14.DLL" (t1 As Double, t2 As 
Double, t3 As Double, t4 As Double, t5 As Double) As Long

Sub test()
    Dim n As String * 30
    Dim i As Integer
    
    n = lptostr(SetParams(0.1, 0.3, 0.9, 0.5, 0.1))
    i = MsgBox(n)
End Sub