Want to make a multipurpose function in PB for VB.

[Edwin Knoppert]

I want to return a double or string as dword like this

PB:

Function ReadIt( ByVal what as Long ) Export As Dword

    Dim T       As String
    Dim DBL     As Double
    Dim Temp    As Dword

    Select Case What
    Case 0

     T = "1234"

     ! MOV EAX,  T
     ! MOV TEMP, EAX
     ! MOV DWORD T, 0

     FUNCTION = Temp

    Case 1

'Example from PB but i need to set a double instead..

        DBL = 1234567

        ! mov AL, Byte Ptr rgb_value[0]
        ! xor AH, AH
        ! mov FUNCTION[0], AX

    End Select

End Function

VB:
Declare Function ReadItSTRING Lib "MY.DLL" Alias "ReadIt" (ByVal What As Long ) As String
Declare Function ReadItDouble Lib "MY.DLL" Alias "ReadIt" (ByVal What As Long ) As Double

The Double part is not working (Not with the example above of course but i tried it with MKD$ etc.. )

???

Or can use VB variants somehow?
VB6<>PB6


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[email protected]

[Tom Hanlin]

It is not quite clear to me what you want to accomplish...

1) Convert a DOUBLE or string to a DWORD? Consider CLNG and VAL functions.

2) Put the contents of a DOUBLE or string in a DWORD? Well, you can fit up
to four characters of a string in a DWORD, but a DOUBLE isn't going to fit
nohow. Storing only half of a DOUBLE isn't likely to be useful.

3) Return a pointer to a DOUBLE or a string? In that case, you'll need a
STATIC buffer rather than LOCAL dim'ed values, or they'll disappear when
the function exits. You also can't use a regular STRING this way, as
they're inherently dynamic, but you can use a fixed-length string, e.g.:

STATIC foo AS STRING * 10

To return a pointer, use VARPTR on the variable name-- or, if you're
using asm, load the OFFSET of the value rather than the value itself:

!mov eax, offset T

------------------
Tom Hanlin
PowerBASIC Staff

[Edwin Knoppert]

Tom,
The string part i showed is provided in the PB examples (somewhere)
It does it ok.

Simply speaking:
Why couldn't i use it on a double instead?

That's what i like to do with it.

Passing from VB to PB i could simply use "as Any" wich unf. doesn't thell WHAT type it is.

But returnning different types USING a function return value is a bit unclear to me.
I'm willing to declare a few VB declares/aliases to return a double or string whatever.
But in PB there must be a way to use one procedure only.
Therefore my question, can the string-return-stuff be rebuild to returning a double.
I have 0 knowledge of ASM so...

With my tries VB returns an error 16 "string to ..."

I also try the offset technique tommorow (whatever it might mean.. )

Thanks,
Maybe you can help me out retuning the double using a dword pointer..


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[email protected]

[Tom Hanlin]

Problem is, here, Visual Basic has about zero understanding of what a pointer is.
If you return a pointer to a DOUBLE, I don't think there's any easy way to use
that in VB. If you defined ReadIt as a SUB instead of a FUNCTION, and returned
the value through a parameter, it would be more practical but, perhaps, not what
you had in mind.

An abbreviated version of your function, to return a DOUBLE PTR, might go:

FUNCTION ReadIt (BYVAL what AS LONG) EXPORT AS DWORD
    STATIC dbl AS DOUBLE
    LOCAL dblptr AS DWORD
    dbl = 1234567
    !mov eax, offset dbl
    !mov dblptr, eax
    FUNCTION = dblptr
END FUNCTION

I'm assuming you want to use asm code for some reason. Otherwise, VARPTR
would be a better approach.

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Tom Hanlin
PowerBASIC Staff