pointers

[Doug McDonald]

Ok I'm lost, I'm tring to pass a pointer for a UDT from VB to pb6
then send it to an I/O port a byte at a time. This code will not
compile but it will if i pass a VARPRT of a string from VB (changing
some of the code of course). The problem is value = @t2. I thought, and
I'm wrong, that @t2 would be a pointer the the first byte of the
structure.

'pb code:

#COMPILE DLL "c:\windows\system\port32.dll"
'#INCLUDE "win32api.inc"

TYPE myType1
t1mytype2 AS LONG
END TYPE

TYPE myType2
testInt AS INTEGER
testUDT AS myType1
testLong AS LONG

END TYPE

SUB PBOUT(BYVAL PT AS INTEGER, StAddress AS DWORD) EXPORT
DIM t2 AS myType2 PTR
t2 = StAddress



DIM i AS LONG
DIM value AS BYTE
FOR i = 0 TO LEN(myType2)
value = @t2
! mov AL, value
! mov DX, PT
! out DX, AL
INCR t2
MSGBOX HEX$(value)
NEXT i

END SUB

FUNCTION PBINP(BYVAL PT AS INTEGER) EXPORT AS LONG
! mov DX, PT
! in AL, DX
! mov FUNCTION[0], AL
END FUNCTION


'VB Code:

Type myType1
t1mytype2 As Long
End Type

Type myType2

testInt As Integer
testUDT As myType1
testLong As Long

End Type


Declare Sub PBOUT Lib "port32.dll" (pt As Integer, mtype As myType2)


Dim t1 As myType1
Dim t2 As myType2

Private Sub Command1_Click()
t1.t1mytype2 = &HFFFFFFFF
t2.testInt = &HFFFF
t2.testLong = &HFFFFFFFF

PBOUT 300, t2

End Sub

Private Sub Command2_Click()
End
End Sub

[Tom Hanlin]

Originally posted by Doug McDonald:
SUB PBOUT(BYVAL PT AS INTEGER, StAddress AS DWORD) EXPORT

Since you're passing the UDT from Visual Basic BYREF, and you want to see it as a pointer on the PowerBASIC side, you need to receive the value BYVAL on the PowerBASIC side.

SUB PBOUT(BYVAL PT AS INTEGER, BYVAL StAddress AS DWORD) EXPORT

Also, in your VB code you've declared PT as being passed BYREF, whereas you've told PowerBASIC that it's passed BYVAL. Since we're not expecting to convert the value to a pointer, here, you want the two to match up. In this case, the best place to change it is probably on the VB side:

Declare Sub PBOUT Lib "port32.dll" (ByVal pt As Integer, mtype As myType2)

Finally, it's very important to realize that Visual Basic uses a unique alignment method for UDT members, so a UDT in VB may not match the same UDT in PowerBASIC! See the FAQ for more information on this.

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

[Doug McDonald]

Tom, Thanks for replying. I had the arguements passed byval at one time. The code above was just the last state it was in and I should have corrected that before posting it. The problem is that the PB6 code won't compile. I get an error at value = @t2

Tanks

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[Semen Matusovski]

Doug --
You can simply declare Sub PBOUT(ByVal PT As Integer, ByVal t2 As Byte Ptr) Export and do not use StAddress at all, but:
1) You forgot, that alignment in VB UDT and PB UDT are different.
The easyiest way in your case to declare all parameters in UDT as Long or to pass string from VB (MKI$ ... + MKL$ + ...).
2) Don't forget that under NT/2000 you can't use IN/OUT.

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[Doug McDonald]

Semen, thank you it was just what i needed. Don't know how i overlooked that. I know about the UDT alignment issues and that In /Out won't work under NT / 2000.

Thanks
Doug

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