Tow small questions about using structures in UDF

[amel27]

$t = DllStructCreate("int")
DllStructSetData($t, 1, 111)

; Question 1: Is Structures passed ALWAYS "ByRef"?
ConsoleWrite(DllStructGetData($t,1)&@CRLF)
_Test1($t)
ConsoleWrite(DllStructGetData($t,1)&@CRLF&@CRLF)

; Question 2: Is Structures returned ALWAYS By Reference too?
ConsoleWrite(DllStructGetPtr($t)&@CRLF)
$u=_Test1($t)
ConsoleWrite(DllStructGetPtr($u)&@CRLF&@CRLF)

Func _Test1($x)
    DllStructSetData($x, 1, 888) ; ReSet Structure
    Return $x
EndFunc

Edited June 25, 2008 by amel27

[PsaltyDS]

$t = DllStructCreate("int")
DllStructSetData($t, 1, 111)

; Question 1: Is Structures passed ALWAYS "ByRef"?
ConsoleWrite(DllStructGetData($t,1)&@CRLF)
_Test1($t)
ConsoleWrite(DllStructGetData($t,1)&@CRLF&@CRLF)

No. It's not ByRef, but it is a kind of pointer variant deep in its hidden AutoIt heart.

; Question 2: Is Structures returned ALWAYS By Reference too?
ConsoleWrite(DllStructGetPtr($t)&@CRLF)
$u=_Test1($t)
ConsoleWrite(DllStructGetPtr($u)&@CRLF&@CRLF)

Func _Test1($x)
    DllStructSetData($x, 1, 888); ReSet Structure
    Return $x
EndFunc

Again, since it is kind of a hidden pointer, $u = $t gets you the same struct.

To show that it is not ByRef, try this:

$t = DllStructCreate("int")
DllStructSetData($t, 1, 111)

; Question 1: Is Structures passed ALWAYS "ByRef"?
ConsoleWrite(DllStructGetData($t,1)&@CRLF)
_Test1($t)
ConsoleWrite(DllStructGetData($t,1)&@CRLF&@CRLF)

; Question 2: Is Structures returned ALWAYS By Reference too?
ConsoleWrite(DllStructGetPtr($t)&@CRLF)
$u=_Test1($t)
ConsoleWrite(DllStructGetData($t,1)&@CRLF)
ConsoleWrite(DllStructGetData($u,1)&@CRLF)
ConsoleWrite(DllStructGetPtr($u)&@CRLF&@CRLF)

Func _Test1($x)
; Create new struct over old
    $x = DllStructCreate("int")
    DllStructSetData($x, 1, 888); Set struct data
    ConsoleWrite("_Test1: struct $x: " & DllStructGetData($x, 1) & @LF)
    Return $x
EndFunc

[amel27]

No. It's not ByRef, but it is a kind of pointer variant deep in its hidden AutoIt heart.

Thanks for answer! Yes, I see that structures works by pointers - direct passing have increment internal AutoIT counter of pointers, passing ByRef use original pointer. But it is not obvious that structures must work as Objects (via pointers) rather than as Arrays (via data).