How to copy an address into a pointer

**Tom Shelton** · Nov 21 '05, 05:52 PM

Re: How to copy an address into a pointer

In article <unVgrAIaFHA.33 20@TK2MSFTNGP12 .phx.gbl>, Just Me wrote:[color=blue]
> I know (or at least think) the following is not correct.
>
> The comment says what I want to do, but I think the code will copy the data
> not the address.
>
> Is this one of the things that can't be done with VB?
>
> Any suggestions?
>
> Thanks
>
>
>
>
>
> Public Declare Auto Sub CopyMemory1 Lib "KERNEL32" Alias "RtlMoveMem ory"
> (ByVal pDest As Integer, ByRef Source As Byte, ByVal cbCopy As Integer)
>
>
>
>
> 'Copy address of lDevModeAsByte into lPrtInfo2 structure
>
> Kernel.CopyMemo ry1(lPrtInfo2.p DevMode, lDevModeAsByte( 0), 4)
>
>[/color]

CopyMemory is a almost always a bad idea to use in VB.NET. There are
almost always better alternatives. If you need to pass an address of a
managed object to an unmanaged function, then the address needs to be
pinned for the duration of that operation. The reason being, that GC
could kick in which may result in the relocation of the object - and
that could be bad ju-ju for the unmanaged code. However, there are
performance issues involved here, since leaving a lot of objects pinned
for a long time can result in heap fragmentation. So the idea, is pin
the object, do your deed, and unpin as soon as possible.

You can achive this pinning using the GCHandle class's Allocate method:

Dim objHandle As GCHandle = _
GCHandle.Alloca te (myObject, GCHandleType.Pi nned)

Try

Dim objectAddress As IntPtr = objHandle.AddrO fPinnedObject ()

Call MyFunckyUnmanag edCodeWithObjec tAddress (objectAddress)

Finally
'Were done, so unpin this sucker...
objHandle.Free ()
End Try

You have to make sure that for each handle that Free is only called
once. Anyway, it would be more helpful if we knew exactly what you were
trying to accomplish. It's pretty obvious that your trying to call a
Win32 api of some sort - but knowing which one would be helpful.
Working with API's is, IMHO, significantly different in VB.NET then
VB.CLASSIC.

--
Tom Shelton [MVP]

**Just Me** · Nov 21 '05, 05:52 PM

Re: How to copy an address into a pointer

> Anyway, it would be more helpful if we knew exactly what you were[color=blue]
> trying to accomplish. It's pretty obvious that your trying to call a
> Win32 api of some sort - but knowing which one would be helpful.
> Working with API's is, IMHO, significantly different in VB.NET then
> VB.CLASSIC.
>
> --
> Tom Shelton [MVP][/color]

Thanks

I'm trying to use an old routine for setting the system default printer's
Landscape mode.

Any other suggestion?

Thanks again

Public Shared Sub SetPrinterSetti ngs(ByRef windowHandle As IntPtr, ByRef
printerName As String, ByRef isLandscape As Boolean) ', ByRef aNewPaperSize
As Short, ByRef aNewDuplex As Short)

Dim lPrinterHandle As IntPtr

Dim lDevMode As GDI.DEVMODE

Dim lDevModeAsByte( ) As Byte

Dim lDevModeAsByteS ize As Integer

Dim lPrtInfo2 As WinSpool.PRINTE R_INFO_2

Dim lPrtInfo2AsByte () As Byte

Dim lPrtInfo2AsByte Size As Integer

Dim lFlag As Integer

Dim lPrinterDefault s As WinSpool.PRINTE R_DEFAULTS

Dim lErrorCode As Integer

'You should probably look at the PtrToStructure and StructureToPtr methods
rather than Copy.

Kernel.ZeroMemo ry(lPrinterDefa ults, Marshal.SizeOf( lPrinterDefault s))

lPrinterDefault s.DesiredAccess = WinSpool.PRINTE R_ALL_ACCESS

'lPrinterDefaul ts.DesiredAcces s = WinSpool.PRINTE R_ACCESS_ADMINI STER

'Get a handle to the printer.

lFlag = WinSpool.OpenPr inter(printerNa me, lPrinterHandle, lPrinterDefault s)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

If lErrorCode = User.ERROR_ACCE SS_DENIED Then

MessageBox.Show ("Requires adminstrative rights to change default printer",
"Error", MessageBoxButto ns.OK, MessageBoxIcon. Exclamation)

End If

Exit Sub

End If

'This GetPrinter call determines the size needed for lPrtInfo2AsByte

lFlag = WinSpool.GetPri nter(lPrinterHa ndle, 2, 0, 0, lPrtInfo2AsByte Size)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

If lErrorCode <> 122 Then GoTo CLEAN_UP

End If

'Allocate space for lPrtInfo2AsByte

ReDim lPrtInfo2AsByte (lPrtInfo2AsByt eSize - 1)

'The second GetPrinter call fills lPrtInfo2AsByte with the current settings

lFlag = WinSpool.GetPri nter(lPrinterHa ndle, 2, lPrtInfo2AsByte (0),
lPrtInfo2AsByte Size, lPrtInfo2AsByte Size)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

'Console.WriteL ine("GetPrinter exited with code : {0}", lErrorCode)

End If

'Copy lPrtInfo2AsByte to the structure

Kernel.CopyMemo ry2(lPrtInfo2, lPrtInfo2AsByte (0), Marshal.SizeOf( lPrtInfo2))

'Get the total size of the DeviceMode bytes (lDevModeAsByte )

lDevModeAsByteS ize = WinSpool.Docume ntProperties(wi ndowHandle,
lPrinterHandle, printerName, 0, 0, 0)

'Reserve memory for the total size of the DeviceMode bytes

ReDim lDevModeAsByte( lDevModeAsByteS ize - 1)

'Fill the DeviceMode bytes from the printer.

lFlag = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, lDevModeAsByte( 0), 0, GDI.DM_OUT_BUFF ER)

If lFlag < 0 Then

lErrorCode = Marshal.GetLast Win32Error()

Console.WriteLi ne("DocumentPro perties exited with code: {0}", lErrorCode)

End If

'Copy the Public shared (predefined) portion of the DeviceMode bytes to the
structure

Kernel.CopyMemo ry3(lDevMode, lDevModeAsByte( 0), Marshal.SizeOf( lDevMode))

'Set the dmFields bit flag to indicate what we are changing

lDevMode.dmFiel ds = GDI.DM_ORIENTAT ION 'Or DM_DUPLEX Or DM_PAPERSIZE

If isLandscape Then

lDevMode.u.dmOr ientation = GDI.DMORIENT_LA NDSCAPE

Else

lDevMode.u.dmOr ientation = GDI.DMORIENT_PO RTRAIT

End If

'Set/Change PaperSize

'lDevMode.dmPap erSize = aNewPaperSize

'On Error Resume Next

'lDevMode.dmDup lex = aNewDuplex

'On Error GoTo 0

'Copy changed structure back to the bytes

Kernel.CopyMemo ry4(lDevModeAsB yte(0), lDevMode, Marshal.SizeOf( lDevMode))

'Merge the printer driver's current print settings with the settings in the
lDevModeAsByte

lFlag = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, lDevModeAsByte( 0), lDevModeAsByte( 0), GDI.DM_IN_BUFFE R Or
GDI.DM_OUT_BUFF ER)

' lFlag = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, lDevModeAsByte( 0), lDevModeAsByte( 0), GDI.DM_IN_PROMP T)

'Copy address of lDevModeAsByte into lPrtInfo2 structure

' Kernel.CopyMemo ry1(lPrtInfo2.p DevMode, lDevModeAsByte( 0),
Marshal.SizeOf( lDevMode))

Kernel.CopyMemo ry1(lPrtInfo2.p DevMode, lDevModeAsByte( 0), 4)

'Update lPrinterInfoAsB yte with the updated structure

Kernel.CopyMemo ry5(lPrtInfo2As Byte(0), lPrtInfo2, Marshal.SizeOf( lDevMode))

lFlag = WinSpool.SetPri nter(lPrinterHa ndle, 2, lPrtInfo2AsByte (0), 0)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

Console.WriteLi ne("SetPrinter exited with code : {0}", lErrorCode)

End If

CLEAN_UP:

WinSpool.CloseP rinter(lPrinter Handle) 'Close the handle

End Sub

**Tom Shelton** · Nov 21 '05, 05:52 PM

Re: How to copy an address into a pointer

On 2005-06-03, Just Me <groups@a-znet.com> wrote:[color=blue][color=green]
>> Anyway, it would be more helpful if we knew exactly what you were
>> trying to accomplish. It's pretty obvious that your trying to call a
>> Win32 api of some sort - but knowing which one would be helpful.
>> Working with API's is, IMHO, significantly different in VB.NET then
>> VB.CLASSIC.
>>
>> --
>> Tom Shelton [MVP][/color]
>
> Thanks
>
> I'm trying to use an old routine for setting the system default printer's
> Landscape mode.
>
> Any other suggestion?[/color]

The System.Drawing. Printing.PageSe ttings class?

Dim doc As New PrintDocument ()

doc.DefaultPage Settings.Landsc ape = True

' Do your printing...

--
Tom Shelton [MVP]

**Just Me** · Nov 21 '05, 05:53 PM

Re: How to copy an address into a pointer

I'm trying to set the system wide orientation properties.

BTW
what are
doc.PrinterSett ings.DefaultPag eSettings
used for?

I've been trying for a while to find out.

Thanks

"Tom Shelton" <tshelton@YOUKN OWTHEDRILLcomca st.net> wrote in message
news:%23CFJutKa FHA.2212@TK2MSF TNGP14.phx.gbl. ..[color=blue]
> On 2005-06-03, Just Me <groups@a-znet.com> wrote:[color=green][color=darkred]
>>> Anyway, it would be more helpful if we knew exactly what you were
>>> trying to accomplish. It's pretty obvious that your trying to call a
>>> Win32 api of some sort - but knowing which one would be helpful.
>>> Working with API's is, IMHO, significantly different in VB.NET then
>>> VB.CLASSIC.
>>>
>>> --
>>> Tom Shelton [MVP][/color]
>>
>> Thanks
>>
>> I'm trying to use an old routine for setting the system default
>> printer's
>> Landscape mode.
>>
>> Any other suggestion?[/color]
>
> The System.Drawing. Printing.PageSe ttings class?
>
> Dim doc As New PrintDocument ()
>
> doc.DefaultPage Settings.Landsc ape = True
>
> ' Do your printing...
>
> --
> Tom Shelton [MVP][/color]

**Tom Shelton** · Nov 21 '05, 05:53 PM

Re: How to copy an address into a pointer

On 2005-06-04, Just Me <groups@a-znet.com> wrote:[color=blue]
> I'm trying to set the system wide orientation properties.
>[/color]

Well... What can I say. I'm looking at the code. First off, you may
want to spend some time with the interop and marshalling documentation.
At first glance, I think you can dispense with all of the calls to
RtlMoveMemory.. . You probably can do this using Marshalling attributes
and the methods of the System.Runtime. InteropServices .Marshal class -
though, I will say that this routine would probably be easier to write
in C# using unsafe code (and probably would performe better). I will
try and see if I can get time to convert this function, but right now I
can't promise anything.

Also, you should not EVER call GetLastError from VB.NET (or from VB.CLASSIC
for that matter). The return result is meaningless since the runtime
may call API functions that set that value before you call it. You should
either use Marshal.GetLast Win32Error () or the intrinsic VB.NET Err object's
LastDllError property. Both of thes methods preserve the last user called API
error codes.
[color=blue]
> BTW
> what are
> doc.PrinterSett ings.DefaultPag eSettings
> used for?
>[/color]

Setting printer settings... System.Drawing. Printing would be the
relavent namespace to start looking at the docs..
[color=blue]
> I've been trying for a while to find out.
>
> Thanks
>
>
>
> "Tom Shelton" <tshelton@YOUKN OWTHEDRILLcomca st.net> wrote in message
> news:%23CFJutKa FHA.2212@TK2MSF TNGP14.phx.gbl. ..[color=green]
>> On 2005-06-03, Just Me <groups@a-znet.com> wrote:[color=darkred]
>>>> Anyway, it would be more helpful if we knew exactly what you were
>>>> trying to accomplish. It's pretty obvious that your trying to call a
>>>> Win32 api of some sort - but knowing which one would be helpful.
>>>> Working with API's is, IMHO, significantly different in VB.NET then
>>>> VB.CLASSIC.
>>>>
>>>> --
>>>> Tom Shelton [MVP]
>>>
>>> Thanks
>>>
>>> I'm trying to use an old routine for setting the system default
>>> printer's
>>> Landscape mode.
>>>
>>> Any other suggestion?[/color]
>>
>> The System.Drawing. Printing.PageSe ttings class?
>>
>> Dim doc As New PrintDocument ()
>>
>> doc.DefaultPage Settings.Landsc ape = True
>>
>> ' Do your printing...
>>
>> --
>> Tom Shelton [MVP][/color]
>
>[/color]

--
Tom Shelton [MVP]

**Just Me** · Nov 21 '05, 05:53 PM

Re: How to copy an address into a pointer

Thanks

I took your eariler advise and got rid of the RtlMoveMemory's

I'll keep plugging and learning as I go along.

Thanks

BTW this is where I am now:

Public Shared Sub SetPrinterSetti ngs(ByRef windowHandle As IntPtr, ByRef
printerName As String, ByRef isLandscape As Boolean) ', ByRef aNewPaperSize
As Short, ByRef aNewDuplex As Short)

Dim lPrinterHandle As IntPtr

Dim lFlag As Integer

Dim lPrinterDefault s As WinSpool.PRINTE R_DEFAULTS

Dim lErrorCode As Integer

Dim lDevMode As GDI.DEVMODE

Dim lDevModeSize As Integer

Dim lPointerToDevMo de As IntPtr

Dim lPrtInfo2 As WinSpool.PRINTE R_INFO_2 = New WinSpool.PRINTE R_INFO_2

Dim lPrtInfo2Size As Integer

Dim lPointerToPrint erInfo2 As IntPtr

lPrinterDefault s.DesiredAccess = WinSpool.PRINTE R_ALL_ACCESS

'lPrinterDefaul ts.DesiredAcces s = WinSpool.PRINTE R_ACCESS_ADMINI STER

'Get a handle to the printer.

lFlag = WinSpool.OpenPr inter(printerNa me, lPrinterHandle, lPrinterDefault s)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

If lErrorCode = User.ERROR_ACCE SS_DENIED Then

MessageBox.Show ("Requires adminstrative rights to change default printer",
"Error", MessageBoxButto ns.OK, MessageBoxIcon. Exclamation)

End If

Exit Sub

End If

'This GetPrinter call determines the size needed for lPointerToPrint erInfo2

lFlag = WinSpool.GetPri nter(lPrinterHa ndle, 2, IntPtr.Zero, 0,
lPrtInfo2Size)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

If lErrorCode <> 122 Then GoTo CLEAN_UP

End If

'Allocate space for lPointerToPrint erInfo2 data

lPointerToPrint erInfo2 = Marshal.AllocCo TaskMem(lPrtInf o2Size)

'The second GetPrinter call fills lPointerToPrint erInfo2 data with the
current settings

lFlag = WinSpool.GetPri nter(lPrinterHa ndle, 2, lPointerToPrint erInfo2,
lPrtInfo2Size, lPrtInfo2Size)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

'Console.WriteL ine("GetPrinter exited with code : {0}", lErrorCode)

End If

'Copy lPointerToPrint erInfo2 data to the structure

lPrtInfo2 = Marshal.PtrToSt ructure(lPointe rToPrinterInfo2 ,
lPrtInfo2.GetTy pe)

'Get the total size of the DeviceMode

lDevModeSize = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, 0, 0, 0)

'Reserve lPointerToDevMo de data memory for the total size of the DeviceMode

lPointerToDevMo de = Marshal.AllocCo TaskMem(lDevMod eSize)

'Fill the lPointerToDevMo de data from the printer driver

lFlag = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, lPointerToDevMo de, IntPtr.Zero, GDI.DM_OUT_BUFF ER)

If lFlag < 0 Then

lErrorCode = Marshal.GetLast Win32Error()

Console.WriteLi ne("DocumentPro perties exited with code: {0}", lErrorCode)

End If

'Copy the lPointerToDevMo de data to the structure

lDevMode = Marshal.PtrToSt ructure(lPointe rToDevMode, lDevMode.GetTyp e)

'Set the dmFields bit flag to indicate what we are changing

lDevMode.dmFiel ds = GDI.DM_ORIENTAT ION 'Or DM_DUPLEX Or DM_PAPERSIZE

If isLandscape Then

lDevMode.dmOrie ntation = GDI.DMORIENT_LA NDSCAPE

Else

lDevMode.dmOrie ntation = GDI.DMORIENT_PO RTRAIT

End If

'Set/Change PaperSize

'lDevMode.dmPap erSize = aNewPaperSize

'On Error Resume Next

'lDevMode.dmDup lex = aNewDuplex

'On Error GoTo 0

'Copy changed structure back to the lPointerToDevMo de data

Marshal.Structu reToPtr(lDevMod e, lPointerToDevMo de, True)

'Merge the printer driver's current print settings with the settings in the
lPointerToDevMo de data

' lFlag = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, lPointerToDevMo de, lPointerToDevMo de, GDI.DM_IN_BUFFE R Or
GDI.DM_OUT_BUFF ER)

lFlag = WinSpool.Docume ntProperties(wi ndowHandle, lPrinterHandle,
printerName, lPointerToDevMo de, lPointerToDevMo de, GDI.DM_IN_BUFFE R Or
GDI.DM_OUT_BUFF ER Or GDI.DM_IN_PROMP T)

lDevMode = Marshal.PtrToSt ructure(lPointe rToDevMode, lDevMode.GetTyp e)

'Copy address of lPointerToDevMo de into lPrtInfo2 structure

'Dim objHandle As GCHandle = GCHandle.Alloc( lPointerToDevMo de,
GCHandleType.Pi nned)

Dim objHandle As GCHandle = GCHandle.Alloc( lDevMode, GCHandleType.Pi nned)

Dim objectAddress As IntPtr = objHandle.AddrO fPinnedObject()

lPrtInfo2.pDevM ode = objectAddress

lFlag = WinSpool.SetPri nter(lPrinterHa ndle, 2, lPointerToPrint erInfo2, 0)

If lFlag = 0 Then

lErrorCode = Marshal.GetLast Win32Error()

Console.WriteLi ne("SetPrinter exited with code : {0}", lErrorCode)

If lErrorCode = 5 Then

MessageBox.Show ("Access denied", "Unable To Set Printer",
MessageBoxButto ns.OK, MessageBoxIcon. Exclamation)

End If

End If

lFlag = WinSpool.GetPri nter(lPrinterHa ndle, 2, lPointerToPrint erInfo2,
lPrtInfo2Size, lPrtInfo2Size)

Marshal.Structu reToPtr(lDevMod e, lPointerToDevMo de, True)

CLEAN_UP:

objHandle.Free( )

If (lPrinterHandle .ToInt32 <> 0) Then WinSpool.CloseP rinter(lPrinter Handle)

End Sub

**Just Me** · Nov 21 '05, 05:54 PM

Re: How to copy an address into a pointer

Tom,

Thank for the help.
It works now

How to copy an address into a pointer

How to copy an address into a pointer

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