ptr to string ?

[Delfim Da Costa]

Hi,

I have some problems to use GetPrinterData Win32 API. in fact my problem is
: how can get the in a string a buffer known by it's ptr ?
Can anybody help me ?

Thanks,

Delfim.

this a part of my code :

<DllImport("winspool.Drv", CharSet:=CharSet.Ansi,
EntryPoint:="GetPrinterDataA", _
SetLastError:=True, ExactSpelling:=True, _
CallingConvention:=CallingConvention.StdCall)> _
Private Shared Function GetPrinterData( _
ByVal hPrinter As IntPtr, _
<MarshalAs(UnmanagedType.LPStr)> ByVal pValueName As String, _
ByRef pType As Integer, _
ByRef pData As IntPtr, _
ByVal nSize As Integer, _
ByRef pcbNeeded As Integer) As Integer
End Function

Public Function GetPrinterData(ByVal PrinterName As String, ByVal ValueName
As String) As Object
Dim hPrinter As IntPtr
Dim pData As IntPtr = IntPtr.Zero
Dim cBuf As Integer
Dim pcbNeeded As Integer
Dim pType As Integer
Dim ret As Integer
Dim oData As Object

hPrinter = OpenPrinter(PrinterName)
ret = GetPrinterData(hPrinter, ValueName, pType, IntPtr.Zero, 0,
pcbNeeded)
If pcbNeeded <= 0 Then
Throw (New System.Exception("Unable to allocate memory"))
End If

pData = Marshal.AllocHGlobal(pcbNeeded)
ret = GetPrinterData(hPrinter, ValueName, pType, pData, pcbNeeded, cBuf)
If ret <> 0 Then
Throw New Win32Exception(Marshal.GetLastWin32Error())
End If

Select Case pType
Case REG_DWORD
oData = pData.ToInt32

Case REG_SZ
oData = Marshal.PtrToStringAuto(pData)

Case Else
oData = pData
End Select

ClosePrinter(hPrinter)

Return oData
End Function

[Mattias Sjögren]

>I have some problems to use GetPrinterData Win32 API. in fact my problem is

: how can get the in a string a buffer known by it's ptr ?
Can anybody help me ?

Since you're explicitly calling the ANSI version of the API I guess
you should use Marshal.PtrToStringAnsi (not Auto) to read the string.
And don't forget to free the memory allocated with AllocHGlobal.
Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Delfim Da Costa]

I have tried this but it's not working.
I have made some debug session and maybe there is a problem in second call
to GetPrinterData, but i don't find what is it
Delfim.

"Mattias Sjögren" <ma********************@mvps.org> wrote in message
news:eq**************@TK2MSFTNGP14.phx.gbl...

I have some problems to use GetPrinterData Win32 API. in fact my problem
is
: how can get the in a string a buffer known by it's ptr ?
Can anybody help me ?

Since you're explicitly calling the ANSI version of the API I guess
you should use Marshal.PtrToStringAnsi (not Auto) to read the string.
And don't forget to free the memory allocated with AllocHGlobal.
Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[José Manuel Agüero]

Hello Delfim,

Why don't you use a byte array as a buffer for the function call?:
<DllImport("winspool.Drv", CharSet:=CharSet.Ansi, _
EntryPoint:="GetPrinterDataA", _
SetLastError:=True, ExactSpelling:=True, _
CallingConvention:=CallingConvention.StdCall)> _
Private Shared Function GetPrinterData( _
ByVal hPrinter As IntPtr, _
ByVal pValueName As String, _
ByRef pType As Integer, _
[Out] ByVal pData() As Byte, _
ByVal nSize As Integer, _
ByRef pcbNeeded As Integer) As Integer
End Function

Now you have the bytes in an array, only need to use the bitconverter class to transform into a string or a numeric type.

Regards.
"Delfim Da Costa" <de************@arcelor.com> escribió en el mensaje news:dt**********@s1.news.oleane.net...
|
|
| Hi,
|
| I have some problems to use GetPrinterData Win32 API. in fact my problem is
| : how can get the in a string a buffer known by it's ptr ?
| Can anybody help me ?
|
| Thanks,
|
| Delfim.
|
| this a part of my code :
|
|
|
| <DllImport("winspool.Drv", CharSet:=CharSet.Ansi,
| EntryPoint:="GetPrinterDataA", _
| SetLastError:=True, ExactSpelling:=True, _
| CallingConvention:=CallingConvention.StdCall)> _
| Private Shared Function GetPrinterData( _
| ByVal hPrinter As IntPtr, _
| <MarshalAs(UnmanagedType.LPStr)> ByVal pValueName As String, _
| ByRef pType As Integer, _
| ByRef pData As IntPtr, _
| ByVal nSize As Integer, _
| ByRef pcbNeeded As Integer) As Integer
| End Function
|
| Public Function GetPrinterData(ByVal PrinterName As String, ByVal ValueName
| As String) As Object
| Dim hPrinter As IntPtr
| Dim pData As IntPtr = IntPtr.Zero
| Dim cBuf As Integer
| Dim pcbNeeded As Integer
| Dim pType As Integer
| Dim ret As Integer
| Dim oData As Object
|
| hPrinter = OpenPrinter(PrinterName)
| ret = GetPrinterData(hPrinter, ValueName, pType, IntPtr.Zero, 0,
| pcbNeeded)
| If pcbNeeded <= 0 Then
| Throw (New System.Exception("Unable to allocate memory"))
| End If
|
| pData = Marshal.AllocHGlobal(pcbNeeded)
| ret = GetPrinterData(hPrinter, ValueName, pType, pData, pcbNeeded, cBuf)
| If ret <> 0 Then
| Throw New Win32Exception(Marshal.GetLastWin32Error())
| End If
|
| Select Case pType
| Case REG_DWORD
| oData = pData.ToInt32
|
| Case REG_SZ
| oData = Marshal.PtrToStringAuto(pData)
|
| Case Else
| oData = pData
| End Select
|
| ClosePrinter(hPrinter)
|
| Return oData
| End Function