Get string from structure filled by C++ functioncall

[=?Utf-8?B?QXNzaWRv?=]

Hello @all

i need help with the following problem:

Im calling an unmanaged C++ DLL (TAPI32.dll) function (lineGetCallInf o) like
this:

Declare Function lineGetCallInfo Lib "tapi32.dll " (ByVal hCall As Integer,
ByRef lpCallInfo As LINECALLINFO) As Integer

Public Structure LINECALLINFO
Dim dwTotalSize As Integer
Dim dwNeededSize As Integer
Dim dwUsedSize As Integer
Dim hLine As Integer
Dim dwLineDeviceID As Integer
Dim dwAddressID As Integer
Dim dwBearerMode As Integer
Dim dwRate As Integer
Dim dwMediaMode As Integer
Dim dwAppSpecific As Integer
Dim dwCallID As Integer
Dim dwRelatedCallID As Integer
Dim dwCallParamFlag s As Integer
Dim dwCallStates As Integer
Dim dwMonitorDigitM odes As Integer
Dim dwMonitorMediaM odes As Integer
Dim DialParams As LINEDIALPARAMS
Dim dwOrigin As Integer
Dim dwReason As Integer
Dim dwCompletionID As Integer
Dim dwNumOwners As Integer
Dim dwNumMonitors As Integer
Dim dwCountryCode As Integer
Dim dwTrunk As Integer
Dim dwCallerIDFlags As Integer
Dim dwCallerIDSize As Integer
Dim dwCallerIDOffse t As Integer
Dim dwCallerIDNameS ize As Integer
Dim dwCallerIDNameO ffset As Integer
Dim dwCalledIDFlags As Integer
Dim dwCalledIDSize As Integer
Dim dwCalledIDOffse t As Integer
Dim dwCalledIDNameS ize As Integer
Dim dwCalledIDNameO ffset As Integer
Dim dwConnectedIDFl ags As Integer
Dim dwConnectedIDSi ze As Integer
Dim dwConnectedIDOf fset As Integer
Dim dwConnectedIDNa meSize As Integer
Dim dwConnectedIDNa meOffset As Integer
Dim dwRedirectionID Flags As Integer
Dim dwRedirectionID Size As Integer
Dim dwRedirectionID Offset As Integer
Dim dwRedirectionID NameSize As Integer
Dim dwRedirectionID NameOffset As Integer
Dim dwRedirectingID Flags As Integer
Dim dwRedirectingID Size As Integer
Dim dwRedirectingID Offset As Integer
Dim dwRedirectingID NameSize As Integer
Dim dwRedirectingID NameOffset As Integer
Dim dwAppNameSize As Integer
Dim dwAppNameOffset As Integer
Dim dwDisplayableAd dressSize As Integer
Dim dwDisplayableAd dressOffset As Integer
Dim dwCalledPartySi ze As Integer
Dim dwCalledPartyOf fset As Integer
Dim dwCommentSize As Integer
Dim dwCommentOffset As Integer
Dim dwDisplaySize As Integer
Dim dwDisplayOffset As Integer
Dim dwUserUserInfoS ize As Integer
Dim dwUserUserInfoO ffset As Integer
Dim dwHighLevelComp Size As Integer
Dim dwHighLevelComp Offset As Integer
Dim dwLowLevelCompS ize As Integer
Dim dwLowLevelCompO ffset As Integer
Dim dwChargingInfoS ize As Integer
Dim dwChargingInfoO ffset As Integer
Dim dwTerminalModes Size As Integer
Dim dwTerminalModes Offset As Integer
Dim dwDevSpecificSi ze As Integer
Dim dwDevSpecificOf fset As Integer
End Structure

Dim strucCallinfo As LINECALLINFO
strcCallinfo.dw TotalSize = 1024
Dim ret As Integer = lineGetCallInfo (dwDevice, strucCallinfo)
'..... more code

Now the relevant fields in the structure are filled:

- dwCallerIDOffse t
- dwCallerIDSize

Like I understand it, the structure has an address in memory (pointer). Now
I have to add the dwCallerIDOffse t to the address.
I've done that in this way:

Dim CallingID as String

CallingID = GetStringFromSt ructure(strucCa llinfo,
strucCallinfo.d wCallerIDOffset , strucCallinfo.d wCallerIDSize)

Private Function GetStringFromSt ructure(ByVal InputStructure As Object,
ByVal Offset As Integer, ByVal Length As Integer) As String
Dim RetString As String = ""
Dim ptrToStructure As IntPtr
Dim ptrToString As IntPtr

'// Allocate memory for a new pointer
ptrToStructure = Marshal.AllocHG lobal(Marshal.S izeOf(InputStru cture))

'// Marshal the structure to the pointer
Marshal.Structu reToPtr(InputSt ructure, ptrToStructure, True)

'// Create a new pointer with the offset to the string
ptrToString = New IntPtr(ptrToStr ucture.ToInt32 + Offset)

'// Read the string from the new pointer with the specified length
RetString = Marshal.PtrToSt ringAnsi(ptrToS tring, Length)

'// Free allocated memory
Marshal.FreeHGl obal(ptrToStruc ture)

'// Return the extracted string
Return RetString

End Function


But everything i get is some ASCII-Salad like "°oæàoæpæ"

What's wrong here? When i use the same function with an other structure
filled by a functioncall everything works fine :-(

So please help me, before it drives me crazy.

[Armin Zingler]

Re: Get string from structure filled by C++ functioncall

"Assido" <Assido@discuss ions.microsoft. comschrieb

Hello @all
>
i need help with the following problem:

Which OS do you use? It fails on a 64 bit OS. See changes below.

Im calling an unmanaged C++ DLL (TAPI32.dll) function
(lineGetCallInf o) like this:
>
Declare Function lineGetCallInfo Lib "tapi32.dll " (ByVal hCall As
Integer,
ByRef lpCallInfo As LINECALLINFO) As Integer

Declare Function lineGetCallInfo Lib "tapi32.dll " (ByVal hCall As
IntPtr, ByRef lpCallInfo As LINECALLINFO) As Integer

Dim hLine As Integer

Dim hLine As Intptr


At first glance I don't see an error in the code (only replace ToInt32
by ToInt64 on 64 bit OS (see IntPtr.Size)).

...Just one thing: Don't you have to reserve additional memory inside the
structure for the Strings to be returned (after dwDevSpecificOf fset)?
You say "strcCallinfo.d wTotalSize = 1024", but the total size is less.
Maybe I'm wrong(?)


Armin

[=?Utf-8?B?QXNzaWRv?=]

Re: Get string from structure filled by C++ functioncall

Hi Achim,

you are my hero! This is the result of crawling the sourcecode for mistakes
for days without taking a little break!

You are absoutly right! The CALLINFO-Structure has to contain a Bytearray to
reserve enough memory for the strings returned by the functioncall. I just
added
<System.Runtime .InteropService s.MarshalAs(Run time.InteropSer vices.Unmanaged Type.ByValArray , SizeConst:=2048 )Dim ByteBuffer() As Byte

and it works!

Thank you so much!


"Armin Zingler" wrote:

"Assido" <Assido@discuss ions.microsoft. comschrieb

Hello @all

i need help with the following problem:

>
>
Which OS do you use? It fails on a 64 bit OS. See changes below.
>

Im calling an unmanaged C++ DLL (TAPI32.dll) function
(lineGetCallInf o) like this:

Declare Function lineGetCallInfo Lib "tapi32.dll " (ByVal hCall As
Integer,
ByRef lpCallInfo As LINECALLINFO) As Integer

>
Declare Function lineGetCallInfo Lib "tapi32.dll " (ByVal hCall As
IntPtr, ByRef lpCallInfo As LINECALLINFO) As Integer
>

Dim hLine As Integer

>
Dim hLine As Intptr
>
>
At first glance I don't see an error in the code (only replace ToInt32
by ToInt64 on 64 bit OS (see IntPtr.Size)).
>
...Just one thing: Don't you have to reserve additional memory inside the
structure for the Strings to be returned (after dwDevSpecificOf fset)?
You say "strcCallinfo.d wTotalSize = 1024", but the total size is less.
Maybe I'm wrong(?)
>
>
Armin
>
>