passing an array of LPSTR to C++ by reference

From: Gent (gentian.metaj_at_trustasc.com)
Date: 11/03/04 

Date: 3 Nov 2004 13:31:29 -0800

Below is a straightforward C++ question but i'm giving example code to
demonstrate the issue i'm having. THe issue might seem to be out of
the topic but it's mostly related to C++ and is not necessarily
environment specific.

I have written a VB program that passes an array of strings to a C++
dll. The c++ dll is supposed to fill the array of strings with the
appropriate value. The only way i figured out how to pass was it by
reference. I create the array and populate with blank spaces in VB
then pass it be reference to C++ dll.

In my C++ example the only values we are concerned about are LPSTR &
strReturnedJobId. Now what happens is that the only value i populate
is the first element of the VB array. It would be a lot easier if i
could declare the header on the C++ function as long __stdcall
GetJobIds(LPSTR & strReturnedJobId[NUMBER_OF_ELEMENT], int
numberOfJobs, int UserSelection)
 but apparently you cannot put a & in front of an array declaration.

My question is how do i pass an array of strings by value (from VB) to
a C++ (well this has to be by reference so C++ can fill up the array)
dll. I have no problem solving that if i change the data type from
string to int or so. but as strings do not exist in C++ then i'm
stuck.

Thank you for your help!

Gent

vb 6 code:
my call fails:

Public Declare Function GetJobIds Lib "AdminBits.dll" _
    (ByRef strReturnedJobId As String, ByVal intNumberOfJobs As
Integer, ByVal intUserSelection As Integer) As Integer

Private Sub GetBITSJobsGUIDs(ByVal UserSelection As Integer)
        Dim numberOfJobs As Integer
        numberOfJobs = CountJobs(UserSelection)
        
        Dim LoopArr As Long
        Dim arrayOfGUIDs() As String
        
        ReDim arrayOfGUIDs(numberOfJobs - 1) As String
        
        For LoopArr = 0 To numberOfJobs - 1
             arrayOfGUIDs(LoopArr) = Space(100)
                  
        Next LoopArr
        Dim intflag As Integer
'''Attention
        intflag = GetJobIds(arrayOfGUIDs(0), numberOfJobs,
UserSelection)
        

End Sub
c++ code:

long __stdcall GetJobIds(LPSTR & strReturnedJobId, int numberOfJobs,
int UserSelection)
{

        USES_CONVERSION; //Use Atlconv.h macros
        wchar_t sbuff[100];
        LPOLESTR tempstrReturnedJobId = sbuff;
        GUID* ReturnedJobId = NULL;
 
        int retvalue = -1;

        // If passed in 1 than enumerates jobs for all users
        // If passed in 0 than it enumerates job for current user logged on.
        // Function returns the number of JOBS or returns -1 if it failed to
count the jobs

        IEnumBackgroundCopyJobs* pJobs = NULL;
        IBackgroundCopyJob* pJob = NULL;
        ULONG cJobCount = 0;
        ULONG idx = 0;

        IBackgroundCopyManager* g_XferManager = NULL;
        HRESULT hr;

        //Specify the appropriate COM threading model for your application.
        hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
        if (SUCCEEDED(hr))
        {
            retvalue = -2;

                  hr = CoCreateInstance(__uuidof(BackgroundCopyManager), NULL,
                                                                          CLSCTX_LOCAL_SERVER,
                                                                          __uuidof(IBackgroundCopyManager),
                                                                          (void**) &g_XferManager);
                  if (SUCCEEDED(hr))
                  {
                                //failed to enumerate the jobs in the queue.

                                retvalue = -3;

                                //Enumerate jobs in the queue. This example enumerates all jobs in
the transfer
                                //queue. This call fails if the current user does not have
administrator
                                //privileges. To enumerate jobs for only the current user, replace
                                //BG_JOB_ENUM_ALL_USERS with 0.

                                if(UserSelection == 1)
                                {
                                        hr = g_XferManager->EnumJobs(BG_JOB_ENUM_ALL_USERS, &pJobs);
                                }
                                else
                                {
                                        hr = g_XferManager->EnumJobs(0, &pJobs);
                                }

                                if (SUCCEEDED(hr))
                                {
                                  retvalue = -4; // Could not get the job count

                                  //Get the count of jobs in the queue.
                                  pJobs->GetCount(&cJobCount);

                // IdsOfJobs= new GUID*[cJobCount+1];
                                 
                                  //Enumerate the jobs in the queue.
                                  for (idx=0; idx<cJobCount; idx++)
                                  {
                                                hr = pJobs->Next(1, &pJob, NULL);
                                                if (S_OK == hr)
                                                {
                                                        retvalue = 5; //could not retrieve the job properties such as
ID
                                                  //Retrieve or set job properties.
                                                        
                                                        
                                                        GUID JobId;

                                                        pJob->GetId(&JobId);

                                                        int abc = StringFromGUID2(JobId, tempstrReturnedJobId, 100);
                                                        char *buffer = W2A(tempstrReturnedJobId);

                                                        if (40 > strlen(buffer) )
                                                        {
//***********ATTENTION HERE ********************
                                                                 strcpy(&strReturnedJobId[idx], buffer);
//*************end attention *********
                                                                retvalue = 1; //successfully got the job IDs
                                                        }

                                                        pJob->Release();
                                                        pJob = NULL;
                                                }
                                                else
                                                {
                                                  //Handle error
                                                  break;
                                                }
                                  }

                                  pJobs->Release();
                                  pJobs = NULL;

                                }
                  }
        }

        if (g_XferManager)
        {
          g_XferManager->Release();
          g_XferManager = NULL;
        }
        
        CoUninitialize();

        return retvalue;
  
}

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