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Exposing tabular data from your COM object - Part 1

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28 Jul 2000CPOL 100.2K   1.8K   35  
ADO seems to be the ideal way to expose tabular data from your own COM objects and the ATL OLE DB Provider templates can help!
// SimpleDataObject.cpp : Implementation of DLL Exports.


// Note: Proxy/Stub Information
//      To merge the proxy/stub code into the object DLL, add the file 
//      dlldatax.c to the project.  Make sure precompiled headers 
//      are turned off for this file, and add _MERGE_PROXYSTUB to the 
//      defines for the project.  
//
//      If you are not running WinNT4.0 or Win95 with DCOM, then you
//      need to remove the following define from dlldatax.c
//      #define _WIN32_WINNT 0x0400
//
//      Further, if you are running MIDL without /Oicf switch, you also 
//      need to remove the following define from dlldatax.c.
//      #define USE_STUBLESS_PROXY
//
//      Modify the custom build rule for SimpleDataObject.idl by adding the following 
//      files to the Outputs.
//          SimpleDataObject_p.c
//          dlldata.c
//      To build a separate proxy/stub DLL, 
//      run nmake -f SimpleDataObjectps.mk in the project directory.

#include "stdafx.h"
#include "resource.h"
#include <initguid.h>
#include "SimpleDataObject.h"
#include "dlldatax.h"

#include "SimpleDataObject_i.c"
#include "MyDataObject.h"

#ifdef _MERGE_PROXYSTUB
extern "C" HINSTANCE hProxyDll;
#endif

CComModule _Module;

BEGIN_OBJECT_MAP(ObjectMap)
OBJECT_ENTRY(CLSID_MyDataObject, CMyDataObject)
END_OBJECT_MAP()

/////////////////////////////////////////////////////////////////////////////
// DLL Entry Point

extern "C"
BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID lpReserved)
{
    lpReserved;
#ifdef _MERGE_PROXYSTUB
    if (!PrxDllMain(hInstance, dwReason, lpReserved))
        return FALSE;
#endif
    if (dwReason == DLL_PROCESS_ATTACH)
    {
        _Module.Init(ObjectMap, hInstance, &LIBID_SIMPLEDATAOBJECTLib);
        DisableThreadLibraryCalls(hInstance);
    }
    else if (dwReason == DLL_PROCESS_DETACH)
        _Module.Term();
    return TRUE;    // ok
}

/////////////////////////////////////////////////////////////////////////////
// Used to determine whether the DLL can be unloaded by OLE

STDAPI DllCanUnloadNow(void)
{
#ifdef _MERGE_PROXYSTUB
    if (PrxDllCanUnloadNow() != S_OK)
        return S_FALSE;
#endif
    return (_Module.GetLockCount()==0) ? S_OK : S_FALSE;
}

/////////////////////////////////////////////////////////////////////////////
// Returns a class factory to create an object of the requested type

STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)
{
#ifdef _MERGE_PROXYSTUB
    if (PrxDllGetClassObject(rclsid, riid, ppv) == S_OK)
        return S_OK;
#endif
    return _Module.GetClassObject(rclsid, riid, ppv);
}

/////////////////////////////////////////////////////////////////////////////
// DllRegisterServer - Adds entries to the system registry

STDAPI DllRegisterServer(void)
{
#ifdef _MERGE_PROXYSTUB
    HRESULT hRes = PrxDllRegisterServer();
    if (FAILED(hRes))
        return hRes;
#endif
    // registers object, typelib and all interfaces in typelib
    return _Module.RegisterServer(TRUE);
}

/////////////////////////////////////////////////////////////////////////////
// DllUnregisterServer - Removes entries from the system registry

STDAPI DllUnregisterServer(void)
{
#ifdef _MERGE_PROXYSTUB
    PrxDllUnregisterServer();
#endif
    return _Module.UnregisterServer(TRUE);
}


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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Software Developer (Senior) JetByte Limited
United Kingdom United Kingdom
Len has been programming for over 30 years, having first started with a Sinclair ZX-80. Now he runs his own consulting company, JetByte Limited and has a technical blog here.

JetByte provides contract programming and consultancy services. We can provide experience in COM, Corba, C++, Windows NT and UNIX. Our speciality is the design and implementation of systems but we are happy to work with you throughout the entire project life-cycle. We are happy to quote for fixed price work, or, if required, can work for an hourly rate.

We are based in London, England, but, thanks to the Internet, we can work 'virtually' anywhere...

Please note that many of the articles here may have updated code available on Len's blog and that the IOCP socket server framework is also available in a licensed, much improved and fully supported version, see here for details.

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