examples/Base/DLLs/UsingDLLs/UsingDLLs.cpp

// Copyright (c) 2000-2009 Nokia Corporation and/or its subsidiary(-ies).
// All rights reserved.
// This component and the accompanying materials are made available
// under the terms of "Eclipse Public License v1.0"
// which accompanies this distribution, and is available
// at the URL "http://www.eclipse.org/legal/epl-v10.html".
//
// Initial Contributors:
// Nokia Corporation - initial contribution.
//
// Contributors:
//
// Description:
// A program which uses dynamically linked DLLs.
//

// standard example header
#include "CommonFramework.h"
// f32 header needed for loading dlls.
#include <f32file.h>

#include "UsingDLLs.h"

_LIT(KTxtHarry,"Harry");
_LIT(KTxtSally,"Sally");
_LIT(KTxtDr1,"PolymorphicDLL1.DLL");
_LIT(KTxtDr2,"PolymorphicDLL2.DLL");

_LIT(KTxt1,"dynamically linked DLL example \n\n");
_LIT(KTxt2,"checking UID\n");
_LIT(KTxt3,"DLL has incorrect UID... \n");

void UseDllL(const TFileName& aDllName, const TDesC& aName);

LOCAL_C void doExampleL()
    {
        // open file server session.
        RFs fs;
        User::LeaveIfError(fs.Connect());
        console->Printf(KTxt1);
        // use each DLL in turn
        TFileName  dll;
        dll = KTxtDr1;
        UseDllL(dll, KTxtHarry);
        dll = KTxtDr2;
        UseDllL(dll, KTxtSally);
        // close the file server session.
        fs.Close();
        }

// how to use a DLL

void UseDllL(const TFileName& aLibraryName, const TDesC& aName)
        {
                // Use RLibrary object to interface to the DLL
        RLibrary library;
                // Dynamically load DLL
        User::LeaveIfError(library.Load(aLibraryName));
                // Check second UID is as expected; leave if not
        console->Printf(KTxt2);
        
        if (library.Type()[1] != KMessengerUid)
                {
                console->Printf(KTxt3);
                User::Leave(KErrGeneral);
                }
                // Function at ordinal 1 creates  new CMessenger
        TLibraryFunction entry=library.Lookup(1);
                // Call the function to create new CMessenger
        CMessenger* messenger=(CMessenger*) entry();
                // Push pointer to CMessenger onto the cleanup stack
        CleanupStack::PushL(messenger);
                // Second-phase constructor for CMessenger
        messenger->ConstructL(console, aName);
                // Use CMessenger object to issue greeting
        messenger->ShowMessage();
                // Pop CMessenger object off cleanup stack and destroy
        CleanupStack::PopAndDestroy();
                // Finished with the DLL
        library.Close();
        }

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