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examples/SysLibs/Streams/WriteToMany/WriteToMany.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:
// Example to demonstrate how a network of objects can be written 
// to more than one stream in a direct file store, and how the loading
// of an object from the store into memory may be deferred.
// The example:
// creates a direct file store (replacing any existing direct 
// file store of the same name)
// constructs a CClassABC container object and then constructs a 
// contained CClassA, CClassB and CClassC object.
// Displays the content of the CClassA, CClassB and CClassC objects
// externalizes the CClassB object in its own stream and  keeps hold of the
// stream id. Externalizes the CClassA object, the streamid of the
// CClassB object and the CClassC object in a single
// stream. Makes this latter stream the root stream of the store
// closes the store and deletes the container and its contained CClassA, 
// CClassB and CCLassC objects (from memory)
// re-opens the direct file store
// restores the CClassABC container object; in effect, this restores 
// its contained CClassA and CClassC objects and the stream id of its
// CClassB object. The CClassB object is not restored into memory until 
// it is needed.
// displays the content of the CClassA, CClassB and CClassC objects; it is
// at this time that the CClassB object is restored into memory. (This 
// illustrates the necessity of keeping the store open.
// closes the store and deletes the container and its contained CClassA, 
// CClassB and CCLassC objects (from memory)
// Notes:
// The file name and extension of the direct file store is "WriteToMany.dat".
// and will be created in "\data\" folder of the writable drive.
//

#include "WriteToMany.h"


//***************************************************************
//
// Implementations
//
//***************************************************************


// The file name, extension and path for the file store
_LIT(KFullNameOfFileStore,"\\epoc32ex\\data\\WriteToMany.dat");


                                //  Do the example
static void doExampleL()
    {
                            // make sure directory exists
        fsSession.MkDirAll(KFullNameOfFileStore);
        doMakeAndStoreL(KFullNameOfFileStore);
        doRestoreL(KFullNameOfFileStore);
        }
 

static void doMakeAndStoreL(const TDesC& aName)
        {
                                // Create (replace, if it exists) the direct file store
        TParse  filestorename;
        fsSession.Parse(aName,filestorename);
        CFileStore* store = CDirectFileStore::ReplaceLC(fsSession,filestorename.FullName(),EFileWrite);

                                // Must say what kind of file store.
        store->SetTypeL(KDirectFileStoreLayoutUid);

                                // Construct the container object for CClassA,CClassB and CClassC.
                                // Complete the construction of the contained CClassA, CClassB
                                // and CClassC objects.
        _LIT(KTxtDataForClassA,"Data for the CClassA - AAAAA");
        _LIT(KTxtDataForClassB,"Data for the CClassB - BBBBB");
        _LIT(KTxtDataForClassC,"Data for the CClassC - CCCCC");

        CClassABC* theABC = CClassABC::NewLC(*store);
        theABC->ConstructAL(KTxtDataForClassA,-1,2);
        theABC->ConstructB(KTxtDataForClassB,-3,4,5.6);
        theABC->ConstructC(KTxtDataForClassC);

                                // Show contents of the CClassA, CClassB & CClassC objects
        _LIT(KTxtClassAContent,"CClassA content ...");
        _LIT(KTxtClassBContent,"CClassB content ...");
        _LIT(KTxtClassCContent,"CClassC content ...");

        doShow(KTxtClassAContent,*theABC->PtrA());
        doShow(KTxtClassBContent,*theABC->PtrBL());                                     
        doShow(KTxtClassCContent,*theABC->PtrC());                                      

                                // Store the object network by:
                                // storing the CClassB object in its own stream and 
                                // then storing:
                                //              the CClassA object
                                //              the streamid of the CClassB object
                                //      the CClassC object
                                // in a separate stream.
        TStreamId id = theABC->StoreL();                        
        
                                // Set this stream id as the root stream
        store->SetRootL(id);

                                // Destroy:
                                //              the container object.
                                //              the direct file store object (closes the file),
                                //              
        CleanupStack::PopAndDestroy(2); 
        }


static void doRestoreL(const TDesC& aName)
        {
                                // Open the direct file store
        TParse  filestorename;
        fsSession.Parse(aName,filestorename);
        CFileStore* store = CDirectFileStore::OpenLC(fsSession,filestorename.FullName(),EFileRead);

                                // Restore the container object from the root stream.
                                // This constructs a CClassA and a CClassC object 
                                // and restores them from the root stream. 
                                // The swizzle for the CClassB object is
                                // constructed from the streamid in the root stream.
                                // Note that the CClassB object itself is not loaded into 
                                // memory until it is needed.
        CClassABC* theABC = CClassABC::NewLC(*store,store->Root());

                                // Show restored contents of the CClassA, CClassB and CClassC
                                // objects. Note that the CClassB object may not be in memory and
                                // will be loaded in when needed.
        _LIT(KTxtRestoredClassA,"Restored CClassA content ...");
        _LIT(KTxtRestoredClassB,"Restored CClassB content ...");
        _LIT(KTxtRestoredClassC,"Restored CClassC content ...");

        doShow(KTxtRestoredClassA,*theABC->PtrA());
        doShow(KTxtRestoredClassB,*theABC->PtrBL());                                    
        doShow(KTxtRestoredClassC,*theABC->PtrC());     
                                
                                // Destroy:
                                //              the CClassABC object, 
                                //      the direct file store object (closes the file) 
        CleanupStack::PopAndDestroy(2);
        } 

_LIT(KTxtNewLine,"\n");
_LIT(KFormatType1,"\n%S, ");
_LIT(KFormatType2,"%d, ");
_LIT(KFormatType3,"%u  ");
_LIT(KFormatType4,"%u, ");
_LIT(KFormatType5,"%f  ");
                                                                        
static void doShow(const TDesC& aHeading,const CClassA& anA)
        {
        console->Printf(KTxtNewLine);
        console->Printf(aHeading);
        console->Printf(KFormatType1,anA.iVarBuf);
        console->Printf(KFormatType2,anA.iIntValue);
        console->Printf(KFormatType3,anA.iUintValue);
        console->Printf(KTxtNewLine);
        }



static void doShow(const TDesC& aHeading,const CClassB& aB)
        {
        console->Printf(KTxtNewLine);
        console->Printf(aHeading);
        console->Printf(KFormatType1,&aB.iFixBuf);
        console->Printf(KFormatType2,aB.iIntValue);
        console->Printf(KFormatType4,aB.iUintValue);
        console->Printf(KFormatType5,aB.iRealValue);
        console->Printf(KTxtNewLine);
        }

static void doShow(const TDesC& aHeading,const CClassC& aC)
        {
        console->Printf(KTxtNewLine);
        console->Printf(aHeading);
        console->Printf(KFormatType1,&aC.iFixBuf);
        console->Printf(KTxtNewLine);
        }


//***************************************************************
//
// CClassABC Implementation
//
//***************************************************************
CClassABC::CClassABC(CStreamStore& aStore)
        : iStore(aStore)
        {}

CClassABC::CClassABC(CStreamStore& aStore,TStreamId anId)
        : iStore(aStore), iId(anId)
        {}

CClassABC* CClassABC::NewLC(CStreamStore& aStore)
        {
        CClassABC* self = new (ELeave) CClassABC(aStore);
        CleanupStack::PushL(self);
        self->ConstructL();
        return self;
        }

CClassABC* CClassABC::NewLC(CStreamStore& aStore, TStreamId anId)
        {                                                                                                                       
        CClassABC* self = new (ELeave) CClassABC(aStore,anId);
        CleanupStack::PushL(self);
        self->RestoreL();
        return self;
        }
                
void CClassABC::ConstructL()
        {
        iA = CClassA::NewL();
        iB = CClassB::NewL();// assigns CClassB* to TSwizzle<CClassB>. Uses TSwizzle operator=(T*)
        iC = CClassC::NewL();
        }

void CClassABC::ConstructAL(const TDesC& aData,TInt anInt,TUint aUint)
        {
        iA->iVarBuf    = aData.AllocL();        
        iA->iIntValue  = anInt;
        iA->iUintValue = aUint;
        }
                        
void CClassABC::ConstructB(const TDesC& aData,TInt anInt,TUint aUint,TReal aReal)
        {
        iB->iFixBuf    = aData;
        iB->iIntValue  = anInt; 
        iB->iUintValue = aUint;
        iB->iRealValue = aReal;
        }
                        
void CClassABC::ConstructC(const TDesC& aData)
        {
        iC->iFixBuf = aData;
        }


                        // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
                        // Destructor deletes the CClassB object only if it is in memory.
                        // The IsPtr() function can be used to determine whether the 
                        // CClassB object is memory. 
                        // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
CClassABC::~CClassABC()
        {
        delete iA;
        delete iC;
        if (iB.IsPtr())
                delete iB.AsPtr(); // can also "delete iB;" makes implicit call to "operator T*()"
        }

        
                                // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
                                // Stores the CClassB object in its own stream and
                                // then stores:
                                //              the CClassA object,
                                //              the streamid of the CClassB object,
                                //              the CClassC object
                                // in a separate stream.
                                // Returns the streamid of this last stream
                                // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
TStreamId CClassABC::StoreL()
        {
                                // Construct the output stream which is intended
                                // to hold the CClassB object only.
        RStoreWriteStream outstream;
        TStreamId idForB = outstream.CreateLC(iStore);
                                // Stream out the CClassB object.
                                // Note that the right hand side returns a reference
                                // to CClassB
        outstream  << *iB; 
                                // Commit changes to the stream
        outstream.CommitL();
                                // Cleanup the stream object
        CleanupStack::PopAndDestroy();  
                                // Now construct the output stream which is intended
                                // to hold:
                                //              the CClassA object,
                                //              the streamid of the CClassB object,
                                //              the CClassC object
        TStreamId id = outstream.CreateLC(iStore);
                                // Write out the CClassA object.
        outstream  << *iA; 
                                // Write out the stream id of the CClassB object
        outstream  << idForB;
                                // Write out the CClassC object.
        outstream  << *iC;
                                // Commit changes to the stream
        outstream.CommitL();
                                // Cleanup the stream object,
        CleanupStack::PopAndDestroy();  
                                // Return this stream id
        return id;
        }

                                
const CClassA* CClassABC::PtrA()
        {
        return iA;      // Return a pointer to the contained CClassA object
        }

                                
const CClassB* CClassABC::PtrBL()
        {
        if (iB.IsId())          // If the contained CClassB object is not in memory, it must
                RestoreBL();    // be loaded in before a pointer can be returned to the caller
        return iB.AsPtr();
        }

                                
const CClassC* CClassABC::PtrC()
        {
        return iC;      //Returns a pointer to the contained CClassC object
        }
                                
                                // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
                                // Restores the CClassA and CClassC objects and the streamid for the
                                // CClassB object.
                                // The swizzle for the CClassB object is constructed from the
                                // streamid but the CClassB object itself is NOT restored at 
                                // this time.
                                // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
void CClassABC::RestoreL()
        {
                                // Construct the input stream.
        RStoreReadStream instream;
        instream.OpenLC(iStore,iId);
                                // Construct a CClassA object and restore from the stream
        iA = CClassA::NewL();
        instream >> *iA;
                                // Construct the swizzle for the CClassB object. This
                                // stream contains the id of the stream which 
                                // actually contains the full CClassB object. The loading of
                                // the CClassB object into memory is deferred until later.
                                // The resulting swizzle represents the CClassB object as 
                                // a streamid 
        instream >> iB;
                                // Construct a CClassC object and restrore from the stream
        iC = CClassC::NewL();
        instream >> *iC;
                                // Cleanup the stream object
        CleanupStack::PopAndDestroy();
        }


                                // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
                                // Loads the CClassB object into memory and changes the swizzle's
                                // representation from "streamid" to "pointer".
                                // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
void CClassABC::RestoreBL()
        {
                                // Construct the input stream. Assumes we have the correct store (this
                                // emphasizes the need to ensure that the store remain open)
        RStoreReadStream instream;
        instream.OpenLC(iStore,iB.AsId());
                                // Construct a CClassB object and restore from the stream. The 
                                // assignment: CClassB* to TSwizzle<CClassB> changes the
                                // swizzle's representation of the CClassB object 
                                // from "streamid" to "pointer"
        CClassB* ptrB = CClassB::NewLC();
        instream >> *ptrB;
        CleanupStack::Pop();
        iB = ptrB;
                                // Cleanup the stream object                    
        CleanupStack::PopAndDestroy();
        }       

//***************************************************************
//
// CClassA Implementation
//
//***************************************************************
CClassA* CClassA::NewL()
        {
        CClassA* self = CClassA::NewLC();
        CleanupStack::Pop();
        return self;
        }

CClassA* CClassA::NewLC()
        {
        CClassA* self = new (ELeave) CClassA;
        CleanupStack::PushL(self);
        return self;
        }

CClassA::~CClassA()
        {
        delete iVarBuf;
        }

void CClassA::ExternalizeL(RWriteStream& aStream) const
        {
        aStream.WriteInt32L(iVarBuf->Des().MaxLength());
        aStream << *iVarBuf;
        aStream.WriteInt32L(iIntValue);
        aStream.WriteUint32L(iUintValue);
        }  
 
void CClassA::InternalizeL(RReadStream& aStream)
        {
        TInt maxlen;
        maxlen     = aStream.ReadInt32L();
        iVarBuf    = HBufC::NewL(aStream,maxlen);
        iIntValue  = aStream.ReadInt32L();
        iUintValue = aStream.ReadUint32L();
        }  
                

//***************************************************************
//
// CClassB Implementation
//
//***************************************************************
CClassB* CClassB::NewLC()
        {
        CClassB* self = new (ELeave) CClassB;
        CleanupStack::PushL(self);
        return self;
        }

CClassB* CClassB::NewL()        
        {
        CClassB* self = CClassB::NewLC();
        CleanupStack::Pop();    
        return self;
        }

void CClassB::ExternalizeL(RWriteStream& aStream) const
        {
        aStream << iFixBuf;
        aStream.WriteInt32L(iIntValue);
        aStream.WriteUint32L(iUintValue);
        aStream.WriteReal64L(iRealValue);
        }  
 
void CClassB::InternalizeL(RReadStream& aStream)
        {
        aStream >> iFixBuf;
        iIntValue  = aStream.ReadInt32L();
        iUintValue = aStream.ReadUint32L();
        iRealValue = aStream.ReadReal64L();
        }  

//***************************************************************
//
// CClassC Implementation
//
//***************************************************************
CClassC* CClassC::NewL()
        {
        CClassC* self = CClassC::NewLC();
        CleanupStack::Pop();
        return self;
        }

CClassC* CClassC::NewLC()
        {
        CClassC* self = new (ELeave) CClassC;
        CleanupStack::PushL(self);
        return self;
        }

void CClassC::ExternalizeL(RWriteStream& aStream) const
        {
        aStream << iFixBuf;
        }  
 
void CClassC::InternalizeL(RReadStream& aStream)
        {
        aStream >> iFixBuf;
        }  

---

Copyright ©2010 Nokia Corporation and/or its subsidiary(-ies).
All rights reserved. Unless otherwise stated, these materials are provided under the terms of the Eclipse Public License v1.0.