examples/SysLibs/Streams/WriteToMany/WriteToMany.cpp

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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;
        }  

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