From Forum Nokia Wiki

Contents 1 Purpose 2 Example code 3 Example application 4 Internal Link

Purpose

While encrypting/decrypting contact database the common problem is that the static function 'CContactDatabase::DeleteDefaultFileL()' always returns error code -14 (ErrInUse).

Encrypt/Decrypt contact database is explained here: Encrypt-Decrypt Contact Database

The procedure to be followed while encrypting and decrypting contacts database:

1. Create a database of your own (MycontactDB) and copy all contacts from the 
   default database (DefcontactDB) to MycontactDB.
2. Encrypt your database MycontactDB.
3. Delete all contacts from DefcontactDB (as we have a backup of all contacts 
   in encrypted form in MycontactDB) instead of deleting default contact 
   database using CContactDatabase::DeleteDefaultFileL().
4. Decrypt MycontactDB when required.
5. Copy all contacts from the MycontactDB to DefcontactDB.

Example code

The following code creates a database MycontactDB and copies all contacts from the default database (DefcontactDB) to MycontactDB:

// Copy all contacts from default contacts DB to My Db (creates own DB)
void CopyFromDefault()
    {
    // open default contact database
    CContactDatabase* DefcontactDB= CContactDatabase::OpenL();
    CleanupStack::PushL(DefcontactDB);
    // create own database
    CContactDatabase* MycontactDB = CContactDatabase::ReplaceL(KFileName);
    CleanupStack::PushL(MycontactDB);
    //create iterator for DefcontactDB
    TContactIter contact_iterator(*DefcontactDB);
    TContactItemId contact_id;
    //go through contacts while there any info
    while( ( contact_id = contact_iterator.NextL() ) != KNullContactId)
        {
        // Read contact from default database
        CContactItem* contact_item = DefcontactDB->ReadContactL(contact_id);
        CleanupStack::PushL(contact_item);
        // Add it to own database
        MycontactDB->AddNewContactL(*contact_item);
        CleanupStack::PopAndDestroy(contact_item);    
        }
    CleanupStack::PopAndDestroy(2);
    }

The following code encrypt your database MycontactDB:

// Encrypt contacts in my database
void EncryptAll()
    {
    CContactDatabase *MycontactDB = CContactDatabase::OpenL(KFileName);
    CleanupStack::PushL(MycontactDB);
 
    TContactIter iter(*MycontactDB);
 
    // Use Heap based descriptor for large/unknown size of contact items.
    TBuf16<128> aValue; 
 
    const CContactIdArray* contactArray = MycontactDB->SortedItemsL();
 
    TInt cnt=contactArray->Count();
 
    for(TInt i=0;i<cnt;i++)
        {
        CContactItem* contactItem=NULL;
 
        contactItem= MycontactDB->OpenContactL((*contactArray)[i]);
        CleanupStack::PushL(contactItem);
 
        CContactItemFieldSet& fieldSet= contactItem->CardFields();
        TInt fieldCount=fieldSet.Count(); // This will give number 
					  // of contact fields.
 
        for(TInt index=0; index < fieldCount; index++)
            {
            CContactItemField& field = fieldSet[index];
            const CContentType& type = field.ContentType();
            if(!(type.ContainsFieldType(KUidContactFieldBirthday)))
                {
                TPtrC name = 
		    contactItem->CardFields()[index].TextStorage()->Text();
                aValue.Copy(name);
                Encrypt(aValue); // Call real encyption here
                contactItem->CardFields()[index].TextStorage()->SetTextL(aValue);
                }
            } //Inner for loop ends here
        MycontactDB->CommitContactL(*contactItem);
        CleanupStack::PopAndDestroy(contactItem);
        } //Outer for loop ends here
    CleanupStack::PopAndDestroy(MycontactDB);
    }

// Actual encrption - can be changed into a complex one
void Encrypt(TDes& aValue)
    {
    for(TInt iCount=0; iCount< aValue.Length();iCount++)
        {
        aValue[iCount]+=3;
        }
    }

The following code deletes all contacts from Default contact Database:

// Deletes all contacts from default contacts DB as we have 
// back up in encrypted form
void DelAllCnts()
    {
    // open default contact database
    CContactDatabase* DefcontactDB= CContactDatabase::OpenL();
    CleanupStack::PushL(DefcontactDB);
    // An array to hold all conatct items IDs    
    CContactIdArray* cntArray = CContactIdArray::NewL();
    CleanupStack::PushL(cntArray);
    //create iterator for DefcontactDB
    TContactIter contact_iterator(*DefcontactDB);
    TContactItemId contact_id;
    //go through contacts while there any info
    while( ( contact_id = contact_iterator.NextL() ) != KNullContactId)
        {
        cntArray->AddL(contact_id);    
        }
    // deletes all contacts
    DefcontactDB->DeleteContactsL(*cntArray);
    CleanupStack::PopAndDestroy(2);
    }

The following code decrypts MycontactDB:

// Decrypt all contacts in my database
void DecryptAll()
    {
    CContactDatabase *MycontactDB = CContactDatabase::OpenL(KFileName);
    CleanupStack::PushL(MycontactDB);
 
    TContactIter iter(*MycontactDB);
    TBuf16<70> aValue;
 
    const CContactIdArray* contactArray = MycontactDB->SortedItemsL();
 
    TInt cnt=contactArray->Count();
 
    for(TInt i=0;i<cnt;i++)
        {
        CContactItem* contactItem=NULL;
 
        contactItem= MycontactDB->OpenContactL((*contactArray)[i]);
        CleanupStack::PushL(contactItem);
 
        CContactItemFieldSet& fieldSet= contactItem->CardFields();
        TInt fieldCount=fieldSet.Count(); // This will give number 
					  // of contact fields.
 
        for(TInt index=0; index < fieldCount; index++)
            {
            CContactItemField& field = fieldSet[index];
            const CContentType& type = field.ContentType();
            if(!(type.ContainsFieldType(KUidContactFieldBirthday)))
                {
                TPtrC name = 
		    contactItem->CardFields()[index].TextStorage()->Text();
                aValue.Copy(name);
                Decrypt(aValue);
                contactItem->CardFields()[index].TextStorage()->SetTextL(aValue);
                }
            } //Inner for loop ends here
        MycontactDB->CommitContactL(*contactItem);
        CleanupStack::PopAndDestroy(contactItem);
        } //Outer for loop ends here
    CleanupStack::PopAndDestroy(MycontactDB);
    }
 
// Actual decrption 
void Decrypt(TDes& aValue)
    {
    for(TInt iCount=0; iCount< aValue.Length();iCount++)
        {
        aValue[iCount]-=3;
        }
    }

The following code copies back all the contacts from the MycontactDB to Default contact database and deletes MycontactDB:

// Copy all contacts back to default contacts DB from My Db
void CopyBackToDefault()
    {
    // open default contact database
    CContactDatabase* DefcontactDB= CContactDatabase::OpenL();
    CleanupStack::PushL(DefcontactDB);
    // open My contact database
    CContactDatabase* MycontactDB = CContactDatabase::OpenL(KFileName);
    CleanupStack::PushL(MycontactDB);
    //create iterator for MycontactDB
    TContactIter contact_iterator(*MycontactDB);
    TContactItemId contact_id;
    //go through contacts while there any info
    while( ( contact_id = contact_iterator.NextL() ) != KNullContactId)
        {
        // Read contact from own database
        CContactItem* contact_item = MycontactDB->ReadContactL(contact_id);
        CleanupStack::PushL(contact_item);
        // Add it to default database
        DefcontactDB->AddNewContactL(*contact_item);
        CleanupStack::PopAndDestroy(contact_item);    
        }
    CleanupStack::PopAndDestroy(2);
    // delete own database file - no more needed
    CContactDatabase::DeleteDatabaseL(KFileName);
    }

Example application

• An example application on contact database

Internal Link

• Encrypt-Decrypt Contact Database