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CdbRooRoPersistentCollectionR.rdl

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#ifndef CDBROOREADONLY_PERSISTENT_COLLECTION_R_RDL
#define CDBROOREADONLY_PERSISTENT_COLLECTION_R_RDL

// File and Version Information:
//      $Id: CdbRooRoPersistentCollectionR.rdl,v 1.4 2005/11/11 01:41:28 gapon Exp $

#include "CdbBase/CdbCPtr.hh"

#include "CdbRooReadonly/CdbRooRoCollectionAddressR.hh"

#include <TFile.h>

/// A base class for persistent collections of objects
/**
  * This class enforces (and implements) an explicit storage interface for derived 
  * persistent collections.
  *
  * The collection can be stored either on its own or as an "embedded" one being
  * a data member of another persistent class. Two storage methods are provided:
  *
  *   @see CdbRooRoPersistentCollectionR::storeAt()
  *   @see CdbRooRoPersistentCollectionR::storeAsEmbeddedAt()
  *
  * Sub-collections (if any) of derived classes can be stored by reimplementing
  * the below defined "storeSubCollectionsAt()" method:
  *
  *   @see CdbRooRoPersistentCollectionR::storeSubCollectionsAt()
  */
class CdbRooRoPersistentCollectionR {

public:

  /// Constructor

    CdbRooRoPersistentCollectionR( );

  /// Copy constructor

    CdbRooRoPersistentCollectionR( const CdbRooRoPersistentCollectionR& theOther );

  /// Assignment operator

    CdbRooRoPersistentCollectionR& operator=( const CdbRooRoPersistentCollectionR& theOther );

  /// Destructor

    virtual ~CdbRooRoPersistentCollectionR( );

  /// Store a collection (if not embedded) and its elements at the specified location
  /**
    * The collection itself will be stored at the specified file where
    * the collection name will be used as a key in the TDirectory/TFile.
    *
    *   [ If the "isEmbedded" parameter is set to true then the colllection itself
    *     won't be stored. Only its element will be. This level of control is meant
    *     to be used for cases when the collection object is embedded as a data member
    *     into other persistent objects. To help with this the helper storeAsEmbeddedAt
    *     method is present in the class's interface. ]
    *
    *
    * NOTES:
    *
    *   - The collection can be stored just once. If a subsequent attempt to store
    *     it will be made then a error status will be returned by the current
    *     procedure. The transient cache will be used as a source of the stored elements.
    *
    *   - The method won't check a consistency between a name of the passed file
    *     and a collection address. It's up to the method's caller to ensure this.
    *
    * Upon its successfull completion, the method will return a usual CdbStatus::Success
    * and a total number of bytes stored. This number will count both the collection object
    * itself and all sub-collections (if any). The number will be positive in that case.
    */
    CdbStatus storeAt( const CdbRooRoCollectionAddressR& theCollectionAddress,
                       const CdbCPtr<TFile>&             theFilePtr,
                       Int_t&                            theNumBytesStored,
                       bool                              isEmbedded = false );

    CdbStatus storeAsEmbeddedAt( const CdbRooRoCollectionAddressR& theCollectionAddress,
                                 const CdbCPtr<TFile>&             theFilePtr,
                                 Int_t&                            theNumBytesStored )
    {
        return storeAt( theCollectionAddress,
                        theFilePtr,
                        theNumBytesStored,
                        true );
    }

protected:

  /// Store user defined sub-collections
  /**
    * This method is meant to be implemented in a context of a derived collection
    * to store subcollections of that collection. The default implementation of the method
    * won't do anything, just return a successfull status.
    *
    * If the method returns a nono-successfull status then the overall storing sequence
    * will get aborted.
    *
    * NOTE: This method gets called before the current collection gets stored.
    */
    virtual CdbStatus storeSubCollectionsAt( const CdbRooRoCollectionAddressR& theCollectionAddress,
                                             const CdbCPtr<TFile>&             theFilePtr,
                                             Int_t&                            theNumBytesStored );
  // Accessors

    bool isStored( ) const { return _stored; }
    
    const CdbRooRoCollectionAddressR& storedCollectionAddress( ) const { return _collectionAddress; }

private:

  // Persistent context
  //
  // NOTES:
  //
  //    1. The collection address gets filled when the collection is being
  //       stored in the corresponding 'host' file.
  //
  //    2. The collection address is also used to locate the location of
  //       a TTree/TBranch with elements of the collection.

    Bool_t _stored;

    CdbRooRoCollectionAddressR _collectionAddress;

    ClassDef(CdbRooRoPersistentCollectionR,1);
};

#endif /* CDBROOREADONLY_PERSISTENT_COLLECTION_R_RDL */

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