Provides an implementation of the IRowset interface.

template <
   class T,
   class RowsetInterface,
   class RowClass = CSimpleRow,
   class MapClass = CAtlMap <
      RowClass::KeyType,
      RowClass*>>
class ATL_NO_VTABLE IRowsetImpl : public RowsetInterface

T
Your class, derived from IRowsetImpl.

RowsetInterface
A class derived from IRowsetImpl.

RowClass
Storage unit for the HROW.

MapClass
Storage unit for all row handles held by the provider.

Header: atldb.h

IRowset is the base rowset interface.

Adds a reference count to an existing row handle.

STDMETHOD(AddRefRows )(DBCOUNTITEM cRows,
   const HROW rghRows[],
   DBREFCOUNT rgRefCounts[],
   DBROWSTATUS rgRowStatus[]);

See IRowset::AddRefRows in the OLE DB Programmer's Reference.

A helper method called by GetNextRows to allocate a new HROW.

HRESULT CreateRow(DBROWOFFSET lRowsOffset,
   DBCOUNTITEM& cRowsObtained,
   HROW* rgRows);

lRowsOffset
Cursor position of the row being created.

cRowsObtained
A reference passed back to the user indicating the number of rows created.

rgRows
An array of HROWs returned to the caller with the newly created row handles.

If the row exists, this method calls AddRefRows and returns. Otherwise, it allocates a new instance of the RowClass template variable and adds it to m_rgRowHandles.

Retrieves data from the rowset's copy of the row.

STDMETHOD(GetData )(HROW hRow,
   HACCESSOR hAccessor,
   void* pDstData);

See IRowset::GetData in the OLE DB Programmer's Reference.

Some parameters correspond to OLE DB Programmer's Reference parameters of different names, which are described in IRowset::GetData:

Also handles data conversion using the OLE DB data conversion DLL.

Returns the DBSTATUS status flags for the specified field.

virtual DBSTATUS GetDBStatus(RowClass* currentRow,
   ATLCOLUMNINFO* columnNames);

currentRow
[in] The current row.

columnNames
[in] The column for which status is being requested.

The DBSTATUS flags for the column.

Fetches rows sequentially, remembering the previous position.

STDMETHOD(GetNextRows )(HCHAPTER hReserved,
   DBROWOFFSET lRowsOffset,
   DBROWCOUNT cRows,
   DBCOUNTITEM* pcRowsObtained,
   HROW** prghRows);

See IRowset::GetNextRows in the OLE DB Programmer's Reference.

The constructor.

IRowsetImpl();

You usually do not need to call this method directly.

Called by AddRefRows and ReleaseRows to either increment or release a reference count to an existing row handle.

HRESULT RefRows(DBCOUNTITEM cRows,
   const HROWrghRows[],
   DBREFCOUNT rgRefCounts[],
   DBROWSTATUS rgRowStatus[],
   BOOL bAdd);

See IRowset::AddRefRows in the OLE DB Programmer's Reference.

A standard HRESULT value.

Releases rows.

STDMETHOD(ReleaseRows )(DBCOUNTITEM cRows,
   const HROW rghRows[],
   DBROWOPTIONS rgRowOptions[],
   DBREFCOUNT rgRefCounts[],
   DBROWSTATUS rgRowStatus[]);

See IRowset::ReleaseRows in the OLE DB Programmer's Reference.

Repositions the next fetch position to its initial position; that is, its position when the rowset was first created.

STDMETHOD(RestartPosition )(HCHAPTER /* hReserved */);

See IRowset::RestartPosition in the OLE DB Programmer's Reference.

The rowset position is undefined until GetNextRow is called. You can move backwards in a rowet by calling RestartPosition and then fetching or scrolling backwards.

Sets the DBSTATUS status flags for the specified field.

virtual HRESULT SetDBStatus(DBSTATUS* statusFlags,
   RowClass* currentRow,
   ATLCOLUMNINFO* columnInfo);

statusFlags
The DBSTATUS flags to set for the column.

currentRow
The current row.

columnInfo
The column for which status is being set.

A standard HRESULT value.

The provider overrides this function to provide special processing for DBSTATUS_S_ISNULL and DBSTATUS_S_DEFAULT.

Indicates whether a provider supports backward fetching.

unsigned m_bCanFetchBack:1;

Linked to the DBPROP_CANFETCHBACKWARDS property in the DBPROPSET_ROWSET group. The provider must support DBPROP_CANFETCHBACKWARDS for m_bCanFetchBackwards to be true.

Indicates whether a provider can have its cursor scroll backwards.

unsigned  m_bCanScrollBack:1;

Linked to the DBPROP_CANSCROLLBACKWARDS property in the DBPROPSET_ROWSET group. The provider must support DBPROP_CANSCROLLBACKWARDS for m_bCanFetchBackwards to be true.

A bit flag used to determine if the cursor position is defined on the rowset.

unsigned m_bReset:1;

If the consumer calls GetNextRows with a negative lOffset or cRows and m_bReset is true, GetNextRows moves to the end of the rowset. If m_bReset is false, the consumer receives an error code, in conformance with the OLE DB specification. The m_bReset flag gets set to true when the rowset is first created and when the consumer calls IRowsetImpl::RestartPosition. It gets set to false when you call GetNextRows.

An index to the rowset, representing the cursor.

DBROWOFFSET m_iRowset;

A map of row handles currently contained by the provider in response to GetNextRows.

MapClass m_rgRowHandles;

Row handles are removed by calling ReleaseRows. See the IRowsetImpl overview for the definition of MapClass.

OLE DB Provider Templates
OLE DB Provider Template Architecture
CSimpleRow Class