NRAOCASA: casa::MappedArrayEngine< VirtualType, StoredType

MappedArrayEngine is a virtual column engine which maps an array of one type to another type (without any scaling).

An engine object should be used for one column only, because the stored column name is part of the engine. If it would be used for more than one column, they would all share the same stored column. When the engine is bound to a column, it is checked if the name of that column matches the given virtual column name.

The engine can be used for a column containing any kind of array (thus direct or indirect, fixed or variable shaped)) as long as the virtual array can be stored in the stored array. Thus a fixed shaped virtual can use a variable shaped stored, but not vice versa. A fixed shape indirect virtual can use a stored with direct arrays.

Motivation

For precision it is sometimes needed to store the visibility data in a MeasurementSet in double precision. To be able to use other applications on such data, it is needed to map them to single precision.

Because the engine can serve only one column, it was possible to combine the engine and the column functionality in one class. This has been achieved using multiple inheritance. The advantage of this is that only one templated class is used, so less template instantiations are needed.

Example

    // Create the table description and 2 columns with indirect arrays in it.
    // The Int column will be stored, while the double will be
    // used as virtual.
    TableDesc tableDesc ("", TableDesc::Scratch);
    tableDesc.addColumn (ArrayColumnDesc<Int> ("storedArray"));
    tableDesc.addColumn (ArrayColumnDesc<double> ("virtualArray"));
   
    // Create a new table using the table description.
    SetupNewTable newtab (tableDesc, "tab.data", Table::New);
   
    // Create the array mapping engine to map from double to Int
    // and bind it to the double column.
    // Create the table.
    MappedArrayEngine<double,Int> mappingEngine("virtualArray",
                                                "storedArray", 10);
    newtab.bindColumn ("virtualArray", mappingEngine);
    Table table (newtab);
   
    // Store a 3-D array (with dim. 2,3,4) into each row of the column.
    // The shape of each array in the column is implicitly set by the put
    // function. This will also set the shape of the underlying Int array.
    ArrayColumn data (table, "virtualArray");
    Array<double> someArray(IPosition(4,2,3,4));
    someArray = 0;
    for (uInt i=0, i<10; i++) {          // table will have 10 rows
        table.addRow();
        data.put (i, someArray)
    }

Template Type Argument Requirements (VirtualType)

Template Type Argument Requirements (StoredType)

Definition at line 121 of file MappedArrayEngine.h.


Public Member Functions
	MappedArrayEngine (const String &virtualColumnName, const String &storedColumnName)
	Construct an engine to map all arrays in a column.
	MappedArrayEngine (const Record &spec)
	Construct from a record specification as created by dataManagerSpec().
	~MappedArrayEngine ()
	Destructor is mandatory.
virtual String	dataManagerType () const
	Return the type name of the engine (i.e.
virtual String	dataManagerName () const
	Get the name given to the engine (is the virtual column name).
virtual Record	dataManagerSpec () const
	Record a record containing data manager specifications.
Static Public Member Functions
static String	className ()
	Return the name of the class.
static void	registerClass ()
	Register the class name and the static makeObject "constructor".
static DataManager *	makeObject (const String &dataManagerType, const Record &spec)
	Define the "constructor" to construct this engine when a table is read back.
Private Member Functions
	MappedArrayEngine (const MappedArrayEngine< VirtualType, StoredType > &)
	Copy constructor is only used by clone().
MappedArrayEngine< VirtualType, StoredType > &	operator= (const MappedArrayEngine< VirtualType, StoredType > &)
	Assignment is not needed and therefore forbidden (so it is made private and not implemented).
DataManager *	clone () const
	Clone the engine object.
void	getArray (uInt rownr, Array< VirtualType > &array)
	Get an array in the given row.
void	putArray (uInt rownr, const Array< VirtualType > &array)
	Put an array in the given row.
void	getSlice (uInt rownr, const Slicer &slicer, Array< VirtualType > &array)
	Get a section of the array in the given row.
void	putSlice (uInt rownr, const Slicer &slicer, const Array< VirtualType > &array)
	Put into a section of the array in the given row.
void	getArrayColumn (Array< VirtualType > &array)
	Get an entire column.
void	putArrayColumn (const Array< VirtualType > &array)
	Put an entire column.
void	getColumnSlice (const Slicer &slicer, Array< VirtualType > &array)
	Get a section of all arrays in the column.
void	putColumnSlice (const Slicer &slicer, const Array< VirtualType > &array)
	Put a section of all arrays in the column.

Constructor & Destructor Documentation