HDF5DataType.h

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// # HDF5DataType.h: An class representing an HDF5 data type
// # Copyright (C) 2008
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef CASA_HDF5DATATYPE_H
#define CASA_HDF5DATATYPE_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/HDF5/HDF5Object.h>
#include <casacore/casa/HDF5/HDF5HidMeta.h>
#include <casacore/casa/BasicSL/Complex.h>
#include <casacore/casa/BasicSL/String.h>
#include <casacore/casa/Utilities/DataType.h>
#include <vector>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward Declarations
class IPosition;
template <typename T>
class Block;
 
// <summary>
// A class representing an HDF5 data type.
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="" date="" tests="tHDF5DataType.cc">
// </reviewed>
 
// <prerequisite>
//   <li> <a href="http://hdf.ncsa.uiuc.edu">HDF5 system</a>
// </prerequisite>
 
// <synopsis>
// This class wraps the HDF5 functions to create a data type
// for the data in memory and for the file.
// The HDF5 file data type order is set to LittleEndian.
// <br>
// The basic constructors define a scalar of a basic data type or
// data type Complex and DComplex. Strings are also supported.
// However, it is also possible to define a fixed shaped array for any
// HDF5DataType. Furthermore, it is possible to define a compound data
// type consisting of named fields of any HDF5DataType with a fixed size.
// Arrays and/or compounds can be nested at will.
// <br>
// Variable length strings are supported, but cannot be used in compounds.
// <br>
// Older HDF5 versions did not support empty arrays. Therefore they are
// represented as a compound with 3 fields. Also they did not support
// boolean values; they are represented as a signed char.
// HDF5 does not support complex values either. They are represented
// as a compound with fields 're' and 'im'.
// </synopsis>
 
// <motivation>
// The HDF5 C++ interface only supports the HDF5 C functionality and
// resembles that to much. For instance, it does not use STL containers.
// It does not support non-basic data types, in particular Complex.
// </motivation>
 
class HDF5DataType {
 public:
  // The default constructor makes an invalid object.
  // It is needed to make a vector of objects.
  HDF5DataType() : itsSize(0) {}
 
  // Create an HDF5 datatype object for the given fixed length type.
  // It uses the corresponding native HDF5 data type. Only for Bool it
  // uses a uchar, because the HDF5 bool type is a uint.
  // For the complex types it makes a compound HDF5 data type.
  // The String type is meant for an array of strings.
  // <group>
  explicit HDF5DataType(const Bool*);
  explicit HDF5DataType(const uChar*);
  explicit HDF5DataType(const Short*);
  explicit HDF5DataType(const uShort*);
  explicit HDF5DataType(const Int*);
  explicit HDF5DataType(const uInt*);
  explicit HDF5DataType(const Int64*);
  explicit HDF5DataType(const Float*);
  explicit HDF5DataType(const Double*);
  explicit HDF5DataType(const Complex*);
  explicit HDF5DataType(const DComplex*);
  explicit HDF5DataType(const String*);
  // </group>
 
  // Create an HDF5 datatype object for a scalar string.
  // The length of the string is part of the type.
  explicit HDF5DataType(const String& value);
 
  // Create an HDF5 datatype object for an empty array.
  // Both arguments are dummy (needed to distinguish the constructor).
  // An empty array as represented as a compound data type with integer
  // field names emptyarray, rank and casatype.
  HDF5DataType(Int, Int);
 
  // Define a compound data type consisting of the given fields and types.
  // An exception is thrown if the vectors are empty or have mismatching
  // sizes.
  HDF5DataType(const std::vector<String>& names, const std::vector<HDF5DataType>& types);
 
  // Create an array of the given data type.
  // An exception is thrown if the shape is empty.
  HDF5DataType(const HDF5DataType&, const IPosition& shape);
 
  // The copy constructor makes a deep copy.
  HDF5DataType(const HDF5DataType& that);
 
  // The destructor closes the HDF5 data type object.
  ~HDF5DataType();
 
  // Assignment makes a deep copy.
  HDF5DataType& operator=(const HDF5DataType& that);
 
  // Get the Casacore data type for the given HDF5 data type.
  // TpRecord is returned for a compound data type.
  static DataType getDataType(hid_t);
 
  // Get the HID for the data type in memory.
  hid_t getHidMem() const { return itsHidMem; }
 
  // Get the HID for the data type in the file.
  hid_t getHidFile() const { return itsHidFile; }
 
  // Get the size in bytes of the data type (in memory).
  // Note that the size of a string is variable, thus 0.
  uInt size() const { return itsSize; }
 
  // Test if the data type is Complex or DComplex.
  static Bool isComplex(hid_t dtid);
 
  // Test if the data type is an empty array.
  static Bool isEmptyArray(hid_t dtid);
 
  // Get the shape of an array data type.
  // It returns an empty IPosition for non-arrays.
  static IPosition getShape(hid_t dtid);
 
  // Helper functions to convert shapes.
  // It reverses the axes, because HDF5 uses C-order.
  // <group>
  static Block<hsize_t> fromShape(const IPosition& shape);
  static IPosition toShape(const Block<hsize_t>& b);
  // </group>
 
 private:
  // Add a field to a compound data type.
  // It does it for the memory and file data type.
  void addToCompound(const char* name, uInt offset, const HDF5DataType& dtype);
 
  // # Data members
  HDF5HidDataType itsHidMem;
  HDF5HidDataType itsHidFile;
  uInt itsSize;
};
 
}  // namespace casacore
 
#endif