HDF5Record.h

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00001 //# HDF5Record.h: A class to write/read a record into HDF5
00002 //# Copyright (C) 2008
00003 //# Associated Universities, Inc. Washington DC, USA.
00004 //#
00005 //# This library is free software; you can redistribute it and/or modify it
00006 //# under the terms of the GNU Library General Public License as published by
00007 //# the Free Software Foundation; either version 2 of the License, or (at your
00008 //# option) any later version.
00009 //#
00010 //# This library is distributed in the hope that it will be useful, but WITHOUT
00011 //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
00012 //# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
00013 //# License for more details.
00014 //#
00015 //# You should have received a copy of the GNU Library General Public License
00016 //# along with this library; if not, write to the Free Software Foundation,
00017 //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
00018 //#
00019 //# Correspondence concerning AIPS++ should be addressed as follows:
00020 //#        Internet email: aips2-request@nrao.edu.
00021 //#        Postal address: AIPS++ Project Office
00022 //#                        National Radio Astronomy Observatory
00023 //#                        520 Edgemont Road
00024 //#                        Charlottesville, VA 22903-2475 USA
00025 //#
00026 //# $Id$
00027 
00028 #ifndef CASA_HDF5RECORD_H
00029 #define CASA_HDF5RECORD_H
00030 
00031 //# Includes
00032 #include <casacore/casa/aips.h>
00033 #include <casacore/casa/HDF5/HDF5Object.h>
00034 #include <casacore/casa/HDF5/HDF5DataType.h>
00035 #include <casacore/casa/Containers/Record.h>
00036 
00037 namespace casacore { //# NAMESPACE CASACORE - BEGIN
00038 
00039   // <summary>
00040   // A class to write/read a record into HDF5.
00041   // </summary>
00042 
00043   // <use visibility=export>
00044 
00045   // <reviewed reviewer="" date="" tests="tHDF5Record.cc">
00046   // </reviewed>
00047 
00048   // <prerequisite>
00049   //   <li> <a href="http://hdf.ncsa.uiuc.edu">HDF5 system</a>
00050   //   <li> <linkto class=Record>class Record</linkto>
00051   // </prerequisite>
00052 
00053   // <synopsis>
00054   // This class has a static function to write a Record (or TableRecord)
00055   // into an HDF5 file by storing it as attributes for the given group.
00056   // Another static function can read back the Record.
00057   // It can handle all types of fields in a record.
00058   // <br>
00059   // A few remarks:
00060   // <ul>
00061   //  <li> When writing the record, it first deletes all attributes of the group
00062   //   to be sure that the group's attributes only contain the record.
00063   //  <li> A Casacore Record is a recursive structure, so it is written as
00064   //   nested groups. The name of a subgroup is the name of the subrecord.
00065   // <li> HDF5 cannot deal with empty arrays. Therefore they are written as
00066   //   a special compound type holding the rank and type of the empty array.
00067   // <li> HDF5 cannot hold empty fixed length strings. This is solved by
00068   //   storing an empty string with the special value <tt>__empty__</tt>.
00069   // </ul>
00070   // </synopsis> 
00071 
00072   // <motivation>
00073   // Record is a very important class in Casacore images, so it has to be
00074   // possible to read and write them from/to HDF5.
00075   // </motivation>
00076 
00077   class HDF5Record
00078   {
00079   public: 
00080     // Read a record from the attributes of the given group.
00081     // Nested records are read back correctly.
00082     // An empty record is returned if the group does not exist.
00083     static Record readRecord (const HDF5Object& parentHid,
00084                               const String& groupName);
00085 
00086     // Write the record as attributes of a group of the given parent.
00087     // Nested records are written as nested groups.
00088     // The group is deleted first if it already exists.
00089     static void writeRecord (const HDF5Object& parentHid,
00090                              const String& recordName,
00091                              const RecordInterface& rec);
00092 
00093     // Remove the record (i.e. group) from the given parent.
00094     // Nothing is done if the record does not exist.
00095     static void remove (const HDF5Object& parentHid,
00096                         const String& recordName);
00097 
00098     // Read the (possibly nested) record values from the given group hid.
00099     static Record doReadRecord (hid_t parentHid);
00100 
00101     // Write the (possibly nested) record values into the given group hid.
00102     static void doWriteRecord (const HDF5Object& groupHid,
00103                                const RecordInterface& rec);
00104 
00105   private:
00106     // Read a scalar value and add it to the record.
00107     static void readScalar (hid_t attrId, hid_t dtid,
00108                             const String& name, RecordInterface& rec);
00109 
00110     // Read an array value and add it to the record.
00111     static void readArray (hid_t attrId, hid_t dtid, const IPosition&,
00112                            const String& name, RecordInterface& rec);
00113 
00114     // Read a scalar string from an attribute and add it to the record.
00115     static void readScaString (hid_t attrId, Int sz,
00116                                const String& name, RecordInterface& rec);
00117 
00118     // Read a array of strings from an atrribute and add it to the record.
00119     static void readArrString (hid_t attrId, const IPosition&,
00120                                const String& name, RecordInterface& rec);
00121 
00122     // Read a field containing an empty array.
00123     static void readEmptyArray (hid_t attrId,
00124                                 const String& name, RecordInterface& rec);
00125 
00126     // Read a field containing a scalar of fixed length.
00127     template<typename T>
00128     static void readSca (hid_t attrId, const String& name,
00129                          RecordInterface& rec)
00130     {
00131       T value;
00132       HDF5DataType dtype((T*)0);
00133       read (attrId, &value, dtype);
00134       rec.define (name, value);
00135     }
00136 
00137     // Read a field containing an array of fixed length elements.
00138     template<typename T>
00139     static void readArr (hid_t attrId, const IPosition& shape,
00140                          const String& name,
00141                          RecordInterface& rec)
00142     {
00143       Array<T> value(shape);
00144       HDF5DataType dtype((T*)0);
00145       read (attrId, value.data(), dtype);
00146       rec.define (name, value);
00147     }
00148 
00149     // Read fixed length values from an attribute (scalar and array).
00150     static void read (hid_t attrId, void* value,
00151                       const HDF5DataType& dtype);
00152 
00153     // Write a fixed length scalar value as attribute.
00154     static void writeScalar (hid_t parentHid, const String& name,
00155                              const void* value,
00156                              const HDF5DataType& dtype);
00157 
00158     // Write an array of fixed length values as attribute.
00159     static void writeArray (hid_t parentHid, const String& name,
00160                             const void* value, const IPosition& shape,
00161                             const HDF5DataType& dtype);
00162 
00163     // Write a scalar string as attribute.
00164     // HDF5 cannot handle empty strings, so for empty strings a special
00165     // value is written.
00166     static void writeScaString (hid_t parentHid, const String& name,
00167                                 const String& value);
00168 
00169     // Write an array of strings as attribute.
00170     // HDF5 cannot handle empty strings, so for empty strings a special
00171     // value is written.
00172     static void writeArrString (hid_t parentHid, const String& name,
00173                                 const Array<String>& value);
00174 
00175     // Write a field containing an empty array.
00176     static void writeEmptyArray (hid_t groupHid, const String& name,
00177                                  Int rank, DataType dtype);
00178 
00179     // Write a field containing a fixed length scalar value.
00180     template<typename T>
00181     static void writeSca (hid_t parentHid, const String& name,
00182                           const RecordInterface& rec, Int i)
00183     {
00184       T value;
00185       rec.get (i, value);
00186       HDF5DataType dtype((T*)0);
00187       writeScalar (parentHid, name, &value, dtype);
00188     }
00189 
00190     // Write a field containing an array of fixed length elements.
00191     template<typename T>
00192     static void writeArr (hid_t parentHid, const String& name,
00193                           const RecordInterface& rec, Int i)
00194     {
00195       Array<T> value;
00196       rec.get (i, value);
00197       HDF5DataType dtype((T*)0);
00198       writeArray (parentHid, name, value.data(), value.shape(), dtype);
00199     }
00200 
00201   };
00202 
00203 }
00204 
00205 #endif
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