EpochEngine.h

Go to the documentation of this file.

// # EpochEngine.h: Engine for TaQL UDF Epoch conversions
// # Copyright (C) 2011
// # 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 MEAS_EPOCHENGINE_H
#define MEAS_EPOCHENGINE_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/meas/MeasUDF/MeasEngine.h>
#include <casacore/measures/Measures/MEpoch.h>
#include <casacore/measures/Measures/MCEpoch.h>
#include <casacore/measures/Measures/MeasConvert.h>
 
namespace casacore {
 
// # Forward declarations
class PositionEngine;
 
// <summary>
// Engine for TaQL UDF Epoch conversions
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="" date="" tests="tMeas.cc">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> EngineBase
// </prerequisite>
 
// <synopsis>
// EpochEngine defines Engines (user defined functions) that can be used in TaQL
// to convert Measures for epochs.
// In this way such derived values appear to be ordinary TaQL functions.
//
// In TaQL these functions can be called like:
// <srcblock>
//   meas.epoch (toref, time, fromref)
//   meas.last (time, fromref, pos, posref)
// For example,
//   meas.epoch ('UTC', 1e9 s, 'WGS84')
// </srcblock>
// <ul>
//  <li>
//  <src>toref</src> is a single constant string.
//  <li>
// <src>pos</src> can have various value types. A single numeric array is
// a series of RA,DEC in J2000. If given as a set, the last argument of the
// set can be the reference types of the values in the set. The values can
// be strings (indicating planetary objects) or value pairs giving lon,lat.
// The default reference type is J2000.
// </ul>
// All functions have data type double and unit radian.
 
// A epoch can also be a table column which usually knows its type.
// It can also be an expression (e.g. EPOCH[0,]) which also knows the type.
// </synopsis>
 
// <motivation>
// It makes it possible to handle measures in TaQL.
// </motivation>
 
class EpochEngine : public MeasEngine<MEpoch> {
 public:
  EpochEngine();
 
  virtual ~EpochEngine();
 
  // Tell if the fraction has to be used for sidereal times.
  Bool sidFrac() const { return itsSidFrac; }
 
  // Get the values.
  Array<Double> getArrayDouble(const TableExprId& id);
 
  // Get the epochs.
  Array<MEpoch> getEpochs(const TableExprId& id);
 
  // Handle the argument(s) giving the input epochs and reference type.
  // The epoch can be a column in a table.
  void handleEpoch(std::vector<TENShPtr>& args, uInt& argnr);
 
  // Set the MeasConvert object.
  void setConverter(MEpoch::Types toType, Bool sidFrac);
 
  // Set the possible position engine.
  // It can be done only once.
  void setPositionEngine(PositionEngine& engine);
 
 private:
  // Strip a possible prefix from the epoch type.
  virtual String stripMeasType(const String& type);
  virtual void handleValues(TableExprNode& operand, const TableExprId& id, Array<MEpoch>& epochs);
 
  // # Data members.
  Bool itsSidFrac;     // # T = fraction for sidereal
  MeasFrame itsFrame;  // # frame used by converter
  MEpoch::Convert itsConverter;
  PositionEngine* itsPositionEngine;
};
 
}  // namespace casacore
 
#endif