FITSDateUtil.h

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// # FITSDateUtil.h: Class of static functions to help with FITS dates.
// # Copyright (C) 2002
// # 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 FITS_FITSDATEUTIL_H
#define FITS_FITSDATEUTIL_H
 
#include <casacore/casa/aips.h>
#include <casacore/measures/Measures/MEpoch.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
class String;
class MVTime;
 
// <summary>
// A class with static functions to help deal with FITS dates
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="Eric Sessoms" date="2002/08/19" tests="tFITSDateUtil.cc">
// </reviewed>
 
// <prerequisite>
//   <li> General knowledge of FITS, particularly FITS date keywords,
//        is assumed.
// </prerequisite>
//
// <etymology>
// This is a collection of static utility functions for creating and
// interpreting FITS date keywords (e.g. DATE-OBS).
// </etymology>
//
// <synopsis>
// Its never necessary to construct a FITSDateUtil, just use the
// static functions to help handle FITS dates.
// </synopsis>
//
// <motivation>
// The strings that make up the value of FITS dates have a
// precise format.  This class encompasses knowlege of the formats
// used and hopefully simplifies their creation and conversion
// to and from Casacore MVTimes.
// </motivation>
//
 
class FITSDateUtil {
 public:
  enum DateStyle {
    // dd/mm/yy
    OLD,
    // yyyy-mm-dd
    NEW_DATEONLY,
    // yyyy-mm-ddThh:mm:ss[.ss...]
    NEW_DATEANDTIME,
    // OLD if the current year is before 1998 AND "time" is before 1998,
    // otherwise NEW_DATEANDTIME.
    AUTO_PICK
  };
 
  // Convert an MVTime to a FITS date string and timesys string.  The
  // time system must also be supplied.
  // Precision is only used when the time as well as the date is used
  // (NEW_DATEANDTIME or AUTO_PICK).
  // The default (16) gives 10^(-10) second accuracy, 6 gives second level
  // accuracy. Default is 10^(-6)s (1 micro-s) accuracy. 0 means date only,
  // no time (equivalent to NEW_DATEONLY).
  static void toFITS(String &date, String &timesys, const MVTime &time,
                     MEpoch::Types system = MEpoch::UTC, DateStyle style = AUTO_PICK,
                     uInt precision = 12);
 
  // Convert a FITS date string and TIMESYS keyword value into an MVTime and system.
  // Returns False if it can't decode date and timesys. It tries to convert as
  // much as possible, for example if it can't decode timesys it still
  // attempts to decode the time. It sets the date to Jan 1/1900 if it can't
  // decode the time, and UTC if it can't decode timesys. If timesys is the
  // empty string then UTC is assumed.
  static Bool fromFITS(MVTime &time, MEpoch::Types &system, const String &date,
                       const String &timesys);
 
  // Convert a FITS Date string to the current format. If the "in" format is
  // already correct it is just copied through.
  static Bool convertDateString(String &out, const String &in);
 
  // Determine the precision in a FITS date string.
  // Old style dates or no time returns 0, New style + time returns 6 + the number
  // of decimal points, i.e. if we have a time at all we assume it is at least
  // accurate to the second level. The result of this can be used in the call
  // to toFITS, i.e. it has the same meaning.
  //
  // This is mostly meant to be a helper function for convertDateString, but
  // it may be called by anyone.
  static uInt findPrecision(const String &fitsDate);
};
 
}  // namespace casacore
 
#endif