UnitCompare.c

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/*
*  Copyright (C) 2007 Jolien Creighton, Kipp Cannon, John Whelan
*
*  This program is free software; you can redistribute it and/or modify
*  it under the terms of the GNU General Public License as published by
*  the Free Software Foundation; either version 2 of the License, or
*  (at your option) any later version.
*
*  This program 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 General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with with program; see the file COPYING. If not, write to the
*  Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
*  MA  02110-1301  USA
*/
 
#include <math.h>
#include <string.h>
 
#include <lal/LALStdlib.h>
#include <lal/Units.h>
#include <lal/XLALError.h>
 
/**
 * \addtogroup UnitCompare_c
 * \author J. T. Whelan <john.whelan@ligo.org>
 *
 * \brief Function to compare two \c LALUnit structures.
 */
/** @{ */
 
/** Return 1 if a unit is dimensionless, 0 otherwise */
int XLALUnitIsDimensionless(const LALUnit *unit)
{
  int i;
 
  if(!unit)
    XLAL_ERROR(XLAL_EFAULT);
 
  for(i = 0; i < LALNumUnits; i++)
    if(unit->unitNumerator[i] != unit->unitDenominatorMinusOne[i])
      return 0;
  return 1;
}
 
 
/** Return the unit's prefactor */
REAL8 XLALUnitPrefactor(const LALUnit *unit)
{
  if(!unit)
    XLAL_ERROR_REAL8(XLAL_EFAULT);
  return pow(10.0, unit->powerOfTen);
}
 
 
/**
 * Return the ratio unit1 / unit2
 */
REAL8 XLALUnitRatio(const LALUnit *unit1, const LALUnit *unit2)
{
  LALUnit tmp;
 
  if(!unit1 || !unit2)
    XLAL_ERROR_REAL8(XLAL_EFAULT);
 
  XLALUnitDivide(&tmp, unit1, unit2);
  if(XLALUnitIsDimensionless(&tmp))
    return XLALUnitPrefactor(&tmp);
  XLAL_ERROR_REAL8(XLAL_EDIMS);
}
 
 
 
/**
 * Returns 0 if the the normal form of the two unit
 * structures are the same or > 0 if they are different.  It returns
 * #XLAL_FAILURE and ::xlalErrno is set to #XLAL_EFAULT if
 * one of the input pointers is \c NULL.
 *
 * Example:
 * \code
 * if(XLALUnitCompare(&unit1, &unit2)) {
 *   units_are_not_equal();
 * }
 * \endcode
 */
int XLALUnitCompare( const LALUnit *unit1, const LALUnit *unit2 )
{
  LALUnit  unitOne, unitTwo;
 
  if ( ! unit1 || ! unit2 )
    XLAL_ERROR( XLAL_EFAULT );
 
  unitOne = *unit1;
  unitTwo = *unit2;
 
  /* normalize the units */
  if ( XLALUnitNormalize( &unitOne ) )
    XLAL_ERROR( XLAL_EFUNC );
  if ( XLALUnitNormalize( &unitTwo ) )
    XLAL_ERROR( XLAL_EFUNC );
 
  /* factors of 10 disagree? */
  if ( unitOne.powerOfTen != unitTwo.powerOfTen )
    return 1;
 
  /* powers of dimensions disagree? use memcmp() to compare the arrays */
  if ( memcmp( unitOne.unitNumerator, unitTwo.unitNumerator, LALNumUnits * sizeof( *unitOne.unitNumerator ) ) )
    return 1;
  if ( memcmp( unitOne.unitDenominatorMinusOne, unitTwo.unitDenominatorMinusOne, LALNumUnits * sizeof( *unitOne.unitDenominatorMinusOne ) ) )
    return 1;
 
  /* agree in all possible ways */
  return 0;
}
 
/** @} */