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[occt.git] / src / Quantity / Quantity_ColorHasher.hxx

// Created on: 2016-12-13
// Copyright (c) 2016 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _Quantity_ColorHasher_HeaderFile
#define _Quantity_ColorHasher_HeaderFile

#include <Quantity_Color.hxx>

//! Hasher of Quantity_Color.
struct Quantity_ColorHasher
{
  //! Returns hash code for the given RGB color, in the range [1, theUpperBound]
  //! @param theColor the RGB color object which hash code is to be computed
  //! @param theUpperBound the upper bound of the range a computing range must be within
  //! @return a computed hash code, in the range [1, theUpperBound]
  static Standard_Integer HashCode (const Quantity_Color&  theColor,
                                    const Standard_Integer theUpperBound)
  {
    Standard_Integer aRed   = Standard_Integer (255 * theColor.Red());
    Standard_Integer aGreen = Standard_Integer (255 * theColor.Green());
    Standard_Integer aBlue  = Standard_Integer (255 * theColor.Blue());

    unsigned int aHash = 0;

    updateHash (aHash, aRed);
    updateHash (aHash, aGreen);
    updateHash (aHash, aBlue);
    aHash += (aHash << 3);
    aHash ^= (aHash >> 11);
    aHash += (aHash << 15);

    return IntegerHashCode(aHash, 0x7fff, theUpperBound);
  }

  //! Returns true if two colors are equal.
  static Standard_Boolean IsEqual (const Quantity_Color& theColor1,
                                   const Quantity_Color& theColor2)
  {
    return theColor1 == theColor2;
  }

protected:
  static void updateHash (unsigned int& theHash, const Standard_Integer theValue)
  {
    theHash += theValue;
    theHash += (theHash << 10);
    theHash ^= (theHash >> 6);
  }
};

#endif