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guma_random.h

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/* LIBGUL - Geometry Utility Library
 * Copyright (C) 1998-1999 Norbert Irmer
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifndef GUMA_RANDOM_H
#define GUMA_RANDOM_H

namespace guma {

/*----------------------------------------------------------------------------
  System dependent function to get a seed for pseudo random number generators
----------------------------------------------------------------------------*/
GULAPI gul::uint32 GetSeed();

/*------------------------------------------------------------------
  Function for generating pseudo random numbers with DES crypto
------------------------------------------------------------------*/
GULAPI void PseudoDes( gul::uint32 *lword, gul::uint32 *irword );

/*------------------------------------------------------------------
  Class which can be used as a parameter for templates which need a
  random number generator
------------------------------------------------------------------*/
class random_des
{
public:
  GULAPI static gul::uint32 cycle;
  GULAPI static gul::uint32 sequence;
  GULAPI static bool initialized;

  // can be used for debugging to with a certain sequence/cycle
  static double des_random( bool reset, gul::uint32 *idum )
  {
    const double factor = 1.0/((double)LL(0x100000000));
    gul::uint32 irword,lword;
  
    if( reset )
    {
      sequence = *idum;
      *idum = 1;
    }
    irword = *idum;
    lword = sequence;

    PseudoDes( &lword, &irword );

    (*idum)++;

    return ((double)irword) * factor;
  }

  static double Random( void )
  {
    if( !initialized )
    {
      initialized = true;
      cycle = GetSeed();
      return des_random( true, &cycle );
    }
    return des_random( false, &cycle );
  }
};

}

#endif

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