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guma_random.cpp

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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.
 */

#include "stdafx.h"

#include "gul_types.h"
#include "guma_random.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#ifdef _MSC_VER
  #include <io.h>  
#else
  #include <unistd.h>
#endif
#include <time.h>

#include <iostream>


#if defined(__MINGW32__) || defined(_MSC_VER)

/*-------------------------------------------------------------------------
  linear congruential method, used when platform has no random/srandom
  functions (ms-windows)
-------------------------------------------------------------------------*/

static long random_lastx;

/*
 * Compute x = (7^5 * x) mod (2^31 - 1)
 * wihout overflowing 31 bits:
 *      (2^31 - 1) = 127773 * (7^5) + 2836
 * From "Random number generators: good ones are hard to find",
 * Park and Miller, Communications of the ACM, vol. 31, no. 10,
 * October 1988, p. 1195.
 */

GULAPI long random()
{
  long hi, lo, x;

  x = random_lastx;
  hi = x / 127773;
  lo = x % 127773;
  x = 16807 * lo - 2836 * hi;
  if (x <= 0)
    x += 0x7fffffff;
  random_lastx = x = (x & 0x7fffffff);
  return x;
}

GULAPI void srandom( long x )
{
  random_lastx = x;
}

#endif


namespace guma {

using gul::uint32;
using std::cout;

GULAPI bool random_des::initialized = false;
GULAPI uint32 random_des::sequence = 1;
GULAPI uint32 random_des::cycle = 1;

/*----------------------------------------------------------------------------
  System dependent function to get a seed for pseudo random number generators
----------------------------------------------------------------------------*/

GULAPI uint32 GetSeed()
{
  uint32 seed;
  int fd,n;
   
  fd = open( "/dev/random", O_RDONLY ); 
  if( fd < 0 )
  {
    cout << "GetSeed: Couldn't open \"/dev/random\"\n";
    return (uint32)time(0);
  } 
  n = read( fd, &seed, sizeof(seed) );
  if( n != sizeof(seed) )
  {
    close(fd);

    cout << "GetSeed: Couldn't read " << sizeof(seed) << "bytes\n";
    return (uint32)time(0);
  }  

  close(fd);
  return seed;
}

/*------------------------------------------------------------------
  Function for generating pseudo random numbers with DES crypto
------------------------------------------------------------------*/

GULAPI void PseudoDes( uint32 *lword, uint32 *irword )
{
  static uint32 c1[4] = {
    0xbaa96887L, 0x1e17d32cL, 0x03bcdc3cL, 0x0f33d1b2L };
  static uint32 c2[4] = {
    0x4b0f3b58L, 0xe874f0c3L, 0x6955c5a6L, 0x55a7ca46L };
    
  uint32 i,ia,ib,iswap,itmph=0,itmpl=0;

  for( i = 0; i < 4; i++ )
  {
    ia = (iswap=(*irword)) ^ c1[i];
    itmpl = ia & 0xffff;
    itmph = ia >> 16;
    ib = itmpl*itmpl + ~(itmph*itmph);
    ia = (ib>>16) | ((ib&0xffff)<<16);
    *irword = (*lword) ^ ((ia ^ c2[i]) + itmpl*itmph);
    *lword = iswap;
  }
}

}

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