text: /*
   * 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 this program; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   */
  
  /** \file
   * \ingroup freestyle
   * \brief Pseudo-random number generator
   */
  
  #include "RandGen.h"
  
  namespace Freestyle {
  
  //
  // Macro definitions
  //
  ///////////////////////////////////////////////////////////////////////////////
  
  #define N 16
  #define MASK ((unsigned)(1 << (N - 1)) + (1 << (N - 1)) - 1)
  #define X0 0x330E
  #define X1 0xABCD
  #define X2 0x1234
  #define A0 0xE66D
  #define A1 0xDEEC
  #define A2 0x5
  #define C 0xB
  #if 0  // XXX Unused
  #  define HI_BIT (1L << (2 * N - 1))
  #endif
  
  #define LOW(x) ((unsigned)(x)&MASK)
  #define HIGH(x) LOW((x) >> N)
  
  #define MUL(x, y, z) \
    { \
      long l = (long)(x) * (long)(y); \
      (z)[0] = LOW(l); \
      (z)[1] = HIGH(l); \
    } \
    ((void)0)
  
  #define CARRY(x, y) ((unsigned long)((long)(x) + (long)(y)) > MASK)
  #define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y)))
  #define SET3(x, x0, x1, x2) ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
  #if 0  // XXX, unused
  #  define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n) + 1]), LOW((y)[(n) + 2]))
  #endif
  #define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
  
  #if 0  // XXX, unused
  #  define REST(v) \
      for (i = 0; i < 3; i++) { \
        xsubi[i] = x[i]; \
        x[i] = temp[i]; \
      } \
      return (v); \
      (void)0
  
  #  define NEST(TYPE, f, F) \
      TYPE f(unsigned short *xsubi) \
      { \
        int i; \
        TYPE v; \
        unsigned temp[3]; \
        for (i = 0; i < 3; i++) { \
          temp[i] = x[i]; \
          x[i] = LOW(xsubi[i]); \
        } \
        v = F(); \
        REST(v); \
      }
  #endif
  
  static unsigned x[3] = {
      X0,
      X1,
      X2,
  };
  static unsigned a[3] = {
      A0,
      A1,
      A2,
  };
  static unsigned c = C;
  
  //
  // Methods implementation
  //
  ///////////////////////////////////////////////////////////////////////////////
  
  real RandGen::drand48()
  {
    static real two16m = 1.0 / (1L << N);
    next();
    return (two16m * (two16m * (two16m * x[0] + x[1]) + x[2]));
  }
  
  void RandGen::srand48(long seedval)
  {
    SEED(X0, LOW(seedval), HIGH(seedval));
  }
  
  void RandGen::next()
  {
    unsigned p[2], q[2], r[2], carry0, carry1;
  
    MUL(a[0], x[0], p);
    ADDEQU(p[0], c, carry0);
    ADDEQU(p[1], carry0, carry1);
    MUL(a[0], x[1], q);
    ADDEQU(p[1], q[0], carry0);
    MUL(a[1], x[0], r);
    x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] + a[0] * x[2] + a[1] * x[1] +
               a[2] * x[0]);
    x[1] = LOW(p[1] + r[0]);
    x[0] = LOW(p[0]);
  }
  
  } /* namespace Freestyle */
  