//
//  Copyright (C) : Please refer to the COPYRIGHT file distributed 
//   with this source distribution. 
//
//  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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
///////////////////////////////////////////////////////////////////////////////

#include "RandGen.h"

//
// 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
#define HI_BIT	(1L << (2 * N - 1))

#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); }
#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))
#define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
#define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
#define REST(v)	for (i = 0; i < 3; i++) { xsubi[i] = x[i]; x[i] = temp[i]; } \
		return (v);
#define NEST(TYPE, f, F)	TYPE f(register unsigned short *xsubi) { \
	register int i; register TYPE v; unsigned temp[3]; \
	for (i = 0; i < 3; i++) { temp[i] = x[i]; x[i] = LOW(xsubi[i]); }  \
	v = F(); REST(v); }

static unsigned x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, 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]);
}