/*
 * 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 blender/freestyle/intern/system/RandGen.cpp
 *  \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);               \
	}

#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(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);                             \
	}
#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 */