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/* SPDX-License-Identifier: GPL-2.0-or-later */
/** \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 */
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