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/* -*- c++ -*- */
/*
* Copyright 2004 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio 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 3, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef INCLUDED_GR_FXPT_H
#define INCLUDED_GR_FXPT_H
#include <gr_core_api.h>
#include <gr_types.h>
/*!
* \brief fixed point sine and cosine and friends.
* \ingroup misc
*
* fixed pt radians
* --------- --------
* -2**31 -pi
* 0 0
* 2**31-1 pi - epsilon
*
*/
class GR_CORE_API gr_fxpt
{
static const int WORDBITS = 32;
static const int NBITS = 10;
static const float s_sine_table[1 << NBITS][2];
static const float PI;
static const float TWO_TO_THE_31;
public:
static gr_int32
float_to_fixed (float x)
{
// Fold x into -PI to PI.
int d = (int)floor(x/2/PI+0.5);
x -= d*2*PI;
// And convert to an integer.
return (gr_int32) ((float) x * TWO_TO_THE_31 / PI);
}
static float
fixed_to_float (gr_int32 x)
{
return x * (PI / TWO_TO_THE_31);
}
/*!
* \brief Given a fixed point angle x, return float sine (x)
*/
static float
sin (gr_int32 x)
{
gr_uint32 ux = x;
int index = ux >> (WORDBITS - NBITS);
return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
}
/*
* \brief Given a fixed point angle x, return float cosine (x)
*/
static float
cos (gr_int32 x)
{
gr_uint32 ux = x + 0x40000000;
int index = ux >> (WORDBITS - NBITS);
return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
}
/*
* \brief Given a fixedpoint angle x, return float cos(x) and sin (x)
*/
static void sincos(gr_int32 x, float *s, float *c)
{
gr_uint32 ux = x;
int sin_index = ux >> (WORDBITS - NBITS);
*s = s_sine_table[sin_index][0] * (ux >> 1) + s_sine_table[sin_index][1];
ux = x + 0x40000000;
int cos_index = ux >> (WORDBITS - NBITS);
*c = s_sine_table[cos_index][0] * (ux >> 1) + s_sine_table[cos_index][1];
return;
}
};
#endif /* INCLUDED_GR_FXPT_H */
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