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/* -*- c++ -*- */
/*
* Copyright 2004,2013 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifndef INCLUDED_GR_FXPT_H
#define INCLUDED_GR_FXPT_H
#include <gnuradio/api.h>
#include <gnuradio/types.h>
#include <cstdint>
namespace gr {
/*!
* \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_RUNTIME_API fxpt
{
static constexpr int WORDBITS = 32;
static constexpr int NBITS = 10;
static constexpr uint32_t ACCUM_MASK = ((1 << (WORDBITS - NBITS)) - 1);
static const float s_sine_table[1 << NBITS][2];
static const float PI;
static const float TAU;
static const float TWO_TO_THE_31;
public:
static int32_t float_to_fixed(float x)
{
// Fold x into -PI to PI.
int d = (int)std::floor(x / TAU + 0.5);
x -= d * TAU;
// And convert to an integer.
return (int32_t)((float)x * TWO_TO_THE_31 / PI);
}
static float fixed_to_float(int32_t x) { return x * (PI / TWO_TO_THE_31); }
/*!
* \brief Given a fixed point angle x, return float sine (x)
*/
static float sin(int32_t x)
{
uint32_t ux = x;
int index = ux >> (WORDBITS - NBITS);
return s_sine_table[index][0] * (ux & ACCUM_MASK) + s_sine_table[index][1];
}
/*
* \brief Given a fixed point angle x, return float cosine (x)
*/
static float cos(int32_t x)
{
uint32_t ux = x + 0x40000000;
int index = ux >> (WORDBITS - NBITS);
return s_sine_table[index][0] * (ux & ACCUM_MASK) + s_sine_table[index][1];
}
/*
* \brief Given a fixedpoint angle x, return float cos(x) and sin (x)
*/
static void sincos(int32_t x, float* s, float* c)
{
uint32_t ux = x;
int sin_index = ux >> (WORDBITS - NBITS);
*s = s_sine_table[sin_index][0] * (ux & ACCUM_MASK) + s_sine_table[sin_index][1];
ux = x + 0x40000000;
int cos_index = ux >> (WORDBITS - NBITS);
*c = s_sine_table[cos_index][0] * (ux & ACCUM_MASK) + s_sine_table[cos_index][1];
return;
}
};
} /* namespace gr */
#endif /* INCLUDED_GR_FXPT_H */
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