GNU Radio C++ API Reference: fxpt.h Source File

| GNU Radio C++ API Reference 3.10.12.0 The Free & Open Software Radio Ecosystem |

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fxpt.h
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1/* -*- c++ -*- */
2/*
3 * Copyright 2004,2013 Free Software Foundation, Inc.
4 *
5 * This file is part of GNU Radio
6 *
7 * SPDX-License-Identifier: GPL-3.0-or-later
8 *
9 */
10
11#ifndef INCLUDED_GR_FXPT_H
12#define INCLUDED_GR_FXPT_H
13
14#include <gnuradio/api.h>
15#include <gnuradio/types.h>
16#include <cstdint>
17
18namespace gr {
19
20/*!
21 * \brief fixed point sine and cosine and friends.
22 * \ingroup misc
23 *
24 * fixed pt radians
25 * --------- --------
26 * -2**31 -pi
27 * 0 0
28 * 2**31-1 pi - epsilon
29 */
30 class GR_RUNTIME_API fxpt
31{
32 static constexpr int WORDBITS = 32;
33 static constexpr int NBITS = 10;
34 static constexpr uint32_t ACCUM_MASK = ((1 << (WORDBITS - NBITS)) - 1);
35 static const float s_sine_table[1 << NBITS][2];
36 static const float PI;
37 static const float TAU;
38 static const float TWO_TO_THE_31;
39
40public:
41 static int32_t float_to_fixed(float x)
42 {
43 // Fold x into -PI to PI.
44 int d = (int)std::floor(x / TAU + 0.5);
45 x -= d * TAU;
46 // And convert to an integer.
47 return (int32_t)((float)x * TWO_TO_THE_31 / PI);
48 }
49
50 static float fixed_to_float(int32_t x) { return x * (PI / TWO_TO_THE_31); }
51
52 /*!
53 * \brief Given a fixed point angle x, return float sine (x)
54 */
55 static float sin(int32_t x)
56 {
57 uint32_t ux = x;
58 int index = ux >> (WORDBITS - NBITS);
59 return s_sine_table[index][0] * (ux & ACCUM_MASK) + s_sine_table[index][1];
60 }
61
62 /*
63 * \brief Given a fixed point angle x, return float cosine (x)
64 */
65 static float cos(int32_t x)
66 {
67 uint32_t ux = (uint32_t)x + 0x40000000;
68 int index = ux >> (WORDBITS - NBITS);
69 return s_sine_table[index][0] * (ux & ACCUM_MASK) + s_sine_table[index][1];
70 }
71
72 /*
73 * \brief Given a fixedpoint angle x, return float cos(x) and sin (x)
74 */
75 static void sincos(int32_t x, float* s, float* c)
76 {
77 uint32_t ux = x;
78 int sin_index = ux >> (WORDBITS - NBITS);
79 *s = s_sine_table[sin_index][0] * (ux & ACCUM_MASK) + s_sine_table[sin_index][1];
80
81 ux = (uint32_t)x + 0x40000000;
82 int cos_index = ux >> (WORDBITS - NBITS);
83 *c = s_sine_table[cos_index][0] * (ux & ACCUM_MASK) + s_sine_table[cos_index][1];
84
85 return;
86 }
87};
88
89} /* namespace gr */
90
91#endif /* INCLUDED_GR_FXPT_H */
gr::fxpt
fixed point sine and cosine and friends.
Definition fxpt.h:31
gr::fxpt::sincos
static void sincos(int32_t x, float *s, float *c)
Definition fxpt.h:75
gr::fxpt::cos
static float cos(int32_t x)
Definition fxpt.h:65
gr::fxpt::float_to_fixed
static int32_t float_to_fixed(float x)
Definition fxpt.h:41
gr::fxpt::sin
static float sin(int32_t x)
Given a fixed point angle x, return float sine (x).
Definition fxpt.h:55
gr::fxpt::fixed_to_float
static float fixed_to_float(int32_t x)
Definition fxpt.h:50
api.h
GR_RUNTIME_API
#define GR_RUNTIME_API
Definition gnuradio-runtime/include/gnuradio/api.h:18
gr
GNU Radio logging wrapper.
Definition basic_block.h:29
types.h