GNU Radio C++ API
gr_fxpt.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2004 Free Software Foundation, Inc.
4  *
5  * This file is part of GNU Radio
6  *
7  * GNU Radio is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 3, or (at your option)
10  * any later version.
11  *
12  * GNU Radio is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with GNU Radio; see the file COPYING. If not, write to
19  * the Free Software Foundation, Inc., 51 Franklin Street,
20  * Boston, MA 02110-1301, USA.
21  */
22 #ifndef INCLUDED_GR_FXPT_H
23 #define INCLUDED_GR_FXPT_H
24 
25 #include <gr_core_api.h>
26 #include <gr_types.h>
27 
28 /*!
29  * \brief fixed point sine and cosine and friend GR_CORE_APIs.
30  * \ingroup misc
31  *
32  * fixed pt radians
33  * --------- --------
34  * -2**31 -pi
35  * 0 0
36  * 2**31-1 pi - epsilon
37  *
38  */
40 {
41  static const int WORDBITS = 32;
42  static const int NBITS = 10;
43  static const float s_sine_table[1 << NBITS][2];
44  static const float PI;
45  static const float TWO_TO_THE_31;
46 public:
47 
48  static gr_int32
49  float_to_fixed (float x)
50  {
51  return (gr_int32) ((float) x * TWO_TO_THE_31 / PI);
52  }
53 
54  static float
55  fixed_to_float (gr_int32 x)
56  {
57  return x * (PI / TWO_TO_THE_31);
58  }
59 
60  /*!
61  * \brief Given a fixed point angle x, return float sine (x)
62  */
63  static float
64  sin (gr_int32 x)
65  {
66  gr_uint32 ux = x;
67  int index = ux >> (WORDBITS - NBITS);
68  return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
69  }
70 
71  /*
72  * \brief Given a fixed point angle x, return float cosine (x)
73  */
74  static float
75  cos (gr_int32 x)
76  {
77  gr_uint32 ux = x + 0x40000000;
78  int index = ux >> (WORDBITS - NBITS);
79  return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
80  }
81 
82 };
83 
84 #endif /* INCLUDED_GR_FXPT_H */