gr-baz Package
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 friends.
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  // Fold x into -PI to PI.
52  int d = (int)floor(x/2/PI+0.5);
53  x -= d*2*PI;
54  // And convert to an integer.
55  return (gr_int32) ((float) x * TWO_TO_THE_31 / PI);
56  }
57 
58  static float
59  fixed_to_float (gr_int32 x)
60  {
61  return x * (PI / TWO_TO_THE_31);
62  }
63 
64  /*!
65  * \brief Given a fixed point angle x, return float sine (x)
66  */
67  static float
68  sin (gr_int32 x)
69  {
70  gr_uint32 ux = x;
71  int index = ux >> (WORDBITS - NBITS);
72  return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
73  }
74 
75  /*
76  * \brief Given a fixed point angle x, return float cosine (x)
77  */
78  static float
79  cos (gr_int32 x)
80  {
81  gr_uint32 ux = x + 0x40000000;
82  int index = ux >> (WORDBITS - NBITS);
83  return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
84  }
85 
86  /*
87  * \brief Given a fixedpoint angle x, return float cos(x) and sin (x)
88  */
89  static void sincos(gr_int32 x, float *s, float *c)
90  {
91  gr_uint32 ux = x;
92  int sin_index = ux >> (WORDBITS - NBITS);
93  *s = s_sine_table[sin_index][0] * (ux >> 1) + s_sine_table[sin_index][1];
94 
95  ux = x + 0x40000000;
96  int cos_index = ux >> (WORDBITS - NBITS);
97  *c = s_sine_table[cos_index][0] * (ux >> 1) + s_sine_table[cos_index][1];
98 
99  return;
100  }
101 
102 };
103 
104 #endif /* INCLUDED_GR_FXPT_H */