root / gnuradio-core / src / lib / general / gr_fxpt.h @ cda71d95
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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_types.h> |
| 26 | |
| 27 | /*!
|
| 28 | * \brief fixed point sine and cosine and friends. |
| 29 | * \ingroup math |
| 30 | * |
| 31 | * fixed pt radians |
| 32 | * --------- -------- |
| 33 | * -2**31 -pi |
| 34 | * 0 0 |
| 35 | * 2**31-1 pi - epsilon |
| 36 | * |
| 37 | */ |
| 38 | class gr_fxpt |
| 39 | {
|
| 40 | static const int WORDBITS = 32; |
| 41 | static const int NBITS = 10; |
| 42 | static const float s_sine_table[1 << NBITS][2]; |
| 43 | static const float PI = 3.14159265358979323846; |
| 44 | static const float TWO_TO_THE_31 = 2147483648.0; |
| 45 | public:
|
| 46 | |
| 47 | static gr_int32
|
| 48 | float_to_fixed (float x)
|
| 49 | {
|
| 50 | return (gr_int32) ((float) x * TWO_TO_THE_31 / PI); |
| 51 | } |
| 52 | |
| 53 | static float |
| 54 | fixed_to_float (gr_int32 x) |
| 55 | {
|
| 56 | return x * (PI / TWO_TO_THE_31);
|
| 57 | } |
| 58 | |
| 59 | /*!
|
| 60 | * \brief Given a fixed point angle x, return float sine (x) |
| 61 | */ |
| 62 | static float |
| 63 | sin (gr_int32 x) |
| 64 | {
|
| 65 | gr_uint32 ux = x; |
| 66 | int index = ux >> (WORDBITS - NBITS);
|
| 67 | return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1]; |
| 68 | } |
| 69 | |
| 70 | /*
|
| 71 | * \brief Given a fixed point angle x, return float cosine (x) |
| 72 | */ |
| 73 | static float |
| 74 | cos (gr_int32 x) |
| 75 | {
|
| 76 | gr_uint32 ux = x + 0x40000000;
|
| 77 | int index = ux >> (WORDBITS - NBITS);
|
| 78 | return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1]; |
| 79 | } |
| 80 | |
| 81 | }; |
| 82 | |
| 83 | #endif /* INCLUDED_GR_FXPT_H */ |