GNU Radio 3.6.2 C++ API
gri_lfsr_15_1_0.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 
23 #ifndef INCLUDED_GRI_LFSR_15_1_0_H
24 #define INCLUDED_GRI_LFSR_15_1_0_H
25 
26 #include <gr_core_api.h>
27 
28 /*!
29  * \brief Linear Feedback Shift Register using primitive polynomial x^15 + x + 1
30  * \ingroup misc
31  *
32  * Generates a maximal length pseudo-random sequence of length 2^15 - 1 bits.
33  */
34 
36  unsigned long d_sr; // shift register
37 
38  public:
39 
40  gri_lfsr_15_1_0 () { reset (); }
41 
42  void reset () { d_sr = 0x7fff; }
43 
44  int next_bit (){
45  d_sr = ((((d_sr >> 1) ^ d_sr) & 0x1) << 14) | (d_sr >> 1);
46  return d_sr & 0x1;
47  }
48 
49  int next_byte (){
50  int v = 0;
51  for (int i = 0; i < 8; i++){
52  v >>= 1;
53  if (next_bit ())
54  v |= 0x80;
55  }
56  return v;
57  }
58 };
59 
60 #endif /* INCLUDED_GRI_LFSR_15_1_0_H */