GNU Radio 3.5.1 C++ API
gri_lfsr_15_1_0.h
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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2004 Free Software Foundation, Inc.
00004  * 
00005  * This file is part of GNU Radio
00006  * 
00007  * GNU Radio is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU General Public License as published by
00009  * the Free Software Foundation; either version 3, or (at your option)
00010  * any later version.
00011  * 
00012  * GNU Radio is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  * 
00017  * You should have received a copy of the GNU General Public License
00018  * along with GNU Radio; see the file COPYING.  If not, write to
00019  * the Free Software Foundation, Inc., 51 Franklin Street,
00020  * Boston, MA 02110-1301, USA.
00021  */
00022 
00023 #ifndef INCLUDED_GRI_LFSR_15_1_0_H
00024 #define INCLUDED_GRI_LFSR_15_1_0_H
00025 
00026 #include <gr_core_api.h>
00027 
00028 /*!
00029  * \brief Linear Feedback Shift Register using primitive polynomial x^15 + x + 1
00030  * \ingroup misc
00031  *
00032  * Generates a maximal length pseudo-random sequence of length 2^15 - 1 bits.
00033  */
00034 
00035 class GR_CORE_API gri_lfsr_15_1_0 {
00036   unsigned long d_sr;           // shift register
00037 
00038  public:
00039 
00040   gri_lfsr_15_1_0 () { reset (); }
00041 
00042   void reset () { d_sr = 0x7fff; }
00043   
00044   int next_bit (){
00045     d_sr = ((((d_sr >> 1) ^ d_sr) & 0x1) << 14) | (d_sr >> 1);
00046     return d_sr & 0x1;
00047   }
00048 
00049   int next_byte (){
00050     int v = 0;
00051     for (int i = 0; i < 8; i++){
00052       v >>= 1;
00053       if (next_bit ())
00054         v |= 0x80;
00055     }
00056     return v;
00057   }
00058 };
00059 
00060 #endif /* INCLUDED_GRI_LFSR_15_1_0_H */