GNU Radio 3.6.5 C++ API

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 <blocks/api.h>
00027 
00028 namespace gr {
00029   namespace blocks {
00030 
00031     /*!
00032      * \brief Linear Feedback Shift Register using primitive polynomial x^15 + x + 1
00033      * \ingroup misc
00034      *
00035      * \details
00036      * Generates a maximal length pseudo-random sequence of length
00037      * 2^15 - 1 bits.
00038      */
00039     class BLOCKS_API lfsr_15_1_0
00040     {
00041     private:
00042       unsigned long d_sr;    // shift register
00043 
00044     public:
00045       lfsr_15_1_0() { reset(); }
00046 
00047       void reset() { d_sr = 0x7fff; }
00048 
00049       int next_bit()
00050       {
00051         d_sr = ((((d_sr >> 1) ^ d_sr) & 0x1) << 14) | (d_sr >> 1);
00052         return d_sr & 0x1;
00053       }
00054 
00055       int next_byte ()
00056       {
00057         int     v = 0;
00058         for(int i = 0; i < 8; i++) {
00059           v >>= 1;
00060           if(next_bit ())
00061             v |= 0x80;
00062         }
00063         return v;
00064       }
00065     };
00066 
00067   } /* namespace blocks */
00068 } /* namespace gr */
00069 
00070 #endif /* INCLUDED_GRI_LFSR_15_1_0_H */