107 lines
2.3 KiB
C++
107 lines
2.3 KiB
C++
/*
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* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#include "lfsr_random.hpp"
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static void lfsr_iterate_internal(lfsr_word_t& v)
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{
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/*
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Generated with lfsr-generator:
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http://lfsr-generator.sourceforge.net
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=============================================
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config : fibonacci
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length : 31
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taps : (31, 18)
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shift-amounts : (12, 12, 8)
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shift-direction : left
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*/
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enum {
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length = 31,
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tap_0 = 31,
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tap_1 = 18,
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shift_amount_0 = 12,
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shift_amount_1 = 12,
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shift_amount_2 = 8
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};
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const lfsr_word_t zero = 0;
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v = (
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(
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v << shift_amount_0
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) | (
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(
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(v >> (tap_0 - shift_amount_0)) ^
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(v >> (tap_1 - shift_amount_0))
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) & (
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~(~zero << shift_amount_0)
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)
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)
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);
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v = (
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(
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v << shift_amount_1
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) | (
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(
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(v >> (tap_0 - shift_amount_1)) ^
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(v >> (tap_1 - shift_amount_1))
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) & (
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~(~zero << shift_amount_1)
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)
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)
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);
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v = (
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(
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v << shift_amount_2
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) | (
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(
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(v >> (tap_0 - shift_amount_2)) ^
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(v >> (tap_1 - shift_amount_2))
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) & (
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~(~zero << shift_amount_2)
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)
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)
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);
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}
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lfsr_word_t lfsr_iterate(lfsr_word_t v) {
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lfsr_iterate_internal(v);
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return v;
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}
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void lfsr_fill(lfsr_word_t& v, lfsr_word_t* buffer, size_t word_count) {
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while( word_count != 0 ) {
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lfsr_iterate_internal(v);
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*(buffer++) = v;
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word_count--;
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}
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}
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bool lfsr_compare(lfsr_word_t& v, const lfsr_word_t* buffer, size_t word_count) {
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while( word_count != 0 ) {
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lfsr_iterate_internal(v);
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if( *(buffer++) != v ) {
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return false;
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}
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word_count--;
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}
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return true;
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}
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