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Add LFSR random number generator.

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Used for SD card write/read testing, maybe other stuff eventually?
This commit is contained in:
Jared Boone 2016-04-10 16:30:28 -07:00
parent 0a9d7ec8d8
commit f76750e55b
2 changed files with 140 additions and 0 deletions
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106
firmware/common/lfsr_random.cpp Normal file
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/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "lfsr_random.hpp"
static void lfsr_iterate_internal(lfsr_word_t& v)
{
/*
Generated with lfsr-generator:
http://lfsr-generator.sourceforge.net
=============================================
config : fibonacci
length : 31
taps : (31, 18)
shift-amounts : (12, 12, 8)
shift-direction : left
*/
enum {
length = 31,
tap_0 = 31,
tap_1 = 18,
shift_amount_0 = 12,
shift_amount_1 = 12,
shift_amount_2 = 8
};
const lfsr_word_t zero = 0;
v = (
(
v << shift_amount_0
) | (
(
(v >> (tap_0 - shift_amount_0)) ^
(v >> (tap_1 - shift_amount_0))
) & (
~(~zero << shift_amount_0)
)
)
);
v = (
(
v << shift_amount_1
) | (
(
(v >> (tap_0 - shift_amount_1)) ^
(v >> (tap_1 - shift_amount_1))
) & (
~(~zero << shift_amount_1)
)
)
);
v = (
(
v << shift_amount_2
) | (
(
(v >> (tap_0 - shift_amount_2)) ^
(v >> (tap_1 - shift_amount_2))
) & (
~(~zero << shift_amount_2)
)
)
);
}
lfsr_word_t lfsr_iterate(lfsr_word_t v) {
lfsr_iterate_internal(v);
return v;
}
void lfsr_fill(lfsr_word_t& v, lfsr_word_t* buffer, size_t word_count) {
while( word_count != 0 ) {
lfsr_iterate_internal(v);
*(buffer++) = v;
word_count--;
}
}
bool lfsr_compare(lfsr_word_t& v, const lfsr_word_t* buffer, size_t word_count) {
while( word_count != 0 ) {
lfsr_iterate_internal(v);
if( *(buffer++) != v ) {
return false;
}
word_count--;
}
return true;
}

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firmware/common/lfsr_random.hpp Normal file
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/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef __LFSR_RANDOM_HPP__
#define __LFSR_RANDOM_HPP__
#include <cstdint>
#include <cstddef>
using lfsr_word_t = uint32_t;
lfsr_word_t lfsr_iterate(lfsr_word_t v);
void lfsr_fill(lfsr_word_t& v, lfsr_word_t* buffer, size_t word_count);
bool lfsr_compare(lfsr_word_t& v, const lfsr_word_t* buffer, size_t word_count);
#endif/*__LFSR_RANDOM_HPP__*/