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/*
* Copyright 2019-2022 Great Scott Gadgets <info@greatscottgadgets.com>
* Copyright 2019 Jared Boone <jared@sharebrained.com>
*
* This file is part of HackRF.
*
* 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 "crc.h"
#include <stdbool.h>
void crc32_init(crc32_t* const crc)
{
crc->remainder = 0xffffffff;
crc->reversed_polynomial = 0xedb88320;
crc->final_xor = 0xffffffff;
}
void crc32_update(crc32_t* const crc, const uint8_t* const data, const size_t byte_count)
{
uint32_t remainder = crc->remainder;
const size_t bit_count = byte_count * 8;
for (size_t bit_n = 0; bit_n < bit_count; bit_n++) {
const bool bit_in = data[bit_n >> 3] & (1 << (bit_n & 7));
remainder ^= (bit_in ? 1 : 0);
const bool bit_out = (remainder & 1);
remainder >>= 1;
if (bit_out) {
remainder ^= crc->reversed_polynomial;
}
}
crc->remainder = remainder;
}
uint32_t crc32_digest(const crc32_t* const crc)
{
return crc->remainder ^ crc->final_xor;
}
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