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92 lines
3.1 KiB
C++
92 lines
3.1 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
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// written by Christian Daniel //
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// Copyright (C) 2015-2020 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
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// Copyright (C) 2020 Jon Beniston, M7RCE <jon@beniston.com> //
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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 as version 3 of the License, or //
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// (at your option) 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 V3 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. If not, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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#include "crc.h"
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// Reverse bit ordering
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uint32_t crc::reverse(uint32_t val, int bits)
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{
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uint32_t temp;
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int i;
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temp = 0;
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for (i = 0; i < bits; i++)
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temp |= ((val >> i) & 1) << (bits - 1 - i);
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return temp;
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}
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// Calculate CRC for specified number of bits
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void crc::calculate(uint32_t data, int data_bits)
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{
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uint32_t tmp;
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uint32_t mask;
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uint32_t msb;
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int bit, i;
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if (m_msb_first)
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{
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mask = (1 << m_poly_bits) - 1;
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msb = 1 << (m_poly_bits - 1);
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tmp = m_crc ^ (data << (m_poly_bits - data_bits));
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for (i = 0; i < data_bits; i++)
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{
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if (tmp & msb)
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tmp = (tmp << 1) ^ m_polynomial;
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else
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tmp = tmp << 1;
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tmp = tmp & mask;
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}
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m_crc = tmp;
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}
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else
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{
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tmp = m_crc;
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for (i = 0; i < data_bits; i++) {
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bit = ((data >> i) & 1) ^ (tmp & 1);
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if (bit)
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tmp = (tmp >> 1) ^ m_polynomial_rev;
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else
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tmp = tmp >> 1;
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}
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m_crc = tmp;
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}
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}
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// Calculate CRC for specified array
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void crc::calculate(const uint8_t *data, int length)
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{
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int i;
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uint32_t mask1;
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uint32_t mask2;
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if (m_msb_first)
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{
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mask1 = (1 << m_poly_bits) - 1;
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mask2 = 0xff << (m_poly_bits - 8);
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for (i = 0; i < length; i++)
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m_crc = mask1 & ((m_crc << 8) ^ m_lut[data[i] ^ ((m_crc & mask2) >> (m_poly_bits-8))]);
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}
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else
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{
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for (i = 0; i < length; i++)
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m_crc = (m_crc >> 8) ^ m_lut[data[i] ^ (m_crc & 0xff)];
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}
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}
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