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74 lines
1.9 KiB
C++
74 lines
1.9 KiB
C++
// This file is part of LeanSDR Copyright (C) 2016-2018 <pabr@pabr.org>.
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// See the toplevel README for more information.
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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 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 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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#ifndef LEANSDR_CRC_H
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#define LEANSDR_CRC_H
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#include <stdint.h>
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#include "leansdr/discrmath.h"
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namespace leansdr
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{
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// EN 302 307-1 section 5.1.4 CRC-8 encoder
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struct crc8_engine
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{
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crc8_engine()
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{
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// Precompute
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// EN 302 307-1 5.1.4 Figure 2
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bitvect<uint8_t, 8> g = POLY_DVBS2_CRC8;
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for (int u = 0; u < 256; ++u)
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{
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uint8_t u8 = u;
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bitvect<uint8_t, 8> c = shiftdivmod(&u8, 1, g);
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table[u] = c.v[0];
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}
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}
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uint8_t compute(const uint8_t *buf, int len)
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{
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uint8_t c = 0;
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for (; len--; ++buf)
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c = table[c ^ *buf];
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return c;
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}
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private:
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static const uint8_t POLY_DVBS2_CRC8 = 0xd5; // (1)11010101
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uint8_t table[256];
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};
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// CRC-32 ITU V.42 for FINGERPRINT
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uint32_t crc32(const uint8_t *buf, int len)
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{
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static const uint32_t poly = 0xedb88320;
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uint32_t c = 0xffffffff;
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for (int i = 0; i < len; ++i)
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{
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c ^= buf[i];
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for (int bit = 8; bit--;)
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c = (c & 1) ? (c >> 1) ^ poly : (c >> 1);
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}
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return c ^ 0xffffffff;
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}
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} // namespace leansdr
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#endif // LEANSDR_CRC_H
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