85 lines
1.9 KiB
C
85 lines
1.9 KiB
C
/*
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*
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* BlueZ - Bluetooth protocol stack for Linux
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*
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* Copyright (C) 2011-2014 Intel Corporation
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* Copyright (C) 2002-2010 Marcel Holtmann <marcel@holtmann.org>
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*
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include "crc.h"
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uint32_t crc24_bit_reverse(uint32_t value)
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{
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uint32_t result = 0;
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uint8_t i;
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for (i = 0; i < 24; i++)
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result |= ((value >> i) & 1) << (23 - i);
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return result;
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}
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uint32_t crc24_calculate(uint32_t preset, const uint8_t *data, uint8_t len)
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{
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uint32_t state = preset;
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uint8_t i;
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for (i = 0; i < len; i++) {
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uint8_t n, cur = data[i];
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for (n = 0; n < 8; n++) {
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int next_bit = (state ^ cur) & 1;
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cur >>= 1;
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state >>= 1;
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if (next_bit) {
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state |= 1 << 23;
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state ^= 0x5a6000;
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}
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}
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}
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return state;
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}
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uint32_t crc24_reverse(uint32_t crc, const uint8_t *data, uint8_t len)
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{
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uint32_t state = crc;
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uint8_t i;
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for (i = 0; i < len; i++) {
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uint8_t n, cur = data[len - i - 1];
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for (n = 0; n < 8; n++) {
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int top_bit = state >> 23;
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state = (state << 1) & 0xffffff;
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state |= top_bit ^ ((cur >> (7 - n)) & 1);
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if (top_bit)
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state ^= 0xb4c000;
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}
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}
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return state;
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}
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