bluez/monitor/crc.c

// SPDX-License-Identifier: LGPL-2.1-or-later
/*
 *
 *  BlueZ - Bluetooth protocol stack for Linux
 *
 *  Copyright (C) 2011-2014  Intel Corporation
 *  Copyright (C) 2002-2010  Marcel Holtmann <marcel@holtmann.org>
 *
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "crc.h"

uint32_t crc24_bit_reverse(uint32_t value)
{
	uint32_t result = 0;
	uint8_t i;

	for (i = 0; i < 24; i++)
		result |= ((value >> i) & 1) << (23 - i);

	return result;
}

uint32_t crc24_calculate(uint32_t preset, const uint8_t *data, uint8_t len)
{
	uint32_t state = preset;
	uint8_t i;

	for (i = 0; i < len; i++) {
		uint8_t n, cur = data[i];

		for (n = 0; n < 8; n++) {
			int next_bit = (state ^ cur) & 1;

			cur >>= 1;
			state >>= 1;
			if (next_bit) {
				state |= 1 << 23;
				state ^= 0x5a6000;
			}
		}
	}

	return state;
}

uint32_t crc24_reverse(uint32_t crc, const uint8_t *data, uint8_t len)
{
	uint32_t state = crc;
	uint8_t i;

	for (i = 0; i < len; i++) {
		uint8_t n, cur = data[len - i - 1];

		for (n = 0; n < 8; n++) {
			int top_bit = state >> 23;

			state = (state << 1) & 0xffffff;
			state |= top_bit ^ ((cur >> (7 - n)) & 1);
			if (top_bit)
				state ^= 0xb4c000;
		}
	}

	return state;
}