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sys/checksum: add crc8 implementation

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This moves the crc8 implementation of the sht3x driver to common code.
This commit is contained in:
Benjamin Valentin 2019-12-11 16:25:57 +01:00
parent 1d54137295
commit e4a33ca413
2 changed files with 93 additions and 0 deletions
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42
sys/checksum/crc8.c Normal file
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/*
* Copyright (C) 2018 Gunar Schorcht
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup sys_checksum_crc8
* @brief CRC-8 checksum algorithms
*
* @{
*
* @file
* @brief CRC-8 implementation
*
* @author Gunar Schorcht <gunar@schorcht.net>
*/
#include <stdbool.h>
#include "checksum/crc8.h"
uint8_t crc8(const uint8_t *data, size_t len, uint8_t g_polynom, uint8_t crc)
{
/* iterate over all bytes */
for (size_t i=0; i < len; i++)
{
crc ^= data[i];
for (int i = 0; i < 8; i++)
{
bool xor = crc & 0x80;
crc = crc << 1;
crc = xor ? crc ^ g_polynom : crc;
}
}
return crc;
}
/** @} */

51
sys/include/checksum/crc8.h Normal file
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/*
* Copyright (C) 2018 Gunar Schorcht
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup sys_checksum_crc8 CRC-8
* @ingroup sys_checksum
* @brief CRC-8 checksum algorithms
*
* @{
*
* @file
* @brief CRC-8 definitions
*
* @author Gunar Schorcht <gunar@schorcht.net>
*/
#ifndef CHECKSUM_CRC8_H
#define CHECKSUM_CRC8_H
#include <stddef.h>
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Calculate CRC-8
*
* @param[in] data Start of memory area to checksum
* @param[in] len Number of bytes in @p buf to calculate checksum for
* @param[in] poly The generator polynomial for the checksum
* @param[in] seed The seed (starting value) for the checksum
*
* @note Reflected inputs or outputs and final XOR must be realized
* by the caller if needed.
*
* @return Checksum of the specified memory area.
*/
uint8_t crc8(const uint8_t *data, size_t len, uint8_t poly, uint8_t seed);
#ifdef __cplusplus
}
#endif
#endif /* CHECKSUM_CRC8_H */
/** @} */