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/*
* Copyright 2016 Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
*
* 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_crc16_ccitt CRC16-CCITT
* @ingroup sys_checksum
*
* @brief CRC16-CCITT checksum algorithm
* @details This implementation of CRC16 is based on the CCITT
* specification using 0x1D0F as a start value.
* Using a different start value is possible by calling
* crc16_ccitt_update() with the desired start value
* instead of crc16_ccitt_calc().
*
* There is a more generalized version in @ref sys_checksum_ucrc16,
* that does not utilize a look-up table as this implementation
* does (and is thus also for more memory efficient). Its caveat
* however is that it is slower by about factor 8 than this version.
*
* @{
* @file
* @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
*/
#ifndef CHECKSUM_CRC16_CCITT_H
#define CHECKSUM_CRC16_CCITT_H
#include <stdint.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Update CRC16-CCITT
*
* @param[in] crc A start value for the CRC calculation, usually the
* return value of a previous call to
* crc16_ccitt_calc() or crc16_ccitt_update()
* @param[in] buf Start of the memory area to checksum
* @param[in] len Number of bytes to checksum
*
* @return Checksum of the specified memory area based on the
* given start value
*/
uint16_t crc16_ccitt_update(uint16_t crc, const unsigned char *buf, size_t len);
/**
* @brief Calculate CRC16-CCITT
*
* @param[in] buf Start of the memory area to checksum
* @param[in] len Number of bytes to checksum
*
* @return Checksum of the specified memory area
*/
uint16_t crc16_ccitt_calc(const unsigned char *buf, size_t len);
#ifdef __cplusplus
}
#endif
#endif /* CHECKSUM_CRC16_CCITT_H */
/** @} */