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/*
* Copyright (C) 2016 Freie Universität Berlin
*
* 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_ucrc16 CRC16 (lightweight)
* @ingroup sys_checksum
* @brief Lightweight CRC16 checksum algorithms
*
* This CRC16 implementation does not use pre-calculated lookup tables and is
* thus very lightweight (memory-wise), but as a caveat slower (about factor 8)
* than the version with pre-calculated lookup tables.
*
* Additionally compared to @ref sys_checksum_crc16_ccitt this is a generalized
* implementation. One can easily exchange generator polynomials and starting
* seeds.
*
* @{
*
* @file
* @brief ucrc16 definitions
*
* @author Martine Lenders <m.lenders@fu-berlin.de>
*/
#ifndef CHECKSUM_UCRC16_H
#define CHECKSUM_UCRC16_H
#include <stdint.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @{
* @brief Various generator polynomials
*/
#define UCRC16_CCITT_POLY_BE (0x1021) /**< CRC16-CCITT polynomial (big-endian) */
#define UCRC16_CCITT_POLY_LE (0x8408) /**< CRC16-CCITT polynomial (little-endian) */
/** @} */
/**
* @brief Calculate CRC16 (big-endian version)
*
* @param[in] buf Start of memory are 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
*
* @return Checksum of the specified memory area based on @p seed and @p poly
*
* @note The return value is not the complement of the sum but the sum itself
*/
uint16_t ucrc16_calc_be(const uint8_t *buf, size_t len, uint16_t poly,
uint16_t seed);
/**
* @brief Calculate CRC16 (little-endian version)
*
* @param[in] buf Start of memory are 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
*
* @return Checksum of the specified memory area based on @p seed and @p poly
*
* @note The return value is not the complement of the sum but the sum itself
*/
uint16_t ucrc16_calc_le(const uint8_t *buf, size_t len, uint16_t poly,
uint16_t seed);
#ifdef __cplusplus
}
#endif
#endif /* CHECKSUM_UCRC16_H */
/** @} */