114 lines
3.0 KiB
C
114 lines
3.0 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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/** @file
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* @brief CRC 16 computation function
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*/
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#ifndef __CRC16_H
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#define __CRC16_H
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#include <zephyr/types.h>
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#include <stdbool.h>
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#include <stddef.h>
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/**
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* @defgroup checksum Checksum
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*/
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/**
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* @defgroup crc16 CRC 16
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* @ingroup checksum
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* @{
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*/
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/**
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* @brief Generic function for computing CRC 16
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*
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* Compute CRC 16 by passing in the address of the input, the input length
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* and polynomial used in addition to the initial value.
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*
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* @param src Input bytes for the computation
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* @param len Length of the input in bytes
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* @param polynomial The polynomial to use omitting the leading x^16
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* coefficient
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* @param initial_value Initial value for the CRC computation
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* @param pad Adds padding with zeros at the end of input bytes
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*
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* @return The computed CRC16 value
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*/
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u16_t crc16(const u8_t *src, size_t len, u16_t polynomial,
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u16_t initial_value, bool pad);
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/**
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* @brief Compute the CRC-16/CCITT checksum of a buffer.
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*
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* See ITU-T Recommendation V.41 (November 1988). Uses 0x1021 as the
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* polynomial, reflects the input, and reflects the output.
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*
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* To calculate the CRC across non-contigious blocks use the return
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* value from block N-1 as the seed for block N.
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*
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* For CRC-16/CCITT, use 0 as the initial seed. Other checksums in
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* the same family can be calculated by changing the seed and/or
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* XORing the final value. Examples include:
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*
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* - X-25 (used in PPP): seed=0xffff, xor=0xffff, residual=0xf0b8
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*
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* @note API changed in Zephyr 1.11.
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*
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* @param seed Value to seed the CRC with
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* @param src Input bytes for the computation
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* @param len Length of the input in bytes
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*
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* @return The computed CRC16 value
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*/
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u16_t crc16_ccitt(u16_t seed, const u8_t *src, size_t len);
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/**
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* @brief Compute the CRC-16/XMODEM checksum of a buffer.
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*
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* The MSB first version of ITU-T Recommendation V.41 (November 1988).
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* Uses 0x1021 as the polynomial with no reflection.
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*
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* To calculate the CRC across non-contigious blocks use the return
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* value from block N-1 as the seed for block N.
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*
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* For CRC-16/XMODEM, use 0 as the initial seed. Other checksums in
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* the same family can be calculated by changing the seed and/or
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* XORing the final value. Examples include:
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*
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* - CCIITT-FALSE: seed=0xffff
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* - GSM: seed=0, xorout=0xffff, residue=0x1d0f
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*
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* @param seed Value to seed the CRC with
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* @param src Input bytes for the computation
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* @param len Length of the input in bytes
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*
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* @return The computed CRC16 value
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*/
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u16_t crc16_itu_t(u16_t seed, const u8_t *src, size_t len);
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/**
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* @brief Compute ANSI variant of CRC 16
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*
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* ANSI variant of CRC 16 is using 0x8005 as its polynomial with the initial
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* value set to 0xffff.
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*
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* @param src Input bytes for the computation
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* @param len Length of the input in bytes
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*
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* @return The computed CRC16 value
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*/
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static inline u16_t crc16_ansi(const u8_t *src, size_t len)
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{
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return crc16(src, len, 0x8005, 0xffff, true);
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}
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/**
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* @}
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*/
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#endif
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