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92 lines
2.3 KiB
C
92 lines
2.3 KiB
C
/*
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* Copyright (C) 2015 Eistec AB
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @defgroup sys_checksum_fletcher32 Fletcher32
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* @ingroup sys_checksum
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*
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* @brief Fletcher32 checksum algorithm
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* @{
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*
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* @file
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* @author Joakim Nohlgård <joakim.nohlgard@eistec.se>
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* @author Koen Zandberg <koen@bergzand.net>
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*/
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#ifndef CHECKSUM_FLETCHER32_H
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#define CHECKSUM_FLETCHER32_H
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#include <stdlib.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Fletcher's 32 bit checksum context struct
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*/
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typedef struct {
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uint32_t sum1; /**< First sum of the checksum */
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uint32_t sum2; /**< Second sum of the checksum */
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} fletcher32_ctx_t;
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/**
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* @brief Fletcher's 32 bit checksum
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*
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* found on
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* http://en.wikipedia.org/w/index.php?title=Fletcher%27s_checksum&oldid=661273016#Optimizations
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*
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* @note the returned sum is never 0
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* @note pay attention to the @p words parameter buffer containing 16 bit words, not bytes.
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*
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* @param buf input buffer to hash
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* @param words length of buffer, in 16 bit words
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* @return 32 bit sized hash in the interval [1..2^32]
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*/
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uint32_t fletcher32(const uint16_t *buf, size_t words);
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/**
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* @brief Initialize a fletcher32 context
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*
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* Multi-part version of @ref fletcher32.
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*
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* @param[in] ctx fletcher32 context to initialize
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*/
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void fletcher32_init(fletcher32_ctx_t *ctx);
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/**
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* @brief Incrementally update the fletcher32 context with new data. Can be an arbitrary amount of
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* times with new data to checksum.
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*
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* @note @p words is the number of 16 bit words in the buffer
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* @note @p data should contain an integer number of 16 bit words
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*
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* @param[in] ctx fletcher32 context
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* @param[in] data Data to add to the context
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* @param[in] words Length of the data in 16 bit words
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*/
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void fletcher32_update(fletcher32_ctx_t *ctx, const void *data, size_t words);
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/**
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* @brief Finalize the checksum operation and return the checksum
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*
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* @param[in] ctx fletcher32 context
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*
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* @return 32 bit sized hash in the interval [1..2^32]
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*/
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uint32_t fletcher32_finish(fletcher32_ctx_t *ctx);
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#ifdef __cplusplus
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}
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#endif
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#endif /* CHECKSUM_FLETCHER32_H */
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/** @} */
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