103 lines
3.0 KiB
C
103 lines
3.0 KiB
C
/*
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* Library: libcrc
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* File: src/crcsick.c
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* Author: Lammert Bies
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*
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* This file is licensed under the MIT License as stated below
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*
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* Copyright (c) 2007-2016 Lammert Bies
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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* Description
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* -----------
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* The source file src/crcsick.c contains routines that help in calculating the
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* CRC value that is used as dataprotection measure in communications with Sick
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* electronic devices.
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*/
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#include <stdlib.h>
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#include "checksum.h"
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/*
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* uint16_t crc_sick( const unsigned char *input_str, size_t num_bytes );
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*
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* The function crc_sick() calculates the SICK CRC value of an input string in
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* one pass.
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*/
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uint16_t crc_sick( const unsigned char *input_str, size_t num_bytes ) {
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uint16_t crc;
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uint16_t low_byte;
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uint16_t high_byte;
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uint16_t short_c;
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uint16_t short_p;
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const unsigned char *ptr;
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size_t a;
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crc = CRC_START_SICK;
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ptr = input_str;
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short_p = 0;
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if ( ptr != NULL ) for (a=0; a<num_bytes; a++) {
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short_c = 0x00FF & (uint16_t) *ptr;
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if ( crc & 0x8000 ) crc = ( crc << 1 ) ^ CRC_POLY_SICK;
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else crc = crc << 1;
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crc ^= ( short_c | short_p );
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short_p = short_c << 8;
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ptr++;
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}
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low_byte = (crc & 0xFF00) >> 8;
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high_byte = (crc & 0x00FF) << 8;
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crc = low_byte | high_byte;
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return crc;
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} /* crc_sick */
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/*
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* uint16_t update_crc_sick( uint16_t crc, unsigned char c, unsigned char prev_byte );
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*
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* The function update_crc_sick() calculates a new CRC-SICK value based on the
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* previous value of the CRC and the next byte of the data to be checked.
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*/
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uint16_t update_crc_sick( uint16_t crc, unsigned char c, unsigned char prev_byte ) {
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uint16_t short_c;
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uint16_t short_p;
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short_c = 0x00FF & (uint16_t) c;
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short_p = ( 0x00FF & (uint16_t) prev_byte ) << 8;
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if ( crc & 0x8000 ) crc = ( crc << 1 ) ^ CRC_POLY_SICK;
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else crc = crc << 1;
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crc ^= ( short_c | short_p );
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return crc;
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} /* update_crc_sick */
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