mirror of https://github.com/rusefi/rusefi-1.git
45 lines
837 B
C
45 lines
837 B
C
/**
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* @file crc.c
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* @date Sep 20, 2013
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* @author Andrey Belomutskiy, (c) 2012-2014
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*/
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#include "crc.h"
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#define WIDTH (8)
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#define TOPBIT (1 << (WIDTH - 1))
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#define POLYNOMIAL 0xD8
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crc calc_crc(const crc message[], int nBytes) {
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crc remainder = 0;
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/*
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* Perform modulo-2 division, a byte at a time.
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*/
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for (int byte = 0; byte < nBytes; ++byte) {
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/*
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* Bring the next byte into the remainder.
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*/
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remainder ^= (message[byte] << (WIDTH - 8));
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/*
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* Perform modulo-2 division, a bit at a time.
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*/
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for (unsigned char bit = 8; bit > 0; --bit) {
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/*
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* Try to divide the current data bit.
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*/
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if (remainder & TOPBIT) {
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remainder = (remainder << 1) ^ POLYNOMIAL;
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} else {
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remainder = (remainder << 1);
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}
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}
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}
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/*
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* The final remainder is the CRC result.
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*/
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return remainder;
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}
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