Matthias Biermann
110 lines
3.1 KiB
C
110 lines
3.1 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <stdint.h>
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#include <stdlib.h>
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// Berechnen einer 8 Bit CRC-Pruefsumme
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uint8_t crc8(uint8_t* data, size_t size);
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// Berechnen einer 32 Bit CRC-Pruefsumme
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uint32_t crc32(uint8_t* inBytes, size_t size, uint32_t polynomial);
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// Check einer 32 Bit CRC-Pruefsumme
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int checkCrc32(uint8_t* data, size_t size, uint32_t crc, uint32_t polynomial);
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int main()
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{
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char msg[] = "Hello World!\0\0\0\0";
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uint32_t crc = crc32((uint8_t*) msg, strlen(msg)+4, 0x4C11DB7);
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printf("CRC32 of '%s': 0x%08x\n\n", msg, crc);
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int crcValid = checkCrc32((uint8_t*) msg, strlen(msg), crc, 0x4C11DB7);
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// String einlesen und CRC32 ausgeben
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// char input[1024];
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// printf("String eingeben:\n");
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// while (1)
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// {
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// // Liest eine Zeile von stdin ein und speichert sie in 'eingabe'
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// if (fgets(input, sizeof(input), stdin) != NULL) {
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// // Entfernt das Newline-Zeichen, das fgets hinzufügt
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// size_t laenge = strlen(input);
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// if (laenge > 0 && input[laenge - 1] == '\n') {
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// input[laenge - 1] = '\0';
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// }
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// }
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// crc = crc32((uint8_t*) input, strlen(input));
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// printf("'%s' -> 0x%08x\n\n", input, crc);
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// }
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return 0;
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}
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uint8_t crc8(uint8_t* inBytes, size_t size)
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{
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uint8_t crc = 0x0; // initial value
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uint8_t polynomial = 0x7;
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for (size_t i = 0; i < size; i++) {
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for (int bit = 7; bit >= 0; bit--) {
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// get next bit
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uint8_t inBit = (inBytes[i] & (1<<bit)) ? 1 : 0;
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// check if MSB is set
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uint8_t MSB_high = crc & 0x80;
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// input Bit reinschieben
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crc = (uint8_t) (crc << 1);
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crc ^= inBit;
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if (MSB_high) {
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crc ^= polynomial;
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}
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// for (int in = 0; in < 8; in++) {
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// printf("%d", !!((crc << in) & 0x80));
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// }
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// printf("\n");
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}
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}
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return crc;
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}
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uint32_t crc32(uint8_t* inBytes, size_t size, uint32_t polynomial)
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{
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uint32_t crc = 0x0; // initial value
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for (size_t i = 0; i < size; i++) {
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for (int bit = 7; bit >= 0; bit--) {
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// get next bit
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uint8_t inBit = (inBytes[i] & (1<<bit)) ? 1 : 0;
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// check if MSB is set
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uint32_t MSB_high = crc & 0x80000000;
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// input Bit reinschieben
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crc <<= 1;
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crc ^= inBit;
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if (MSB_high) {
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crc ^= polynomial;
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}
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// for (int in = 0; in < 8; in++) {
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// printf("%d", !!((crc << in) & 0x80));
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// }
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// printf("\n");
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}
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// printf("0x%x\n", crc);
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}
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return crc;
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}
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int checkCrc32(uint8_t* data, size_t size, uint32_t crc, uint32_t polynomial)
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{
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// Daten und CRC zusammenhaengend in den HEAP Speicher kopieren
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uint8_t *dataCrc = malloc(size + 4);
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memcpy_s(dataCrc, size+4, data, size);
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memcpy_s(dataCrc+size, 4, &crc, 4);
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if (crc32(dataCrc, size+4, polynomial) == 0) return 1;
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else return 0;
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} |