crcsum.c

FAT16 Filesystem on Philips LPC2000 series processors

#include <stdio.h>
#include <stdlib.h>

unsigned int CRC = 0;
FILE * binary;

unsigned int vectors [8];

int main (int argc, char * argv[])
{ // read first few 8 words of binary image and create CRC.
int	i;
	if (argc == 1) {
		printf ("We need at least a filename...\n");
		exit (-1);
	}
		// attempt to open binary image.
//	printf ("CRC summing %s\n", argv[1]);
	if ((binary = fopen (argv[1], "rb")) == NULL) {
		printf ("Failed to open %s\n", argv[1]);
		exit (-2);
	}
	fread (vectors, sizeof(unsigned int), 8, binary);
	fclose (binary);
		// calculate CRC value.
	vectors [5] = 0;
	for (i = 0, CRC = 0; i<8; i++) {
		CRC += vectors [i];
	}
	CRC = 0 - CRC;
//	printf ("CRC is %8x\n", CRC);
		// put the CRC into the file now.
	if ((binary = fopen (argv[1], "r+")) == NULL) {
		printf ("Failed to open %s\n", argv[1]);
		exit (-2);
	}
	fseek (binary, 5 * sizeof(unsigned int), SEEK_SET);
	fwrite (&CRC, sizeof(unsigned int), 1, binary);
	fclose (binary);
	
	exit (0);
}