#include <stdio.h>


#define	BLKSIZ	512


char	ibuf[BLKSIZ];
int	blksiz = BLKSIZ;


int	dbgflg = 0;			/* Debug; print entry and value */


int	main(argc, argv)
	int	argc;
	char	*argv[];

{			char	*arg;
			char	*ifnm, *ofnm;
	register	FILE	*in, *out;
			int	blkno, nblks, lstblk, cblk;
			int	maxblk, eblksz;
			long	size;


	if ((argc < 5) || (argc > 6)) {
		printf("\nblkex {-d} <ifile> <ofile> <blkno> <nblks>\n");
		exit(1);
		}

	argv++;
	argc--;
	

	for (;;) {
		arg = *argv;
		if (*arg++ != '-')
			break;

		argv++;
		argc--;

		switch (*arg) {

		  case 'd':	dbgflg++;
				printf("\n");
				break;

		  default:	printf("Bad flag: %c", *arg);
				exit(1);
		  }
		}


	ifnm = *argv++;
	argc--;
	
	in = fopen(ifnm, "rb");
	if (in == NULL) {
		printf("Error opening input file: '%s'\n", ifnm);
		exit(1);
		}

	ofnm = *argv++;
	argc--;
	
	out = fopen(ofnm, "wb");
	if (out == NULL) {
		printf("Error opening output file: '%s'\n", ofnm);
		exit(1);
		}


	arg = *argv++;
	argc--;

	blkno = atoi(arg);
	if (blkno < 0) {
		printf("Bad block number: %d\n", blkno);
		exit(1);
		}

	arg = *argv++;
	argc--;

	nblks = atoi(arg);
	if (nblks < 0) {
		printf("Bad transfer size: %d\n", nblks);
		exit(1);
		}

	lstblk = (blkno + nblks);

	
	if (argc > 0) {
		printf("Unneeded extra arg '%s'", *argv);
		exit(1);		
		}


	if (fseek(in, 0, SEEK_END) != 0) {
		printf("Size seek failed\n");
		exit(1);
		}

	size = ftell(in);
	maxblk = (size / BLKSIZ);
	eblksz = (size - (maxblk * BLKSIZ));

	printf("\nStart/End Block: %d %d\n", blkno, lstblk);
	printf("Size: %ld %d %d\n", size, eblksz, maxblk);

	if ((blkno + nblks) > maxblk) {
		printf("Block number/size too large\n");
		exit(1);
		}

	if (fseek(in, (blkno * BLKSIZ), SEEK_SET) != 0) {
		printf("Read seek failed\n");
		exit(1);
		}
	

	for (cblk = blkno; (cblk < lstblk); cblk++) {
		if (cblk == maxblk)
			blksiz = eblksz;

		if (fread(&ibuf[0], sizeof(char), blksiz, in) != blksiz) {
			printf("Read failed: block %d\n", cblk);
			exit(1);
			}

		if (fwrite(&ibuf[0], sizeof(char), blksiz, out) != blksiz) {
			printf("Write failed: block %d\n", cblk);
			exit(1);
			}
		}

	fclose(in);
	fclose(out);

	printf("%d blocks read\n", (cblk - blkno));
}