# include <stdio.h># include <errno.h># include <string.h># include <stdlib.h># define RAID5_ALGORITHM_LEFT_ASYMMETRIC 	(0)# define RAID5_ALGORITHM_RIGHT_ASYMMETRIC 	(1)# define RAID5_ALGORITHM_LEFT_SYMMETRIC 	(2)# define RAID5_ALGORITHM_RIGHT_SYMMETRIC 	(3)char *progname = "sectors";static unsigned longraid5_compute_block (unsigned long r_sector, 	unsigned int raid_disks,	unsigned int data_disks, 	unsigned int *dd_idx,	unsigned int *pd_idx, int blocks_per_chunk);main (){	unsigned long block;	int dd_idx, pd_idx;	int blocks_per_chunk;	for (block = 0; block < 32; block++) {		raid5_compute_block (block, 3, 2, &dd_idx, &pd_idx, 1);		raid5_compute_block (block, 4, 3, &dd_idx, &pd_idx, 1);		putchar ('\n');	}#if 0	for (blocks_per_chunk = 1; 	     blocks_per_chunk <= 512; 	     blocks_per_chunk <<= 1) {		raid5_compute_block (5002, 3, 2, &dd_idx, &pd_idx, 		    blocks_per_chunk);		raid5_compute_block (5011, 3, 2, &dd_idx, &pd_idx, 		    blocks_per_chunk);	}	for (block = 5000; block < 5012; block++)		raid5_compute_block (block, 3, 2, &dd_idx, &pd_idx, 32);	for (block = 5000; block < 5012; block++)		raid5_compute_block (block, 3, 2, &dd_idx, &pd_idx, 64);	for (block = 5000; block < 5012; block++)		raid5_compute_block (block, 3, 2, &dd_idx, &pd_idx, 128);#endif		exit (0);}static unsigned longraid5_compute_block (unsigned long r_sector, 	unsigned int raid_disks,	unsigned int data_disks, 	unsigned int *dd_idx,	unsigned int *pd_idx, int blocks_per_chunk){	unsigned long stripe;	unsigned long chunk_number;	unsigned int chunk_offset;	unsigned long new_sector;	int algorithm = RAID5_ALGORITHM_LEFT_SYMMETRIC;# define TESTING# ifdef TESTING# define PU(V)	printf ("%s = %6lu ", #V, V)# else# define PU(V)# endif /* TESTING */	PU (r_sector);	/* First compute the information on this sector */	/*	 * Compute the chunk number and the sector offset inside the chunk	 */	chunk_number = r_sector / blocks_per_chunk;	chunk_offset = r_sector % blocks_per_chunk;#if 0	PU (chunk_number);	PU (chunk_offset);#endif	/*	 * Compute the stripe number	 */	stripe = chunk_number / data_disks;#if 0	PU (stripe);#endif	/*	 * Compute the data disk and parity disk indexes inside the stripe	 */	*dd_idx = chunk_number % data_disks;	/*	 * Select the parity disk based on the user selected algorithm.	 */	switch (algorithm) {	case RAID5_ALGORITHM_LEFT_ASYMMETRIC:		*pd_idx = data_disks - stripe % raid_disks;		if (*dd_idx >= *pd_idx)			(*dd_idx)++;		break;	case RAID5_ALGORITHM_RIGHT_ASYMMETRIC:		*pd_idx = stripe % raid_disks;		if (*dd_idx >= *pd_idx)			(*dd_idx)++;		break;	case RAID5_ALGORITHM_LEFT_SYMMETRIC:		*pd_idx = data_disks - stripe % raid_disks;		*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;		break;	case RAID5_ALGORITHM_RIGHT_SYMMETRIC:		*pd_idx = stripe % raid_disks;		*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;		break;	default:		fprintf (stderr, "raid5: unsupported algorithm %d\n", 		    algorithm);	}	PU (*dd_idx);#if 0	PU (*pd_idx);#endif	/*	 * Finally, compute the new sector number	 */	new_sector = stripe * blocks_per_chunk + chunk_offset;	PU (new_sector);	putchar ('\n');	return new_sector;}