#include <u.h>#include <libc.h>#include <bio.h>#include <ctype.h>#include <disk.h> static Disk*mkwidth(Disk *disk){	char buf[40]; 	sprint(buf, "%lld", disk->size);	disk->width = strlen(buf);	return disk;} /* * Discover the disk geometry by various sleazeful means. *  * First, if there is a partition table in sector 0, * see if all the partitions have the same end head * and sector; if so, we'll assume that that's the  * right count. *  * If that fails, we'll try looking at the geometry that the ATA * driver supplied, if any, and translate that as a * BIOS might.  *  * If that too fails, which should only happen on a SCSI * disk with no currently defined partitions, we'll try * various common (h, s) pairs used by BIOSes when faking * the geometries. */typedef struct Table  Table;typedef struct Tentry Tentry;struct Tentry {	uchar	active;			/* active flag */	uchar	starth;			/* starting head */	uchar	starts;			/* starting sector */	uchar	startc;			/* starting cylinder */	uchar	type;			/* partition type */	uchar	endh;			/* ending head */	uchar	ends;			/* ending sector */	uchar	endc;			/* ending cylinder */	uchar	xlba[4];			/* starting LBA from beginning of disc */	uchar	xsize[4];		/* size in sectors */};enum {	Toffset		= 446,		/* offset of partition table in sector */	Magic0		= 0x55,	Magic1		= 0xAA,	NTentry		= 4,};struct Table {	Tentry	entry[NTentry];	uchar	magic[2];};static intpartitiongeometry(Disk *disk){	int i, h, s;	uchar buf[512];	Table *t;  	if(seek(disk->fd, 0, 0) < 0) {		return -1;	} 	if(readn(disk->fd, buf, 512) != 512) {		return -1;	} 	t = (Table*)(buf+Toffset);	if(t->magic[0] != Magic0 || t->magic[1] != Magic1)		return -1; 	h = s = -1;		for(i=0; i<NTentry; i++) {		if(t->entry[i].type == 0)			continue; 		t->entry[i].ends &= 63;		if(h == -1) {			h = t->entry[i].endh;			s = t->entry[i].ends;		} else {			/*			 * Only accept the partition info if every			 * partition is consistent.			 */			if(h != t->entry[i].endh || s != t->entry[i].ends)				return -1;		}	} 	if(h == -1)		return -1; 	disk->h = h+1;	/* heads count from 0 */	disk->s = s;	/* sectors count from 1 */	disk->c = disk->secs / (disk->h*disk->s);	disk->chssrc = Gpart;	return 0;} /* * If there is ATA geometry, use it, perhaps massaged. */static intdrivergeometry(Disk *disk){	int m; 	if(disk->c == 0 || disk->h == 0 || disk->s == 0)		return -1; 	disk->chssrc = Gdisk;	if(disk->c < 1024)		return 0; 	switch(disk->h) {	case 15:		disk->h = 255;		disk->c /= 17;		return 0; 	default:		for(m = 2; m*disk->h < 256; m *= 2) {			if(disk->c/m < 1024) {				disk->c /= m;				disk->h *= m;				return 0;			}		} 		/* set to 255, 63 and be done with it */		disk->h = 255;		disk->s = 63;		disk->c = disk->secs / (disk->h * disk->s);		return 0;	}	return -1;	/* not reached */} /* * There's no ATA geometry and no partitions. * Our guess is as good as anyone's. */static struct {	int h;	int s;} guess[] = {	64, 32,	64, 63,	128, 63,	255, 63,};static intguessgeometry(Disk *disk){	int i;	long c; 	disk->chssrc = Gguess;	c = 1024;	for(i=0; i<nelem(guess); i++)		if(c*guess[i].h*guess[i].s >= disk->secs) {			disk->h = guess[i].h;			disk->s = guess[i].s;			disk->c = disk->secs / (disk->h * disk->s);			return 0;		} 	/* use maximum values */	disk->h = 255;	disk->s = 63;	disk->c = disk->secs / (disk->h * disk->s);	return 0;} static voidfindgeometry(Disk *disk){	if(partitiongeometry(disk) < 0	&& drivergeometry(disk) < 0	&& guessgeometry(disk) < 0) {	/* can't happen */		print("we're completely confused about your disk; sorry\n");		assert(0);	}} static Disk*openfile(Disk *disk){	Dir dir; 	if(dirfstat(disk->fd, &dir) < 0) {		free(disk);		return nil;	} 	disk->secsize = 512;	disk->size = dir.length;	disk->secs = disk->size / disk->secsize;	disk->offset = 0; 	findgeometry(disk);	return mkwidth(disk);} static Disk*opensd(Disk *disk){	Biobuf b;	char *p, *f[10];	int nf; 	Binit(&b, disk->ctlfd, OREAD);	while(p = Brdline(&b, '\n')) {		p[Blinelen(&b)-1] = '\0';		nf = tokenize(p, f, nelem(f));		if(nf >= 3 && strcmp(f[0], "geometry") == 0) {			disk->secsize = strtoll(f[2], 0, 0);			if(nf >= 6) {				disk->c = strtol(f[3], 0, 0);				disk->h = strtol(f[4], 0, 0);				disk->s = strtol(f[5], 0, 0);			}		}		if(nf >= 4 && strcmp(f[0], "part") == 0 && strcmp(f[1], disk->part) == 0) {			disk->offset = strtoll(f[2], 0, 0);			disk->secs = strtoll(f[3], 0, 0) - disk->offset;		}	} 		disk->size = disk->secs * disk->secsize;	if(disk->size <= 0) {		strcpy(disk->part, "");		disk->type = Tfile;		return openfile(disk);	} 	findgeometry(disk);	return mkwidth(disk);} Disk*opendisk(char *disk, int rdonly, int noctl){	char *p, *q;	Disk *d; 	d = malloc(sizeof(*d));	if(d == nil)		return nil; 	d->fd = d->wfd = d->ctlfd = -1;	d->rdonly = rdonly; 	d->fd = open(disk, OREAD);	if(d->fd < 0) {		werrstr("cannot open disk file");		free(d);		return nil;	} 	if(rdonly == 0) {		d->wfd = open(disk, OWRITE);		if(d->wfd < 0)			d->rdonly = 1;	} 	if(noctl)		return openfile(d); 	p = strdup(disk);	if(p == nil) {		close(d->wfd);		close(d->fd);		free(d);		return nil;	} 	/* check for floppy(3) disk */	if(strlen(p) >= 7) {		q = p+strlen(p)-7;		if(q[0] == 'f' && q[1] == 'd' && isdigit(q[2]) && strcmp(q+3, "disk") == 0) {			strcpy(q+3, "ctl");			if((d->ctlfd = open(p, ORDWR)) >= 0) {				*q = '\0';				d->prefix = p;				d->type = Tfloppy;				return openfile(d);			}		}	} 	/* attempt to find sd(3) disk or partition */	if(q = strrchr(p, '/'))		q++;	else		q = p; 	strcpy(q, "ctl");	if((d->ctlfd = open(p, ORDWR)) >= 0) {		*q = '\0';		d->prefix = p;		d->type = Tsd;		strncpy(d->part, disk+(q-p), NAMELEN);		d->part[NAMELEN-1] = '\0';		return opensd(d);	} 	/* assume we just have a normal file */	d->type = Tfile;	return openfile(d);}