fdisk.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

		return n<4;
	}

	/* 
	 * secondary partitions can be inserted between two primary
	 * partitions only if there is an empty primary slot.
	 * otherwise, we can put a new secondary partition next
	 * to a secondary partition no problem.
	 */
	n = 0;
	for(i=0; i<edit->npart; i++){
		p = (Dospart*)edit->part[i];
		if(p->primary)
			n++;
		pend = p->end;
		if(i+1<edit->npart){
			q = (Dospart*)edit->part[i+1];
			qstart = q->start;
		}else{
			qstart = edit->end;
			q = nil;
		}
		if(start < pend || start >= qstart)
			continue;
		/* we go between these two */
		if(p->primary==0 || (q && q->primary==0))
			return 1;
	}
	/* not next to a secondary, need a new primary */
	return n<4;
}

static void
autopart(Edit *edit)
{
	char *err;
	int active, i;
	vlong bigstart, bigsize, start;
	Dospart *p;

	for(i=0; i<edit->npart; i++)
		if(((Dospart*)edit->part[i])->type == Type9)
			return;

	/* look for the biggest gap in which we can put a primary partition */
	start = 0;
	bigsize = 0;
	SET(bigstart);
	for(i=0; i<edit->npart; i++) {
		p = (Dospart*)edit->part[i];
		if(p->start > start && p->start - start > bigsize && haveroom(edit, 1, start)) {
			bigsize = p->start - start;
			bigstart = start;
		}
		start = p->end;
	}

	if(edit->end - start > bigsize && haveroom(edit, 1, start)) {
		bigsize = edit->end - start;
		bigstart = start;
	}
	if(bigsize < 1) {
		fprint(2, "couldn't find space or partition slot for plan 9 partition\n");
		return;
	}

	/* set new partition active only if no others are */
	active = Active;	
	for(i=0; i<edit->npart; i++)
		if(((Dospart*)edit->part[i])->primary && (((Dospart*)edit->part[i])->active & Active))
			active = 0;

	/* add new plan 9 partition */
	bigsize *= sec2cyl;
	bigstart *= sec2cyl;
	if(bigstart == 0) {
		bigstart += edit->disk->s;
		bigsize -= edit->disk->s;
	}
	p = mkpart(nil, 1, bigstart, bigsize, nil);
	p->active = active;
	p->changed = 1;
	p->type = Type9;
	edit->changed = 1;
	if(err = addpart(edit, p)) {
		fprint(2, "error adding plan9 partition: %s\n", err);
		return;
	}
}

typedef struct Name Name;
struct Name {
	char *name;
	Name *link;
};
Name *namelist;
static void
plan9print(Dospart *part, int fd)
{
	int i, ok;
	char *name, *vname;
	Name *n;
	vlong start, end;
	char *sep;

	vname = types[part->type].name;
	if(vname==nil || strcmp(vname, "")==0) {
		part->ctlname = "";
		return;
	}

	start = mbroffset+part->lba;
	end = start+part->size;

	/* avoid names like plan90 */
	i = strlen(vname) - 1;
	if(vname[i] >= '0' && vname[i] <= '9')
		sep = ".";
	else
		sep = "";

	i = 0;
	name = emalloc(strlen(vname)+10);

	sprint(name, "%s", vname);
	do {
		ok = 1;
		for(n=namelist; n; n=n->link) {
			if(strcmp(name, n->name) == 0) {
				i++;
				sprint(name, "%s%s%d", vname, sep, i);
				ok = 0;
			}
		}
	} while(ok == 0);

	n = emalloc(sizeof(*n));
	n->name = name;
	n->link = namelist;
	namelist = n;
	part->ctlname = name;

	if(fd >= 0)
		print("part %s %lld %lld\n", name, start, end);
}

static void
freenamelist(void)
{
	Name *n, *next;

	for(n=namelist; n; n=next) {
		next = n->link;
		free(n);
	}
	namelist = nil;
}

static void
cmdprintctl(Edit *edit, int ctlfd)
{
	int i;

	freenamelist();
	for(i=0; i<edit->npart; i++)
		plan9print((Dospart*)edit->part[i], -1);
	ctldiff(edit, ctlfd);
}

static char*
cmdokname(Edit*, char *name)
{
	char *q;

	if(name[0] != 'p' && name[0] != 's')
		return "name must be pN or sN";

	strtol(name+1, &q, 10);
	if(*q != '\0')
		return "name must be pN or sN";

	return nil;
}

#define GB (1024*1024*1024)
#define MB (1024*1024)
#define KB (1024)

static void
cmdsum(Edit *edit, Part *vp, vlong a, vlong b)
{
	char *name, *ty;
	char buf[3];
	char *suf;
	Dospart *p;
	vlong sz, div;

	p = (Dospart*)vp;

	buf[0] = p && p->changed ? '\'' : ' ';
	buf[1] = p && (p->active & Active) ? '*' : ' ';
	buf[2] = '\0';

	name = p ? p->name : "empty";
	ty = p ? typestr0(p->type) : "";

	sz = (b-a)*edit->disk->secsize*sec2cyl;
	if(sz >= 1*GB){
		suf = "GB";
		div = GB;
	}else if(sz >= 1*MB){
		suf = "MB";
		div = MB;
	}else if(sz >= 1*KB){
		suf = "KB";
		div = KB;
	}else{
		suf = "B ";
		div = 1;
	}

	if(div == 1)
		print("%s %-12s %*lld %-*lld (%lld cylinders, %lld %s) %s\n", buf, name,
			edit->disk->width, a, edit->disk->width, b, b-a, sz, suf, ty);
	else
		print("%s %-12s %*lld %-*lld (%lld cylinders, %lld.%.2d %s) %s\n", buf, name,
			edit->disk->width, a, edit->disk->width, b,  b-a,
			sz/div, (int)(((sz%div)*100)/div), suf, ty);
}

static char*
cmdadd(Edit *edit, char *name, vlong start, vlong end)
{
	Dospart *p;

	if(!haveroom(edit, name[0]=='p', start))
		return "no room for partition";
	start *= sec2cyl;
	end *= sec2cyl;
	if(start == 0 || name[0] != 'p')
		start += edit->disk->s;
	p = mkpart(name, name[0]=='p', start, end-start, nil);
	p->changed = 1;
	p->type = Type9;
	return addpart(edit, p);
}

static char*
cmddel(Edit *edit, Part *p)
{
	return delpart(edit, p);
}

static char*
cmdwrite(Edit *edit)
{
	wrpart(edit);
	return nil;
}

static char *help = 
	"A name - set partition active\n"
	"P - print table in ctl format\n"
	"R - restore disk back to initial configuration and exit\n"
	"e - show empty dos partitions\n"
	"t name [type] - set partition type\n";

static char*
cmdhelp(Edit*)
{
	print("%s\n", help);
	return nil;
}

static char*
cmdactive(Edit *edit, int nf, char **f)
{
	int i;
	Dospart *p, *ip;

	if(nf != 2)
		return "args";

	if(f[1][0] != 'p')
		return "cannot set secondary partition active";

	if((p = (Dospart*)findpart(edit, f[1])) == nil)
		return "unknown partition";

	for(i=0; i<edit->npart; i++) {
		ip = (Dospart*)edit->part[i];
		if(ip->active & Active) {
			ip->active &= ~Active;
			ip->changed = 1;
			edit->changed = 1;
		}
	}

	if((p->active & Active) == 0) {
		p->active |= Active;
		p->changed = 1;
		edit->changed = 1;
	}

	return nil;
}

static char*
strupr(char *s)
{
	char *p;

	for(p=s; *p; p++)
		*p = toupper(*p);
	return s;
}

static void
dumplist(void)
{
	int i, n;

	n = 0;
	for(i=0; i<256; i++) {
		if(types[i].desc) {
			print("%-16s", types[i].desc);
			if(n++%4 == 3)
				print("\n");
		}
	}
	if(n%4)
		print("\n");
}

static char*
cmdtype(Edit *edit, int nf, char **f)
{
	char *q;
	Dospart *p;
	int i;

	if(nf < 2)
		return "args";

	if((p = (Dospart*)findpart(edit, f[1])) == nil)
		return "unknown partition";

	if(nf == 2) {
		for(;;) {
			fprint(2, "new partition type [? for list]: ");
			q = getline(edit);
			if(q[0] == '?')
				dumplist();
			else
				break;
		}
	} else
		q = f[2];

	strupr(q);
	for(i=0; i<256; i++)
		if(types[i].desc && strcmp(types[i].desc, q) == 0)
			break;
	if(i < 256 && p->type != i) {
		p->type = i;
		p->changed = 1;
		edit->changed = 1;
	}
	return nil;
}

static char*
cmdext(Edit *edit, int nf, char **f)
{
	switch(f[0][0]) {
	case 'A':
		return cmdactive(edit, nf, f);
	case 't':
		return cmdtype(edit, nf, f);
	case 'R':
		recover(edit);
		return nil;
	default:
		return "unknown command";
	}
}

static int
Dfmt(Fmt *f)
{
	char buf[60];
	uchar *p;
	int c, h, s;

	p = va_arg(f->args, uchar*);
	h = p[0];
	c = p[2];
	c |= (p[1]&0xC0)<<2;
	s = (p[1] & 0x3F);

	sprint(buf, "%d/%d/%d", c, h, s);
	return fmtstrcpy(f, buf);
}

static void
writechs(Disk *disk, uchar *p, vlong lba)
{
	int c, h, s;

	s = lba % disk->s;
	h = (lba / disk->s) % disk->h;
	c = lba / (disk->s * disk->h);

	if(c >= 1024) {
		c = 1023;
		h = disk->h - 1;
		s = disk->s - 1;
	}

	p[0] = h;
	p[1] = ((s+1) & 0x3F) | ((c>>2) & 0xC0);
	p[2] = c;
}

static void
wrtentry(Disk *disk, Tentry *tp, int type, u32int xbase, u32int lba, u32int end)
{
	tp->type = type;
	writechs(disk, &tp->starth, lba);
	writechs(disk, &tp->endh, end-1);
	putle32(tp->xlba, lba-xbase);
	putle32(tp->xsize, end-lba);
}

static int
wrextend(Edit *edit, int i, vlong xbase, vlong startlba, vlong *endlba)
{
	int ni;
	Table table;
	Tentry *tp, *ep;
	Dospart *p;
	Disk *disk;

	if(i == edit->npart){
		*endlba = edit->disk->secs;
	Finish:
		if(startlba < *endlba){
			disk = edit->disk;
			diskread(disk, &table, sizeof table, mbroffset+startlba, Toffset);
			tp = table.entry;
			ep = tp+NTentry;
			for(; tp<ep; tp++)
				memset(tp, 0, sizeof *tp);
			table.magic[0] = Magic0;
			table.magic[1] = Magic1;

			if(diskwrite(edit->disk, &table, sizeof table, mbroffset+startlba, Toffset) < 0)
				recover(edit);
		}
		return i;
	}

	p = (Dospart*)edit->part[i];
	if(p->primary){
		*endlba = (vlong)p->start*sec2cyl;
		goto Finish;
	}

	disk = edit->disk;
	diskread(disk, &table, sizeof table, mbroffset+startlba, Toffset);
	tp = table.entry;
	ep = tp+NTentry;

	ni = wrextend(edit, i+1, xbase, p->end*sec2cyl, endlba);

	*tp = p->Tentry;
	wrtentry(disk, tp, p->type, startlba, startlba+disk->s, p->end*sec2cyl);
	tp++;

	if(p->end*sec2cyl != *endlba){
		memset(tp, 0, sizeof *tp);
		wrtentry(disk, tp, TypeEXTENDED, xbase, p->end*sec2cyl, *endlba);
		tp++;
	}

	for(; tp<ep; tp++)
		memset(tp, 0, sizeof *tp);

	table.magic[0] = Magic0;
	table.magic[1] = Magic1;

	if(diskwrite(edit->disk, &table, sizeof table, mbroffset+startlba, Toffset) < 0)
		recover(edit);
	return ni;
}	

static void
wrpart(Edit *edit)
{	
	int i, ni, t;
	Table table;
	Tentry *tp, *ep;
	Disk *disk;
	vlong s, endlba;
	Dospart *p;

	disk = edit->disk;

	diskread(disk, &table, sizeof table, mbroffset, Toffset);

	tp = table.entry;
	ep = tp+NTentry;
	for(i=0; i<edit->npart && tp<ep; ) {
		p = (Dospart*)edit->part[i];
		if(p->start == 0)
			s = disk->s;
		else
			s = p->start*sec2cyl;
		if(p->primary) {
			*tp = p->Tentry;
			wrtentry(disk, tp, p->type, 0, s, p->end*sec2cyl);
			tp++;
			i++;
		} else {
			ni = wrextend(edit, i, p->start*sec2cyl, p->start*sec2cyl, &endlba);
			memset(tp, 0, sizeof *tp);
			if(endlba >= 1024*sec2cyl)
				t = TypeEXTHUGE;
			else
				t = TypeEXTENDED;
			wrtentry(disk, tp, t, 0, s, endlba);
			tp++;
			i = ni;
		}
	}
	for(; tp<ep; tp++)
		memset(tp, 0, sizeof(*tp));
		
	if(i != edit->npart)
		sysfatal("cannot happen #1");

	if(diskwrite(disk, &table, sizeof table, mbroffset, Toffset) < 0)
		recover(edit);

	/* bring parts up to date */
	freenamelist();
	for(i=0; i<edit->npart; i++)
		plan9print((Dospart*)edit->part[i], -1);

	if(ctldiff(edit, disk->ctlfd) < 0)
		fprint(2, "?warning: partitions could not be updated in devsd\n");
}