dossubs.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

	bp = xf->ptr;
	first = 1;
	len = utftorunes(longname, name, DOSNAMELEN);
	if(chatty){
		chat("utftorunes %s =", name);
		for(i=0; i<len; i++)
			chat(" %.4X", longname[i]);
		chat("\n");
	}
	for(nds = (len + DOSRUNE-1) / DOSRUNE; nds > 0; nds--){
		putnamesect(&ndp->p->iobuf[ndp->offset], longname, nds, first, sum);
		first = 0;
		ndp->offset += 32;
		if(ndp->offset == bp->sectsize){
			chat("long name moving over sector boundary\n");
			ndp->p->flags |= BMOD;
			putsect(ndp->p);
			ndp->p = nil;

			/*
			 * switch to the next cluster for a long entry
			 * naddr should be set up correctly by searchdir
			 */
			ndp->prevaddr = ndp->addr;
			ndp->addr = ndp->naddr;
			ndp->naddr = -1;
			if(ndp->addr == -1)
				return -1;
			ndp->p = getsect(xf, ndp->addr);
			if(ndp->p == nil)
				return -1;
			ndp->offset = 0;
			ndp->d = (Dosdir *)&ndp->p->iobuf[ndp->offset];
		}
	}
	return 0;
}

long
getfat(Xfs *xf, int n)
{
	Dosbpb *bp = xf->ptr;
	Iosect *p;
	ulong k, sect;
	int o, fb;

	if(n < FATRESRV || n >= bp->fatclusters)
		return -1;
	fb = bp->fatbits;
	k = (fb * n) >> 3;
	if(k >= bp->fatsize*bp->sectsize)
		panic("getfat");
	sect = k/bp->sectsize + bp->fataddr;
	o = k%bp->sectsize;
	p = getsect(xf, sect);
	if(p == nil)
		return -1;
	k = p->iobuf[o++];
	if(o >= bp->sectsize){
		putsect(p);
		p = getsect(xf, sect+1);
		if(p == nil)
			return -1;
		o = 0;
	}
	k |= p->iobuf[o++]<<8;
	if(fb == 32){
		/* fat32 is really fat28 */
		k |= p->iobuf[o++] << 16;
		k |= (p->iobuf[o] & 0x0f) << 24;
		fb = 28;
	}
	putsect(p);
	if(fb == 12){
		if(n&1)
			k >>= 4;
		else
			k &= 0xfff;
	}
	if(chatty > 1)
		chat("fat(%#x)=%#lx...", n, k);

	/*
	 * This is a very strange check for out of range.
	 * As a concrete example, for a 16-bit FAT,
	 * FFF8 through FFFF all signify ``end of cluster chain.''
	 * This generalizes to other-sized FATs.
	 */
	if(k >= (1 << fb) - 8)
		return -1;

	return k;
}

void
putfat(Xfs *xf, int n, ulong val)
{
	Fatinfo *fi;
	Dosbpb *bp;
	Iosect *p;
	ulong k, sect, esect;
	int o;

	bp = xf->ptr;
	if(n < FATRESRV || n >= bp->fatclusters)
		panic("putfat n=%d", n);
	k = (bp->fatbits * n) >> 3;
	if(k >= bp->fatsize*bp->sectsize)
		panic("putfat");
	sect = k/bp->sectsize + bp->fataddr;
	esect = sect + bp->nfats * bp->fatsize;
	for(; sect<esect; sect+=bp->fatsize){
		o = k%bp->sectsize;
		p = getsect(xf, sect);
		if(p == nil)
			continue;
		switch(bp->fatbits){
		case 12:
			if(n&1){
				p->iobuf[o] &= 0x0f;
				p->iobuf[o++] |= val<<4;
				if(o >= bp->sectsize){
					p->flags |= BMOD;
					putsect(p);
					p = getsect(xf, sect+1);
					if(p == nil)
						continue;
					o = 0;
				}
				p->iobuf[o] = val>>4;
			}else{
				p->iobuf[o++] = val;
				if(o >= bp->sectsize){
					p->flags |= BMOD;
					putsect(p);
					p = getsect(xf, sect+1);
					if(p == nil)
						continue;
					o = 0;
				}
				p->iobuf[o] &= 0xf0;
				p->iobuf[o] |= (val>>8) & 0x0f;
			}
			break;
		case 16:
			p->iobuf[o++] = val;
			p->iobuf[o] = val>>8;
			break;
		case 32:	/* fat32 is really fat28 */
			p->iobuf[o++] = val;
			p->iobuf[o++] = val>>8;
			p->iobuf[o++] = val>>16;
			p->iobuf[o] = (p->iobuf[o] & 0xf0) | ((val>>24) & 0x0f);
			break;
		default:
			panic("putfat fatbits");
		}
		p->flags |= BMOD;
		putsect(p);
	}

	if(val == 0)
		bp->freeclusters++;
	else
		bp->freeclusters--;

	if(bp->fatinfo){
		p = getsect(xf, bp->fatinfo);
		if(p != nil){
			fi = (Fatinfo*)p->iobuf;
			PLONG(fi->nextfree, bp->freeptr);
			PLONG(fi->freeclust, bp->freeclusters);
			p->flags |= BMOD;
			putsect(p);
		}
	}
}

/*
 * Contiguous falloc; if we can, use lastclust+1.
 * Otherwise, move the file to get some space.
 * If there just isn't enough contiguous space
 * anywhere on disk, fail.
 */
int
cfalloc(Xfile *f)
{
	int l;

	if((l=makecontig(f, 8)) >= 0)
		return l;
	return makecontig(f, 1);
}

/*
 * Check whether a file is contiguous.
 */
int
iscontig(Xfs *xf, Dosdir *d)
{
	long clust, next;

	clust = getstart(xf, d);
	if(clust <= 0)
		return 1;

	for(;;) {
		next = getfat(xf, clust);
		if(next < 0)
			return 1;
		if(next != clust+1)
			return 0;
		clust = next;
	}
}

/*
 * Make a file contiguous, with nextra clusters of 
 * free space after it for later expansion.
 * Return the number of the first new cluster.
 */
int
makecontig(Xfile *f, int nextra)
{
	Dosbpb *bp;
	Dosdir *d;
	Dosptr *dp;
	Xfs *xf;
	Iosect *wp, *rp;
	long clust, next, last, start, rclust, wclust, eclust, ostart;
	int isok, i, n, nclust, nrun, rs, ws;

	xf = f->xf;
	bp = xf->ptr;
	dp = f->ptr;
	d = dp->d;

	isok = 1;
	nclust = 0;
	clust = fileclust(f, 0, 0);
	chat("clust %#lux", clust);
	if(clust != -1) {
		for(;;) {
			nclust++;
			chat(".");
			next = getfat(xf, clust);
			if(next <= 0)
				break;
			if(next != clust+1)
				isok = 0;
			clust = next;
		}
	}
	chat("nclust %d\n", nclust);

	if(isok && clust != -1) {
		eclust = clust+1;	/* eclust = first cluster past file */
		assert(eclust == fileclust(f, 0, 0)+nclust);
		for(i=0; i<nextra; i++)
			if(getfat(xf, eclust+i) != 0)
				break;
		if(i == nextra) {	/* they were all free */
			chat("eclust=%#lx, getfat eclust-1 = %#lux\n", eclust, getfat(xf, eclust-1));
			assert(getfat(xf, eclust-1) == 0xffffffff);
			putfat(xf, eclust-1, eclust);
			putfat(xf, eclust, 0xffffffff);
			bp->freeptr = clust+1;	/* to help keep the blocks free */
			return eclust;
		}
	}

	/* need to search for nclust+nextra contiguous free blocks */
	last = -1;
	n = bp->freeptr;
	nrun = 0;
	for(;;){
		if(getfat(xf, n) == 0) {
			if(last+1 == n)
				nrun++;
			else
				nrun = 1;
			if(nrun >= nclust+nextra)
				break;
			last = n;
		}
		if(++n >= bp->fatclusters)
			n = FATRESRV;
		if(n == bp->freeptr) {
			errno = Econtig;
			return -1;
		}
	}
	bp->freeptr = n+1;

	/* copy old data over */
	start = n+1 - nrun;

	/* sanity check */
	for(i=0; i<nclust+nextra; i++)
		assert(getfat(xf, start+i) == 0);

	chat("relocate chain %lux -> 0x%lux len %d\n", fileclust(f, 0, 0), start, nclust);

	wclust = start;
	for(rclust = fileclust(f, 0, 0); rclust > 0; rclust = next){
		rs = clust2sect(bp, rclust);
		ws = clust2sect(bp, wclust);
		for(i=0; i<bp->clustsize; i++, rs++, ws++){
			rp = getsect(xf, rs);
			if(rp == nil)
				return -1;
			wp = getosect(xf, ws);
			assert(wp != nil);
			memmove(wp->iobuf, rp->iobuf, bp->sectsize);
			wp->flags = BMOD;
			putsect(rp);
			putsect(wp);
		}
		chat("move cluster %#lx -> %#lx...", rclust, wclust);
		next = getfat(xf, rclust);
		putfat(xf, wclust, wclust+1);
		wclust++;
	}

	/* now wclust points at the first new cluster; chain it in */
	chat("wclust 0x%lux start 0x%lux (fat->0x%lux) nclust %d\n", wclust, start, getfat(xf, start), nclust);
	assert(wclust == start+nclust);
	putfat(xf, wclust, 0xffffffff);	/* end of file */

	/* update directory entry to point at new start */
	ostart = fileclust(f, 0, 0);
	putstart(xf, d, start);

	/* check our work */
	i = 0;
	clust = fileclust(f, 0, 0);
	if(clust != -1) {
		for(;;) {
			i++;
			next = getfat(xf, clust);
			if(next <= 0)
				break;
			assert(next == clust+1);
			clust = next;
		}
	}
	chat("chain check: len %d\n", i);
	assert(i == nclust+1);

	/* succeeded; remove old chain. */
	for(rclust = ostart; rclust > 0; rclust = next){
		next = getfat(xf, rclust);
		putfat(xf, rclust, 0);	/* free cluster */
	}

	return start+nclust;
}	

int
falloc(Xfs *xf)
{
	Dosbpb *bp = xf->ptr;
	Iosect *p;
	int n, i, k;

	n = bp->freeptr;
	for(;;){
		if(getfat(xf, n) == 0)
			break;
		if(++n >= bp->fatclusters)
			n = FATRESRV;
		if(n == bp->freeptr)
			return -1;
	}
	bp->freeptr = n+1;
	if(bp->freeptr >= bp->fatclusters)
		bp->freeptr = FATRESRV;
	putfat(xf, n, 0xffffffff);
	k = clust2sect(bp, n);
	for(i=0; i<bp->clustsize; i++){
		p = getosect(xf, k+i);
		memset(p->iobuf, 0, bp->sectsize);
		p->flags = BMOD;
		putsect(p);
	}
	return n;
}

void
ffree(Xfs *xf, long start)
{
	putfat(xf, start, 0);
}

long
clust2sect(Dosbpb *bp, long clust)
{
	return bp->dataaddr + (clust - FATRESRV) * bp->clustsize;
}

long
sect2clust(Dosbpb *bp, long sect)
{
	long c;

	c = (sect - bp->dataaddr) / bp->clustsize + FATRESRV;
	assert(sect == clust2sect(bp, c));
	return c;
}

void
puttime(Dosdir *d, long s)
{
	Tm *t;
	ushort x;

	if(s == 0)
		s = time(0);
	t = localtime(s);

	x = (t->hour<<11) | (t->min<<5) | (t->sec>>1);
	PSHORT(d->time, x);
	x = ((t->year-80)<<9) | ((t->mon+1)<<5) | t->mday;
	PSHORT(d->date, x);
}

long
gtime(Dosdir *dp)
{
	Tm tm;
	int i;

	i = GSHORT(dp->time);
	tm.hour = i >> 11;
	tm.min = (i >> 5) & 63;
	tm.sec = (i & 31) << 1;
	i = GSHORT(dp->date);
	tm.year = 80 + (i >> 9);
	tm.mon = ((i >> 5) & 15) - 1;
	tm.mday = i & 31;
	tm.zone[0] = '\0';
	tm.tzoff = 0;
	tm.yday = 0;

	return tm2sec(&tm);
}

/*
 * structure dumps for debugging
 */
void
bootdump(int fd, Dosboot *b)
{
	Biobuf bp;

	Binit(&bp, fd, OWRITE);
	Bprint(&bp, "magic: 0x%2.2x 0x%2.2x 0x%2.2x\n",
		b->magic[0], b->magic[1], b->magic[2]);
	Bprint(&bp, "version: \"%8.8s\"\n", (char*)b->version);
	Bprint(&bp, "sectsize: %d\n", GSHORT(b->sectsize));
	Bprint(&bp, "clustsize: %d\n", b->clustsize);
	Bprint(&bp, "nresrv: %d\n", GSHORT(b->nresrv));
	Bprint(&bp, "nfats: %d\n", b->nfats);
	Bprint(&bp, "rootsize: %d\n", GSHORT(b->rootsize));
	Bprint(&bp, "volsize: %d\n", GSHORT(b->volsize));
	Bprint(&bp, "mediadesc: 0x%2.2x\n", b->mediadesc);
	Bprint(&bp, "fatsize: %d\n", GSHORT(b->fatsize));
	Bprint(&bp, "trksize: %d\n", GSHORT(b->trksize));
	Bprint(&bp, "nheads: %d\n", GSHORT(b->nheads));
	Bprint(&bp, "nhidden: %ld\n", GLONG(b->nhidden));
	Bprint(&bp, "bigvolsize: %ld\n", GLONG(b->bigvolsize));
	Bprint(&bp, "driveno: %d\n", b->driveno);
	Bprint(&bp, "reserved0: 0x%2.2x\n", b->reserved0);
	Bprint(&bp, "bootsig: 0x%2.2x\n", b->bootsig);
	Bprint(&bp, "volid: 0x%8.8lux\n", GLONG(b->volid));
	Bprint(&bp, "label: \"%11.11s\"\n", (char*)b->label);
	Bterm(&bp);
}

void
bootdump32(int fd, Dosboot32 *b)
{
	Biobuf bp;

	Binit(&bp, fd, OWRITE);
	Bprint(&bp, "magic: 0x%2.2x 0x%2.2x 0x%2.2x\n",
		b->magic[0], b->magic[1], b->magic[2]);
	Bprint(&bp, "version: \"%8.8s\"\n", (char*)b->version);
	Bprint(&bp, "sectsize: %d\n", GSHORT(b->sectsize));
	Bprint(&bp, "clustsize: %d\n", b->clustsize);
	Bprint(&bp, "nresrv: %d\n", GSHORT(b->nresrv));
	Bprint(&bp, "nfats: %d\n", b->nfats);
	Bprint(&bp, "rootsize: %d\n", GSHORT(b->rootsize));
	Bprint(&bp, "volsize: %d\n", GSHORT(b->volsize));
	Bprint(&bp, "mediadesc: 0x%2.2x\n", b->mediadesc);
	Bprint(&bp, "fatsize: %d\n", GSHORT(b->fatsize));
	Bprint(&bp, "trksize: %d\n", GSHORT(b->trksize));
	Bprint(&bp, "nheads: %d\n", GSHORT(b->nheads));
	Bprint(&bp, "nhidden: %ld\n", GLONG(b->nhidden));
	Bprint(&bp, "bigvolsize: %ld\n", GLONG(b->bigvolsize));
	Bprint(&bp, "fatsize32: %ld\n", GLONG(b->fatsize32));
	Bprint(&bp, "extflags: %d\n", GSHORT(b->extflags));
	Bprint(&bp, "version: %d\n", GSHORT(b->version1));
	Bprint(&bp, "rootstart: %ld\n", GLONG(b->rootstart));
	Bprint(&bp, "infospec: %d\n", GSHORT(b->infospec));
	Bprint(&bp, "backupboot: %d\n", GSHORT(b->backupboot));
	Bprint(&bp, "reserved: %d %d %d %d %d %d %d %d %d %d %d %d\n",
		b->reserved[0], b->reserved[1], b->reserved[2], b->reserved[3],
		b->reserved[4], b->reserved[5], b->reserved[6], b->reserved[7],
		b->reserved[8], b->reserved[9], b->reserved[10], b->reserved[11]);
	Bterm(&bp);
}

void
bootsecdump32(int fd, Xfs *xf, Dosboot32 *b32)
{
	Fatinfo *fi;
	Iosect *p1;
	int fisec, bsec, res;

	fprint(fd, "\nfat32\n");
	bootdump32(fd, b32);
	res = GSHORT(b32->nresrv);
	bsec = GSHORT(b32->backupboot);
	if(bsec < res && bsec != 0){
		p1 = getsect(xf, bsec);
		if(p1 == nil)
			fprint(fd, "\ncouldn't get backup boot sector: %r\n");
		else{
			fprint(fd, "\nbackup boot\n");
			bootdump32(fd, (Dosboot32*)p1->iobuf);
			putsect(p1);
		}
	}else if(bsec != 0xffff)
		fprint(fd, "bad backup boot sector: %d reserved %d\n", bsec, res);
	fisec = GSHORT(b32->infospec);
	if(fisec < res && fisec != 0){
		p1 = getsect(xf, fisec);
		if(p1 == nil)
			fprint(fd, "\ncouldn't get fat info sector: %r\n");
		else{
			fprint(fd, "\nfat info %d\n", fisec);
			fi = (Fatinfo*)p1->iobuf;
			fprint(fd, "sig1: 0x%lux sb 0x%lux\n", GLONG(fi->sig1), FATINFOSIG1);
			fprint(fd, "sig: 0x%lux sb 0x%lux\n", GLONG(fi->sig), FATINFOSIG);
			fprint(fd, "freeclust: %lud\n", GLONG(fi->freeclust));
			fprint(fd, "nextfree: %lud\n", GLONG(fi->nextfree));
			fprint(fd, "reserved: %lud %lud %lud\n", GLONG(fi->resrv), GLONG(fi->resrv+4), GLONG(fi->resrv+8));
			putsect(p1);
		}
	}else if(fisec != 0xffff)
		fprint(2, "bad fat info sector: %d reserved %d\n", bsec, res);
}

void
dirdump(void *vdbuf)
{
	static char attrchar[] = "rhsvda67";
	Dosdir *d;
	char *name, namebuf[DOSNAMELEN];
	char buf[128], *s, *ebuf;
	uchar *dbuf;
	int i;

	if(!chatty)
		return;

	d = vdbuf;

	ebuf = buf + sizeof(buf);
	if(d->attr == 0xf){
		dbuf = vdbuf;
		name = namebuf + DOSNAMELEN;
		*--name = '\0';
		name = getnamerunes(name, dbuf, 1);
		seprint(buf, ebuf, "\"%s\" %2.2x %2.2ux %2.2ux %d", name, dbuf[0], dbuf[12], dbuf[13], GSHORT(d->start));
	}else{
		s = seprint(buf, ebuf, "\"%.8s.%.3s\" ", (char*)d->name, (char*)d->ext);
		for(i=7; i>=0; i--)
			*s++ = d->attr&(1<<i) ? attrchar[i] : '-';
	
		i = GSHORT(d->time);
		s = seprint(s, ebuf, " %2.2d:%2.2d:%2.2d", i>>11, (i>>5)&63, (i&31)<<1);
		i = GSHORT(d->date);
		s = seprint(s, ebuf, " %2.2d.%2.2d.%2.2d", 80+(i>>9), (i>>5)&15, i&31);
	
		i = GSHORT(d->ctime);
		s = seprint(s, ebuf, " %2.2d:%2.2d:%2.2d", i>>11, (i>>5)&63, (i&31)<<1);
		i = GSHORT(d->cdate);
		s = seprint(s, ebuf, " %2.2d.%2.2d.%2.2d", 80+(i>>9), (i>>5)&15, i&31);
	
		i = GSHORT(d->adate);
		s = seprint(s, ebuf, " %2.2d.%2.2d.%2.2d", 80+(i>>9), (i>>5)&15, i&31);

		seprint(s, ebuf, " %d %d", GSHORT(d->start), GSHORT(d->length));
	}
	chat("%s\n", buf);
}

int
cistrcmp(char *s1, char *s2)
{
	int c1, c2;

	while(*s1){
		c1 = *s1++;
		c2 = *s2++;

		if(c1 >= 'A' && c1 <= 'Z')
			c1 -= 'A' - 'a';

		if(c2 >= 'A' && c2 <= 'Z')
			c2 -= 'A' - 'a';

		if(c1 != c2)
			return c1 - c2;
	}
	return -*s2;
}

int
utftorunes(Rune *rr, char *s, int n)
{
	Rune *r, *re;
	int c;

	r = rr;
	re = r + n - 1;
	while(c = (uchar)*s){
		if(c < Runeself){
			*r = c;
			s++;
		}else
			s += chartorune(r, s);
		r++;
		if(r >= re)
			break;
	}
	*r = 0;
	return r - rr;
}