9660srv.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

	if(d->reclen == 0)
		return 0;
	fprint(fd, "%d %d %ld %ld ",
		d->reclen, d->attrlen, l32(d->addr), l32(d->size));
	fprint(fd, "%s 0x%2.2x %d %d %ld ",
		rdate(d->date, fmt), (fmt=='z' ? d->flags : d->r_flags),
		d->unitsize, d->gapsize, l16(d->vseqno));
	fprint(fd, "%d %s", d->namelen, nstr(d->name, d->namelen));
	if(fmt != 'J'){
		namelen = d->namelen + (1-(d->namelen&1));
		syslen = d->reclen - 33 - namelen;
		if(syslen != 0)
			fprint(fd, " %s", nstr(&d->name[namelen], syslen));
	}
	fprint(fd, "\n");
	return d->reclen + (d->reclen&1);
}

static void
newdrec(Xfile *f, Drec *dp)
{
	Isofile *x = f->ptr;
	Isofile *n;
	int len;

	len = sizeof(Isofile) - sizeof(Drec) + dp->reclen;
	n = ealloc(len);
	n->fmt = x->fmt;
	n->blksize = x->blksize;
	n->offset = 0;
	n->doffset = 0;
	memmove(&n->d, dp, dp->reclen);
	free(x);
	f->ptr = n;
	f->len = len;
}

static void
ungetdrec(Xfile *f)
{
	Isofile *ip = f->ptr;

	if(ip->offset >= ip->odelta){
		ip->offset -= ip->odelta;
		ip->odelta = 0;
	}
}

static int
getdrec(Xfile *f, void *buf)
{
	Isofile *ip = f->ptr;
	int len = 0, boff = 0;
	long size, addr;
	Iobuf *p = 0;

	if(!ip)
		return -1;
	size = l32(ip->d.size);
	while(ip->offset<size){
		addr = (l32(ip->d.addr)+ip->d.attrlen)*ip->blksize + ip->offset;
		boff = (ulong)addr % Sectorsize;
		if(boff > Sectorsize-34){
			ip->offset += Sectorsize-boff;
			continue;
		}
		p = getbuf(f->xf->d, (ulong)addr/Sectorsize);
		len = p->iobuf[boff];
		if(len >= 34)
			break;
		putbuf(p);
		p = 0;
		ip->offset += Sectorsize-boff;
	}
	if(p) {
		memmove(buf, &p->iobuf[boff], len);
		putbuf(p);
		ip->odelta = len + (len&1);
		ip->offset += ip->odelta;
	}
	if(p)
		return 0;
	return -1;
}

static int
opendotdot(Xfile *f, Xfile *pf)
{
	uchar dbuf[256];
	Drec *d = (Drec *)dbuf;
	Isofile *ip = f->ptr, *pip = pf->ptr;

	ip->offset = 0;
	if(getdrec(f, d) < 0){
		chat("opendotdot: getdrec(.) failed...");
		return -1;
	}
	if(d->namelen != 1 || d->name[0] != 0){
		chat("opendotdot: no . entry...");
		return -1;
	}
	if(l32(d->addr) != l32(ip->d.addr)){
		chat("opendotdot: bad . address...");
		return -1;
	}
	if(getdrec(f, d) < 0){
		chat("opendotdot: getdrec(..) failed...");
		return -1;
	}
	if(d->namelen != 1 || d->name[0] != 1){
		chat("opendotdot: no .. entry...");
		return -1;
	}

	pf->xf = f->xf;
	pip->fmt = ip->fmt;
	pip->blksize = ip->blksize;
	pip->offset = 0;
	pip->doffset = 0;
	pip->d = *d;
	return 0;
}

enum {
	Hname = 1,
	Hmode = 2,
};

static int
rzdir(Xfs *fs, Dir *d, int fmt, Drec *dp)
{
	int n, flags, i, j, lj, nl, vers, sysl, mode, l, have;
	uchar *s;
	char *p;
	char buf[Maxname+UTFmax+1];
	uchar *q;
	Rune r;
	enum { ONAMELEN = 28 };	/* old Plan 9 directory name length */

	have = 0;
	flags = 0;
	vers = -1;
	d->qid.path = l32(dp->addr);
	d->qid.type = 0;
	d->qid.vers = 0;
	n = dp->namelen;
	memset(d->name, 0, Maxname);
	if(n == 1) {
		switch(dp->name[0]){
		case 1:
			d->name[1] = '.';
			/* fall through */
		case 0:
			d->name[0] = '.';
			have = Hname;
			break;
		default:
			d->name[0] = tolower(dp->name[0]);
		}
	} else {
		if(fmt == 'J'){	/* Joliet, 16-bit Unicode */
			q = (uchar*)dp->name;
			for(i=j=lj=0; i<n && j<Maxname; i+=2){
				lj = j;
				r = (q[i]<<8)|q[i+1];
				j += runetochar(buf+j, &r);
			}
			if(j >= Maxname)
				j = lj;
			memmove(d->name, buf, j);
		}else{
			if(n >= Maxname)
				n = Maxname-1;
			for(i=0; i<n; i++)
				d->name[i] = tolower(dp->name[i]);
		}
	}

	sysl = dp->reclen-(34+dp->namelen);
	s = (uchar*)dp->name + dp->namelen;
	if(((uintptr)s) & 1) {
		s++;
		sysl--;
	}
	if(fs->isplan9 && sysl > 0) {
		/*
		 * get gid, uid, mode and possibly name
		 * from plan9 directory extension
		 */
		nl = *s;
		if(nl >= ONAMELEN)
			nl = ONAMELEN-1;
		if(nl) {
			memset(d->name, 0, ONAMELEN);
			memmove(d->name, s+1, nl);
		}
		s += 1 + *s;
		nl = *s;
		if(nl >= ONAMELEN)
			nl = ONAMELEN-1;
		memset(d->uid, 0, ONAMELEN);
		memmove(d->uid, s+1, nl);
		s += 1 + *s;
		nl = *s;
		if(nl >= ONAMELEN)
			nl = ONAMELEN-1;
		memset(d->gid, 0, ONAMELEN);
		memmove(d->gid, s+1, nl);
		s += 1 + *s;
		if(((uintptr)s) & 1)
			s++;
		d->mode = l32(s);
		if(d->mode & DMDIR)
			d->qid.type |= QTDIR;
	} else {
		d->mode = 0444;
		switch(fmt) {
		case 'z':
			if(fs->isrock)
				strcpy(d->gid, "ridge");
			else
				strcpy(d->gid, "iso9660");
			flags = dp->flags;
			break;
		case 'r':
			strcpy(d->gid, "sierra");
			flags = dp->r_flags;
			break;
		case 'J':
			strcpy(d->gid, "joliet");
			flags = dp->flags;
			break;
		case '9':
			strcpy(d->gid, "plan9");
			flags = dp->flags;
			break;
		}
		if(flags & 0x02){
			d->qid.type |= QTDIR;
			d->mode |= DMDIR|0111;
		}
		strcpy(d->uid, "cdrom");
		if(fmt!='9' && !(d->mode&DMDIR)){
			/*
			 * ISO 9660 actually requires that you always have a . and a ;,
			 * even if there is no version and no extension.  Very few writers
			 * do this.  If the version is present, we use it for qid.vers.
			 * If there is no extension but there is a dot, we strip it off.
			 * (VMS heads couldn't comprehend the dot as a file name character
			 * rather than as just a separator between name and extension.)
			 *
			 * We don't do this for directory names because directories are
			 * not allowed to have extensions and versions.
			 */
			if((p=strchr(d->name, ';')) != nil){
				vers = strtoul(p+1, 0, 0);
				d->qid.vers = vers;
				*p = '\0';
			}
			if((p=strchr(d->name, '.')) != nil && *(p+1)=='\0')
				*p = '\0';
		}
		if(fs->issusp){
			nl = 0;
			s += fs->suspoff;
			sysl -= fs->suspoff;
			for(; sysl >= 4 && have != (Hname|Hmode); sysl -= l, s += l){
				if(s[0] == 0 && ((uintptr)s & 1)){
					/* MacOS pads individual entries, contrary to spec */
					s++;
					sysl--;
				}
				l = s[2];
				if(s[0] == 'P' && s[1] == 'X' && s[3] == 1){
					/* posix file attributes */
					mode = l32(s+4);
					d->mode = mode & 0777;
					if((mode & 0170000) == 040000){
						d->mode |= DMDIR;
						d->qid.type |= QTDIR;
					}
					have |= Hmode;
				} else if(s[0] == 'N' && s[1] == 'M' && s[3] == 1){
					/* alternative name */
					if((s[4] & ~1) == 0){
						i = nl+l-5;
						if(i >= Maxname)
							i = Maxname-1;
						if((i -= nl) > 0){
							memmove(d->name+nl, s+5, i);
							nl += i;
						}
						if(s[4] == 0)
							have |= Hname;
					}
				} else if(s[0] == 'C' && s[1] == 'E' && s[2] >= 28){
					sysl = getcontin(fs->d, s, &s);
					continue;
				} else if(s[0] == 'S' && s[1] == 'T')
					break;
			}
		}
	}
	d->length = 0;
	if((d->mode & DMDIR) == 0)
		d->length = l32(dp->size);
	d->type = 0;
	d->dev = 0;
	d->atime = gtime(dp->date);
	d->mtime = d->atime;
	return vers;
}

static int
getcontin(Xdata *dev, uchar *p, uchar **s)
{
	long bn, off, len;
	Iobuf *b;

	bn = l32(p+4);
	off = l32(p+12);
	len = l32(p+20);
	chat("getcontin %d...", bn);
	b = getbuf(dev, bn);
	if(b == 0){
		*s = 0;
		return 0;
	}
	*s = b->iobuf+off;
	putbuf(b);
	return len;
}

static char *
nstr(uchar *p, int n)
{
	static char buf[132];
	char *q = buf;

	while(--n >= 0){
		if(*p == '\\')
			*q++ = '\\';
		if(' ' <= *p && *p <= '~')
			*q++ = *p++;
		else
			q += sprint(q, "\\%2.2ux", *p++);
	}
	*q = 0;
	return buf;
}

static char *
rdate(uchar *p, int fmt)
{
	static char buf[64];
	int htz, s, n;

	n = sprint(buf, "%2.2d.%2.2d.%2.2d %2.2d:%2.2d:%2.2d",
		p[0], p[1], p[2], p[3], p[4], p[5]);
	if(fmt == 'z'){
		htz = p[6];
		if(htz >= 128){
			htz = 256-htz;
			s = '-';
		}else
			s = '+';
		sprint(&buf[n], " (%c%.1f)", s, (float)htz/2);
	}
	return buf;
}

static char
dmsize[12] =
{
	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
};

static int
dysize(int y)
{

	if((y%4) == 0)
		return 366;
	return 365;
}

static long
gtime(uchar *p)	/* yMdhmsz */
{
	long t;
	int i, y, M, d, h, m, s, tz;
	y=p[0]; M=p[1]; d=p[2];
	h=p[3]; m=p[4]; s=p[5]; tz=p[6];
	USED(tz);
	if (y < 70)
		return 0;
	if (M < 1 || M > 12)
		return 0;
	if (d < 1 || d > dmsize[M-1])
		return 0;
	if (h > 23)
		return 0;
	if (m > 59)
		return 0;
	if (s > 59)
		return 0;
	y += 1900;
	t = 0;
	for(i=1970; i<y; i++)
		t += dysize(i);
	if (dysize(y)==366 && M >= 3)
		t++;
	while(--M)
		t += dmsize[M-1];
	t += d-1;
	t = 24*t + h;
	t = 60*t + m;
	t = 60*t + s;
	return t;
}

#define	p	((uchar*)arg)

static long
l16(void *arg)
{
	long v;

	v = ((long)p[1]<<8)|p[0];
	if (v >= 0x8000L)
		v -= 0x10000L;
	return v;
}

static long
l32(void *arg)
{
	return ((((((long)p[3]<<8)|p[2])<<8)|p[1])<<8)|p[0];
}

#undef	p