dosfs.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

#include <u.h>
#include <libc.h>
#include <auth.h>
#include <fcall.h>
#include "iotrack.h"
#include "dat.h"
#include "dosfs.h"
#include "fns.h"

void
rversion(void)
{
	if(req->msize > Maxiosize)
		rep->msize = Maxiosize;
	else
		rep->msize = req->msize;
	rep->version = "9P2000";
}

void
rauth(void)
{
	errno = Enoauth;
}

void
rflush(void)
{
}

void
rattach(void)
{
	Xfs *xf;
	Xfile *root;
	Dosptr *dp;

	root = xfile(req->fid, Clean);
	if(!root){
		errno = Enomem;
		goto error;
	}
	root->xf = xf = getxfs(req->uname, req->aname);
	if(!xf)
		goto error;
	if(xf->fmt == 0 && dosfs(xf) < 0){
		errno = Eformat;
		goto error;
	}
	root->qid.type = QTDIR;
	root->qid.path = 0;
	root->qid.vers = 0;
	root->xf->rootqid = root->qid;
	dp = malloc(sizeof(Dosptr));
	if(dp == nil){
		errno = Enomem;
		goto error;
	}
	root->ptr = dp;
	rootfile(root);
	rep->qid = root->qid;
	return;
error:
	if(root)
		xfile(req->fid, Clunk);
}

Xfile*
doclone(Xfile *of, int newfid)
{
	Xfile *nf, *next;
	Dosptr *dp;

	nf = xfile(newfid, Clean);
	if(!nf){
		errno = Enomem;
		return nil;
	}
	dp = malloc(sizeof(Dosptr));
	if(dp == nil){
		errno = Enomem;
		return nil;
	}
	next = nf->next;
	*nf = *of;
	nf->next = next;
	nf->fid = req->newfid;
	nf->ptr = dp;
	refxfs(nf->xf, 1);
	memmove(dp, of->ptr, sizeof(Dosptr));
	dp->p = nil;
	dp->d = nil;
	return nf;
}

void
rwalk(void)
{
	Xfile *f, *nf;
	Dosptr dp[1], savedp[1];
	int r, longtype;
	Qid saveqid;

	rep->nwqid = 0;
	nf = nil;
	f = xfile(req->fid, Asis);
	if(f == nil){
		chat("\tno xfile\n");
		goto error2;
	}
	if(req->fid != req->newfid){
		nf = doclone(f, req->newfid);
		if(nf == nil){
			chat("\tclone failed\n");
			goto error2;
		}
		f = nf;
	}

	saveqid = f->qid;
	memmove(savedp, f->ptr, sizeof(Dosptr));
	for(; rep->nwqid < req->nwname && rep->nwqid < MAXWELEM; rep->nwqid++){
		chat("\twalking %s\n", req->wname[rep->nwqid]);
		if(!(f->qid.type & QTDIR)){
			chat("\tnot dir: type=%#x\n", f->qid.type);
			goto error;
		}
		if(strcmp(req->wname[rep->nwqid], ".") == 0){
			;
		}else if(strcmp(req->wname[rep->nwqid], "..") == 0){
			if(f->qid.path != f->xf->rootqid.path){
				r = walkup(f, dp);
				if(r < 0)
					goto error;
				memmove(f->ptr, dp, sizeof(Dosptr));
				if(isroot(dp->addr))
					f->qid.path = f->xf->rootqid.path;
				else
					f->qid.path = QIDPATH(dp);
			}
		}else{
			fixname(req->wname[rep->nwqid]);
			longtype = classifyname(req->wname[rep->nwqid]);
			if(longtype==Invalid || getfile(f) < 0)
				goto error;

			/*
			 * always do a search for the long name,
			 * because it could be filed as such
			 */
			r = searchdir(f, req->wname[rep->nwqid], dp, 0, longtype);
			putfile(f);
			if(r < 0)
				goto error;
			memmove(f->ptr, dp, sizeof(Dosptr));
			f->qid.path = QIDPATH(dp);
			f->qid.type = QTFILE;
			if(isroot(dp->addr))
				f->qid.path = f->xf->rootqid.path;
			else if(dp->d->attr & DDIR)
				f->qid.type = QTDIR;
			else if(dp->d->attr & DSYSTEM){
				f->qid.type |= QTEXCL;
				if(iscontig(f->xf, dp->d))
					f->qid.type |= QTAPPEND;
			}
//ZZZ maybe use other bits than qtexcl & qtapppend
			putfile(f);
		}
		rep->wqid[rep->nwqid] = f->qid;
	}
	return;
error:
	f->qid = saveqid;
	memmove(f->ptr, savedp, sizeof(Dosptr));
	if(nf != nil)
		xfile(req->newfid, Clunk);
error2:
	if(!errno && !rep->nwqid)
		errno = Enonexist;
}

void
ropen(void)
{
	Xfile *f;
	Iosect *p;
	Dosptr *dp;
	int attr, omode;

	f = xfile(req->fid, Asis);
	if(!f || (f->flags&Omodes)){
		errno = Eio;
		return;
	}
	dp = f->ptr;
	omode = 0;
	if(!isroot(dp->paddr) && (req->mode & ORCLOSE)){
		/*
		 * check on parent directory of file to be deleted
		 */
		p = getsect(f->xf, dp->paddr);
		if(p == nil){
			errno = Eio;
			return;
		}
		attr = ((Dosdir *)&p->iobuf[dp->poffset])->attr;
		putsect(p);
		if(attr & DRONLY){
			errno = Eperm;
			return;
		}
		omode |= Orclose;
	}else if(req->mode & ORCLOSE)
		omode |= Orclose;
	if(getfile(f) < 0){
		errno = Enonexist;
		return;
	}
	if(!isroot(dp->addr))
		attr = dp->d->attr;
	else
		attr = DDIR;
	switch(req->mode & 7){
	case OREAD:
	case OEXEC:
		omode |= Oread;
		break;
	case ORDWR:
		omode |= Oread;
		/* fall through */
	case OWRITE:
		omode |= Owrite;
		if(attr & DRONLY){
			errno = Eperm;
			goto out;
		}
		break;
	default:
		errno = Eio;
		goto out;
	}
	if(req->mode & OTRUNC){
		if(attr & DDIR || attr & DRONLY){
			errno = Eperm;
			goto out;
		}
		if(truncfile(f, 0) < 0){
			errno = Eio;
			goto out;
		}
	}
	f->flags |= omode;
	rep->qid = f->qid;
	rep->iounit = 0;
out:
	putfile(f);
}

static int
mk8dot3name(Xfile *f, Dosptr *ndp, char *name, char *sname)
{
	Dosptr tmpdp;
	int i, longtype;

	if(strcmp(name, ".") == 0 || strcmp(name, "..") == 0)
		return Invalid;

	/*
	 * always do a search for the long name,
	 * because it could be filed as such
	 */
	fixname(name);
	longtype = classifyname(name);
	if(longtype==Invalid || searchdir(f, name, ndp, 1, longtype) < 0)
		return Invalid;

	if(longtype==Short)
		return Short;

	if(longtype==ShortLower){
		/*
		 * alias is the upper-case version, which we
		 * already know does not exist.
		 */
		strcpy(sname, name);
		for(i=0; sname[i]; i++)
			if('a' <= sname[i] && sname[i] <= 'z')
				sname[i] += 'A'-'a';
		return ShortLower;
	}

	/*
	 * find alias for the long name
	 */
	for(i=1;; i++){
		mkalias(name, sname, i);
		if(searchdir(f, sname, &tmpdp, 0, 0) < 0)
			return Long;
		putsect(tmpdp.p);
	}
}

/*
 * fill in a directory entry for a new file
 */
static int
mkdentry(Xfs *xf, Dosptr *ndp, char *name, char *sname, int longtype, int nattr, long start, long length)
{
	Dosdir *nd;

	/*
	 * fill in the entry
	 */
	ndp->p = getsect(xf, ndp->addr);
	if(ndp->p == nil
	|| longtype!=Short && putlongname(xf, ndp, name, sname) < 0){
		errno = Eio;
		return -1;
	}

	ndp->d = (Dosdir *)&ndp->p->iobuf[ndp->offset];
	nd = ndp->d;
	memset(nd, 0, DOSDIRSIZE);

	if(longtype!=Short)
		name = sname;
	putname(name, nd);

	nd->attr = nattr;
	puttime(nd, 0);
	putstart(xf, nd, start);
	nd->length[0] = length;
	nd->length[1] = length>>8;
	nd->length[2] = length>>16;
	nd->length[3] = length>>24;

	ndp->p->flags |= BMOD;

	return 0;
}

void
rcreate(void)
{
	Dosbpb *bp;
	Xfile *f;
	Dosptr *pdp, *ndp;
	Iosect *xp;
	Dosdir *pd, *xd;
	char sname[13];
	long start;
	int longtype, attr, omode, nattr;

	f = xfile(req->fid, Asis);
	if(!f || (f->flags&Omodes) || getfile(f)<0){
		errno = Eio;
		return;
	}
	pdp = f->ptr;
	pd = pdp->d;
	/*
	 * perm check
	 */
	if(isroot(pdp->addr) && pd != nil)
		panic("root pd != nil");
	attr = pd ? pd->attr : DDIR;
	if(!(attr & DDIR) || (attr & DRONLY)){
badperm:
		putfile(f);
		errno = Eperm;
		return;
	}
	omode = 0;
	if(req->mode & ORCLOSE)
		omode |= Orclose;
	switch(req->mode & 7){
	case OREAD:
	case OEXEC:
		omode |= Oread;
		break;
	case ORDWR:
		omode |= Oread;
		/* fall through */
	case OWRITE:
		omode |= Owrite;
		if(req->perm & DMDIR)
			goto badperm;
		break;
	default:
		goto badperm;
	}

	/*
	 * check the name, find the slot for the dentry,
	 * and find a good alias for a long name
	 */
	ndp = malloc(sizeof(Dosptr));
	if(ndp == nil){
		putfile(f);
		errno = Enomem;
		return;
	}
	longtype = mk8dot3name(f, ndp, req->name, sname);
	chat("rcreate %s longtype %d...\n", req->name, longtype);
	if(longtype == Invalid){
		free(ndp);
		goto badperm;
	}

	/*
	 * allocate first cluster, if making directory
	 */
	start = 0;
	bp = nil;
	if(req->perm & DMDIR){
		bp = f->xf->ptr;
		mlock(bp);
		start = falloc(f->xf);
		unmlock(bp);
		if(start <= 0){
			free(ndp);
			putfile(f);
			errno = Eio;
			return;
		}
	}

	/*
	 * make the entry
	 */
	nattr = 0;
	if((req->perm & 0222) == 0)
		nattr |= DRONLY;
	if(req->perm & DMDIR)
		nattr |= DDIR;

	if(mkdentry(f->xf, ndp, req->name, sname, longtype, nattr, start, 0) < 0){
		if(ndp->p != nil)
			putsect(ndp->p);
		free(ndp);
		if(start > 0)
			ffree(f->xf, start);
		putfile(f);
		return;
	}

	if(pd != nil){
		puttime(pd, 0);
		pdp->p->flags |= BMOD;
	}

	/*
	 * fix up the fid
	 */
	f->ptr = ndp;
	f->qid.type = QTFILE;
	f->qid.path = QIDPATH(ndp);