fs.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 "common.h"
#include <auth.h>
#include <fcall.h>
#include <libsec.h>
#include <ctype.h>
#include "dat.h"

enum
{
	OPERM	= 0x3,		// mask of all permission types in open mode
};

typedef struct Fid Fid;

struct Fid
{
	Qid	qid;
	short	busy;
	short	open;
	int	fid;
	Fid	*next;
	Mailbox	*mb;
	Message	*m;
	Message *mtop;		// top level message

	//finger pointers to speed up reads of large directories
	long	foff;	// offset/DIRLEN of finger
	Message	*fptr;	// pointer to message at off
	int	fvers;	// mailbox version when finger was saved
};

ulong	path;		// incremented for each new file
Fid	*fids;
int	mfd[2];
char	user[Elemlen];
int	messagesize = 4*1024*IOHDRSZ;
uchar	mdata[8*1024*IOHDRSZ];
uchar	mbuf[8*1024*IOHDRSZ];
Fcall	thdr;
Fcall	rhdr;
int	fflg;
char	*mntpt;
int	biffing;
int	plumbing = 1;

QLock	mbllock;
Mailbox	*mbl;

Fid		*newfid(int);
void		error(char*);
void		io(void);
void		*erealloc(void*, ulong);
void		*emalloc(ulong);
void		usage(void);
void		reader(void);
int		readheader(Message*, char*, int, int);
int		cistrncmp(char*, char*, int);
int		tokenconvert(String*, char*, int);
String*		stringconvert(String*, char*, int);
void		post(char*, char*, int);

char	*rflush(Fid*), *rauth(Fid*),
	*rattach(Fid*), *rwalk(Fid*),
	*ropen(Fid*), *rcreate(Fid*),
	*rread(Fid*), *rwrite(Fid*), *rclunk(Fid*),
	*rremove(Fid*), *rstat(Fid*), *rwstat(Fid*),
	*rversion(Fid*);

char 	*(*fcalls[])(Fid*) = {
	[Tflush]	rflush,
	[Tversion]	rversion,
	[Tauth]	rauth,
	[Tattach]	rattach,
	[Twalk]		rwalk,
	[Topen]		ropen,
	[Tcreate]	rcreate,
	[Tread]		rread,
	[Twrite]	rwrite,
	[Tclunk]	rclunk,
	[Tremove]	rremove,
	[Tstat]		rstat,
	[Twstat]	rwstat,
};

char	Eperm[] =	"permission denied";
char	Enotdir[] =	"not a directory";
char	Enoauth[] =	"upas/fs: authentication not required";
char	Enotexist[] =	"file does not exist";
char	Einuse[] =	"file in use";
char	Eexist[] =	"file exists";
char	Enotowner[] =	"not owner";
char	Eisopen[] = 	"file already open for I/O";
char	Excl[] = 	"exclusive use file already open";
char	Ename[] = 	"illegal name";
char	Ebadctl[] =	"unknown control message";

char *dirtab[] =
{
[Qdir]		".",
[Qbody]		"body",
[Qbcc]		"bcc",
[Qcc]		"cc",
[Qdate]		"date",
[Qdigest]	"digest",
[Qdisposition]	"disposition",
[Qfilename]	"filename",
[Qfrom]		"from",
[Qheader]	"header",
[Qinfo]		"info",
[Qinreplyto]	"inreplyto",
[Qlines]	"lines",
[Qmimeheader]	"mimeheader",
[Qmessageid]	"messageid",
[Qraw]		"raw",
[Qrawunix]	"rawunix",
[Qrawbody]	"rawbody",
[Qrawheader]	"rawheader",
[Qreplyto]	"replyto",
[Qsender]	"sender",
[Qsubject]	"subject",
[Qto]		"to",
[Qtype]		"type",
[Qunixdate]	"unixdate",
[Qunixheader]	"unixheader",
[Qctl]		"ctl",
[Qmboxctl]	"ctl",
};

enum
{
	Hsize=	1277,
};

Hash	*htab[Hsize];

int	debug;
int	fflag;
int	logging;

void
usage(void)
{
	fprint(2, "usage: upas/fs [-bdlnps] [-f mboxfile] [-m mountpoint]\n");
	exits("usage");
}

void
notifyf(void *a, char *s)
{
	USED(a);
	if(strncmp(s, "interrupt", 9) == 0)
		noted(NCONT);
	noted(NDFLT);
}

void
main(int argc, char *argv[])
{
	int p[2], std, nodflt;
	char maildir[128];
	char mbox[128];
	char *mboxfile, *err;
	char srvfile[64];
	int srvpost;

	rfork(RFNOTEG);
	mntpt = nil;
	fflag = 0;
	mboxfile = nil;
	std = 0;
	nodflt = 0;
	srvpost = 0;

	ARGBEGIN{
	case 'b':
		biffing = 1;
		break;
	case 'f':
		fflag = 1;
		mboxfile = EARGF(usage());
		break;
	case 'm':
		mntpt = EARGF(usage());
		break;
	case 'd':
		debug = 1;
		break;
	case 'p':
		plumbing = 0;
		break;
	case 's':
		srvpost = 1;
		break;
	case 'l':
		logging = 1;
		break;
	case 'n':
		nodflt = 1;
		break;
	default:
		usage();
	}ARGEND

	if(argc)
		usage();
	if(pipe(p) < 0)
		error("pipe failed");
	mfd[0] = p[0];
	mfd[1] = p[0];

	notify(notifyf);
	strcpy(user, getuser());
	if(mntpt == nil){
		snprint(maildir, sizeof(maildir), "/mail/fs");
		mntpt = maildir;
	}
	if(mboxfile == nil && !nodflt){
		snprint(mbox, sizeof(mbox), "/mail/box/%s/mbox", user);
		mboxfile = mbox;
		std = 1;
	}

	if(debug)
		fmtinstall('F', fcallfmt);

	if(mboxfile != nil){
		err = newmbox(mboxfile, "mbox", std);
		if(err != nil)
			sysfatal("opening mailbox: %s", err);
	}

	switch(rfork(RFFDG|RFPROC|RFNAMEG|RFNOTEG|RFREND)){
	case -1:
		error("fork");
	case 0:
		henter(PATH(0, Qtop), dirtab[Qctl],
			(Qid){PATH(0, Qctl), 0, QTFILE}, nil, nil);
		close(p[1]);
		io();
		postnote(PNGROUP, getpid(), "die yankee pig dog");
		break;
	default:
		close(p[0]);	/* don't deadlock if child fails */
		if(srvpost){
			sprint(srvfile, "/srv/upasfs.%s", user);
			post(srvfile, "upasfs", p[1]);
		} else {
			if(mount(p[1], -1, mntpt, MREPL, "") < 0)
				error("mount failed");
		}
	}
	exits(0);
}

static int
fileinfo(Message *m, int t, char **pp)
{
	char *p;
	int len;

	p = "";
	len = 0;
	switch(t){
	case Qbody:
		p = m->body;
		len = m->bend - m->body;
		break;
	case Qbcc:
		if(m->bcc822){
			p = s_to_c(m->bcc822);
			len = strlen(p);
		}
		break;
	case Qcc:
		if(m->cc822){
			p = s_to_c(m->cc822);
			len = strlen(p);
		}
		break;
	case Qdisposition:
		switch(m->disposition){
		case Dinline:
			p = "inline";
			break;
		case Dfile:
			p = "file";
			break;
		}
		len = strlen(p);
		break;
	case Qdate:
		if(m->date822){
			p = s_to_c(m->date822);
			len = strlen(p);
		} else if(m->unixdate != nil){
			p = s_to_c(m->unixdate);
			len = strlen(p);
		}
		break;
	case Qfilename:
		if(m->filename){
			p = s_to_c(m->filename);
			len = strlen(p);
		}
		break;
	case Qinreplyto:
		if(m->inreplyto822){
			p = s_to_c(m->inreplyto822);
			len = strlen(p);
		}
		break;
	case Qmessageid:
		if(m->messageid822){
			p = s_to_c(m->messageid822);
			len = strlen(p);
		}
		break;
	case Qfrom:
		if(m->from822){
			p = s_to_c(m->from822);
			len = strlen(p);
		} else if(m->unixfrom != nil){
			p = s_to_c(m->unixfrom);
			len = strlen(p);
		}
		break;
	case Qheader:
		p = m->header;
		len = headerlen(m);
		break;
	case Qlines:
		p = m->lines;
		if(*p == 0)
			countlines(m);
		len = strlen(m->lines);
		break;
	case Qraw:
		p = m->start;
		if(strncmp(m->start, "From ", 5) == 0){
			p = strchr(p, '\n');
			if(p == nil)
				p = m->start;
			else
				p++;
		}
		len = m->end - p;
		break;
	case Qrawunix:
		p = m->start;
		len = m->end - p;
		break;
	case Qrawbody:
		p = m->rbody;
		len = m->rbend - p;
		break;
	case Qrawheader:
		p = m->header;
		len = m->hend - p;
		break;
	case Qmimeheader:
		p = m->mheader;
		len = m->mhend - p;
		break;
	case Qreplyto:
		p = nil;
		if(m->replyto822 != nil){
			p = s_to_c(m->replyto822);
			len = strlen(p);
		} else if(m->from822 != nil){
			p = s_to_c(m->from822);
			len = strlen(p);
		} else if(m->sender822 != nil){
			p = s_to_c(m->sender822);
			len = strlen(p);
		} else if(m->unixfrom != nil){
			p = s_to_c(m->unixfrom);
			len = strlen(p);
		}
		break;
	case Qsender:
		if(m->sender822){
			p = s_to_c(m->sender822);
			len = strlen(p);
		}
		break;
	case Qsubject:
		p = nil;
		if(m->subject822){
			p = s_to_c(m->subject822);
			len = strlen(p);
		}
		break;
	case Qto:
		if(m->to822){
			p = s_to_c(m->to822);
			len = strlen(p);
		}
		break;
	case Qtype:
		if(m->type){
			p = s_to_c(m->type);
			len = strlen(p);
		}
		break;
	case Qunixdate:
		if(m->unixdate){
			p = s_to_c(m->unixdate);
			len = strlen(p);
		}
		break;
	case Qunixheader:
		if(m->unixheader){
			p = s_to_c(m->unixheader);
			len = s_len(m->unixheader);
		}
		break;
	case Qdigest:
		if(m->sdigest){
			p = s_to_c(m->sdigest);
			len = strlen(p);
		}
		break;
	}
	*pp = p;
	return len;
}

int infofields[] = {
	Qfrom,
	Qto,
	Qcc,
	Qreplyto,
	Qunixdate,
	Qsubject,
	Qtype,
	Qdisposition,
	Qfilename,
	Qdigest,
	Qbcc,
	Qinreplyto,
	Qdate,
	Qsender,
	Qmessageid,
	Qlines,
	-1,
};

static int
readinfo(Message *m, char *buf, long off, int count)
{
	char *p;
	int len, i, n;
	String *s;

	s = s_new();
	len = 0;
	for(i = 0; len < count && infofields[i] >= 0; i++){
		n = fileinfo(m, infofields[i], &p);
		s = stringconvert(s, p, n);
		s_append(s, "\n");
		p = s_to_c(s);
		n = strlen(p);
		if(off > 0){
			if(off >= n){
				off -= n;
				continue;
			}
			p += off;
			n -= off;
			off = 0;
		}
		if(n > count - len)
			n = count - len;
		if(buf)
			memmove(buf+len, p, n);
		len += n;
	}
	s_free(s);
	return len;
}

static void
mkstat(Dir *d, Mailbox *mb, Message *m, int t)
{
	char *p;

	d->uid = user;
	d->gid = user;
	d->muid = user;
	d->mode = 0444;
	d->qid.vers = 0;
	d->qid.type = QTFILE;
	d->type = 0;
	d->dev = 0;
	if(mb != nil && mb->d != nil){
		d->atime = mb->d->atime;
		d->mtime = mb->d->mtime;
	} else {
		d->atime = time(0);
		d->mtime = d->atime;
	}

	switch(t){
	case Qtop:
		d->name = ".";
		d->mode = DMDIR|0555;
		d->atime = d->mtime = time(0);
		d->length = 0;
		d->qid.path = PATH(0, Qtop);
		d->qid.type = QTDIR;
		break;
	case Qmbox:
		d->name = mb->name;
		d->mode = DMDIR|0555;
		d->length = 0;
		d->qid.path = PATH(mb->id, Qmbox);
		d->qid.type = QTDIR;
		d->qid.vers = mb->vers;
		break;
	case Qdir:
		d->name = m->name;
		d->mode = DMDIR|0555;
		d->length = 0;
		d->qid.path = PATH(m->id, Qdir);
		d->qid.type = QTDIR;
		break;
	case Qctl:
		d->name = dirtab[t];
		d->mode = 0666;
		d->atime = d->mtime = time(0);
		d->length = 0;
		d->qid.path = PATH(0, Qctl);
		break;
	case Qmboxctl:
		d->name = dirtab[t];
		d->mode = 0222;
		d->atime = d->mtime = time(0);
		d->length = 0;
		d->qid.path = PATH(mb->id, Qmboxctl);
		break;
	case Qinfo:
		d->name = dirtab[t];
		d->length = readinfo(m, nil, 0, 1<<30);
		d->qid.path = PATH(m->id, t);
		break;
	default:
		d->name = dirtab[t];
		d->length = fileinfo(m, t, &p);
		d->qid.path = PATH(m->id, t);
		break;
	}
}

char*
rversion(Fid*)
{
	Fid *f;

	if(thdr.msize < 256)
		return "max messagesize too small";
	if(thdr.msize < messagesize)
		messagesize = thdr.msize;
	rhdr.msize = messagesize;
	if(strncmp(thdr.version, "9P2000", 6) != 0)
		return "unknown 9P version";
	else
		rhdr.version = "9P2000";
	for(f = fids; f; f = f->next)
		if(f->busy)
			rclunk(f);
	return nil;
}

char*
rauth(Fid*)
{
	return Enoauth;
}

char*
rflush(Fid *f)
{
	USED(f);
	return 0;
}

char*
rattach(Fid *f)
{
	f->busy = 1;
	f->m = nil;
	f->mb = nil;
	f->qid.path = PATH(0, Qtop);
	f->qid.type = QTDIR;
	f->qid.vers = 0;
	rhdr.qid = f->qid;
	if(strcmp(thdr.uname, user) != 0)
		return Eperm;
	return 0;
}

static Fid*
doclone(Fid *f, int nfid)
{
	Fid *nf;

	nf = newfid(nfid);
	if(nf->busy)
		return nil;
	nf->busy = 1;
	nf->open = 0;
	nf->m = f->m;
	nf->mtop = f->mtop;
	nf->mb = f->mb;
	if(f->mb != nil)
		mboxincref(f->mb);
	if(f->mtop != nil){
		qlock(f->mb);
		msgincref(f->mtop);
		qunlock(f->mb);
	}
	nf->qid = f->qid;
	return nf;
}

char*
dowalk(Fid *f, char *name)
{
	int t;
	Mailbox *omb, *mb;
	char *rv, *p;
	Hash *h;

	t = FILE(f->qid.path);

	rv = Enotexist;

	omb = f->mb;
	if(omb)
		qlock(omb);
	else
		qlock(&mbllock);

	// this must catch everything except . and ..
retry:
	h = hlook(f->qid.path, name);
	if(h != nil){
		f->mb = h->mb;
		f->m = h->m;
		switch(t){
		case Qtop:
			if(f->mb != nil)
				mboxincref(f->mb);
			break;
		case Qmbox:
			if(f->m){
				msgincref(f->m);
				f->mtop = f->m;
			}
			break;
		}
		f->qid = h->qid;
		rv = nil;
	} else if((p = strchr(name, '.')) != nil && *name != '.'){
		*p = 0;
		goto retry;
	}

	if(omb)
		qunlock(omb);
	else
		qunlock(&mbllock);
	if(rv == nil)
		return rv;

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

	if(f->qid.type != QTDIR)
		return Enotdir;

	if(strcmp(name, "..") == 0){
		switch(t){
		case Qtop:
			f->qid.path = PATH(0, Qtop);
			f->qid.type = QTDIR;
			f->qid.vers = 0;
			break;
		case Qmbox:
			f->qid.path = PATH(0, Qtop);
			f->qid.type = QTDIR;
			f->qid.vers = 0;
			qlock(&mbllock);
			mb = f->mb;
			f->mb = nil;
			mboxdecref(mb);
			qunlock(&mbllock);
			break;
		case Qdir:
			qlock(f->mb);
			if(f->m->whole == f->mb->root){
				f->qid.path = PATH(f->mb->id, Qmbox);
				f->qid.type = QTDIR;
				f->qid.vers = f->mb->d->qid.vers;
				msgdecref(f->mb, f->mtop);
				f->m = f->mtop = nil;
			} else {
				f->m = f->m->whole;
				f->qid.path = PATH(f->m->id, Qdir);
				f->qid.type = QTDIR;
			}
			qunlock(f->mb);
			break;
		}
		rv = nil;
	}
	return rv;
}

char*
rwalk(Fid *f)
{
	Fid *nf;
	char *rv;
	int i;

	if(f->open)
		return Eisopen;

	rhdr.nwqid = 0;
	nf = nil;

	/* clone if requested */
	if(thdr.newfid != thdr.fid){
		nf = doclone(f, thdr.newfid);
		if(nf == nil)
			return "new fid in use";
		f = nf;
	}

	/* if it's just a clone, return */
	if(thdr.nwname == 0 && nf != nil)
		return nil;

	/* walk each element */
	rv = nil;
	for(i = 0; i < thdr.nwname; i++){
		rv = dowalk(f, thdr.wname[i]);
		if(rv != nil){
			if(nf != nil)	
				rclunk(nf);
			break;
		}
		rhdr.wqid[i] = f->qid;
	}
	rhdr.nwqid = i;

	/* we only error out if no walk  */
	if(i > 0)
		rv = nil;

	return rv;
}

char *
ropen(Fid *f)
{
	int file;

	if(f->open)
		return Eisopen;

	file = FILE(f->qid.path);
	if(thdr.mode != OREAD)
		if(file != Qctl && file != Qmboxctl)
			return Eperm;

	// make sure we've decoded
	if(file == Qbody){
		if(f->m->decoded == 0)
			decode(f->m);
		if(f->m->converted == 0)
			convert(f->m);
	}

	rhdr.iounit = 0;
	rhdr.qid = f->qid;
	f->open = 1;
	return 0;
}

char *
rcreate(Fid*)
{
	return Eperm;
}

int
readtopdir(Fid*, uchar *buf, long off, int cnt, int blen)
{
	Dir d;
	int m, n;
	long pos;
	Mailbox *mb;

	n = 0;
	pos = 0;
	mkstat(&d, nil, nil, Qctl);
	m = convD2M(&d, &buf[n], blen);
	if(off <= pos){
		if(m <= BIT16SZ || m > cnt)
			return 0;
		n += m;
		cnt -= m;
	}
	pos += m;
		
	for(mb = mbl; mb != nil; mb = mb->next){
		mkstat(&d, mb, nil, Qmbox);
		m = convD2M(&d, &buf[n], blen-n);
		if(off <= pos){
			if(m <= BIT16SZ || m > cnt)
				break;
			n += m;
			cnt -= m;
		}