searchfs.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

		free(q->pat);
	q->pat = nil;
}

char *
quicksearch(Quick *q, char *s, char *e)
{
	char *pat, *up, *m, *ee;
	uchar *j;
	int len, n, c, mc;

	len = q->len;
	if(len < 0)
		return s;
	j = q->jump;
	pat = q->pat;
	up = q->up;
	s += len;
	ee = e - (len * 4 + 4);
	while(s < e){
		/*
		 * look for a match on the last char
		 */
		while(s < ee && (n = j[(uchar)*s])){
			s += n;
			s += j[(uchar)*s];
			s += j[(uchar)*s];
			s += j[(uchar)*s];
		}
		if(s >= e)
			return nil;
		while(n = j[(uchar)*s]){
			s += n;
			if(s >= e)
				return nil;
		}

		/*
		 * does the string match?
		 */
		m = s - len;
		for(n = 0; c = pat[n]; n++){
			mc = *m++;
			if(c != mc && mc != up[n])
				break;
		}
		if(!c)
			return s - len;
		s += q->miss;
	}
	return nil;
}

void
fsrun(Fs *fs, int fd)
{
	Fcall rpc;
	char *err;
	uchar *buf;
	int n;

	buf = emalloc(messagesize);
	for(;;){
		/*
		 * reading from a pipe or a network device
		 * will give an error after a few eof reads
		 * however, we cannot tell the difference
		 * between a zero-length read and an interrupt
		 * on the processes writing to us,
		 * so we wait for the error
		 */
		n = read9pmsg(fd, buf, messagesize);
		if(n == 0)
			continue;
		if(n < 0)
			fatal("mount read");

		rpc.data = (char*)buf + IOHDRSZ;
		if(convM2S(buf, n, &rpc) == 0)
			continue;
		// fprint(2, "recv: %F\n", &rpc);


		/*
		 * flushes are way too hard.
		 * a reply to the original message seems to work
		 */
		if(rpc.type == Tflush)
			continue;
		else if(rpc.type >= Tmax || !fcalls[rpc.type])
			err = "bad fcall type";
		else
			err = (*fcalls[rpc.type])(fs, &rpc);
		if(err){
			rpc.type = Rerror;
			rpc.ename = err;
		}else
			rpc.type++;
		n = convS2M(&rpc, buf, messagesize);
		// fprint(2, "send: %F\n", &rpc);
		if(write(fd, buf, n) != n)
			fatal("mount write");
	}
}

Fid*
mkfid(Fs *fs, uint fid)
{
	Fid *f;
	int h;

	h = fid % Nfidhash;
	for(f = fs->hash[h]; f; f = f->next){
		if(f->fid == fid)
			return nil;
	}

	f = emalloc(sizeof *f);
	f->next = fs->hash[h];
	if(f->next != nil)
		f->next->last = &f->next;
	f->last = &fs->hash[h];
	fs->hash[h] = f;

	f->fid = fid;
	f->ref = 1;
	f->attached = 1;
	f->open = 0;
	return f;
}

Fid*
getfid(Fs *fs, uint fid)
{
	Fid *f;
	int h;

	h = fid % Nfidhash;
	for(f = fs->hash[h]; f; f = f->next){
		if(f->fid == fid){
			if(f->attached == 0)
				break;
			f->ref++;
			return f;
		}
	}
	return nil;
}

void
putfid(Fs *, Fid *f)
{
	f->ref--;
	if(f->ref == 0 && f->attached == 0){
		*f->last = f->next;
		if(f->next != nil)
			f->next->last = f->last;
		if(f->search != nil)
			searchfree(f->search);
		free(f);
	}
}

char*
fsversion(Fs *, Fcall *rpc)
{
	if(rpc->msize < 256)
		return "version: message size too small";
	if(rpc->msize > messagesize)
		rpc->msize = messagesize;
	messagesize = rpc->msize;
	if(strncmp(rpc->version, "9P2000", 6) != 0)
		return "unrecognized 9P version";
	rpc->version = "9P2000";
	return nil;
}

char*
fsauth(Fs *, Fcall *)
{
	return "searchfs: authentication not required";
}

char*
fsattach(Fs *fs, Fcall *rpc)
{
	Fid *f;

	f = mkfid(fs, rpc->fid);
	if(f == nil)
		return Einuse;
	f->open = 0;
	f->qid.type = QTDIR;
	f->qid.path = Qroot;
	f->qid.vers = 0;
	rpc->qid = f->qid;
	putfid(fs, f);
	return nil;
}

char*
fswalk(Fs *fs, Fcall *rpc)
{
	Fid *f, *nf;
	int nqid, nwname, type;
	char *err, *name;
	ulong path;

	f = getfid(fs, rpc->fid);
	if(f == nil)
		return Enofid;
	nf = nil;
	if(rpc->fid != rpc->newfid){
		nf = mkfid(fs, rpc->newfid);
		if(nf == nil){
			putfid(fs, f);
			return Einuse;
		}
		nf->qid = f->qid;
		putfid(fs, f);
		f = nf;	/* walk f */
	}

	err = nil;
	path = f->qid.path;
	nwname = rpc->nwname;
	for(nqid=0; nqid<nwname; nqid++){
		if(path != Qroot){
			err = Enotdir;
			break;
		}
		name = rpc->wname[nqid];
		if(strcmp(name, "search") == 0){
			type = QTFILE;
			path = Qsearch;
		}else if(strcmp(name, "stats") == 0){
			type = QTFILE;
			path = Qstats;
		}else if(strcmp(name, ".") == 0 || strcmp(name, "..") == 0){
			type = QTDIR;
			path = path;
		}else{
			err = Enotexist;
			break;
		}
		rpc->wqid[nqid] = (Qid){path, 0, type};
	}

	if(nwname > 0){
		if(nf != nil && nqid < nwname)
			nf->attached = 0;
		if(nqid == nwname)
			f->qid = rpc->wqid[nqid-1];
	}

	putfid(fs, f);
	rpc->nwqid = nqid;
	f->open = 0;
	return err;
}

char *
fsopen(Fs *fs, Fcall *rpc)
{
	Fid *f;
	int mode;

	f = getfid(fs, rpc->fid);
	if(f == nil)
		return Enofid;
	if(f->open){
		putfid(fs, f);
		return Eisopen;
	}
	mode = rpc->mode & OPERM;
	if(mode == OEXEC
	|| f->qid.path == Qroot && (mode == OWRITE || mode == ORDWR)){
		putfid(fs, f);
		return Eperm;
	}
	f->open = 1;
	f->where = nil;
	f->n = 0;
	f->search = nil;
	rpc->qid = f->qid;
	rpc->iounit = messagesize-IOHDRSZ;
	putfid(fs, f);
	return nil;
}

char *
fscreate(Fs *, Fcall *)
{
	return Eperm;
}

char*
fsread(Fs *fs, Fcall *rpc)
{
	Fid *f;
	int n, off, count, len;

	f = getfid(fs, rpc->fid);
	if(f == nil)
		return Enofid;
	if(!f->open){
		putfid(fs, f);
		return Enotopen;
	}
	count = rpc->count;
	off = rpc->offset;
	rpc->count = 0;
	if(f->qid.path == Qroot){
		if(off > 0)
			rpc->count = 0;
		else
			rpc->count = dostat(Qsearch, (uchar*)rpc->data, count);
		putfid(fs, f);
		if(off == 0 && rpc->count <= BIT16SZ)
			return "directory read count too small";
		return nil;
	}
	if(f->qid.path == Qstats){
		len = 0;
	}else{
		for(len = 0; len < count; len += n){
			if(f->where == nil || f->search == nil)
				break;
			if(f->n == 0)
				f->where = searchsearch(f->search, f->where, edatabase, &f->n);
			n = f->n;
			if(n != 0){
				if(n > count-len)
					n = count-len;
				memmove(rpc->data+len, f->where, n);
				f->where += n;
				f->n -= n;
			}
		}
	}
	putfid(fs, f);
	rpc->count = len;
	return nil;
}

char*
fswrite(Fs *fs, Fcall *rpc)
{
	Fid *f;

	f = getfid(fs, rpc->fid);
	if(f == nil)
		return Enofid;
	if(!f->open || f->qid.path != Qsearch){
		putfid(fs, f);
		return Enotopen;
	}

	if(f->search != nil)
		searchfree(f->search);
	f->search = searchparse(rpc->data, rpc->data + rpc->count);
	if(f->search == nil){
		putfid(fs, f);
		return Ebadsearch;
	}
	f->where = database;
	f->n = 0;
	putfid(fs, f);
	return nil;
}

char *
fsclunk(Fs *fs, Fcall *rpc)
{
	Fid *f;

	f = getfid(fs, rpc->fid);
	if(f != nil){
		f->attached = 0;
		putfid(fs, f);
	}
	return nil;
}

char *
fsremove(Fs *, Fcall *)
{
	return Eperm;
}

char *
fsstat(Fs *fs, Fcall *rpc)
{
	Fid *f;

	f = getfid(fs, rpc->fid);
	if(f == nil)
		return Enofid;
	rpc->stat = fs->statbuf;
	rpc->nstat = dostat(f->qid.path, rpc->stat, sizeof fs->statbuf);
	putfid(fs, f);
	if(rpc->nstat <= BIT16SZ)
		return "stat count too small";
	return nil;
}

char *
fswstat(Fs *, Fcall *)
{
	return Eperm;
}

int
dostat(int path, uchar *buf, int nbuf)
{
	Dir d;

	switch(path){
	case Qroot:
		d.name = ".";
		d.mode = DMDIR|0555;
		d.qid.type = QTDIR;
		break;
	case Qsearch:
		d.name = "search";
		d.mode = 0666;
		d.qid.type = QTFILE;
		break;
	case Qstats:
		d.name = "stats";
		d.mode = 0666;
		d.qid.type = QTFILE;
		break;
	}
	d.qid.path = path;
	d.qid.vers = 0;
	d.length = 0;
	d.uid = d.gid = d.muid = "none";
	d.atime = d.mtime = time(nil);
	return convD2M(&d, buf, nbuf);
}

char *
urlunesc(char *s, char *e)
{
	char *t, *v;
	int c, n;

	v = emalloc((e - s) + 1);
	for(t = v; s < e; s++){
		c = *s;
		if(c == '%'){
			if(s + 2 >= e)
				break;
			n = s[1];
			if(n >= '0' && n <= '9')
				n = n - '0';
			else if(n >= 'A' && n <= 'F')
				n = n - 'A' + 10;
			else if(n >= 'a' && n <= 'f')
				n = n - 'a' + 10;
			else
				break;
			c = n;
			n = s[2];
			if(n >= '0' && n <= '9')
				n = n - '0';
			else if(n >= 'A' && n <= 'F')
				n = n - 'A' + 10;
			else if(n >= 'a' && n <= 'f')
				n = n - 'a' + 10;
			else
				break;
			s += 2;
			c = c * 16 + n;
		}
		*t++ = c;
	}
	*t = 0;
	return v;
}

int
toupper(int c)
{
	if(c >= 'a' && c <= 'z')
		c += 'A' - 'a';
	return c;
}

int
tolower(int c)
{
	if(c >= 'A' && c <= 'Z')
		c += 'a' - 'A';
	return c;
}

void
fatal(char *fmt, ...)
{
	va_list arg;
	char buf[1024];

	write(2, "searchfs: ", 8);
	va_start(arg, fmt);
	vseprint(buf, buf+1024, fmt, arg);
	va_end(arg);
	write(2, buf, strlen(buf));
	write(2, "\n", 1);
	exits(fmt);
}

void *
emalloc(uint n)
{
	void *p;

	p = malloc(n);
	if(p == nil)
		fatal("out of memory");
	memset(p, 0, n);
	return p;
}

void
usage(void)
{
	fprint(2, "usage: searchfs [-m mountpoint] [-s srvfile] database\n");
	exits("usage");
}