util.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

int
isclient(char *role)
{
	if(role == nil){
		werrstr("role not specified");
		return -1;
	}
	if(strcmp(role, "server") == 0)
		return 0;
	if(strcmp(role, "client") == 0)
		return 1;
	werrstr("unknown role %q", role);
	return -1;
}

static int
hasname(Attr *a0, Attr *a1, char *name)
{
	return _findattr(a0, name) || _findattr(a1, name);
}

static int
hasnameval(Attr *a0, Attr *a1, char *name, char *val)
{
	Attr *a;

	for(a=_findattr(a0, name); a; a=_findattr(a->next, name))
		if(strcmp(a->val, val) == 0)
			return 1;
	for(a=_findattr(a1, name); a; a=_findattr(a->next, name))
		if(strcmp(a->val, val) == 0)
			return 1;
	return 0;
}

int
matchattr(Attr *pat, Attr *a0, Attr *a1)
{
	int type;

	for(; pat; pat=pat->next){
		type = pat->type;
		if(ignoreattr(pat->name))
			type = AttrDefault;
		switch(type){
		case AttrQuery:		/* name=something be present */
			if(!hasname(a0, a1, pat->name))
				return 0;
			break;
		case AttrNameval:	/* name=val must be present */
			if(!hasnameval(a0, a1, pat->name, pat->val))
				return 0;
			break;
		case AttrDefault:	/* name=val must be present if name=anything is present */
			if(hasname(a0, a1, pat->name) && !hasnameval(a0, a1, pat->name, pat->val))
				return 0;
			break;
		}
	}
	return 1;		
}

void
memrandom(void *p, int n)
{
	uchar *cp;

	for(cp = (uchar*)p; n > 0; n--)
		*cp++ = fastrand();
}

/*
 *  keep caphash fd open since opens of it could be disabled
 */
static int caphashfd;

void
initcap(void)
{
	caphashfd = open("#¤/caphash", OWRITE);
//	if(caphashfd < 0)
//		fprint(2, "%s: opening #¤/caphash: %r\n", argv0);
}

/*
 *  create a change uid capability 
 */
char*
mkcap(char *from, char *to)
{
	uchar rand[20];
	char *cap;
	char *key;
	int nfrom, nto;
	uchar hash[SHA1dlen];

	if(caphashfd < 0)
		return nil;

	/* create the capability */
	nto = strlen(to);
	nfrom = strlen(from);
	cap = emalloc(nfrom+1+nto+1+sizeof(rand)*3+1);
	sprint(cap, "%s@%s", from, to);
	memrandom(rand, sizeof(rand));
	key = cap+nfrom+1+nto+1;
	enc64(key, sizeof(rand)*3, rand, sizeof(rand));

	/* hash the capability */
	hmac_sha1((uchar*)cap, strlen(cap), (uchar*)key, strlen(key), hash, nil);

	/* give the kernel the hash */
	key[-1] = '@';
	if(write(caphashfd, hash, SHA1dlen) < 0){
		free(cap);
		return nil;
	}

	return cap;
}

int
phaseerror(Fsstate *s, char *op)
{
	char tmp[32];

	werrstr("protocol phase error: %s in state %s", op, phasename(s, s->phase, tmp));	
	return RpcPhase;
}

char*
phasename(Fsstate *fss, int phase, char *tmp)
{
	char *name;

	if(fss->phase == Broken)
		name = "Broken";
	else if(phase == Established)
		name = "Established";
	else if(phase == Notstarted)
		name = "Notstarted";
	else if(phase < 0 || phase >= fss->maxphase
	|| (name = fss->phasename[phase]) == nil){
		sprint(tmp, "%d", phase);
		name = tmp;
	}
	return name;
}

static int
outin(char *prompt, char *def, int len)
{
	char *s;

	s = readcons(prompt, def, 0);
	if(s == nil)
		return -1;
	if(s == nil)
		sysfatal("s==nil???");
	strncpy(def, s, len);
	def[len-1] = 0;
	free(s);
	return strlen(def);
}

/*
 *  get host owner and set it
 */
void
promptforhostowner(void)
{
	char owner[64], *p;

	/* hack for bitsy; can't prompt during boot */
	if(p = getenv("user")){
		writehostowner(p);
		free(p);
		return;
	}
	free(p);

	strcpy(owner, "none");
	do{
		outin("user", owner, sizeof(owner));
	} while(*owner == 0);
	writehostowner(owner);
}

char*
estrappend(char *s, char *fmt, ...)
{
	char *t;
	va_list arg;

	va_start(arg, fmt);
	t = vsmprint(fmt, arg);
	if(t == nil)
		sysfatal("out of memory");
	va_end(arg);
	s = erealloc(s, strlen(s)+strlen(t)+1);
	strcat(s, t);
	free(t);
	return s;
}


/*
 *  prompt for a string with a possible default response
 */
char*
readcons(char *prompt, char *def, int raw)
{
	int fdin, fdout, ctl, n;
	char line[10];
	char *s;

	fdin = open("/dev/cons", OREAD);
	if(fdin < 0)
		fdin = 0;
	fdout = open("/dev/cons", OWRITE);
	if(fdout < 0)
		fdout = 1;
	if(def != nil)
		fprint(fdout, "%s[%s]: ", prompt, def);
	else
		fprint(fdout, "%s: ", prompt);
	if(raw){
		ctl = open("/dev/consctl", OWRITE);
		if(ctl >= 0)
			write(ctl, "rawon", 5);
	} else
		ctl = -1;
	s = estrdup("");
	for(;;){
		n = read(fdin, line, 1);
		if(n == 0){
		Error:
			close(fdin);
			close(fdout);
			if(ctl >= 0)
				close(ctl);
			free(s);
			return nil;
		}
		if(n < 0)
			goto Error;
		if(line[0] == 0x7f)
			goto Error;
		if(n == 0 || line[0] == '\n' || line[0] == '\r'){
			if(raw){
				write(ctl, "rawoff", 6);
				write(fdout, "\n", 1);
			}
			close(ctl);
			close(fdin);
			close(fdout);
			if(*s == 0 && def != nil)
				s = estrappend(s, "%s", def);
			return s;
		}
		if(line[0] == '\b'){
			if(strlen(s) > 0)
				s[strlen(s)-1] = 0;
		} else if(line[0] == 0x15) {	/* ^U: line kill */
			if(def != nil)
				fprint(fdout, "\n%s[%s]: ", prompt, def);
			else
				fprint(fdout, "\n%s: ", prompt);
			
			s[0] = 0;
		} else {
			s = estrappend(s, "%c", line[0]);
		}
	}
}

/*
 * Insert a key into the keyring.
 * If the public attributes are identical to some other key, replace that one.
 */
int
replacekey(Key *kn, int before)
{
	int i;
	Key *k;

	for(i=0; i<ring->nkey; i++){
		k = ring->key[i];
		if(matchattr(kn->attr, k->attr, nil) && matchattr(k->attr, kn->attr, nil)){
			closekey(k);
			kn->ref++;
			ring->key[i] = kn;
			return 0;
		}
	}
	if(ring->nkey%16 == 0)
		ring->key = erealloc(ring->key, (ring->nkey+16)*sizeof(ring->key[0]));
	kn->ref++;
	if(before){
		memmove(ring->key+1, ring->key, ring->nkey*sizeof ring->key[0]);
		ring->key[0] = kn;
		ring->nkey++;
	}else
		ring->key[ring->nkey++] = kn;
	return 0;
}

char*
safecpy(char *to, char *from, int n)
{
	memset(to, 0, n);
	if(n == 1)
		return to;
	if(from==nil)
		sysfatal("safecpy called with from==nil, pc=%#p\n",
			getcallerpc(&to));
	strncpy(to, from, n-1);
	return to;
}

Attr*
setattr(Attr *a, char *fmt, ...)
{
	char buf[1024];
	va_list arg;
	Attr *b;

	va_start(arg, fmt);
	vseprint(buf, buf+sizeof buf, fmt, arg);
	va_end(arg);
	b = _parseattr(buf);
	a = setattrs(a, b);
	setmalloctag(a, getcallerpc(&a));
	_freeattr(b);
	return a;
}

/*
 *  add attributes in list b to list a.  If any attributes are in
 *  both lists, replace those in a by those in b.
 */
Attr*
setattrs(Attr *a, Attr *b)
{
	int found;
	Attr **l, *freea;

	for(; b; b=b->next){
		found = 0;
		for(l=&a; *l; ){
			if(strcmp(b->name, (*l)->name) == 0){
				switch(b->type){
				case AttrNameval:
					if(!found){
						found = 1;
						free((*l)->val);
						(*l)->val = estrdup(b->val);
						(*l)->type = AttrNameval;
						l = &(*l)->next;
					}else{
						freea = *l;
						*l = (*l)->next;
						freea->next = nil;
						_freeattr(freea);
					}
					break;
				case AttrQuery:
					goto continue2;
				}
			}else
				l = &(*l)->next;
		}
		if(found == 0){
			*l = _mkattr(b->type, b->name, b->val, nil);
			setmalloctag(*l, getcallerpc(&a));
		}
continue2:;
	}
	return a;		
}

void
setmalloctaghere(void *v)
{
	setmalloctag(v, getcallerpc(&v));
}

Attr*
sortattr(Attr *a)
{
	int i;
	Attr *anext, *a0, *a1, **l;

	if(a == nil || a->next == nil)
		return a;

	/* cut list in halves */
	a0 = nil;
	a1 = nil;
	i = 0;
	for(; a; a=anext){
		anext = a->next;
		if(i++%2){
			a->next = a0;
			a0 = a;
		}else{
			a->next = a1;
			a1 = a;
		}
	}

	/* sort */
	a0 = sortattr(a0);
	a1 = sortattr(a1);

	/* merge */
	l = &a;
	while(a0 || a1){
		if(a1==nil){
			anext = a0;
			a0 = a0->next;
		}else if(a0==nil){
			anext = a1;
			a1 = a1->next;
		}else if(strcmp(a0->name, a1->name) < 0){
			anext = a0;
			a0 = a0->next;
		}else{
			anext = a1;
			a1 = a1->next;
		}
		*l = anext;
		l = &(*l)->next;
	}
	*l = nil;
	return a;
}

int
toosmall(Fsstate *fss, uint n)
{
	fss->rpc.nwant = n;
	return RpcToosmall;
}

void
writehostowner(char *owner)
{
	int fd;
	char *s;

	if((s = strchr(owner,'@')) != nil){
		*s++ = 0;
		strncpy(secstore, s, (sizeof secstore)-1);
	}
	fd = open("#c/hostowner", OWRITE);
	if(fd >= 0){
		if(fprint(fd, "%s", owner) < 0)
			fprint(2, "factotum: setting #c/hostowner to %q: %r\n",
				owner);
		close(fd);
	}
}

int
attrnamefmt(Fmt *fmt)
{
	char *b, buf[1024], *ebuf;
	Attr *a;

	ebuf = buf+sizeof buf;
	b = buf;
	strcpy(buf, " ");
	for(a=va_arg(fmt->args, Attr*); a; a=a->next){
		if(a->name == nil)
			continue;
		b = seprint(b, ebuf, " %q?", a->name);
	}
	return fmtstrcpy(fmt, buf+1);
}

void
disablekey(Key *k)
{
	Attr *a;

	if(sflag)	/* not on servers */
		return;
	for(a=k->attr; a; a=a->next){
		if(a->type==AttrNameval && strcmp(a->name, "disabled") == 0)
			return;
		if(a->next == nil)
			break;
	}
	if(a)
		a->next = _mkattr(AttrNameval, "disabled", "by.factotum", nil);
	else
		k->attr = _mkattr(AttrNameval, "disabled", "by.factotum", nil);	/* not reached: always a proto attribute */
}