rc: fix slow Xqdol(), avoid recursion in conclist(), estrdup(), avoid copying

Xqdol() used to take quadratic time because of strcat(),
the code isnt really needed as list2str() aready does the
same thing in linear time without the strcat().

add estrdup() which uses emalloc() so allocation error are
catched.

move strdups() of name from callers into newvar().

avoid recursion of conclist(), and avoid copying of word
strings by providing Newword() function which doesnt copy
the word string.

1 files changed, 36 insertions, 39 deletions

diff --git a/sys/src/cmd/rc/exec.c b/sys/src/cmd/rc/exec.c
index c0fb8593f..a037d1df4 100644
--- a/sys/src/cmd/rc/exec.c
+++ b/sys/src/cmd/rc/exec.c
@@ -28,20 +28,30 @@ start(code *c, int pc, var *local)
 }
 
 word*
-newword(char *wd, word *next)
+Newword(char *wd, word *next)
 {
 	word *p = new(word);
-	p->word = strdup(wd);
+	p->word = wd;
 	p->next = next;
 	return p;
 }
-
 void
-pushword(char *wd)
+Pushword(char *wd)
 {
 	if(runq->argv==0)
 		panic("pushword but no argv!", 0);
-	runq->argv->words = newword(wd, runq->argv->words);
+	runq->argv->words = Newword(wd, runq->argv->words);
+}
+
+word*
+newword(char *wd, word *next)
+{
+	return Newword(estrdup(wd), next);
+}
+void
+pushword(char *wd)
+{
+	Pushword(estrdup(wd));
 }
 
 void
@@ -113,7 +123,7 @@ var*
 newvar(char *name, var *next)
 {
 	var *v = new(var);
-	v->name = name;
+	v->name = estrdup(name);
 	v->val = 0;
 	v->fn = 0;
 	v->changed = 0;
@@ -174,7 +184,7 @@ main(int argc, char *argv[])
 	start(bootstrap, 1, (var *)0);
 	/* prime bootstrap argv */
 	pushlist();
-	argv0 = strdup(argv[0]);
+	argv0 = estrdup(argv[0]);
 	for(i = argc-1;i!=0;--i) pushword(argv[i]);
 	for(;;){
 		if(flag['r'])
@@ -304,7 +314,7 @@ Xexit(void)
 			--runq->pc;
 			starval = vlook("*")->val;
 			start(trapreq->fn, trapreq->pc, (struct var *)0);
-			runq->local = newvar(strdup("*"), runq->local);
+			runq->local = newvar("*", runq->local);
 			runq->local->val = copywords(starval, (struct word *)0);
 			runq->local->changed = 1;
 			runq->redir = runq->startredir = 0;
@@ -548,16 +558,21 @@ Xcase(void)
 word*
 conclist(word *lp, word *rp, word *tail)
 {
-	char *buf;
-	word *v;
-	if(lp->next || rp->next)
-		tail = conclist(lp->next==0? lp: lp->next,
-			rp->next==0? rp: rp->next, tail);
-	buf = emalloc(strlen(lp->word)+strlen((char *)rp->word)+1);
-	strcpy(buf, lp->word);
-	strcat(buf, rp->word);
-	v = newword(buf, tail);
-	efree(buf);
+	word *v, *p, **end;
+	int ln, rn;
+
+	for(end = &v;;){
+		ln = strlen(lp->word), rn = strlen(rp->word);
+		p = Newword(emalloc(ln+rn+1), (word *)0);
+		Memcpy(p->word, lp->word, ln);
+		Memcpy(p->word+ln, rp->word, rn+1);
+		*end = p, end = &p->next;
+		if(lp->next == 0 && rp->next == 0)
+			break;
+		if(lp->next) lp = lp->next;
+		if(rp->next) rp = rp->next;
+	}
+	*end = tail;
 	return v;
 }
 
@@ -647,9 +662,8 @@ Xdol(void)
 void
 Xqdol(void)
 {
-	word *a, *p;
 	char *s;
-	int n;
+	word *a;
 	if(count(runq->argv->words)!=1){
 		Xerror1("variable name not singleton!");
 		return;
@@ -658,24 +672,7 @@ Xqdol(void)
 	deglob(s);
 	a = vlook(s)->val;
 	poplist();
-	n = count(a);
-	if(n==0){
-		pushword("");
-		return;
-	}
-	for(p = a;p;p = p->next) n+=strlen(p->word);
-	s = emalloc(n);
-	if(a){
-		strcpy(s, a->word);
-		for(p = a->next;p;p = p->next){
-			strcat(s, " ");
-			strcat(s, p->word);
-		}
-	}
-	else
-		s[0]='\0';
-	pushword(s);
-	efree(s);
+	Pushword(list2str(a));
 }
 
 word*
@@ -780,7 +777,7 @@ Xlocal(void)
 		return;
 	}
 	deglob(runq->argv->words->word);
-	runq->local = newvar(strdup(runq->argv->words->word), runq->local);
+	runq->local = newvar(runq->argv->words->word, runq->local);
 	poplist();
 	globlist();
 	runq->local->val = runq->argv->words;