take goroutines out of regexp so they can be created

during initialization.

R=rsc
CC=go-dev
http://go/go-review/1016023

src/pkg/regexp/regexp.go

@@ -27,7 +27,6 @@ import (
 	"container/vector";
 	"io";
 	"os";
-	"runtime";
 	"utf8";
 )
 
@@ -72,8 +71,6 @@ func (c *common) setIndex(i int) { c._index = i }
 // The public interface is entirely through methods.
 type Regexp struct {
 	expr	string;	// the original expression
-	ch	chan<- *Regexp;	// reply channel when we're done
-	error	os.Error;	// compile- or run-time error; nil if OK
 	inst	*vector.Vector;
 	start	instr;
 	nbra	int;	// number of brackets in expression, for subexpressions
@@ -244,13 +241,6 @@ type _Nop struct {
 func (nop *_Nop) kind() int { return _NOP }
 func (nop *_Nop) print() { print("nop") }
 
-// report error and exit compiling/executing goroutine
-func (re *Regexp) setError(err os.Error) {
-	re.error = err;
-	re.ch <- re;
-	runtime.Goexit();
-}
-
 func (re *Regexp) add(i instr) instr {
 	i.setIndex(re.inst.Len());
 	re.inst.Push(i);
@@ -259,6 +249,7 @@ func (re *Regexp) add(i instr) instr {
 
 type parser struct {
 	re	*Regexp;
+	error	os.Error;
 	nlpar	int;	// number of unclosed lpars
 	pos	int;
 	ch	int;
@@ -288,8 +279,6 @@ func newParser(re *Regexp) *parser {
 	return p;
 }
 
-var iNULL instr
-
 func special(c int) bool {
 	s := `\.+*?()|[]^$`;
 	for i := 0; i < len(s); i++ {
@@ -321,7 +310,8 @@ func (p *parser) charClass() instr {
 		switch c := p.c(); c {
 		case ']', endOfFile:
 			if left >= 0 {
-				p.re.setError(ErrBadRange);
+				p.error = ErrBadRange;
+				return nil;
 			}
 			// Is it [^\n]?
 			if cc.negate && cc.ranges.Len() == 2 &&
@@ -333,18 +323,21 @@ func (p *parser) charClass() instr {
 			p.re.add(cc);
 			return cc;
 		case '-':	// do this before backslash processing
-			p.re.setError(ErrBadRange);
+			p.error = ErrBadRange;
+			return nil;
 		case '\\':
 			c = p.nextc();
 			switch {
 			case c == endOfFile:
-				p.re.setError(ErrExtraneousBackslash);
+				p.error = ErrExtraneousBackslash;
+				return nil;
 			case c == 'n':
 				c = '\n';
 			case specialcclass(c):
 				// c is as delivered
 			default:
-				p.re.setError(ErrBadBackslash);
+				p.error = ErrBadBackslash;
+				return nil;
 			}
 			fallthrough;
 		default:
@@ -361,26 +354,37 @@ func (p *parser) charClass() instr {
 				cc.addRange(left, c);
 				left = -1;
 			default:
-				p.re.setError(ErrBadRange);
+				p.error = ErrBadRange;
+				return nil;
 			}
 		}
 	}
-	return iNULL
+	return nil
 }
 
 func (p *parser) term() (start, end instr) {
+	// term() is the leaf of the recursion, so it's sufficient to pick off the
+	// error state here for early exit.
+	// The other functions (closure(), concatenation() etc.) assume
+	// it's safe to recur to here.
+	if p.error != nil {
+		return
+	}
 	switch c := p.c(); c {
 	case '|', endOfFile:
-		return iNULL, iNULL;
+		return nil, nil;
 	case '*', '+':
-		p.re.setError(ErrBareClosure);
+		p.error = ErrBareClosure;
+		return;
 	case ')':
 		if p.nlpar == 0 {
-			p.re.setError(ErrUnmatchedRpar);
+			p.error = ErrUnmatchedRpar;
+			return;
 		}
-		return iNULL, iNULL;
+		return nil, nil;
 	case ']':
-		p.re.setError(ErrUnmatchedRbkt);
+		p.error = ErrUnmatchedRbkt;
+		return;
 	case '^':
 		p.nextc();
 		start = p.re.add(new(_Bot));
@@ -396,8 +400,12 @@ func (p *parser) term() (start, end instr) {
 	case '[':
 		p.nextc();
 		start = p.charClass();
+		if p.error != nil {
+			return;
+		}
 		if p.c() != ']' {
-			p.re.setError(ErrUnmatchedLbkt);
+			p.error = ErrUnmatchedLbkt;
+			return;
 		}
 		p.nextc();
 		return start, start;
@@ -408,7 +416,8 @@ func (p *parser) term() (start, end instr) {
 		nbra := p.re.nbra;
 		start, end = p.regexp();
 		if p.c() != ')' {
-			p.re.setError(ErrUnmatchedLpar);
+			p.error = ErrUnmatchedLpar;
+			return;
 		}
 		p.nlpar--;
 		p.nextc();
@@ -418,9 +427,10 @@ func (p *parser) term() (start, end instr) {
 		p.re.add(ebra);
 		bra.n = nbra;
 		ebra.n = nbra;
-		if start == iNULL {
+		if start == nil {
-			if end == iNULL {
+			if end == nil {
-				p.re.setError(ErrInternal)
+				p.error = ErrInternal;
+				return;
 			}
 			start = ebra
 		} else {
@@ -432,13 +442,15 @@ func (p *parser) term() (start, end instr) {
 		c = p.nextc();
 		switch {
 		case c == endOfFile:
-			p.re.setError(ErrExtraneousBackslash);
+			p.error = ErrExtraneousBackslash;
+			return;
 		case c == 'n':
 			c = '\n';
 		case special(c):
 			// c is as delivered
 		default:
-			p.re.setError(ErrBadBackslash);
+			p.error = ErrBadBackslash;
+			return;
 		}
 		fallthrough;
 	default:
@@ -452,7 +464,7 @@ func (p *parser) term() (start, end instr) {
 
 func (p *parser) closure() (start, end instr) {
 	start, end = p.term();
-	if start == iNULL {
+	if start == nil || p.error != nil {
 		return
 	}
 	switch p.c() {
@@ -487,23 +499,25 @@ func (p *parser) closure() (start, end instr) {
 	}
 	switch p.nextc() {
 	case '*', '+', '?':
-		p.re.setError(ErrBadClosure);
+		p.error = ErrBadClosure;
 	}
 	return
 }
 
 func (p *parser) concatenation() (start, end instr) {
-	start, end = iNULL, iNULL;
 	for {
 		nstart, nend := p.closure();
+		if p.error != nil {
+			return
+		}
 		switch {
-		case nstart == iNULL:	// end of this concatenation
+		case nstart == nil:	// end of this concatenation
-			if start == iNULL {	// this is the empty string
+			if start == nil {	// this is the empty string
 				nop := p.re.add(new(_Nop));
 				return nop, nop;
 			}
 			return;
-		case start == iNULL:	// this is first element of concatenation
+		case start == nil:	// this is first element of concatenation
 			start, end = nstart, nend;
 		default:
 			end.setNext(nstart);
@@ -515,6 +529,9 @@ func (p *parser) concatenation() (start, end instr) {
 
 func (p *parser) regexp() (start, end instr) {
 	start, end = p.concatenation();
+	if p.error != nil {
+		return
+	}
 	for {
 		switch p.c() {
 		default:
@@ -522,6 +539,9 @@ func (p *parser) regexp() (start, end instr) {
 		case '|':
 			p.nextc();
 			nstart, nend := p.concatenation();
+			if p.error != nil {
+				return
+			}
 			alt := new(_Alt);
 			p.re.add(alt);
 			alt.left = start;
@@ -569,11 +589,14 @@ func (re *Regexp) dump() {
 	}
 }
 
-func (re *Regexp) doParse() {
+func (re *Regexp) doParse() os.Error{
 	p := newParser(re);
 	start := new(_Start);
 	re.add(start);
 	s, e := p.regexp();
+	if p.error != nil {
+		return p.error;
+	}
 	start.setNext(s);
 	re.start = start;
 	e.setNext(re.add(new(_End)));
@@ -584,31 +607,32 @@ func (re *Regexp) doParse() {
 	}
 
 	re.eliminateNops();
-
 	if debug {
 		re.dump();
 		println();
 	}
-}
+	return p.error;
-
-
-func compiler(str string, ch chan *Regexp) {
-	re := new(Regexp);
-	re.expr = str;
-	re.inst = vector.New(0);
-	re.ch = ch;
-	re.doParse();
-	ch <- re;
 }
 
 // Compile parses a regular expression and returns, if successful, a Regexp
 // object that can be used to match against text.
 func Compile(str string) (regexp *Regexp, error os.Error) {
-	// Compile in a separate goroutine and wait for the result.
+	regexp = new(Regexp);
-	ch := make(chan *Regexp);
+	regexp.expr = str;
-	go compiler(str, ch);
+	regexp.inst = vector.New(0);
-	re := <-ch;
+	error = regexp.doParse();
-	return re, re.error
+	return;
+}
+
+// MustCompile is like Compile but panics if the expression cannot be parsed.
+// It simplifies safe initialization of global variables holding compiled regular
+// expressions.
+func MustCompile(str string) *Regexp {
+	regexp, error := Compile(str);
+	if error != nil {
+		panicln(`regexp: compiling "`, str, `": `, error);
+	}
+	return regexp;
 }
 
 type state struct {