make a simpler regexp implementation with fewer dependencies and put it inside testing.

remove "regexp." from regexp tests.

R=rsc
DELTA=1173  (1152 added, 1 deleted, 20 changed)
OCL=33028
CL=33037

src/pkg/regexp/all_test.go

@@ -37,18 +37,18 @@ type stringError struct {
 	err	os.Error;
 }
 var bad_re = []stringError{
-	stringError{ `*`,	 	regexp.ErrBareClosure },
-	stringError{ `(abc`,	regexp.ErrUnmatchedLpar },
-	stringError{ `abc)`,	regexp.ErrUnmatchedRpar },
-	stringError{ `x[a-z`,	regexp.ErrUnmatchedLbkt },
-	stringError{ `abc]`,	regexp.ErrUnmatchedRbkt },
-	stringError{ `[z-a]`,	regexp.ErrBadRange },
-	stringError{ `abc\`,	regexp.ErrExtraneousBackslash },
-	stringError{ `a**`,	regexp.ErrBadClosure },
-	stringError{ `a*+`,	regexp.ErrBadClosure },
-	stringError{ `a??`,	regexp.ErrBadClosure },
-	stringError{ `*`,	 	regexp.ErrBareClosure },
-	stringError{ `\x`,	regexp.ErrBadBackslash },
+	stringError{ `*`,	 	ErrBareClosure },
+	stringError{ `(abc`,	ErrUnmatchedLpar },
+	stringError{ `abc)`,	ErrUnmatchedRpar },
+	stringError{ `x[a-z`,	ErrUnmatchedLbkt },
+	stringError{ `abc]`,	ErrUnmatchedRbkt },
+	stringError{ `[z-a]`,	ErrBadRange },
+	stringError{ `abc\`,	ErrExtraneousBackslash },
+	stringError{ `a**`,	ErrBadClosure },
+	stringError{ `a*+`,	ErrBadClosure },
+	stringError{ `a??`,	ErrBadClosure },
+	stringError{ `*`,	 	ErrBareClosure },
+	stringError{ `\x`,	ErrBadBackslash },
 }
 
 type vec []int;
@@ -88,8 +88,8 @@ var matches = []tester {
 	tester{ `a*(|(b))c*`,	"aacc",	vec{0,4, 2,2, -1,-1} },
 }
 
-func compileTest(t *testing.T, expr string, error os.Error) *regexp.Regexp {
-	re, err := regexp.Compile(expr);
+func compileTest(t *testing.T, expr string, error os.Error) *Regexp {
+	re, err := Compile(expr);
 	if err != error {
 		t.Error("compiling `", expr, "`; unexpected error: ", err.String());
 	}

src/pkg/testing/Makefile

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
+
 # DO NOT EDIT.  Automatically generated by gobuild.
 # gobuild -m >Makefile
 
@@ -20,7 +21,7 @@ test: packages
 
 coverage: packages
 	gotest
-	6cov -g `pwd` | grep -v '_test\.go:'
+	6cov -g $$(pwd) | grep -v '_test\.go:'
 
 %.$O: %.go
 	$(GC) -I_obj $*.go
@@ -32,16 +33,23 @@ coverage: packages
 	$(AS) $*.s
 
 O1=\
+	regexp.$O\
+
+O2=\
 	testing.$O\
 
 
-phases: a1
+phases: a1 a2
 _obj$D/testing.a: phases
 
 a1: $(O1)
-	$(AR) grc _obj$D/testing.a testing.$O
+	$(AR) grc _obj$D/testing.a regexp.$O
 	rm -f $(O1)
 
+a2: $(O2)
+	$(AR) grc _obj$D/testing.a testing.$O
+	rm -f $(O2)
+
 
 newpkg: clean
 	mkdir -p _obj$D
@@ -49,6 +57,7 @@ newpkg: clean
 
 $(O1): newpkg
 $(O2): a1
+$(O3): a2
 
 nuke: clean
 	rm -f $(GOROOT)/pkg/$(GOOS)_$(GOARCH)$D/testing.a

src/pkg/testing/regexp.go

@@ -0,0 +1,863 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The testing package implements a simple regular expression library.
+// It is a reduced version of the regular expression package suitable
+// for use in tests; it avoids many dependencies.
+//
+// The syntax of the regular expressions accepted is:
+//
+//	regexp:
+//		concatenation { '|' concatenation }
+//	concatenation:
+//		{ closure }
+//	closure:
+//		term [ '*' | '+' | '?' ]
+//	term:
+//		'^'
+//		'$'
+//		'.'
+//		character
+//		'[' [ '^' ] character-ranges ']'
+//		'(' regexp ')'
+//
+package testing
+
+import (
+	"runtime";
+	"utf8";
+)
+
+var debug = false;
+
+// Error codes returned by failures to parse an expression.
+var (
+	ErrInternal = "internal error";
+	ErrUnmatchedLpar = "unmatched ''";
+	ErrUnmatchedRpar = "unmatched ''";
+	ErrUnmatchedLbkt = "unmatched '['";
+	ErrUnmatchedRbkt = "unmatched ']'";
+	ErrBadRange = "bad range in character class";
+	ErrExtraneousBackslash = "extraneous backslash";
+	ErrBadClosure = "repeated closure **, ++, etc.";
+	ErrBareClosure = "closure applies to nothing";
+	ErrBadBackslash = "illegal backslash escape";
+)
+
+// An instruction executed by the NFA
+type instr interface {
+	kind()	int;	// the type of this instruction: _CHAR, _ANY, etc.
+	next()	instr;	// the instruction to execute after this one
+	setNext(i instr);
+	index()	int;
+	setIndex(i int);
+	print();
+}
+
+// Fields and methods common to all instructions
+type common struct {
+	_next	instr;
+	_index	int;
+}
+
+func (c *common) next() instr { return c._next }
+func (c *common) setNext(i instr) { c._next = i }
+func (c *common) index() int { return c._index }
+func (c *common) setIndex(i int) { c._index = i }
+
+// The representation of a compiled regular expression.
+// The public interface is entirely through methods.
+type Regexp struct {
+	expr	string;	// the original expression
+	ch	chan<- *Regexp;	// reply channel when we're done
+	error	string;	// compile- or run-time error; nil if OK
+	inst	[]instr;
+	start	instr;
+	nbra	int;	// number of brackets in expression, for subexpressions
+}
+
+const (
+	_START	// beginning of program
+		= iota;
+	_END;		// end of program: success
+	_BOT;		// '^' beginning of text
+	_EOT;		// '$' end of text
+	_CHAR;	// 'a' regular character
+	_CHARCLASS;	// [a-z] character class
+	_ANY;		// '.' any character including newline
+	_NOTNL;		// [^\n] special case: any character but newline
+	_BRA;		// '(' parenthesized expression
+	_EBRA;	// ')'; end of '(' parenthesized expression
+	_ALT;		// '|' alternation
+	_NOP;		// do nothing; makes it easy to link without patching
+)
+
+// --- START start of program
+type _Start struct {
+	common
+}
+
+func (start *_Start) kind() int { return _START }
+func (start *_Start) print() { print("start") }
+
+// --- END end of program
+type _End struct {
+	common
+}
+
+func (end *_End) kind() int { return _END }
+func (end *_End) print() { print("end") }
+
+// --- BOT beginning of text
+type _Bot struct {
+	common
+}
+
+func (bot *_Bot) kind() int { return _BOT }
+func (bot *_Bot) print() { print("bot") }
+
+// --- EOT end of text
+type _Eot struct {
+	common
+}
+
+func (eot *_Eot) kind() int { return _EOT }
+func (eot *_Eot) print() { print("eot") }
+
+// --- CHAR a regular character
+type _Char struct {
+	common;
+	char	int;
+}
+
+func (char *_Char) kind() int { return _CHAR }
+func (char *_Char) print() { print("char ", string(char.char)) }
+
+func newChar(char int) *_Char {
+	c := new(_Char);
+	c.char = char;
+	return c;
+}
+
+// --- CHARCLASS [a-z]
+
+type _CharClass struct {
+	common;
+	char	int;
+	negate	bool;	// is character class negated? ([^a-z])
+	// stored pairwise: [a-z] is (a,z); x is (x,x):
+	ranges	[]int;
+}
+
+func (cclass *_CharClass) kind() int { return _CHARCLASS }
+
+func (cclass *_CharClass) print() {
+	print("charclass");
+	if cclass.negate {
+		print(" (negated)");
+	}
+	for i := 0; i < len(cclass.ranges); i += 2 {
+		l := cclass.ranges[i];
+		r := cclass.ranges[i+1];
+		if l == r {
+			print(" [", string(l), "]");
+		} else {
+			print(" [", string(l), "-", string(r), "]");
+		}
+	}
+}
+
+func (cclass *_CharClass) addRange(a, b int) {
+	// range is a through b inclusive
+	n := len(cclass.ranges);
+	if n >= cap(cclass.ranges) {
+		nr := make([]int, n, 2*n);
+		for i, j := range nr {
+			nr[i] = j
+		}
+		cclass.ranges = nr;
+	}
+	cclass.ranges = cclass.ranges[0:n+2];
+	cclass.ranges[n] = a;
+	n++;
+	cclass.ranges[n] = b;
+	n++;
+}
+
+func (cclass *_CharClass) matches(c int) bool {
+	for i := 0; i < len(cclass.ranges); i = i+2 {
+		min := cclass.ranges[i];
+		max := cclass.ranges[i+1];
+		if min <= c && c <= max {
+			return !cclass.negate
+		}
+	}
+	return cclass.negate
+}
+
+func newCharClass() *_CharClass {
+	c := new(_CharClass);
+	c.ranges = make([]int, 0, 20);
+	return c;
+}
+
+// --- ANY any character
+type _Any struct {
+	common
+}
+
+func (any *_Any) kind() int { return _ANY }
+func (any *_Any) print() { print("any") }
+
+// --- NOTNL any character but newline
+type _NotNl struct {
+	common
+}
+
+func (notnl *_NotNl) kind() int { return _NOTNL }
+func (notnl *_NotNl) print() { print("notnl") }
+
+// --- BRA parenthesized expression
+type _Bra struct {
+	common;
+	n	int;	// subexpression number
+}
+
+func (bra *_Bra) kind() int { return _BRA }
+func (bra *_Bra) print() { print("bra", bra.n); }
+
+// --- EBRA end of parenthesized expression
+type _Ebra struct {
+	common;
+	n	int;	// subexpression number
+}
+
+func (ebra *_Ebra) kind() int { return _EBRA }
+func (ebra *_Ebra) print() { print("ebra ", ebra.n); }
+
+// --- ALT alternation
+type _Alt struct {
+	common;
+	left	instr;	// other branch
+}
+
+func (alt *_Alt) kind() int { return _ALT }
+func (alt *_Alt) print() { print("alt(", alt.left.index(), ")"); }
+
+// --- NOP no operation
+type _Nop struct {
+	common
+}
+
+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 string) {
+	re.error = err;
+	re.ch <- re;
+	runtime.Goexit();
+}
+
+func (re *Regexp) add(i instr) instr {
+	n := len(re.inst);
+	i.setIndex(len(re.inst));
+	if n >= cap(re.inst) {
+		ni := make([]instr, n, 2*n);
+		for i, j := range ni {
+			ni[i] = j
+		}
+		re.inst = ni;
+	}
+	re.inst = re.inst[0:n+1];
+	re.inst[n] = i;
+	return i;
+}
+
+type parser struct {
+	re	*Regexp;
+	nlpar	int;	// number of unclosed lpars
+	pos	int;
+	ch	int;
+}
+
+const endOfFile = -1
+
+func (p *parser) c() int {
+	return p.ch;
+}
+
+func (p *parser) nextc() int {
+	if p.pos >= len(p.re.expr) {
+		p.ch = endOfFile
+	} else {
+		c, w := utf8.DecodeRuneInString(p.re.expr[p.pos:len(p.re.expr)]);
+		p.ch = c;
+		p.pos += w;
+	}
+	return p.ch;
+}
+
+func newParser(re *Regexp) *parser {
+	p := new(parser);
+	p.re = re;
+	p.nextc();	// load p.ch
+	return p;
+}
+
+func (p *parser) regexp() (start, end instr)
+
+var iNULL instr
+
+func special(c int) bool {
+	s := `\.+*?()|[]^$`;
+	for i := 0; i < len(s); i++ {
+		if c == int(s[i]) {
+			return true
+		}
+	}
+	return false
+}
+
+func specialcclass(c int) bool {
+	s := `\-[]`;
+	for i := 0; i < len(s); i++ {
+		if c == int(s[i]) {
+			return true
+		}
+	}
+	return false
+}
+
+func (p *parser) charClass() instr {
+	cc := newCharClass();
+	if p.c() == '^' {
+		cc.negate = true;
+		p.nextc();
+	}
+	left := -1;
+	for {
+		switch c := p.c(); c {
+		case ']', endOfFile:
+			if left >= 0 {
+				p.re.setError(ErrBadRange);
+			}
+			// Is it [^\n]?
+			if cc.negate && len(cc.ranges) == 2 &&
+				cc.ranges[0] == '\n' && cc.ranges[1] == '\n' {
+				nl := new(_NotNl);
+				p.re.add(nl);
+				return nl;
+			}
+			p.re.add(cc);
+			return cc;
+		case '-':	// do this before backslash processing
+			p.re.setError(ErrBadRange);
+		case '\\':
+			c = p.nextc();
+			switch {
+			case c == endOfFile:
+				p.re.setError(ErrExtraneousBackslash);
+			case c == 'n':
+				c = '\n';
+			case specialcclass(c):
+				// c is as delivered
+			default:
+				p.re.setError(ErrBadBackslash);
+			}
+			fallthrough;
+		default:
+			p.nextc();
+			switch {
+			case left < 0:	// first of pair
+				if p.c() == '-' {	// range
+					p.nextc();
+					left = c;
+				} else {	// single char
+					cc.addRange(c, c);
+				}
+			case left <= c:	// second of pair
+				cc.addRange(left, c);
+				left = -1;
+			default:
+				p.re.setError(ErrBadRange);
+			}
+		}
+	}
+	return iNULL
+}
+
+func (p *parser) term() (start, end instr) {
+	switch c := p.c(); c {
+	case '|', endOfFile:
+		return iNULL, iNULL;
+	case '*', '+':
+		p.re.setError(ErrBareClosure);
+	case ')':
+		if p.nlpar == 0 {
+			p.re.setError(ErrUnmatchedRpar);
+		}
+		return iNULL, iNULL;
+	case ']':
+		p.re.setError(ErrUnmatchedRbkt);
+	case '^':
+		p.nextc();
+		start = p.re.add(new(_Bot));
+		return start, start;
+	case '$':
+		p.nextc();
+		start = p.re.add(new(_Eot));
+		return start, start;
+	case '.':
+		p.nextc();
+		start = p.re.add(new(_Any));
+		return start, start;
+	case '[':
+		p.nextc();
+		start = p.charClass();
+		if p.c() != ']' {
+			p.re.setError(ErrUnmatchedLbkt);
+		}
+		p.nextc();
+		return start, start;
+	case '(':
+		p.nextc();
+		p.nlpar++;
+		p.re.nbra++;	// increment first so first subexpr is \1
+		nbra := p.re.nbra;
+		start, end = p.regexp();
+		if p.c() != ')' {
+			p.re.setError(ErrUnmatchedLpar);
+		}
+		p.nlpar--;
+		p.nextc();
+		bra := new(_Bra);
+		p.re.add(bra);
+		ebra := new(_Ebra);
+		p.re.add(ebra);
+		bra.n = nbra;
+		ebra.n = nbra;
+		if start == iNULL {
+			if end == iNULL {
+				p.re.setError(ErrInternal)
+			}
+			start = ebra
+		} else {
+			end.setNext(ebra);
+		}
+		bra.setNext(start);
+		return bra, ebra;
+	case '\\':
+		c = p.nextc();
+		switch {
+		case c == endOfFile:
+			p.re.setError(ErrExtraneousBackslash);
+		case c == 'n':
+			c = '\n';
+		case special(c):
+			// c is as delivered
+		default:
+			p.re.setError(ErrBadBackslash);
+		}
+		fallthrough;
+	default:
+		p.nextc();
+		start = newChar(c);
+		p.re.add(start);
+		return start, start
+	}
+	panic("unreachable");
+}
+
+func (p *parser) closure() (start, end instr) {
+	start, end = p.term();
+	if start == iNULL {
+		return
+	}
+	switch p.c() {
+	case '*':
+		// (start,end)*:
+		alt := new(_Alt);
+		p.re.add(alt);
+		end.setNext(alt);	// after end, do alt
+		alt.left = start;	// alternate brach: return to start
+		start = alt;	// alt becomes new (start, end)
+		end = alt;
+	case '+':
+		// (start,end)+:
+		alt := new(_Alt);
+		p.re.add(alt);
+		end.setNext(alt);	// after end, do alt
+		alt.left = start;	// alternate brach: return to start
+		end = alt;	// start is unchanged; end is alt
+	case '?':
+		// (start,end)?:
+		alt := new(_Alt);
+		p.re.add(alt);
+		nop := new(_Nop);
+		p.re.add(nop);
+		alt.left = start;	// alternate branch is start
+		alt.setNext(nop);	// follow on to nop
+		end.setNext(nop);	// after end, go to nop
+		start = alt;	// start is now alt
+		end = nop;	// end is nop pointed to by both branches
+	default:
+		return
+	}
+	switch p.nextc() {
+	case '*', '+', '?':
+		p.re.setError(ErrBadClosure);
+	}
+	return
+}
+
+func (p *parser) concatenation() (start, end instr) {
+	start, end = iNULL, iNULL;
+	for {
+		nstart, nend := p.closure();
+		switch {
+		case nstart == iNULL:	// end of this concatenation
+			if start == iNULL {	// this is the empty string
+				nop := p.re.add(new(_Nop));
+				return nop, nop;
+			}
+			return;
+		case start == iNULL:	// this is first element of concatenation
+			start, end = nstart, nend;
+		default:
+			end.setNext(nstart);
+			end = nend;
+		}
+	}
+	panic("unreachable");
+}
+
+func (p *parser) regexp() (start, end instr) {
+	start, end = p.concatenation();
+	for {
+		switch p.c() {
+		default:
+			return;
+		case '|':
+			p.nextc();
+			nstart, nend := p.concatenation();
+			alt := new(_Alt);
+			p.re.add(alt);
+			alt.left = start;
+			alt.setNext(nstart);
+			nop := new(_Nop);
+			p.re.add(nop);
+			end.setNext(nop);
+			nend.setNext(nop);
+			start, end = alt, nop;
+		}
+	}
+	panic("unreachable");
+}
+
+func unNop(i instr) instr {
+	for i.kind() == _NOP {
+		i = i.next()
+	}
+	return i
+}
+
+func (re *Regexp) eliminateNops() {
+	for i := 0; i < len(re.inst); i++ {
+		inst := re.inst[i];
+		if inst.kind() == _END {
+			continue
+		}
+		inst.setNext(unNop(inst.next()));
+		if inst.kind() == _ALT {
+			alt := inst.(*_Alt);
+			alt.left = unNop(alt.left);
+		}
+	}
+}
+
+func (re *Regexp) dump() {
+	for i := 0; i < len(re.inst); i++ {
+		inst := re.inst[i];
+		print(inst.index(), ": ");
+		inst.print();
+		if inst.kind() != _END {
+			print(" -> ", inst.next().index())
+		}
+		print("\n");
+	}
+}
+
+func (re *Regexp) doParse() {
+	p := newParser(re);
+	start := new(_Start);
+	re.add(start);
+	s, e := p.regexp();
+	start.setNext(s);
+	re.start = start;
+	e.setNext(re.add(new(_End)));
+
+	if debug {
+		re.dump();
+		println();
+	}
+
+	re.eliminateNops();
+
+	if debug {
+		re.dump();
+		println();
+	}
+}
+
+
+func compiler(str string, ch chan *Regexp) {
+	re := new(Regexp);
+	re.expr = str;
+	re.inst = make([]instr, 0, 20);
+	re.ch = ch;
+	re.doParse();
+	ch <- re;
+}
+
+// CompileRegexp parses a regular expression and returns, if successful, a Regexp
+// object that can be used to match against text.
+func CompileRegexp(str string) (regexp *Regexp, error string) {
+	// Compile in a separate goroutine and wait for the result.
+	ch := make(chan *Regexp);
+	go compiler(str, ch);
+	re := <-ch;
+	return re, re.error
+}
+
+type state struct {
+	inst	instr;	// next instruction to execute
+	match	[]int;	// pairs of bracketing submatches. 0th is start,end
+}
+
+// Append new state to to-do list.  Leftmost-longest wins so avoid
+// adding a state that's already active.
+func addState(s []state, inst instr, match []int) []state {
+	index := inst.index();
+	l := len(s);
+	pos := match[0];
+	// TODO: Once the state is a vector and we can do insert, have inputs always
+	// go in order correctly and this "earlier" test is never necessary,
+	for i := 0; i < l; i++ {
+		if s[i].inst.index() == index && // same instruction
+		   s[i].match[0] < pos {	// earlier match already going; lefmost wins
+		   	return s
+		 }
+	}
+	if l == cap(s) {
+		s1 := make([]state, 2*l)[0:l];
+		for i := 0; i < l; i++ {
+			s1[i] = s[i];
+		}
+		s = s1;
+	}
+	s = s[0:l+1];
+	s[l].inst = inst;
+	s[l].match = match;
+	return s;
+}
+
+// Accepts either string or bytes - the logic is identical either way.
+// If bytes == nil, scan str.
+func (re *Regexp) doExecute(str string, bytes []byte, pos int) []int {
+	var s [2][]state;	// TODO: use a vector when state values (not ptrs) can be vector elements
+	s[0] = make([]state, 10)[0:0];
+	s[1] = make([]state, 10)[0:0];
+	in, out := 0, 1;
+	var final state;
+	found := false;
+	end := len(str);
+	if bytes != nil {
+		end = len(bytes)
+	}
+	for pos <= end {
+		if !found {
+			// prime the pump if we haven't seen a match yet
+			match := make([]int, 2*(re.nbra+1));
+			for i := 0; i < len(match); i++ {
+				match[i] = -1;	// no match seen; catches cases like "a(b)?c" on "ac"
+			}
+			match[0]  = pos;
+			s[out] = addState(s[out], re.start.next(), match);
+		}
+		in, out = out, in;	// old out state is new in state
+		s[out] = s[out][0:0];	// clear out state
+		if len(s[in]) == 0 {
+			// machine has completed
+			break;
+		}
+		charwidth := 1;
+		c := endOfFile;
+		if pos < end {
+			if bytes == nil {
+				c, charwidth = utf8.DecodeRuneInString(str[pos:end]);
+			} else {
+				c, charwidth = utf8.DecodeRune(bytes[pos:end]);
+			}
+		}
+		for i := 0; i < len(s[in]); i++ {
+			st := s[in][i];
+			switch s[in][i].inst.kind() {
+			case _BOT:
+				if pos == 0 {
+					s[in] = addState(s[in], st.inst.next(), st.match)
+				}
+			case _EOT:
+				if pos == end {
+					s[in] = addState(s[in], st.inst.next(), st.match)
+				}
+			case _CHAR:
+				if c == st.inst.(*_Char).char {
+					s[out] = addState(s[out], st.inst.next(), st.match)
+				}
+			case _CHARCLASS:
+				if st.inst.(*_CharClass).matches(c) {
+					s[out] = addState(s[out], st.inst.next(), st.match)
+				}
+			case _ANY:
+				if c != endOfFile {
+					s[out] = addState(s[out], st.inst.next(), st.match)
+				}
+			case _NOTNL:
+				if c != endOfFile && c != '\n' {
+					s[out] = addState(s[out], st.inst.next(), st.match)
+				}
+			case _BRA:
+				n := st.inst.(*_Bra).n;
+				st.match[2*n] = pos;
+				s[in] = addState(s[in], st.inst.next(), st.match);
+			case _EBRA:
+				n := st.inst.(*_Ebra).n;
+				st.match[2*n+1] = pos;
+				s[in] = addState(s[in], st.inst.next(), st.match);
+			case _ALT:
+				s[in] = addState(s[in], st.inst.(*_Alt).left, st.match);
+				// give other branch a copy of this match vector
+				s1 := make([]int, 2*(re.nbra+1));
+				for i := 0; i < len(s1); i++ {
+					s1[i] = st.match[i]
+				}
+				s[in] = addState(s[in], st.inst.next(), s1);
+			case _END:
+				// choose leftmost longest
+				if !found ||	// first
+				   st.match[0] < final.match[0] ||	// leftmost
+				   (st.match[0] == final.match[0] && pos > final.match[1]) {	// longest
+					final = st;
+					final.match[1] = pos;
+				}
+				found = true;
+			default:
+				st.inst.print();
+				panic("unknown instruction in execute");
+			}
+		}
+		pos += charwidth;
+	}
+	return final.match;
+}
+
+
+// ExecuteString matches the Regexp against the string s.
+// The return value is an array of integers, in pairs, identifying the positions of
+// substrings matched by the expression.
+//    s[a[0]:a[1]] is the substring matched by the entire expression.
+//    s[a[2*i]:a[2*i+1]] for i > 0 is the substring matched by the ith parenthesized subexpression.
+// A negative value means the subexpression did not match any element of the string.
+// An empty array means "no match".
+func (re *Regexp) ExecuteString(s string) (a []int) {
+	return re.doExecute(s, nil, 0)
+}
+
+
+// Execute matches the Regexp against the byte slice b.
+// The return value is an array of integers, in pairs, identifying the positions of
+// subslices matched by the expression.
+//    b[a[0]:a[1]] is the subslice matched by the entire expression.
+//    b[a[2*i]:a[2*i+1]] for i > 0 is the subslice matched by the ith parenthesized subexpression.
+// A negative value means the subexpression did not match any element of the slice.
+// An empty array means "no match".
+func (re *Regexp) Execute(b []byte) (a []int) {
+	return re.doExecute("", b, 0)
+}
+
+
+// MatchString returns whether the Regexp matches the string s.
+// The return value is a boolean: true for match, false for no match.
+func (re *Regexp) MatchString(s string) bool {
+	return len(re.doExecute(s, nil, 0)) > 0
+}
+
+
+// Match returns whether the Regexp matches the byte slice b.
+// The return value is a boolean: true for match, false for no match.
+func (re *Regexp) Match(b []byte) bool {
+	return len(re.doExecute("", b, 0)) > 0
+}
+
+
+// MatchStrings matches the Regexp against the string s.
+// The return value is an array of strings matched by the expression.
+//    a[0] is the substring matched by the entire expression.
+//    a[i] for i > 0 is the substring matched by the ith parenthesized subexpression.
+// An empty array means ``no match''.
+func (re *Regexp) MatchStrings(s string) (a []string) {
+	r := re.doExecute(s, nil, 0);
+	if r == nil {
+		return nil
+	}
+	a = make([]string, len(r)/2);
+	for i := 0; i < len(r); i += 2 {
+		if r[i] != -1 {	// -1 means no match for this subexpression
+			a[i/2] = s[r[i] : r[i+1]]
+		}
+	}
+	return
+}
+
+// MatchSlices matches the Regexp against the byte slice b.
+// The return value is an array of subslices matched by the expression.
+//    a[0] is the subslice matched by the entire expression.
+//    a[i] for i > 0 is the subslice matched by the ith parenthesized subexpression.
+// An empty array means ``no match''.
+func (re *Regexp) MatchSlices(b []byte) (a [][]byte) {
+	r := re.doExecute("", b, 0);
+	if r == nil {
+		return nil
+	}
+	a = make([][]byte, len(r)/2);
+	for i := 0; i < len(r); i += 2 {
+		if r[i] != -1 {	// -1 means no match for this subexpression
+			a[i/2] = b[r[i] : r[i+1]]
+		}
+	}
+	return
+}
+
+// MatchString checks whether a textual regular expression
+// matches a string.  More complicated queries need
+// to use Compile and the full Regexp interface.
+func MatchString(pattern string, s string) (matched bool, error string) {
+	re, err := CompileRegexp(pattern);
+	if err != "" {
+		return false, err
+	}
+	return re.MatchString(s), ""
+}
+
+// Match checks whether a textual regular expression
+// matches a byte slice.  More complicated queries need
+// to use Compile and the full Regexp interface.
+func Match(pattern string, b []byte) (matched bool, error string) {
+	re, err := CompileRegexp(pattern);
+	if err != "" {
+		return false, err
+	}
+	return re.Match(b), ""
+}

src/pkg/testing/regexp_test.go

@@ -0,0 +1,281 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testing
+
+import (
+	"strings";
+	"testing";
+)
+
+var good_re = []string{
+	``,
+	`.`,
+	`^.$`,
+	`a`,
+	`a*`,
+	`a+`,
+	`a?`,
+	`a|b`,
+	`a*|b*`,
+	`(a*|b)(c*|d)`,
+	`[a-z]`,
+	`[a-abc-c\-\]\[]`,
+	`[a-z]+`,
+	`[]`,
+	`[abc]`,
+	`[^1234]`,
+	`[^\n]`,
+}
+
+// TODO: nice to do this with a map
+type stringError struct {
+	re	string;
+	err	string;
+}
+var bad_re = []stringError{
+	stringError{ `*`,	 	ErrBareClosure },
+	stringError{ `(abc`,	ErrUnmatchedLpar },
+	stringError{ `abc)`,	ErrUnmatchedRpar },
+	stringError{ `x[a-z`,	ErrUnmatchedLbkt },
+	stringError{ `abc]`,	ErrUnmatchedRbkt },
+	stringError{ `[z-a]`,	ErrBadRange },
+	stringError{ `abc\`,	ErrExtraneousBackslash },
+	stringError{ `a**`,	ErrBadClosure },
+	stringError{ `a*+`,	ErrBadClosure },
+	stringError{ `a??`,	ErrBadClosure },
+	stringError{ `*`,	 	ErrBareClosure },
+	stringError{ `\x`,	ErrBadBackslash },
+}
+
+type vec []int;
+
+type tester struct {
+	re	string;
+	text	string;
+	match	vec;
+}
+
+var matches = []tester {
+	tester{ ``,	"",	vec{0,0} },
+	tester{ `a`,	"a",	vec{0,1} },
+	tester{ `x`,	"y",	vec{} },
+	tester{ `b`,	"abc",	vec{1,2} },
+	tester{ `.`,	"a",	vec{0,1} },
+	tester{ `.*`,	"abcdef",	vec{0,6} },
+	tester{ `^abcd$`,	"abcd",	vec{0,4} },
+	tester{ `^bcd'`,	"abcdef",	vec{} },
+	tester{ `^abcd$`,	"abcde",	vec{} },
+	tester{ `a+`,	"baaab",	vec{1,4} },
+	tester{ `a*`,	"baaab",	vec{0,0} },
+	tester{ `[a-z]+`,	"abcd",	vec{0,4} },
+	tester{ `[^a-z]+`,	"ab1234cd",	vec{2,6} },
+	tester{ `[a\-\]z]+`,	"az]-bcz",	vec{0,4} },
+	tester{ `[^\n]+`,	"abcd\n",	vec{0,4} },
+	tester{ `[日本語]+`,	"日本語日本語",	vec{0,18} },
+	tester{ `()`,	"",	vec{0,0, 0,0} },
+	tester{ `(a)`,	"a",	vec{0,1, 0,1} },
+	tester{ `(.)(.)`,	"日a",	vec{0,4, 0,3, 3,4} },
+	tester{ `(.*)`,	"",	vec{0,0, 0,0} },
+	tester{ `(.*)`,	"abcd",	vec{0,4, 0,4} },
+	tester{ `(..)(..)`,	"abcd",	vec{0,4, 0,2, 2,4} },
+	tester{ `(([^xyz]*)(d))`,	"abcd",	vec{0,4, 0,4, 0,3, 3,4} },
+	tester{ `((a|b|c)*(d))`,	"abcd",	vec{0,4, 0,4, 2,3, 3,4} },
+	tester{ `(((a|b|c)*)(d))`,	"abcd",	vec{0,4, 0,4, 0,3, 2,3, 3,4} },
+	tester{ `a*(|(b))c*`,	"aacc",	vec{0,4, 2,2, -1,-1} },
+}
+
+func compileTest(t *testing.T, expr string, error string) *Regexp {
+	re, err := CompileRegexp(expr);
+	if err != error {
+		t.Error("compiling `", expr, "`; unexpected error: ", err);
+	}
+	return re
+}
+
+func printVec(t *testing.T, m []int) {
+	l := len(m);
+	if l == 0 {
+		t.Log("\t<no match>");
+	} else {
+		for i := 0; i < l; i = i+2 {
+			t.Log("\t", m[i], ",", m[i+1])
+		}
+	}
+}
+
+func printStrings(t *testing.T, m []string) {
+	l := len(m);
+	if l == 0 {
+		t.Log("\t<no match>");
+	} else {
+		for i := 0; i < l; i = i+2 {
+			t.Logf("\t%q", m[i])
+		}
+	}
+}
+
+func printBytes(t *testing.T, b [][]byte) {
+	l := len(b);
+	if l == 0 {
+		t.Log("\t<no match>");
+	} else {
+		for i := 0; i < l; i = i+2 {
+			t.Logf("\t%q", b[i])
+		}
+	}
+}
+
+func equal(m1, m2 []int) bool {
+	l := len(m1);
+	if l != len(m2) {
+		return false
+	}
+	for i := 0; i < l; i++ {
+		if m1[i] != m2[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func equalStrings(m1, m2 []string) bool {
+	l := len(m1);
+	if l != len(m2) {
+		return false
+	}
+	for i := 0; i < l; i++ {
+		if m1[i] != m2[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func equalBytes(m1 [][]byte, m2 []string) bool {
+	l := len(m1);
+	if l != len(m2) {
+		return false
+	}
+	for i := 0; i < l; i++ {
+		if string(m1[i]) != m2[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func executeTest(t *testing.T, expr string, str string, match []int) {
+	re := compileTest(t, expr, "");
+	if re == nil {
+		return
+	}
+	m := re.ExecuteString(str);
+	if !equal(m, match) {
+		t.Error("ExecuteString failure on `", expr, "` matching `", str, "`:");
+		printVec(t, m);
+		t.Log("should be:");
+		printVec(t, match);
+	}
+	// now try bytes
+	m = re.Execute(strings.Bytes(str));
+	if !equal(m, match) {
+		t.Error("Execute failure on `", expr, "` matching `", str, "`:");
+		printVec(t, m);
+		t.Log("should be:");
+		printVec(t, match);
+	}
+}
+
+func TestGoodCompile(t *testing.T) {
+	for i := 0; i < len(good_re); i++ {
+		compileTest(t, good_re[i], "");
+	}
+}
+
+func TestBadCompile(t *testing.T) {
+	for i := 0; i < len(bad_re); i++ {
+		compileTest(t, bad_re[i].re, bad_re[i].err)
+	}
+}
+
+func TestExecute(t *testing.T) {
+	for i := 0; i < len(matches); i++ {
+		test := &matches[i];
+		executeTest(t, test.re, test.text, test.match)
+	}
+}
+
+func matchTest(t *testing.T, expr string, str string, match []int) {
+	re := compileTest(t, expr, "");
+	if re == nil {
+		return
+	}
+	m := re.MatchString(str);
+	if m != (len(match) > 0) {
+		t.Error("MatchString failure on `", expr, "` matching `", str, "`:", m, "should be", len(match) > 0);
+	}
+	// now try bytes
+	m = re.Match(strings.Bytes(str));
+	if m != (len(match) > 0) {
+		t.Error("Match failure on `", expr, "` matching `", str, "`:", m, "should be", len(match) > 0);
+	}
+}
+
+func TestMatch(t *testing.T) {
+	for i := 0; i < len(matches); i++ {
+		test := &matches[i];
+		matchTest(t, test.re, test.text, test.match)
+	}
+}
+
+func matchStringsTest(t *testing.T, expr string, str string, match []int) {
+	re := compileTest(t, expr, "");
+	if re == nil {
+		return
+	}
+	strs := make([]string, len(match)/2);
+	for i := 0; i < len(match); i++ {
+		strs[i/2] = str[match[i] : match[i+1]]
+	}
+	m := re.MatchStrings(str);
+	if !equalStrings(m, strs) {
+		t.Error("MatchStrings failure on `", expr, "` matching `", str, "`:");
+		printStrings(t, m);
+		t.Log("should be:");
+		printStrings(t, strs);
+	}
+	// now try bytes
+	s := re.MatchSlices(strings.Bytes(str));
+	if !equalBytes(s, strs) {
+		t.Error("MatchSlices failure on `", expr, "` matching `", str, "`:");
+		printBytes(t, s);
+		t.Log("should be:");
+		printStrings(t, strs);
+	}
+}
+
+func TestMatchStrings(t *testing.T) {
+	for i := 0; i < len(matches); i++ {
+		test := &matches[i];
+		matchTest(t, test.re, test.text, test.match)
+	}
+}
+
+func matchFunctionTest(t *testing.T, expr string, str string, match []int) {
+	m, err := MatchString(expr, str);
+	if err == "" {
+		return
+	}
+	if m != (len(match) > 0) {
+		t.Error("function Match failure on `", expr, "` matching `", str, "`:", m, "should be", len(match) > 0);
+	}
+}
+
+func TestMatchFunction(t *testing.T) {
+	for i := 0; i < len(matches); i++ {
+		test := &matches[i];
+		matchFunctionTest(t, test.re, test.text, test.match)
+	}
+}

src/pkg/testing/testing.go

@@ -15,8 +15,8 @@ import (
 	"flag";
 	"fmt";
 	"os";
-	"regexp";
 	"runtime";
+	"testing";
 )
 
 // Report as tests are run; default is silent for success.
@@ -122,9 +122,9 @@ func Main(tests []Test) {
 	if len(tests) == 0 {
 		println("testing: warning: no tests to run");
 	}
-	re, err := regexp.Compile(*match);
-	if err != nil {
-		println("invalid regexp for -match:", err.String());
+	re, err := CompileRegexp(*match);
+	if err != "" {
+		println("invalid regexp for -match:", err);
 		os.Exit(1);
 	}
 	for i := 0; i < len(tests); i++ {