// 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:
// '^'
// '$'
// '.'
// character
// '[' [ '^' ] character-ranges ']'
// '(' regexp ')'
//
package testing
import (
"utf8";
)
var debug = false
// Error codes returned by failures to parse an expression.
var (
ErrInternal = "internal error";
ErrUnmatchedLpar = "unmatched ''";
ErrUnmatchedRpar = "unmatched ''";
ErrUnmatchedLbkt = "unmatched '['";
ErrUnmatchedRbkt = "unmatched ']'";
ErrBadRange = "bad range in character class";
ErrExtraneousBackslash = "extraneous backslash";
ErrBadClosure = "repeated closure **, ++, etc.";
ErrBareClosure = "closure applies to nothing";
ErrBadBackslash = "illegal backslash escape";
)
// An instruction executed by the NFA
type instr interface {
kind() int; // the type of this instruction: _CHAR, _ANY, etc.
next() instr; // the instruction to execute after this one
setNext(i instr);
index() int;
setIndex(i int);
print();
}
// Fields and methods common to all instructions
type common struct {
_next instr;
_index int;
}
func (c *common) next() instr { return c._next }
func (c *common) setNext(i instr) { c._next = i }
func (c *common) index() int { return c._index }
func (c *common) setIndex(i int) { c._index = i }
// The representation of a compiled regular expression.
// The public interface is entirely through methods.
type Regexp struct {
expr string; // the original expression
inst []instr;
start instr;
nbra int; // number of brackets in expression, for subexpressions
}
const (
_START = // beginning of program
iota;
_END; // end of program: success
_BOT; // '^' beginning of text
_EOT; // '$' 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") }
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 re.inst {
ni[i] = j
}
re.inst = ni;
}
re.inst = re.inst[0 : n+1];
re.inst[n] = i;
return i;
}
type parser struct {
re *Regexp;
error string;
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:]);
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 special(c int) bool {
s := `\.+*?()|[]^$`;
for i := 0; i < len(s); i++ {
if c == int(s[i]) {
return true
}
}
return false;
}
func specialcclass(c int) bool {
s := `\-[]`;
for i := 0; i < len(s); i++ {
if c == int(s[i]) {
return true
}
}
return false;
}
func (p *parser) charClass() instr {
cc := newCharClass();
if p.c() == '^' {
cc.negate = true;
p.nextc();
}
left := -1;
for {
switch c := p.c(); c {
case ']', endOfFile:
if left >= 0 {
p.error = ErrBadRange;
return nil;
}
// Is it [^\n]?
if cc.negate && len(cc.ranges) == 2 &&
cc.ranges[0] == '\n' && cc.ranges[1] == '\n' {
nl := new(_NotNl);
p.re.add(nl);
return nl;
}
p.re.add(cc);
return cc;
case '-': // do this before backslash processing
p.error = ErrBadRange;
return nil;
case '\\':
c = p.nextc();
switch {
case c == endOfFile:
p.error = ErrExtraneousBackslash;
return nil;
case c == 'n':
c = '\n'
case specialcclass(c):
// c is as delivered
default:
p.error = ErrBadBackslash;
return nil;
}
fallthrough;
default:
p.nextc();
switch {
case left < 0: // first of pair
if p.c() == '-' { // range
p.nextc();
left = c;
} else { // single char
cc.addRange(c, c)
}
case left <= c: // second of pair
cc.addRange(left, c);
left = -1;
default:
p.error = ErrBadRange;
return nil;
}
}
}
return nil;
}
func (p *parser) term() (start, end instr) {
// term() is the leaf of the recursion, so it's sufficient to pick off the
// error state here for early exit.
// The other functions (closure(), concatenation() etc.) assume
// it's safe to recur to here.
if p.error != "" {
return
}
switch c := p.c(); c {
case '|', endOfFile:
return nil, nil
case '*', '+':
p.error = ErrBareClosure;
return;
case ')':
if p.nlpar == 0 {
p.error = ErrUnmatchedRpar;
return;
}
return nil, nil;
case ']':
p.error = ErrUnmatchedRbkt;
return;
case '^':
p.nextc();
start = p.re.add(new(_Bot));
return start, start;
case '$':
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.error != "" {
return
}
if p.c() != ']' {
p.error = ErrUnmatchedLbkt;
return;
}
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.error = ErrUnmatchedLpar;
return;
}
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 == nil {
if end == nil {
p.error = ErrInternal;
return;
}
start = ebra;
} else {
end.setNext(ebra)
}
bra.setNext(start);
return bra, ebra;
case '\\':
c = p.nextc();
switch {
case c == endOfFile:
p.error = ErrExtraneousBackslash;
return;
case c == 'n':
c = '\n'
case special(c):
// c is as delivered
default:
p.error = ErrBadBackslash;
return;
}
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 == nil || p.error != "" {
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.error = ErrBadClosure
}
return;
}
func (p *parser) concatenation() (start, end instr) {
for {
nstart, nend := p.closure();
if p.error != "" {
return
}
switch {
case nstart == nil: // end of this concatenation
if start == nil { // this is the empty string
nop := p.re.add(new(_Nop));
return nop, nop;
}
return;
case start == nil: // 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();
if p.error != "" {
return
}
for {
switch p.c() {
default:
return
case '|':
p.nextc();
nstart, nend := p.concatenation();
if p.error != "" {
return
}
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) doParse() string {
p := newParser(re);
start := new(_Start);
re.add(start);
s, e := p.regexp();
if p.error != "" {
return p.error
}
start.setNext(s);
re.start = start;
e.setNext(re.add(new(_End)));
re.eliminateNops();
return p.error;
}
// 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) {
regexp = new(Regexp);
regexp.expr = str;
regexp.inst = make([]instr, 0, 20);
error = regexp.doParse();
return;
}
// MustCompileRegexp is like CompileRegexp 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 := CompileRegexp(str);
if error != "" {
panicln(`regexp: compiling "`, str, `": `, error)
}
return regexp;
}
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), "";
}
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