/
regexp.go
458 lines (413 loc) · 9.09 KB
/
regexp.go
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package parser
import (
"fmt"
"strconv"
"strings"
"unicode/utf8"
)
const (
WhitespaceChars = " \f\n\r\t\v\u00a0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u2028\u2029\u202f\u205f\u3000\ufeff"
Re2Dot = "[^\r\n\u2028\u2029]"
)
type regexpParseError struct {
offset int
err string
}
type RegexpErrorIncompatible struct {
regexpParseError
}
type RegexpSyntaxError struct {
regexpParseError
}
func (s regexpParseError) Error() string {
return s.err
}
type _RegExp_parser struct {
str string
length int
chr rune // The current character
chrOffset int // The offset of current character
offset int // The offset after current character (may be greater than 1)
err error
goRegexp strings.Builder
passOffset int
}
// TransformRegExp transforms a JavaScript pattern into a Go "regexp" pattern.
//
// re2 (Go) cannot do backtracking, so the presence of a lookahead (?=) (?!) or
// backreference (\1, \2, ...) will cause an error.
//
// re2 (Go) has a different definition for \s: [\t\n\f\r ].
// The JavaScript definition, on the other hand, also includes \v, Unicode "Separator, Space", etc.
//
// If the pattern is valid, but incompatible (contains a lookahead or backreference),
// then this function returns an empty string an error of type RegexpErrorIncompatible.
//
// If the pattern is invalid (not valid even in JavaScript), then this function
// returns an empty string and a generic error.
func TransformRegExp(pattern string) (transformed string, err error) {
if pattern == "" {
return "", nil
}
parser := _RegExp_parser{
str: pattern,
length: len(pattern),
}
err = parser.parse()
if err != nil {
return "", err
}
return parser.ResultString(), nil
}
func (self *_RegExp_parser) ResultString() string {
if self.passOffset != -1 {
return self.str[:self.passOffset]
}
return self.goRegexp.String()
}
func (self *_RegExp_parser) parse() (err error) {
self.read() // Pull in the first character
self.scan()
return self.err
}
func (self *_RegExp_parser) read() {
if self.offset < self.length {
self.chrOffset = self.offset
chr, width := rune(self.str[self.offset]), 1
if chr >= utf8.RuneSelf { // !ASCII
chr, width = utf8.DecodeRuneInString(self.str[self.offset:])
if chr == utf8.RuneError && width == 1 {
self.error(true, "Invalid UTF-8 character")
return
}
}
self.offset += width
self.chr = chr
} else {
self.chrOffset = self.length
self.chr = -1 // EOF
}
}
func (self *_RegExp_parser) stopPassing() {
self.goRegexp.Grow(3 * len(self.str) / 2)
self.goRegexp.WriteString(self.str[:self.passOffset])
self.passOffset = -1
}
func (self *_RegExp_parser) write(p []byte) {
if self.passOffset != -1 {
self.stopPassing()
}
self.goRegexp.Write(p)
}
func (self *_RegExp_parser) writeByte(b byte) {
if self.passOffset != -1 {
self.stopPassing()
}
self.goRegexp.WriteByte(b)
}
func (self *_RegExp_parser) writeString(s string) {
if self.passOffset != -1 {
self.stopPassing()
}
self.goRegexp.WriteString(s)
}
func (self *_RegExp_parser) scan() {
for self.chr != -1 {
switch self.chr {
case '\\':
self.read()
self.scanEscape(false)
case '(':
self.pass()
self.scanGroup()
case '[':
self.scanBracket()
case ')':
self.error(true, "Unmatched ')'")
return
case '.':
self.writeString(Re2Dot)
self.read()
default:
self.pass()
}
}
}
// (...)
func (self *_RegExp_parser) scanGroup() {
str := self.str[self.chrOffset:]
if len(str) > 1 { // A possibility of (?= or (?!
if str[0] == '?' {
ch := str[1]
switch {
case ch == '=' || ch == '!':
self.error(false, "re2: Invalid (%s) <lookahead>", self.str[self.chrOffset:self.chrOffset+2])
return
case ch == '<':
self.error(false, "re2: Invalid (%s) <lookbehind>", self.str[self.chrOffset:self.chrOffset+2])
return
case ch != ':':
self.error(true, "Invalid group")
return
}
}
}
for self.chr != -1 && self.chr != ')' {
switch self.chr {
case '\\':
self.read()
self.scanEscape(false)
case '(':
self.pass()
self.scanGroup()
case '[':
self.scanBracket()
case '.':
self.writeString(Re2Dot)
self.read()
default:
self.pass()
continue
}
}
if self.chr != ')' {
self.error(true, "Unterminated group")
return
}
self.pass()
}
// [...]
func (self *_RegExp_parser) scanBracket() {
str := self.str[self.chrOffset:]
if strings.HasPrefix(str, "[]") {
// [] -- Empty character class
self.writeString("[^\u0000-\U0001FFFF]")
self.offset += 1
self.read()
return
}
if strings.HasPrefix(str, "[^]") {
self.writeString("[\u0000-\U0001FFFF]")
self.offset += 2
self.read()
return
}
self.pass()
for self.chr != -1 {
if self.chr == ']' {
break
} else if self.chr == '\\' {
self.read()
self.scanEscape(true)
continue
}
self.pass()
}
if self.chr != ']' {
self.error(true, "Unterminated character class")
return
}
self.pass()
}
// \...
func (self *_RegExp_parser) scanEscape(inClass bool) {
offset := self.chrOffset
var length, base uint32
switch self.chr {
case '0', '1', '2', '3', '4', '5', '6', '7':
var value int64
size := 0
for {
digit := int64(digitValue(self.chr))
if digit >= 8 {
// Not a valid digit
break
}
value = value*8 + digit
self.read()
size += 1
}
if size == 1 { // The number of characters read
if value != 0 {
// An invalid backreference
self.error(false, "re2: Invalid \\%d <backreference>", value)
return
}
self.passString(offset-1, self.chrOffset)
return
}
tmp := []byte{'\\', 'x', '0', 0}
if value >= 16 {
tmp = tmp[0:2]
} else {
tmp = tmp[0:3]
}
tmp = strconv.AppendInt(tmp, value, 16)
self.write(tmp)
return
case '8', '9':
self.read()
self.error(false, "re2: Invalid \\%s <backreference>", self.str[offset:self.chrOffset])
return
case 'x':
self.read()
length, base = 2, 16
case 'u':
self.read()
if self.chr == '{' {
self.read()
length, base = 0, 16
} else {
length, base = 4, 16
}
case 'b':
if inClass {
self.write([]byte{'\\', 'x', '0', '8'})
self.read()
return
}
fallthrough
case 'B':
fallthrough
case 'd', 'D', 'w', 'W':
// This is slightly broken, because ECMAScript
// includes \v in \s, \S, while re2 does not
fallthrough
case '\\':
fallthrough
case 'f', 'n', 'r', 't', 'v':
self.passString(offset-1, self.offset)
self.read()
return
case 'c':
self.read()
var value int64
if 'a' <= self.chr && self.chr <= 'z' {
value = int64(self.chr - 'a' + 1)
} else if 'A' <= self.chr && self.chr <= 'Z' {
value = int64(self.chr - 'A' + 1)
} else {
self.writeByte('c')
return
}
tmp := []byte{'\\', 'x', '0', 0}
if value >= 16 {
tmp = tmp[0:2]
} else {
tmp = tmp[0:3]
}
tmp = strconv.AppendInt(tmp, value, 16)
self.write(tmp)
self.read()
return
case 's':
if inClass {
self.writeString(WhitespaceChars)
} else {
self.writeString("[" + WhitespaceChars + "]")
}
self.read()
return
case 'S':
if inClass {
self.error(false, "S in class")
return
} else {
self.writeString("[^" + WhitespaceChars + "]")
}
self.read()
return
default:
// $ is an identifier character, so we have to have
// a special case for it here
if self.chr == '$' || self.chr < utf8.RuneSelf && !isIdentifierPart(self.chr) {
// A non-identifier character needs escaping
self.passString(offset-1, self.offset)
self.read()
return
}
// Unescape the character for re2
self.pass()
return
}
// Otherwise, we're a \u.... or \x...
valueOffset := self.chrOffset
if length > 0 {
for length := length; length > 0; length-- {
digit := uint32(digitValue(self.chr))
if digit >= base {
// Not a valid digit
goto skip
}
self.read()
}
} else {
for self.chr != '}' && self.chr != -1 {
digit := uint32(digitValue(self.chr))
if digit >= base {
// Not a valid digit
goto skip
}
self.read()
}
}
if length == 4 || length == 0 {
self.write([]byte{
'\\',
'x',
'{',
})
self.passString(valueOffset, self.chrOffset)
if length != 0 {
self.writeByte('}')
}
} else if length == 2 {
self.passString(offset-1, valueOffset+2)
} else {
// Should never, ever get here...
self.error(true, "re2: Illegal branch in scanEscape")
return
}
return
skip:
self.passString(offset, self.chrOffset)
}
func (self *_RegExp_parser) pass() {
if self.passOffset == self.chrOffset {
self.passOffset = self.offset
} else {
if self.passOffset != -1 {
self.stopPassing()
}
if self.chr != -1 {
self.goRegexp.WriteRune(self.chr)
}
}
self.read()
}
func (self *_RegExp_parser) passString(start, end int) {
if self.passOffset == start {
self.passOffset = end
return
}
if self.passOffset != -1 {
self.stopPassing()
}
self.goRegexp.WriteString(self.str[start:end])
}
func (self *_RegExp_parser) error(fatal bool, msg string, msgValues ...interface{}) {
if self.err != nil {
return
}
e := regexpParseError{
offset: self.offset,
err: fmt.Sprintf(msg, msgValues...),
}
if fatal {
self.err = RegexpSyntaxError{e}
} else {
self.err = RegexpErrorIncompatible{e}
}
self.offset = self.length
self.chr = -1
}