// Copyright 2011 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 syntax
import (
"sort"
"strings"
"unicode"
"unicode/utf8"
)
// An Error describes a failure to parse a regular expression
// and gives the offending expression.
type Error struct {
Code ErrorCode
Expr string
}
func (e *Error) Error() string {
return "error parsing regexp: " + e.Code.String() + ": `" + e.Expr + "`"
}
// An ErrorCode describes a failure to parse a regular expression.
type ErrorCode string
const (
// Unexpected error
ErrInternalError ErrorCode = "regexp/syntax: internal error"
// Parse errors
ErrInvalidCharClass ErrorCode = "invalid character class"
ErrInvalidCharRange ErrorCode = "invalid character class range"
ErrInvalidEscape ErrorCode = "invalid escape sequence"
ErrInvalidNamedCapture ErrorCode = "invalid named capture"
ErrInvalidPerlOp ErrorCode = "invalid or unsupported Perl syntax"
ErrInvalidRepeatOp ErrorCode = "invalid nested repetition operator"
ErrInvalidRepeatSize ErrorCode = "invalid repeat count"
ErrInvalidUTF8 ErrorCode = "invalid UTF-8"
ErrMissingBracket ErrorCode = "missing closing ]"
ErrMissingParen ErrorCode = "missing closing )"
ErrMissingRepeatArgument ErrorCode = "missing argument to repetition operator"
ErrTrailingBackslash ErrorCode = "trailing backslash at end of expression"
ErrUnexpectedParen ErrorCode = "unexpected )"
)
func (e ErrorCode) String() string {
return string(e)
}
// Flags control the behavior of the parser and record information about regexp context.
type Flags uint16
const (
FoldCase Flags = 1 << iota // case-insensitive match
Literal // treat pattern as literal string
ClassNL // allow character classes like [^a-z] and [[:space:]] to match newline
DotNL // allow . to match newline
OneLine // treat ^ and $ as only matching at beginning and end of text
NonGreedy // make repetition operators default to non-greedy
PerlX // allow Perl extensions
UnicodeGroups // allow \p{Han}, \P{Han} for Unicode group and negation
WasDollar // regexp OpEndText was $, not \z
Simple // regexp contains no counted repetition
MatchNL = ClassNL | DotNL
Perl = ClassNL | OneLine | PerlX | UnicodeGroups // as close to Perl as possible
POSIX Flags = 0 // POSIX syntax
)
// Pseudo-ops for parsing stack.
const (
opLeftParen = opPseudo + iota
opVerticalBar
)
type parser struct {
flags Flags // parse mode flags
stack []*Regexp // stack of parsed expressions
free *Regexp
numCap int // number of capturing groups seen
wholeRegexp string
tmpClass []rune // temporary char class work space
}
func (p *parser) newRegexp(op Op) *Regexp {
re := p.free
if re != nil {
p.free = re.Sub0[0]
*re = Regexp{}
} else {
re = new(Regexp)
}
re.Op = op
return re
}
func (p *parser) reuse(re *Regexp) {
re.Sub0[0] = p.free
p.free = re
}
// Parse stack manipulation.
// push pushes the regexp re onto the parse stack and returns the regexp.
func (p *parser) push(re *Regexp) *Regexp {
if re.Op == OpCharClass && len(re.Rune) == 2 && re.Rune[0] == re.Rune[1] {
// Single rune.
if p.maybeConcat(re.Rune[0], p.flags&^FoldCase) {
return nil
}
re.Op = OpLiteral
re.Rune = re.Rune[:1]
re.Flags = p.flags &^ FoldCase
} else if re.Op == OpCharClass && len(re.Rune) == 4 &&
re.Rune[0] == re.Rune[1] && re.Rune[2] == re.Rune[3] &&
unicode.SimpleFold(re.Rune[0]) == re.Rune[2] &&
unicode.SimpleFold(re.Rune[2]) == re.Rune[0] ||
re.Op == OpCharClass && len(re.Rune) == 2 &&
re.Rune[0]+1 == re.Rune[1] &&
unicode.SimpleFold(re.Rune[0]) == re.Rune[1] &&
unicode.SimpleFold(re.Rune[1]) == re.Rune[0] {
// Case-insensitive rune like [Aa] or [Δδ].
if p.maybeConcat(re.Rune[0], p.flags|FoldCase) {
return nil
}
// Rewrite as (case-insensitive) literal.
re.Op = OpLiteral
re.Rune = re.Rune[:1]
re.Flags = p.flags | FoldCase
} else {
// Incremental concatenation.
p.maybeConcat(-1, 0)
}
p.stack = append(p.stack, re)
return re
}
// maybeConcat implements incremental concatenation
// of literal runes into string nodes. The parser calls this
// before each push, so only the top fragment of the stack
// might need processing. Since this is called before a push,
// the topmost literal is no longer subject to operators like *
// (Otherwise ab* would turn into (ab)*.)
// If r >= 0 and there's a node left over, maybeConcat uses it
// to push r with the given flags.
// maybeConcat reports whether r was pushed.
func (p *parser) maybeConcat(r rune, flags Flags) bool {
n := len(p.stack)
if n < 2 {
return false
}
re1 := p.stack[n-1]
re2 := p.stack[n-2]
if re1.Op != OpLiteral || re2.Op != OpLiteral || re1.Flags&FoldCase != re2.Flags&FoldCase {
return false
}
// Push re1 into re2.
re2.Rune = append(re2.Rune, re1.Rune...)
// Reuse re1 if possible.
if r >= 0 {
re1.Rune = re1.Rune0[:1]
re1.Rune[0] = r
re1.Flags = flags
return true
}
p.stack = p.stack[:n-1]
p.reuse(re1)
return false // did not push r
}
// newLiteral returns a new OpLiteral Regexp with the given flags
func (p *parser) newLiteral(r rune, flags Flags) *Regexp {
re := p.newRegexp(OpLiteral)
re.Flags = flags
if flags&FoldCase != 0 {
r = minFoldRune(r)
}
re.Rune0[0] = r
re.Rune = re.Rune0[:1]
return re
}
// minFoldRune returns the minimum rune fold-equivalent to r.
func minFoldRune(r rune) rune {
if r < minFold || r > maxFold {
return r
}
min := r
r0 := r
for r = unicode.SimpleFold(r); r != r0; r = unicode.SimpleFold(r) {
if min > r {
min = r
}
}
return min
}
// literal pushes a literal regexp for the rune r on the stack
// and returns that regexp.
func (p *parser) literal(r rune) {
p.push(p.newLiteral(r, p.flags))
}
// op pushes a regexp with the given op onto the stack
// and returns that regexp.
func (p *parser) op(op Op) *Regexp {
re := p.newRegexp(op)
re.Flags = p.flags
return p.push(re)
}
// repeat replaces the top stack element with itself repeated according to op, min, max.
// before is the regexp suffix starting at the repetition operator.
// after is the regexp suffix following after the repetition operator.
// repeat returns an updated 'after' and an error, if any.
func (p *parser) repeat(op Op, min, max int, before, after, lastRepeat string) (string, error) {
flags := p.flags
if p.flags&PerlX != 0 {
if len(after) > 0 && after[0] == '?' {
after = after[1:]
flags ^= NonGreedy
}
if lastRepeat != "" {
// In Perl it is not allowed to stack repetition operators:
// a** is a syntax error, not a doubled star, and a++ means
// something else entirely, which we don't support!
return "", &Error{ErrInvalidRepeatOp, lastRepeat[:len(lastRepeat)-len(after)]}
}
}
n := len(p.stack)
if n == 0 {
return "", &Error{ErrMissingRepeatArgument, before[:len(before)-len(after)]}
}
sub := p.stack[n-1]
if sub.Op >= opPseudo {
return "", &Error{ErrMissingRepeatArgument, before[:len(before)-len(after)]}
}
re := p.newRegexp(op)
re.Min = min
re.Max = max
re.Flags = flags
re.Sub = re.Sub0[:1]
re.Sub[0] = sub
p.stack[n-1] = re
if op == OpRepeat && (min >= 2 || max >= 2) && !repeatIsValid(re, 1000) {
return "", &Error{ErrInvalidRepeatSize, before[:len(before)-len(after)]}
}
return after, nil
}
// repeatIsValid reports whether the repetition re is valid.
// Valid means that the combination of the top-level repetition
// and any inner repetitions does not exceed n copies of the
// innermost thing.
// This function rewalks the regexp tree and is called for every repetition,
// so we have to worry about inducing quadratic behavior in the parser.
// We avoid this by only calling repeatIsValid when min or max >= 2.
// In that case the depth of any >= 2 nesting can only get to 9 without
// triggering a parse error, so each subtree can only be rewalked 9 times.
func repeatIsValid(re *Regexp, n int) bool {
if re.Op == OpRepeat {
m := re.Max
if m == 0 {
return true
}
if m < 0 {
m = re.Min
}
if m > n {
return false
}
if m > 0 {
n /= m
}
}
for _, sub := range re.Sub {
if !repeatIsValid(sub, n) {
return false
}
}
return true
}
// concat replaces the top of the stack (above the topmost '|' or '(') with its concatenation.
func (p *parser) concat() *Regexp {
p.maybeConcat(-1, 0)
// Scan down to find pseudo-operator | or (.
i := len(p.stack)
for i > 0 && p.stack[i-1].Op < opPseudo {
i--
}
subs := p.stack[i:]
p.stack = p.stack[:i]
// Empty concatenation is special case.
if len(subs) == 0 {
return p.push(p.newRegexp(OpEmptyMatch))
}
return p.push(p.collapse(subs, OpConcat))
}
// alternate replaces the top of the stack (above the topmost '(') with its alternation.
func (p *parser) alternate() *Regexp {
// Scan down to find pseudo-operator (.
// There are no | above (.
i := len(p.stack)
for i > 0 && p.stack[i-1].Op < opPseudo {
i--
}
subs := p.stack[i:]
p.stack = p.stack[:i]
// Make sure top class is clean.
// All the others already are (see swapVerticalBar).
if len(subs) > 0 {
cleanAlt(subs[len(subs)-1])
}
// Empty alternate is special case
// (shouldn't happen but easy to handle).
if len(subs) == 0 {
return p.push(p.newRegexp(OpNoMatch))
}
return p.push(p.collapse(subs, OpAlternate))
}
// cleanAlt cleans re for eventual inclusion in an alternation.
func cleanAlt(re *Regexp) {
switch re.Op {
case OpCharClass:
re.Rune = cleanClass(&re.Rune)
if len(re.Rune) == 2 && re.Rune[0] == 0 && re.Rune[1] == unicode.MaxRune {
re.Rune = nil
re.Op = OpAnyChar
return
}
if len(re.Rune) == 4 && re.Rune[0] == 0 && re.Rune[1] == '\n'-1 && re.Rune[2] == '\n'+1 && re.Rune[3] == unicode.MaxRune {
re.Rune = nil
re.Op = OpAnyCharNotNL
return
}
if cap(re.Rune)-len(re.Rune) > 100 {
// re.Rune will not grow any more.
// Make a copy or inline to reclaim storage.
re.Rune = append(re.Rune0[:0], re.Rune...)
}
}
}
// collapse returns the result of applying op to sub.
// If sub contains op nodes, they all get hoisted up
// so that there is never a concat of a concat or an
// alternate of an alternate.
func (p *parser) collapse(subs []*Regexp, op Op) *Regexp {
if len(subs) == 1 {
return subs[0]
}
re := p.newRegexp(op)
re.Sub = re.Sub0[:0]
for _, sub := range subs {
if sub.Op == op {
re.Sub = append(re.Sub, sub.Sub...)
p.reuse(sub)
} else {
re.Sub = append(re.Sub, sub)
}
}
if op == OpAlternate {
re.Sub = p.factor(re.Sub)
if len(re.Sub) == 1 {
old := re
re = re.Sub[0]
p.reuse(old)
}
}
return re
}
// factor factors common prefixes from the alternation list sub.
// It returns a replacement list that reuses the same storage and
// frees (passes to p.reuse) any removed *Regexps.
//
// For example,
// ABC|ABD|AEF|BCX|BCY
// simplifies by literal prefix extraction to
// A(B(C|D)|EF)|BC(X|Y)
// which simplifies by character class introduction to
// A(B[CD]|EF)|BC[XY]
//
func (p *parser) factor(sub []*Regexp) []*Regexp {
if len(sub) < 2 {
return sub
}
// Round 1: Factor out common literal prefixes.
var str []rune
var strflags Flags
start := 0
out := sub[:0]
for i := 0; i <= len(sub); i++ {
// Invariant: the Regexps that were in sub[0:start] have been
// used or marked for reuse, and the slice space has been reused
// for out (len(out) <= start).
//
// Invariant: sub[start:i] consists of regexps that all begin
// with str as modified by strflags.
var istr []rune
var iflags Flags
if i < len(sub) {
istr, iflags = p.leadingString(sub[i])
if iflags == strflags {
same := 0
for same < len(str) && same < len(istr) && str[same] == istr[same] {
same++
}
if same > 0 {
// Matches at least one rune in current range.
// Keep going around.
str = str[:same]
continue
}
}
}
// Found end of a run with common leading literal string:
// sub[start:i] all begin with str[0:len(str)], but sub[i]
// does not even begin with str[0].
//
// Factor out common string and append factored expression to out.
if i == start {
// Nothing to do - run of length 0.
} else if i == start+1 {
// Just one: don't bother factoring.
out = append(out, sub[start])
} else {
// Construct factored form: prefix(suffix1|suffix2|...)
prefix := p.newRegexp(OpLiteral)
prefix.Flags = strflags
prefix.Rune = append(prefix.Rune[:0], str...)
for j := start; j < i; j++ {
sub[j] = p.removeLeadingString(sub[j], len(str))
}
suffix := p.collapse(sub[start:i], OpAlternate) // recurse
re := p.newRegexp(OpConcat)
re.Sub = append(re.Sub[:0], prefix, suffix)
out = append(out, re)
}
// Prepare for next iteration.
start = i
str = istr
strflags = iflags
}
sub = out
// Round 2: Factor out common simple prefixes,
// just the first piece of each concatenation.
// This will be good enough a lot of the time.
//
// Complex subexpressions (e.g. involving quantifiers)
// are not safe to factor because that collapses their
// distinct paths through the automaton, which affects
// correctness in some cases.
start = 0
out = sub[:0]
var first *Regexp
for i := 0; i <= len(sub); i++ {
// Invariant: the Regexps that were in sub[0:start] have been
// used or marked for reuse, and the slice space has been reused
// for out (len(out) <= start).
//
// Invariant: sub[start:i] consists of regexps that all begin with ifirst.
var ifirst *Regexp
if i < len(sub) {
ifirst = p.leadingRegexp(sub[i])
if first != nil && first.Equal(ifirst) &&
// first must be a character class OR a fixed repeat of a character class.
(isCharClass(first) || (first.Op == OpRepeat && first.Min == first.Max && isCharClass(first.Sub[0]))) {
continue
}
}
// Found end of a run with common leading regexp:
// sub[start:i] all begin with first but sub[i] does not.
//
// Factor out common regexp and append factored expression to out.
if i == start {
// Nothing to do - run of length 0.
} else if i == start+1 {
// Just one: don't bother factoring.
out = append(out, sub[start])
} else {
// Construct factored form: prefix(suffix1|suffix2|...)
prefix := first
for j := start; j < i; j++ {
reuse := j != start // prefix came from sub[start]
sub[j] = p.removeLeadingRegexp(sub[j], reuse)
}
suffix := p.collapse(sub[start:i], OpAlternate) // recurse
re := p.newRegexp(OpConcat)
re.Sub = append(re.Sub[:0], prefix, suffix)
out = append(out, re)
}
// Prepare for next iteration.
start = i
first = ifirst
}
sub = out
// Round 3: Collapse runs of single literals into character classes.
start = 0
out = sub[:0]
for i := 0; i <= len(sub); i++ {
// Invariant: the Regexps that were in sub[0:start] have been
// used or marked for reuse, and the slice space has been reused
// for out (len(out) <= start).
//
// Invariant: sub[start:i] consists of regexps that are either
// literal runes or character classes.
if i < len(sub) && isCharClass(sub[i]) {
continue
}
// sub[i] is not a char or char class;
// emit char class for sub[start:i]...
if i == start {
// Nothing to do - run of length 0.
} else if i == start+1 {
out = append(out, sub[start])
} else {
// Make new char class.
// Start with most complex regexp in sub[start].
max := start
for j := start + 1; j < i; j++ {
if sub[max].Op < sub[j].Op || sub[max].Op == sub[j].Op && len(sub[max].Rune) < len(sub[j].Rune) {
max = j
}
}
sub[start], sub[max] = sub[max], sub[start]
for j := start + 1; j < i; j++ {
mergeCharClass(sub[start], sub[j])
p.reuse(sub[j])
}
cleanAlt(sub[start])
out = append(out, sub[start])
}
// ... and then emit sub[i].
if i < len(sub) {
out = append(out, sub[i])
}
start = i + 1
}
sub = out
// Round 4: Collapse runs of empty matches into a single empty match.
start = 0
out = sub[:0]
for i := range sub {
if i+1 < len(sub) && sub[i].Op == OpEmptyMatch && sub[i+1].Op == OpEmptyMatch {
continue
}
out = append(out, sub[i])
}
sub = out
return sub
}
// leadingString returns the leading literal string that re begins with.
// The string refers to storage in re or its children.
func (p *parser) leadingString(re *Regexp) ([]rune, Flags) {
if re.Op == OpConcat && len(re.Sub) > 0 {
re = re.Sub[0]
}
if re.Op != OpLiteral {
return nil, 0
}
return re.Rune, re.Flags & FoldCase
}
// removeLeadingString removes the first n leading runes
// from the beginning of re. It returns the replacement for re.
func (p *parser) removeLeadingString(re *Regexp, n int) *Regexp {
if re.Op == OpConcat && len(re.Sub) > 0 {
// Removing a leading string in a concatenation
// might simplify the concatenation.
sub := re.Sub[0]
sub = p.removeLeadingString(sub, n)
re.Sub[0] = sub
if sub.Op == OpEmptyMatch {
p.reuse(sub)
switch len(re.Sub) {
case 0, 1:
// Impossible but handle.
re.Op = OpEmptyMatch
re.Sub = nil
case 2:
old := re
re = re.Sub[1]
p.reuse(old)
default:
copy(re.Sub, re.Sub[1:])
re.Sub = re.Sub[:len(re.Sub)-1]
}
}
return re
}
if re.Op == OpLiteral {
re.Rune = re.Rune[:copy(re.Rune, re.Rune[n:])]
if len(re.Rune) == 0 {
re.Op = OpEmptyMatch
}
}
return re
}
// leadingRegexp returns the leading regexp that re begins with.
// The regexp refers to storage in re or its children.
func (p *parser) leadingRegexp(re *Regexp) *Regexp {
if re.Op == OpEmptyMatch {
return nil
}
if re.Op == OpConcat && len(re.Sub) > 0 {
sub := re.Sub[0]
if sub.Op == OpEmptyMatch {
return nil
}
return sub
}
return re
}
// removeLeadingRegexp removes the leading regexp in re.
// It returns the replacement for re.
// If reuse is true, it passes the removed regexp (if no longer needed) to p.reuse.
func (p *parser) removeLeadingRegexp(re *Regexp, reuse bool) *Regexp {
if re.Op == OpConcat && len(re.Sub) > 0 {
if reuse {
p.reuse(re.Sub[0])
}
re.Sub = re.Sub[:copy(re.Sub, re.Sub[1:])]
switch len(re.Sub) {
case 0:
re.Op = OpEmptyMatch
re.Sub = nil
case 1:
old := re
re = re.Sub[0]
p.reuse(old)
}
return re
}
if reuse {
p.reuse(re)
}
return p.newRegexp(OpEmptyMatch)
}
func literalRegexp(s string, flags Flags) *Regexp {
re := &Regexp{Op: OpLiteral}
re.Flags = flags
re.Rune = re.Rune0[:0] // use local storage for small strings
for _, c := range s {
if len(re.Rune) >= cap(re.Rune) {
// string is too long to fit in Rune0. let Go handle it
re.Rune = []rune(s)
break
}
re.Rune = append(re.Rune, c)
}
return re
}
// Parsing.
// Parse parses a regular expression string s, controlled by the specified
// Flags, and returns a regular expression parse tree. The syntax is
// described in the top-level comment.
func Parse(s string, flags Flags) (*Regexp, error) {
if flags&Literal != 0 {
// Trivial parser for literal string.
if err := checkUTF8(s); err != nil {
return nil, err
}
return literalRegexp(s, flags), nil
}
// Otherwise, must do real work.
var (
p parser
err error
c rune
op Op
lastRepeat string
)
p.flags = flags
p.wholeRegexp = s
t := s
for t != "" {
repeat := ""
BigSwitch:
switch t[0] {
default:
if c, t, err = nextRune(t); err != nil {
return nil, err
}
p.literal(c)
case '(':
if p.flags&PerlX != 0 && len(t) >= 2 && t[1] == '?' {
// Flag changes and non-capturing groups.
if t, err = p.parsePerlFlags(t); err != nil {
return nil, err
}
break
}
p.numCap++
p.op(opLeftParen).Cap = p.numCap
t = t[1:]
case '|':
if err = p.parseVerticalBar(); err != nil {
return nil, err
}
t = t[1:]
case ')':
if err = p.parseRightParen(); err != nil {
return nil, err
}
t = t[1:]
case '^':
if p.flags&OneLine != 0 {
p.op(OpBeginText)
} else {
p.op(OpBeginLine)
}
t = t[1:]
case '$':
if p.flags&OneLine != 0 {
p.op(OpEndText).Flags |= WasDollar
} else {
p.op(OpEndLine)
}
t = t[1:]
case '.':
if p.flags&DotNL != 0 {
p.op(OpAnyChar)
} else {
p.op(OpAnyCharNotNL)
}
t = t[1:]
case '[':
if t, err = p.parseClass(t); err != nil {
return nil, err
}
case '*', '+', '?':
before := t
switch t[0] {
case '*':
op = OpStar
case '+':
op = OpPlus
case '?':
op = OpQuest
}
after := t[1:]
if after, err = p.repeat(op, 0, 0, before, after, lastRepeat); err != nil {
return nil, err
}
repeat = before
t = after
case '{':
op = OpRepeat
before := t
min, max, after, ok := p.parseRepeat(t)
if !ok {
// If the repeat cannot be parsed, { is a literal.
p.literal('{')
t = t[1:]
break
}
if min < 0 || min > 1000 || max > 1000 || max >= 0 && min > max {
// Numbers were too big, or max is present and min > max.
return nil, &Error{ErrInvalidRepeatSize, before[:len(before)-len(after)]}
}
if after, err = p.repeat(op, min, max, before, after, lastRepeat); err != nil {
return nil, err
}
repeat = before
t = after
case '\\':
if p.flags&PerlX != 0 && len(t) >= 2 {
switch t[1] {
case 'A':
p.op(OpBeginText)
t = t[2:]
break BigSwitch
case 'b':
p.op(OpWordBoundary)
t = t[2:]
break BigSwitch
case 'B':
p.op(OpNoWordBoundary)
t = t[2:]
break BigSwitch
case 'C':
// any byte; not supported
return nil, &Error{ErrInvalidEscape, t[:2]}
case 'Q':
// \Q ... \E: the ... is always literals
var lit string
if i := strings.Index(t, `\E`); i < 0 {
lit = t[2:]
t = ""
} else {
lit = t[2:i]
t = t[i+2:]
}
for lit != "" {
c, rest, err := nextRune(lit)
if err != nil {
return nil, err
}
p.literal(c)
lit = rest
}
break BigSwitch
case 'z':
p.op(OpEndText)
t = t[2:]
break BigSwitch
}
}
re := p.newRegexp(OpCharClass)
re.Flags = p.flags
// Look for Unicode character group like \p{Han}
if len(t) >= 2 && (t[1] == 'p' || t[1] == 'P') {
r, rest, err := p.parseUnicodeClass(t, re.Rune0[:0])
if err != nil {
return nil, err
}
if r != nil {
re.Rune = r
t = rest
p.push(re)
break BigSwitch
}
}
// Perl character class escape.
if r, rest := p.parsePerlClassEscape(t, re.Rune0[:0]); r != nil {
re.Rune = r
t = rest
p.push(re)
break BigSwitch
}
p.reuse(re)
// Ordinary single-character escape.
if c, t, err = p.parseEscape(t); err != nil {
return nil, err
}
p.literal(c)
}
lastRepeat = repeat
}
p.concat()
if p.swapVerticalBar() {
// pop vertical bar
p.stack = p.stack[:len(p.stack)-1]
}
p.alternate()
n := len(p.stack)
if n != 1 {
return nil, &Error{ErrMissingParen, s}
}
return p.stack[0], nil
}
// parseRepeat parses {min} (max=min) or {min,} (max=-1) or {min,max}.
// If s is not of that form, it returns ok == false.
// If s has the right form but the values are too big, it returns min == -1, ok == true.
func (p *parser) parseRepeat(s string) (min, max int, rest string, ok bool) {
if s == "" || s[0] != '{' {
return
}
s = s[1:]
var ok1 bool
if min, s, ok1 = p.parseInt(s); !ok1 {
return
}
if s == "" {
return
}
if s[0] != ',' {
max = min
} else {
s = s[1:]
if s == "" {
return
}
if s[0] == '}' {
max = -1
} else if max, s, ok1 = p.parseInt(s); !ok1 {
return
} else if max < 0 {
// parseInt found too big a number
min = -1
}
}
if s == "" || s[0] != '}' {
return
}
rest = s[1:]
ok = true
return
}
// parsePerlFlags parses a Perl flag setting or non-capturing group or both,
// like (?i) or (?: or (?i:. It removes the prefix from s and updates the parse state.
// The caller must have ensured that s begins with "(?".
func (p *parser) parsePerlFlags(s string) (rest string, err error) {
t := s
// Check for named captures, first introduced in Python's regexp library.
// As usual, there are three slightly different syntaxes:
//
// (?P<name>expr) the original, introduced by Python
// (?<name>expr) the .NET alteration, adopted by Perl 5.10
// (?'name'expr) another .NET alteration, adopted by Perl 5.10
//
// Perl 5.10 gave in and implemented the Python version too,
// but they claim that the last two are the preferred forms.
// PCRE and languages based on it (specifically, PHP and Ruby)
// support all three as well. EcmaScript 4 uses only the Python form.
//
// In both the open source world (via Code Search) and the
// Google source tree, (?P<expr>name) is the dominant form,
// so that's the one we implement. One is enough.
if len(t) > 4 && t[2] == 'P' && t[3] == '<' {
// Pull out name.
end := strings.IndexRune(t, '>')
if end < 0 {
if err = checkUTF8(t); err != nil {
return "", err
}
return "", &Error{ErrInvalidNamedCapture, s}
}
capture := t[:end+1] // "(?P<name>"
name := t[4:end] // "name"
if err = checkUTF8(name); err != nil {
return "", err
}
if !isValidCaptureName(name) {
return "", &Error{ErrInvalidNamedCapture, capture}
}
// Like ordinary capture, but named.
p.numCap++
re := p.op(opLeftParen)
re.Cap = p.numCap
re.Name = name
return t[end+1:], nil
}
// Non-capturing group. Might also twiddle Perl flags.
var c rune
t = t[2:] // skip (?
flags := p.flags
sign := +1
sawFlag := false
Loop:
for t != "" {
if c, t, err = nextRune(t); err != nil {
return "", err
}
switch c {
default:
break Loop
// Flags.
case 'i':
flags |= FoldCase
sawFlag = true
case 'm':
flags &^= OneLine
sawFlag = true
case 's':
flags |= DotNL
sawFlag = true
case 'U':
flags |= NonGreedy
sawFlag = true
// Switch to negation.
case '-':
if sign < 0 {
break Loop
}
sign = -1
// Invert flags so that | above turn into &^ and vice versa.
// We'll invert flags again before using it below.
flags = ^flags
sawFlag = false
// End of flags, starting group or not.
case ':', ')':
if sign < 0 {
if !sawFlag {
break Loop
}
flags = ^flags
}
if c == ':' {
// Open new group
p.op(opLeftParen)
}
p.flags = flags
return t, nil
}
}
return "", &Error{ErrInvalidPerlOp, s[:len(s)-len(t)]}
}
// isValidCaptureName reports whether name
// is a valid capture name: [A-Za-z0-9_]+.
// PCRE limits names to 32 bytes.
// Python rejects names starting with digits.
// We don't enforce either of those.
func isValidCaptureName(name string) bool {
if name == "" {
return false
}
for _, c := range name {
if c != '_' && !isalnum(c) {
return false
}
}
return true
}
// parseInt parses a decimal integer.
func (p *parser) parseInt(s string) (n int, rest string, ok bool) {
if s == "" || s[0] < '0' || '9' < s[0] {
return
}
// Disallow leading zeros.
if len(s) >= 2 && s[0] == '0' && '0' <= s[1] && s[1] <= '9' {
return
}
t := s
for s != "" && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
rest = s
ok = true
// Have digits, compute value.
t = t[:len(t)-len(s)]
for i := 0; i < len(t); i++ {
// Avoid overflow.
if n >= 1e8 {
n = -1
break
}
n = n*10 + int(t[i]) - '0'
}
return
}
// can this be represented as a character class?
// single-rune literal string, char class, ., and .|\n.
func isCharClass(re *Regexp) bool {
return re.Op == OpLiteral && len(re.Rune) == 1 ||
re.Op == OpCharClass ||
re.Op == OpAnyCharNotNL ||
re.Op == OpAnyChar
}
// does re match r?
func matchRune(re *Regexp, r rune) bool {
switch re.Op {
case OpLiteral:
return len(re.Rune) == 1 && re.Rune[0] == r
case OpCharClass:
for i := 0; i < len(re.Rune); i += 2 {
if re.Rune[i] <= r && r <= re.Rune[i+1] {
return true
}
}
return false
case OpAnyCharNotNL:
return r != '\n'
case OpAnyChar:
return true
}
return false
}
// parseVerticalBar handles a | in the input.
func (p *parser) parseVerticalBar() error {
p.concat()
// The concatenation we just parsed is on top of the stack.
// If it sits above an opVerticalBar, swap it below
// (things below an opVerticalBar become an alternation).
// Otherwise, push a new vertical bar.
if !p.swapVerticalBar() {
p.op(opVerticalBar)
}
return nil
}
// mergeCharClass makes dst = dst|src.
// The caller must ensure that dst.Op >= src.Op,
// to reduce the amount of copying.
func mergeCharClass(dst, src *Regexp) {
switch dst.Op {
case OpAnyChar:
// src doesn't add anything.
case OpAnyCharNotNL:
// src might add \n
if matchRune(src, '\n') {
dst.Op = OpAnyChar
}
case OpCharClass:
// src is simpler, so either literal or char class
if src.Op == OpLiteral {
dst.Rune = appendLiteral(dst.Rune, src.Rune[0], src.Flags)
} else {
dst.Rune = appendClass(dst.Rune, src.Rune)
}
case OpLiteral:
// both literal
if src.Rune[0] == dst.Rune[0] && src.Flags == dst.Flags {
break
}
dst.Op = OpCharClass
dst.Rune = appendLiteral(dst.Rune[:0], dst.Rune[0], dst.Flags)
dst.Rune = appendLiteral(dst.Rune, src.Rune[0], src.Flags)
}
}
// If the top of the stack is an element followed by an opVerticalBar
// swapVerticalBar swaps the two and returns true.
// Otherwise it returns false.
func (p *parser) swapVerticalBar() bool {
// If above and below vertical bar are literal or char class,
// can merge into a single char class.
n := len(p.stack)
if n >= 3 && p.stack[n-2].Op == opVerticalBar && isCharClass(p.stack[n-1]) && isCharClass(p.stack[n-3]) {
re1 := p.stack[n-1]
re3 := p.stack[n-3]
// Make re3 the more complex of the two.
if re1.Op > re3.Op {
re1, re3 = re3, re1
p.stack[n-3] = re3
}
mergeCharClass(re3, re1)
p.reuse(re1)
p.stack = p.stack[:n-1]
return true
}
if n >= 2 {
re1 := p.stack[n-1]
re2 := p.stack[n-2]
if re2.Op == opVerticalBar {
if n >= 3 {
// Now out of reach.
// Clean opportunistically.
cleanAlt(p.stack[n-3])
}
p.stack[n-2] = re1
p.stack[n-1] = re2
return true
}
}
return false
}
// parseRightParen handles a ) in the input.
func (p *parser) parseRightParen() error {
p.concat()
if p.swapVerticalBar() {
// pop vertical bar
p.stack = p.stack[:len(p.stack)-1]
}
p.alternate()
n := len(p.stack)
if n < 2 {
return &Error{ErrUnexpectedParen, p.wholeRegexp}
}
re1 := p.stack[n-1]
re2 := p.stack[n-2]
p.stack = p.stack[:n-2]
if re2.Op != opLeftParen {
return &Error{ErrUnexpectedParen, p.wholeRegexp}
}
// Restore flags at time of paren.
p.flags = re2.Flags
if re2.Cap == 0 {
// Just for grouping.
p.push(re1)
} else {
re2.Op = OpCapture
re2.Sub = re2.Sub0[:1]
re2.Sub[0] = re1
p.push(re2)
}
return nil
}
// parseEscape parses an escape sequence at the beginning of s
// and returns the rune.
func (p *parser) parseEscape(s string) (r rune, rest string, err error) {
t := s[1:]
if t == "" {
return 0, "", &Error{ErrTrailingBackslash, ""}
}
c, t, err := nextRune(t)
if err != nil {
return 0, "", err
}
Switch:
switch c {
default:
if c < utf8.RuneSelf && !isalnum(c) {
// Escaped non-word characters are always themselves.
// PCRE is not quite so rigorous: it accepts things like
// \q, but we don't. We once rejected \_, but too many
// programs and people insist on using it, so allow \_.
return c, t, nil
}
// Octal escapes.
case '1', '2', '3', '4', '5', '6', '7':
// Single non-zero digit is a backreference; not supported
if t == "" || t[0] < '0' || t[0] > '7' {
break
}
fallthrough
case '0':
// Consume up to three octal digits; already have one.
r = c - '0'
for i := 1; i < 3; i++ {
if t == "" || t[0] < '0' || t[0] > '7' {
break
}
r = r*8 + rune(t[0]) - '0'
t = t[1:]
}
return r, t, nil
// Hexadecimal escapes.
case 'x':
if t == "" {
break
}
if c, t, err = nextRune(t); err != nil {
return 0, "", err
}
if c == '{' {
// Any number of digits in braces.
// Perl accepts any text at all; it ignores all text
// after the first non-hex digit. We require only hex digits,
// and at least one.
nhex := 0
r = 0
for {
if t == "" {
break Switch
}
if c, t, err = nextRune(t); err != nil {
return 0, "", err
}
if c == '}' {
break
}
v := unhex(c)
if v < 0 {
break Switch
}
r = r*16 + v
if r > unicode.MaxRune {
break Switch
}
nhex++
}
if nhex == 0 {
break Switch
}
return r, t, nil
}
// Easy case: two hex digits.
x := unhex(c)
if c, t, err = nextRune(t); err != nil {
return 0, "", err
}
y := unhex(c)
if x < 0 || y < 0 {
break
}
return x*16 + y, t, nil
// C escapes. There is no case 'b', to avoid misparsing
// the Perl word-boundary \b as the C backspace \b
// when in POSIX mode. In Perl, /\b/ means word-boundary
// but /[\b]/ means backspace. We don't support that.
// If you want a backspace, embed a literal backspace
// character or use \x08.
case 'a':
return '\a', t, err
case 'f':
return '\f', t, err
case 'n':
return '\n', t, err
case 'r':
return '\r', t, err
case 't':
return '\t', t, err
case 'v':
return '\v', t, err
}
return 0, "", &Error{ErrInvalidEscape, s[:len(s)-len(t)]}
}
// parseClassChar parses a character class character at the beginning of s
// and returns it.
func (p *parser) parseClassChar(s, wholeClass string) (r rune, rest string, err error) {
if s == "" {
return 0, "", &Error{Code: ErrMissingBracket, Expr: wholeClass}
}
// Allow regular escape sequences even though
// many need not be escaped in this context.
if s[0] == '\\' {
return p.parseEscape(s)
}
return nextRune(s)
}
type charGroup struct {
sign int
class []rune
}
// parsePerlClassEscape parses a leading Perl character class escape like \d
// from the beginning of s. If one is present, it appends the characters to r
// and returns the new slice r and the remainder of the string.
func (p *parser) parsePerlClassEscape(s string, r []rune) (out []rune, rest string) {
if p.flags&PerlX == 0 || len(s) < 2 || s[0] != '\\' {
return
}
g := perlGroup[s[0:2]]
if g.sign == 0 {
return
}
return p.appendGroup(r, g), s[2:]
}
// parseNamedClass parses a leading POSIX named character class like [:alnum:]
// from the beginning of s. If one is present, it appends the characters to r
// and returns the new slice r and the remainder of the string.
func (p *parser) parseNamedClass(s string, r []rune) (out []rune, rest string, err error) {
if len(s) < 2 || s[0] != '[' || s[1] != ':' {
return
}
i := strings.Index(s[2:], ":]")
if i < 0 {
return
}
i += 2
name, s := s[0:i+2], s[i+2:]
g := posixGroup[name]
if g.sign == 0 {
return nil, "", &Error{ErrInvalidCharRange, name}
}
return p.appendGroup(r, g), s, nil
}
func (p *parser) appendGroup(r []rune, g charGroup) []rune {
if p.flags&FoldCase == 0 {
if g.sign < 0 {
r = appendNegatedClass(r, g.class)
} else {
r = appendClass(r, g.class)
}
} else {
tmp := p.tmpClass[:0]
tmp = appendFoldedClass(tmp, g.class)
p.tmpClass = tmp
tmp = cleanClass(&p.tmpClass)
if g.sign < 0 {
r = appendNegatedClass(r, tmp)
} else {
r = appendClass(r, tmp)
}
}
return r
}
var anyTable = &unicode.RangeTable{
R16: []unicode.Range16{{Lo: 0, Hi: 1<<16 - 1, Stride: 1}},
R32: []unicode.Range32{{Lo: 1 << 16, Hi: unicode.MaxRune, Stride: 1}},
}
// unicodeTable returns the unicode.RangeTable identified by name
// and the table of additional fold-equivalent code points.
func unicodeTable(name string) (*unicode.RangeTable, *unicode.RangeTable) {
// Special case: "Any" means any.
if name == "Any" {
return anyTable, anyTable
}
if t := unicode.Categories[name]; t != nil {
return t, unicode.FoldCategory[name]
}
if t := unicode.Scripts[name]; t != nil {
return t, unicode.FoldScript[name]
}
return nil, nil
}
// parseUnicodeClass parses a leading Unicode character class like \p{Han}
// from the beginning of s. If one is present, it appends the characters to r
// and returns the new slice r and the remainder of the string.
func (p *parser) parseUnicodeClass(s string, r []rune) (out []rune, rest string, err error) {
if p.flags&UnicodeGroups == 0 || len(s) < 2 || s[0] != '\\' || s[1] != 'p' && s[1] != 'P' {
return
}
// Committed to parse or return error.
sign := +1
if s[1] == 'P' {
sign = -1
}
t := s[2:]
c, t, err := nextRune(t)
if err != nil {
return
}
var seq, name string
if c != '{' {
// Single-letter name.
seq = s[:len(s)-len(t)]
name = seq[2:]
} else {
// Name is in braces.
end := strings.IndexRune(s, '}')
if end < 0 {
if err = checkUTF8(s); err != nil {
return
}
return nil, "", &Error{ErrInvalidCharRange, s}
}
seq, t = s[:end+1], s[end+1:]
name = s[3:end]
if err = checkUTF8(name); err != nil {
return
}
}
// Group can have leading negation too. \p{^Han} == \P{Han}, \P{^Han} == \p{Han}.
if name != "" && name[0] == '^' {
sign = -sign
name = name[1:]
}
tab, fold := unicodeTable(name)
if tab == nil {
return nil, "", &Error{ErrInvalidCharRange, seq}
}
if p.flags&FoldCase == 0 || fold == nil {
if sign > 0 {
r = appendTable(r, tab)
} else {
r = appendNegatedTable(r, tab)
}
} else {
// Merge and clean tab and fold in a temporary buffer.
// This is necessary for the negative case and just tidy
// for the positive case.
tmp := p.tmpClass[:0]
tmp = appendTable(tmp, tab)
tmp = appendTable(tmp, fold)
p.tmpClass = tmp
tmp = cleanClass(&p.tmpClass)
if sign > 0 {
r = appendClass(r, tmp)
} else {
r = appendNegatedClass(r, tmp)
}
}
return r, t, nil
}
// parseClass parses a character class at the beginning of s
// and pushes it onto the parse stack.
func (p *parser) parseClass(s string) (rest string, err error) {
t := s[1:] // chop [
re := p.newRegexp(OpCharClass)
re.Flags = p.flags
re.Rune = re.Rune0[:0]
sign := +1
if t != "" && t[0] == '^' {
sign = -1
t = t[1:]
// If character class does not match \n, add it here,
// so that negation later will do the right thing.
if p.flags&ClassNL == 0 {
re.Rune = append(re.Rune, '\n', '\n')
}
}
class := re.Rune
first := true // ] and - are okay as first char in class
for t == "" || t[0] != ']' || first {
// POSIX: - is only okay unescaped as first or last in class.
// Perl: - is okay anywhere.
if t != "" && t[0] == '-' && p.flags&PerlX == 0 && !first && (len(t) == 1 || t[1] != ']') {
_, size := utf8.DecodeRuneInString(t[1:])
return "", &Error{Code: ErrInvalidCharRange, Expr: t[:1+size]}
}
first = false
// Look for POSIX [:alnum:] etc.
if len(t) > 2 && t[0] == '[' && t[1] == ':' {
nclass, nt, err := p.parseNamedClass(t, class)
if err != nil {
return "", err
}
if nclass != nil {
class, t = nclass, nt
continue
}
}
// Look for Unicode character group like \p{Han}.
nclass, nt, err := p.parseUnicodeClass(t, class)
if err != nil {
return "", err
}
if nclass != nil {
class, t = nclass, nt
continue
}
// Look for Perl character class symbols (extension).
if nclass, nt := p.parsePerlClassEscape(t, class); nclass != nil {
class, t = nclass, nt
continue
}
// Single character or simple range.
rng := t
var lo, hi rune
if lo, t, err = p.parseClassChar(t, s); err != nil {
return "", err
}
hi = lo
// [a-] means (a|-) so check for final ].
if len(t) >= 2 && t[0] == '-' && t[1] != ']' {
t = t[1:]
if hi, t, err = p.parseClassChar(t, s); err != nil {
return "", err
}
if hi < lo {
rng = rng[:len(rng)-len(t)]
return "", &Error{Code: ErrInvalidCharRange, Expr: rng}
}
}
if p.flags&FoldCase == 0 {
class = appendRange(class, lo, hi)
} else {
class = appendFoldedRange(class, lo, hi)
}
}
t = t[1:] // chop ]
// Use &re.Rune instead of &class to avoid allocation.
re.Rune = class
class = cleanClass(&re.Rune)
if sign < 0 {
class = negateClass(class)
}
re.Rune = class
p.push(re)
return t, nil
}
// cleanClass sorts the ranges (pairs of elements of r),
// merges them, and eliminates duplicates.
func cleanClass(rp *[]rune) []rune {
// Sort by lo increasing, hi decreasing to break ties.
sort.Sort(ranges{rp})
r := *rp
if len(r) < 2 {
return r
}
// Merge abutting, overlapping.
w := 2 // write index
for i := 2; i < len(r); i += 2 {
lo, hi := r[i], r[i+1]
if lo <= r[w-1]+1 {
// merge with previous range
if hi > r[w-1] {
r[w-1] = hi
}
continue
}
// new disjoint range
r[w] = lo
r[w+1] = hi
w += 2
}
return r[:w]
}
// appendLiteral returns the result of appending the literal x to the class r.
func appendLiteral(r []rune, x rune, flags Flags) []rune {
if flags&FoldCase != 0 {
return appendFoldedRange(r, x, x)
}
return appendRange(r, x, x)
}
// appendRange returns the result of appending the range lo-hi to the class r.
func appendRange(r []rune, lo, hi rune) []rune {
// Expand last range or next to last range if it overlaps or abuts.
// Checking two ranges helps when appending case-folded
// alphabets, so that one range can be expanding A-Z and the
// other expanding a-z.
n := len(r)
for i := 2; i <= 4; i += 2 { // twice, using i=2, i=4
if n >= i {
rlo, rhi := r[n-i], r[n-i+1]
if lo <= rhi+1 && rlo <= hi+1 {
if lo < rlo {
r[n-i] = lo
}
if hi > rhi {
r[n-i+1] = hi
}
return r
}
}
}
return append(r, lo, hi)
}
const (
// minimum and maximum runes involved in folding.
// checked during test.
minFold = 0x0041
maxFold = 0x1e943
)
// appendFoldedRange returns the result of appending the range lo-hi
// and its case folding-equivalent runes to the class r.
func appendFoldedRange(r []rune, lo, hi rune) []rune {
// Optimizations.
if lo <= minFold && hi >= maxFold {
// Range is full: folding can't add more.
return appendRange(r, lo, hi)
}
if hi < minFold || lo > maxFold {
// Range is outside folding possibilities.
return appendRange(r, lo, hi)
}
if lo < minFold {
// [lo, minFold-1] needs no folding.
r = appendRange(r, lo, minFold-1)
lo = minFold
}
if hi > maxFold {
// [maxFold+1, hi] needs no folding.
r = appendRange(r, maxFold+1, hi)
hi = maxFold
}
// Brute force. Depend on appendRange to coalesce ranges on the fly.
for c := lo; c <= hi; c++ {
r = appendRange(r, c, c)
f := unicode.SimpleFold(c)
for f != c {
r = appendRange(r, f, f)
f = unicode.SimpleFold(f)
}
}
return r
}
// appendClass returns the result of appending the class x to the class r.
// It assume x is clean.
func appendClass(r []rune, x []rune) []rune {
for i := 0; i < len(x); i += 2 {
r = appendRange(r, x[i], x[i+1])
}
return r
}
// appendFolded returns the result of appending the case folding of the class x to the class r.
func appendFoldedClass(r []rune, x []rune) []rune {
for i := 0; i < len(x); i += 2 {
r = appendFoldedRange(r, x[i], x[i+1])
}
return r
}
// appendNegatedClass returns the result of appending the negation of the class x to the class r.
// It assumes x is clean.
func appendNegatedClass(r []rune, x []rune) []rune {
nextLo := '\u0000'
for i := 0; i < len(x); i += 2 {
lo, hi := x[i], x[i+1]
if nextLo <= lo-1 {
r = appendRange(r, nextLo, lo-1)
}
nextLo = hi + 1
}
if nextLo <= unicode.MaxRune {
r = appendRange(r, nextLo, unicode.MaxRune)
}
return r
}
// appendTable returns the result of appending x to the class r.
func appendTable(r []rune, x *unicode.RangeTable) []rune {
for _, xr := range x.R16 {
lo, hi, stride := rune(xr.Lo), rune(xr.Hi), rune(xr.Stride)
if stride == 1 {
r = appendRange(r, lo, hi)
continue
}
for c := lo; c <= hi; c += stride {
r = appendRange(r, c, c)
}
}
for _, xr := range x.R32 {
lo, hi, stride := rune(xr.Lo), rune(xr.Hi), rune(xr.Stride)
if stride == 1 {
r = appendRange(r, lo, hi)
continue
}
for c := lo; c <= hi; c += stride {
r = appendRange(r, c, c)
}
}
return r
}
// appendNegatedTable returns the result of appending the negation of x to the class r.
func appendNegatedTable(r []rune, x *unicode.RangeTable) []rune {
nextLo := '\u0000' // lo end of next class to add
for _, xr := range x.R16 {
lo, hi, stride := rune(xr.Lo), rune(xr.Hi), rune(xr.Stride)
if stride == 1 {
if nextLo <= lo-1 {
r = appendRange(r, nextLo, lo-1)
}
nextLo = hi + 1
continue
}
for c := lo; c <= hi; c += stride {
if nextLo <= c-1 {
r = appendRange(r, nextLo, c-1)
}
nextLo = c + 1
}
}
for _, xr := range x.R32 {
lo, hi, stride := rune(xr.Lo), rune(xr.Hi), rune(xr.Stride)
if stride == 1 {
if nextLo <= lo-1 {
r = appendRange(r, nextLo, lo-1)
}
nextLo = hi + 1
continue
}
for c := lo; c <= hi; c += stride {
if nextLo <= c-1 {
r = appendRange(r, nextLo, c-1)
}
nextLo = c + 1
}
}
if nextLo <= unicode.MaxRune {
r = appendRange(r, nextLo, unicode.MaxRune)
}
return r
}
// negateClass overwrites r and returns r's negation.
// It assumes the class r is already clean.
func negateClass(r []rune) []rune {
nextLo := '\u0000' // lo end of next class to add
w := 0 // write index
for i := 0; i < len(r); i += 2 {
lo, hi := r[i], r[i+1]
if nextLo <= lo-1 {
r[w] = nextLo
r[w+1] = lo - 1
w += 2
}
nextLo = hi + 1
}
r = r[:w]
if nextLo <= unicode.MaxRune {
// It's possible for the negation to have one more
// range - this one - than the original class, so use append.
r = append(r, nextLo, unicode.MaxRune)
}
return r
}
// ranges implements sort.Interface on a []rune.
// The choice of receiver type definition is strange
// but avoids an allocation since we already have
// a *[]rune.
type ranges struct {
p *[]rune
}
func (ra ranges) Less(i, j int) bool {
p := *ra.p
i *= 2
j *= 2
return p[i] < p[j] || p[i] == p[j] && p[i+1] > p[j+1]
}
func (ra ranges) Len() int {
return len(*ra.p) / 2
}
func (ra ranges) Swap(i, j int) {
p := *ra.p
i *= 2
j *= 2
p[i], p[i+1], p[j], p[j+1] = p[j], p[j+1], p[i], p[i+1]
}
func checkUTF8(s string) error {
for s != "" {
rune, size := utf8.DecodeRuneInString(s)
if rune == utf8.RuneError && size == 1 {
return &Error{Code: ErrInvalidUTF8, Expr: s}
}
s = s[size:]
}
return nil
}
func nextRune(s string) (c rune, t string, err error) {
c, size := utf8.DecodeRuneInString(s)
if c == utf8.RuneError && size == 1 {
return 0, "", &Error{Code: ErrInvalidUTF8, Expr: s}
}
return c, s[size:], nil
}
func isalnum(c rune) bool {
return '0' <= c && c <= '9' || 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z'
}
func unhex(c rune) rune {
if '0' <= c && c <= '9' {
return c - '0'
}
if 'a' <= c && c <= 'f' {
return c - 'a' + 10
}
if 'A' <= c && c <= 'F' {
return c - 'A' + 10
}
return -1
}
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