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-rw-r--r--src/regexp/syntax/parse.go2115
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diff --git a/src/regexp/syntax/parse.go b/src/regexp/syntax/parse.go
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+// 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 )"
+ ErrNestingDepth ErrorCode = "expression nests too deeply"
+ ErrLarge ErrorCode = "expression too large"
+)
+
+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
+)
+
+// maxHeight is the maximum height of a regexp parse tree.
+// It is somewhat arbitrarily chosen, but the idea is to be large enough
+// that no one will actually hit in real use but at the same time small enough
+// that recursion on the Regexp tree will not hit the 1GB Go stack limit.
+// The maximum amount of stack for a single recursive frame is probably
+// closer to 1kB, so this could potentially be raised, but it seems unlikely
+// that people have regexps nested even this deeply.
+// We ran a test on Google's C++ code base and turned up only
+// a single use case with depth > 100; it had depth 128.
+// Using depth 1000 should be plenty of margin.
+// As an optimization, we don't even bother calculating heights
+// until we've allocated at least maxHeight Regexp structures.
+const maxHeight = 1000
+
+// maxSize is the maximum size of a compiled regexp in Insts.
+// It too is somewhat arbitrarily chosen, but the idea is to be large enough
+// to allow significant regexps while at the same time small enough that
+// the compiled form will not take up too much memory.
+// 128 MB is enough for a 3.3 million Inst structures, which roughly
+// corresponds to a 3.3 MB regexp.
+const (
+ maxSize = 128 << 20 / instSize
+ instSize = 5 * 8 // byte, 2 uint32, slice is 5 64-bit words
+)
+
+// maxRunes is the maximum number of runes allowed in a regexp tree
+// counting the runes in all the nodes.
+// Ignoring character classes p.numRunes is always less than the length of the regexp.
+// Character classes can make it much larger: each \pL adds 1292 runes.
+// 128 MB is enough for 32M runes, which is over 26k \pL instances.
+// Note that repetitions do not make copies of the rune slices,
+// so \pL{1000} is only one rune slice, not 1000.
+// We could keep a cache of character classes we've seen,
+// so that all the \pL we see use the same rune list,
+// but that doesn't remove the problem entirely:
+// consider something like [\pL01234][\pL01235][\pL01236]...[\pL^&*()].
+// And because the Rune slice is exposed directly in the Regexp,
+// there is not an opportunity to change the representation to allow
+// partial sharing between different character classes.
+// So the limit is the best we can do.
+const (
+ maxRunes = 128 << 20 / runeSize
+ runeSize = 4 // rune is int32
+)
+
+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
+ numRegexp int // number of regexps allocated
+ numRunes int // number of runes in char classes
+ repeats int64 // product of all repetitions seen
+ height map[*Regexp]int // regexp height, for height limit check
+ size map[*Regexp]int64 // regexp compiled size, for size limit check
+}
+
+func (p *parser) newRegexp(op Op) *Regexp {
+ re := p.free
+ if re != nil {
+ p.free = re.Sub0[0]
+ *re = Regexp{}
+ } else {
+ re = new(Regexp)
+ p.numRegexp++
+ }
+ re.Op = op
+ return re
+}
+
+func (p *parser) reuse(re *Regexp) {
+ if p.height != nil {
+ delete(p.height, re)
+ }
+ re.Sub0[0] = p.free
+ p.free = re
+}
+
+func (p *parser) checkLimits(re *Regexp) {
+ if p.numRunes > maxRunes {
+ panic(ErrLarge)
+ }
+ p.checkSize(re)
+ p.checkHeight(re)
+}
+
+func (p *parser) checkSize(re *Regexp) {
+ if p.size == nil {
+ // We haven't started tracking size yet.
+ // Do a relatively cheap check to see if we need to start.
+ // Maintain the product of all the repeats we've seen
+ // and don't track if the total number of regexp nodes
+ // we've seen times the repeat product is in budget.
+ if p.repeats == 0 {
+ p.repeats = 1
+ }
+ if re.Op == OpRepeat {
+ n := re.Max
+ if n == -1 {
+ n = re.Min
+ }
+ if n <= 0 {
+ n = 1
+ }
+ if int64(n) > maxSize/p.repeats {
+ p.repeats = maxSize
+ } else {
+ p.repeats *= int64(n)
+ }
+ }
+ if int64(p.numRegexp) < maxSize/p.repeats {
+ return
+ }
+
+ // We need to start tracking size.
+ // Make the map and belatedly populate it
+ // with info about everything we've constructed so far.
+ p.size = make(map[*Regexp]int64)
+ for _, re := range p.stack {
+ p.checkSize(re)
+ }
+ }
+
+ if p.calcSize(re, true) > maxSize {
+ panic(ErrLarge)
+ }
+}
+
+func (p *parser) calcSize(re *Regexp, force bool) int64 {
+ if !force {
+ if size, ok := p.size[re]; ok {
+ return size
+ }
+ }
+
+ var size int64
+ switch re.Op {
+ case OpLiteral:
+ size = int64(len(re.Rune))
+ case OpCapture, OpStar:
+ // star can be 1+ or 2+; assume 2 pessimistically
+ size = 2 + p.calcSize(re.Sub[0], false)
+ case OpPlus, OpQuest:
+ size = 1 + p.calcSize(re.Sub[0], false)
+ case OpConcat:
+ for _, sub := range re.Sub {
+ size += p.calcSize(sub, false)
+ }
+ case OpAlternate:
+ for _, sub := range re.Sub {
+ size += p.calcSize(sub, false)
+ }
+ if len(re.Sub) > 1 {
+ size += int64(len(re.Sub)) - 1
+ }
+ case OpRepeat:
+ sub := p.calcSize(re.Sub[0], false)
+ if re.Max == -1 {
+ if re.Min == 0 {
+ size = 2 + sub // x*
+ } else {
+ size = 1 + int64(re.Min)*sub // xxx+
+ }
+ break
+ }
+ // x{2,5} = xx(x(x(x)?)?)?
+ size = int64(re.Max)*sub + int64(re.Max-re.Min)
+ }
+
+ if size < 1 {
+ size = 1
+ }
+ p.size[re] = size
+ return size
+}
+
+func (p *parser) checkHeight(re *Regexp) {
+ if p.numRegexp < maxHeight {
+ return
+ }
+ if p.height == nil {
+ p.height = make(map[*Regexp]int)
+ for _, re := range p.stack {
+ p.checkHeight(re)
+ }
+ }
+ if p.calcHeight(re, true) > maxHeight {
+ panic(ErrNestingDepth)
+ }
+}
+
+func (p *parser) calcHeight(re *Regexp, force bool) int {
+ if !force {
+ if h, ok := p.height[re]; ok {
+ return h
+ }
+ }
+ h := 1
+ for _, sub := range re.Sub {
+ hsub := p.calcHeight(sub, false)
+ if h < 1+hsub {
+ h = 1 + hsub
+ }
+ }
+ p.height[re] = h
+ return h
+}
+
+// Parse stack manipulation.
+
+// push pushes the regexp re onto the parse stack and returns the regexp.
+func (p *parser) push(re *Regexp) *Regexp {
+ p.numRunes += len(re.Rune)
+ 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)
+ p.checkLimits(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
+}
+
+// literal pushes a literal regexp for the rune r on the stack.
+func (p *parser) literal(r rune) {
+ re := p.newRegexp(OpLiteral)
+ re.Flags = p.flags
+ if p.flags&FoldCase != 0 {
+ r = minFoldRune(r)
+ }
+ re.Rune0[0] = r
+ re.Rune = re.Rune0[:1]
+ p.push(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
+}
+
+// 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
+ p.checkLimits(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))
+ p.checkLimits(sub[j])
+ }
+ 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)
+ p.checkLimits(sub[j])
+ }
+ 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) {
+ return parse(s, flags)
+}
+
+func parse(s string, flags Flags) (_ *Regexp, err error) {
+ defer func() {
+ switch r := recover(); r {
+ default:
+ panic(r)
+ case nil:
+ // ok
+ case ErrLarge: // too big
+ err = &Error{Code: ErrLarge, Expr: s}
+ case ErrNestingDepth:
+ err = &Error{Code: ErrNestingDepth, Expr: s}
+ }
+ }()
+
+ 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
+ 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
+ lit, t, _ = strings.Cut(t[2:], `\E`)
+ 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
+}
+
+// appendFoldedClass 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
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-23 13:08:57 +0000