mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
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464 lines
12 KiB
Go
464 lines
12 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package syntax
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// Note to implementers:
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// In this package, re is always a *Regexp and r is always a rune.
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import (
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"slices"
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"strconv"
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"strings"
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"unicode"
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)
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// A Regexp is a node in a regular expression syntax tree.
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type Regexp struct {
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Op Op // operator
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Flags Flags
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Sub []*Regexp // subexpressions, if any
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Sub0 [1]*Regexp // storage for short Sub
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Rune []rune // matched runes, for OpLiteral, OpCharClass
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Rune0 [2]rune // storage for short Rune
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Min, Max int // min, max for OpRepeat
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Cap int // capturing index, for OpCapture
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Name string // capturing name, for OpCapture
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}
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//go:generate stringer -type Op -trimprefix Op
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// An Op is a single regular expression operator.
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type Op uint8
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// Operators are listed in precedence order, tightest binding to weakest.
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// Character class operators are listed simplest to most complex
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// (OpLiteral, OpCharClass, OpAnyCharNotNL, OpAnyChar).
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const (
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OpNoMatch Op = 1 + iota // matches no strings
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OpEmptyMatch // matches empty string
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OpLiteral // matches Runes sequence
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OpCharClass // matches Runes interpreted as range pair list
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OpAnyCharNotNL // matches any character except newline
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OpAnyChar // matches any character
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OpBeginLine // matches empty string at beginning of line
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OpEndLine // matches empty string at end of line
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OpBeginText // matches empty string at beginning of text
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OpEndText // matches empty string at end of text
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OpWordBoundary // matches word boundary `\b`
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OpNoWordBoundary // matches word non-boundary `\B`
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OpCapture // capturing subexpression with index Cap, optional name Name
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OpStar // matches Sub[0] zero or more times
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OpPlus // matches Sub[0] one or more times
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OpQuest // matches Sub[0] zero or one times
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OpRepeat // matches Sub[0] at least Min times, at most Max (Max == -1 is no limit)
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OpConcat // matches concatenation of Subs
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OpAlternate // matches alternation of Subs
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)
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const opPseudo Op = 128 // where pseudo-ops start
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// Equal reports whether x and y have identical structure.
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func (x *Regexp) Equal(y *Regexp) bool {
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if x == nil || y == nil {
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return x == y
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}
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if x.Op != y.Op {
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return false
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}
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switch x.Op {
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case OpEndText:
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// The parse flags remember whether this is \z or \Z.
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if x.Flags&WasDollar != y.Flags&WasDollar {
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return false
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}
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case OpLiteral, OpCharClass:
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return slices.Equal(x.Rune, y.Rune)
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case OpAlternate, OpConcat:
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return slices.EqualFunc(x.Sub, y.Sub, func(a, b *Regexp) bool { return a.Equal(b) })
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case OpStar, OpPlus, OpQuest:
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if x.Flags&NonGreedy != y.Flags&NonGreedy || !x.Sub[0].Equal(y.Sub[0]) {
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return false
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}
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case OpRepeat:
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if x.Flags&NonGreedy != y.Flags&NonGreedy || x.Min != y.Min || x.Max != y.Max || !x.Sub[0].Equal(y.Sub[0]) {
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return false
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}
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case OpCapture:
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if x.Cap != y.Cap || x.Name != y.Name || !x.Sub[0].Equal(y.Sub[0]) {
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return false
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}
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}
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return true
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}
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// printFlags is a bit set indicating which flags (including non-capturing parens) to print around a regexp.
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type printFlags uint8
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const (
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flagI printFlags = 1 << iota // (?i:
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flagM // (?m:
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flagS // (?s:
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flagOff // )
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flagPrec // (?: )
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negShift = 5 // flagI<<negShift is (?-i:
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)
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// addSpan enables the flags f around start..last,
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// by setting flags[start] = f and flags[last] = flagOff.
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func addSpan(start, last *Regexp, f printFlags, flags *map[*Regexp]printFlags) {
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if *flags == nil {
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*flags = make(map[*Regexp]printFlags)
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}
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(*flags)[start] = f
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(*flags)[last] |= flagOff // maybe start==last
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}
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// calcFlags calculates the flags to print around each subexpression in re,
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// storing that information in (*flags)[sub] for each affected subexpression.
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// The first time an entry needs to be written to *flags, calcFlags allocates the map.
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// calcFlags also calculates the flags that must be active or can't be active
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// around re and returns those flags.
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func calcFlags(re *Regexp, flags *map[*Regexp]printFlags) (must, cant printFlags) {
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switch re.Op {
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default:
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return 0, 0
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case OpLiteral:
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// If literal is fold-sensitive, return (flagI, 0) or (0, flagI)
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// according to whether (?i) is active.
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// If literal is not fold-sensitive, return 0, 0.
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for _, r := range re.Rune {
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if minFold <= r && r <= maxFold && unicode.SimpleFold(r) != r {
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if re.Flags&FoldCase != 0 {
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return flagI, 0
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} else {
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return 0, flagI
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}
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}
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}
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return 0, 0
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case OpCharClass:
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// If literal is fold-sensitive, return 0, flagI - (?i) has been compiled out.
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// If literal is not fold-sensitive, return 0, 0.
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for i := 0; i < len(re.Rune); i += 2 {
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lo := max(minFold, re.Rune[i])
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hi := min(maxFold, re.Rune[i+1])
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for r := lo; r <= hi; r++ {
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for f := unicode.SimpleFold(r); f != r; f = unicode.SimpleFold(f) {
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if !(lo <= f && f <= hi) && !inCharClass(f, re.Rune) {
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return 0, flagI
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}
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}
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}
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}
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return 0, 0
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case OpAnyCharNotNL: // (?-s).
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return 0, flagS
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case OpAnyChar: // (?s).
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return flagS, 0
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case OpBeginLine, OpEndLine: // (?m)^ (?m)$
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return flagM, 0
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case OpEndText:
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if re.Flags&WasDollar != 0 { // (?-m)$
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return 0, flagM
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}
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return 0, 0
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case OpCapture, OpStar, OpPlus, OpQuest, OpRepeat:
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return calcFlags(re.Sub[0], flags)
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case OpConcat, OpAlternate:
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// Gather the must and cant for each subexpression.
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// When we find a conflicting subexpression, insert the necessary
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// flags around the previously identified span and start over.
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var must, cant, allCant printFlags
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start := 0
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last := 0
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did := false
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for i, sub := range re.Sub {
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subMust, subCant := calcFlags(sub, flags)
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if must&subCant != 0 || subMust&cant != 0 {
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if must != 0 {
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addSpan(re.Sub[start], re.Sub[last], must, flags)
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}
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must = 0
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cant = 0
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start = i
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did = true
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}
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must |= subMust
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cant |= subCant
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allCant |= subCant
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if subMust != 0 {
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last = i
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}
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if must == 0 && start == i {
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start++
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}
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}
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if !did {
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// No conflicts: pass the accumulated must and cant upward.
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return must, cant
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}
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if must != 0 {
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// Conflicts found; need to finish final span.
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addSpan(re.Sub[start], re.Sub[last], must, flags)
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}
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return 0, allCant
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}
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}
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// writeRegexp writes the Perl syntax for the regular expression re to b.
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func writeRegexp(b *strings.Builder, re *Regexp, f printFlags, flags map[*Regexp]printFlags) {
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f |= flags[re]
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if f&flagPrec != 0 && f&^(flagOff|flagPrec) != 0 && f&flagOff != 0 {
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// flagPrec is redundant with other flags being added and terminated
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f &^= flagPrec
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}
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if f&^(flagOff|flagPrec) != 0 {
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b.WriteString(`(?`)
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if f&flagI != 0 {
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b.WriteString(`i`)
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}
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if f&flagM != 0 {
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b.WriteString(`m`)
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}
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if f&flagS != 0 {
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b.WriteString(`s`)
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}
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if f&((flagM|flagS)<<negShift) != 0 {
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b.WriteString(`-`)
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if f&(flagM<<negShift) != 0 {
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b.WriteString(`m`)
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}
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if f&(flagS<<negShift) != 0 {
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b.WriteString(`s`)
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}
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}
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b.WriteString(`:`)
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}
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if f&flagOff != 0 {
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defer b.WriteString(`)`)
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}
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if f&flagPrec != 0 {
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b.WriteString(`(?:`)
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defer b.WriteString(`)`)
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}
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switch re.Op {
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default:
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b.WriteString("<invalid op" + strconv.Itoa(int(re.Op)) + ">")
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case OpNoMatch:
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b.WriteString(`[^\x00-\x{10FFFF}]`)
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case OpEmptyMatch:
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b.WriteString(`(?:)`)
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case OpLiteral:
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for _, r := range re.Rune {
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escape(b, r, false)
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}
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case OpCharClass:
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if len(re.Rune)%2 != 0 {
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b.WriteString(`[invalid char class]`)
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break
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}
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b.WriteRune('[')
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if len(re.Rune) == 0 {
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b.WriteString(`^\x00-\x{10FFFF}`)
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} else if re.Rune[0] == 0 && re.Rune[len(re.Rune)-1] == unicode.MaxRune && len(re.Rune) > 2 {
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// Contains 0 and MaxRune. Probably a negated class.
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// Print the gaps.
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b.WriteRune('^')
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for i := 1; i < len(re.Rune)-1; i += 2 {
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lo, hi := re.Rune[i]+1, re.Rune[i+1]-1
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escape(b, lo, lo == '-')
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if lo != hi {
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if hi != lo+1 {
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b.WriteRune('-')
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}
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escape(b, hi, hi == '-')
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}
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}
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} else {
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for i := 0; i < len(re.Rune); i += 2 {
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lo, hi := re.Rune[i], re.Rune[i+1]
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escape(b, lo, lo == '-')
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if lo != hi {
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if hi != lo+1 {
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b.WriteRune('-')
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}
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escape(b, hi, hi == '-')
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}
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}
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}
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b.WriteRune(']')
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case OpAnyCharNotNL, OpAnyChar:
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b.WriteString(`.`)
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case OpBeginLine:
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b.WriteString(`^`)
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case OpEndLine:
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b.WriteString(`$`)
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case OpBeginText:
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b.WriteString(`\A`)
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case OpEndText:
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if re.Flags&WasDollar != 0 {
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b.WriteString(`$`)
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} else {
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b.WriteString(`\z`)
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}
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case OpWordBoundary:
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b.WriteString(`\b`)
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case OpNoWordBoundary:
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b.WriteString(`\B`)
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case OpCapture:
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if re.Name != "" {
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b.WriteString(`(?P<`)
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b.WriteString(re.Name)
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b.WriteRune('>')
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} else {
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b.WriteRune('(')
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}
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if re.Sub[0].Op != OpEmptyMatch {
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writeRegexp(b, re.Sub[0], flags[re.Sub[0]], flags)
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}
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b.WriteRune(')')
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case OpStar, OpPlus, OpQuest, OpRepeat:
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p := printFlags(0)
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sub := re.Sub[0]
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if sub.Op > OpCapture || sub.Op == OpLiteral && len(sub.Rune) > 1 {
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p = flagPrec
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}
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writeRegexp(b, sub, p, flags)
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switch re.Op {
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case OpStar:
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b.WriteRune('*')
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case OpPlus:
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b.WriteRune('+')
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case OpQuest:
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b.WriteRune('?')
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case OpRepeat:
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b.WriteRune('{')
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b.WriteString(strconv.Itoa(re.Min))
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if re.Max != re.Min {
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b.WriteRune(',')
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if re.Max >= 0 {
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b.WriteString(strconv.Itoa(re.Max))
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}
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}
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b.WriteRune('}')
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}
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if re.Flags&NonGreedy != 0 {
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b.WriteRune('?')
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}
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case OpConcat:
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for _, sub := range re.Sub {
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p := printFlags(0)
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if sub.Op == OpAlternate {
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p = flagPrec
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}
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writeRegexp(b, sub, p, flags)
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}
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case OpAlternate:
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for i, sub := range re.Sub {
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if i > 0 {
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b.WriteRune('|')
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}
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writeRegexp(b, sub, 0, flags)
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}
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}
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}
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func (re *Regexp) String() string {
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var b strings.Builder
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var flags map[*Regexp]printFlags
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must, cant := calcFlags(re, &flags)
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must |= (cant &^ flagI) << negShift
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if must != 0 {
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must |= flagOff
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}
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writeRegexp(&b, re, must, flags)
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return b.String()
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}
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const meta = `\.+*?()|[]{}^$`
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func escape(b *strings.Builder, r rune, force bool) {
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if unicode.IsPrint(r) {
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if strings.ContainsRune(meta, r) || force {
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b.WriteRune('\\')
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}
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b.WriteRune(r)
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return
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}
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switch r {
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case '\a':
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b.WriteString(`\a`)
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case '\f':
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b.WriteString(`\f`)
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case '\n':
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b.WriteString(`\n`)
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case '\r':
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b.WriteString(`\r`)
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case '\t':
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b.WriteString(`\t`)
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case '\v':
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b.WriteString(`\v`)
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default:
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if r < 0x100 {
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b.WriteString(`\x`)
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s := strconv.FormatInt(int64(r), 16)
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if len(s) == 1 {
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b.WriteRune('0')
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}
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b.WriteString(s)
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break
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}
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b.WriteString(`\x{`)
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b.WriteString(strconv.FormatInt(int64(r), 16))
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b.WriteString(`}`)
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}
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}
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// MaxCap walks the regexp to find the maximum capture index.
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func (re *Regexp) MaxCap() int {
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m := 0
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if re.Op == OpCapture {
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m = re.Cap
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}
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for _, sub := range re.Sub {
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if n := sub.MaxCap(); m < n {
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m = n
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}
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}
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return m
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}
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// CapNames walks the regexp to find the names of capturing groups.
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func (re *Regexp) CapNames() []string {
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names := make([]string, re.MaxCap()+1)
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re.capNames(names)
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return names
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}
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func (re *Regexp) capNames(names []string) {
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if re.Op == OpCapture {
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names[re.Cap] = re.Name
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}
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for _, sub := range re.Sub {
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sub.capNames(names)
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}
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}
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