mirror of
https://github.com/superseriousbusiness/gotosocial
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494 lines
11 KiB
Go
494 lines
11 KiB
Go
// Package html is an HTML5 lexer following the specifications at http://www.w3.org/TR/html5/syntax.html.
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package html
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import (
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"strconv"
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"github.com/tdewolff/parse/v2"
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)
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// TokenType determines the type of token, eg. a number or a semicolon.
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type TokenType uint32
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// TokenType values.
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const (
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ErrorToken TokenType = iota // extra token when errors occur
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CommentToken
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DoctypeToken
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StartTagToken
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StartTagCloseToken
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StartTagVoidToken
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EndTagToken
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AttributeToken
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TextToken
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SvgToken
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MathToken
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)
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// String returns the string representation of a TokenType.
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func (tt TokenType) String() string {
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switch tt {
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case ErrorToken:
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return "Error"
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case CommentToken:
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return "Comment"
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case DoctypeToken:
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return "Doctype"
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case StartTagToken:
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return "StartTag"
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case StartTagCloseToken:
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return "StartTagClose"
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case StartTagVoidToken:
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return "StartTagVoid"
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case EndTagToken:
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return "EndTag"
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case AttributeToken:
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return "Attribute"
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case TextToken:
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return "Text"
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case SvgToken:
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return "Svg"
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case MathToken:
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return "Math"
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}
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return "Invalid(" + strconv.Itoa(int(tt)) + ")"
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}
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////////////////////////////////////////////////////////////////
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// Lexer is the state for the lexer.
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type Lexer struct {
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r *parse.Input
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err error
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rawTag Hash
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inTag bool
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text []byte
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attrVal []byte
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}
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// NewLexer returns a new Lexer for a given io.Reader.
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func NewLexer(r *parse.Input) *Lexer {
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return &Lexer{
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r: r,
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}
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}
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// Err returns the error encountered during lexing, this is often io.EOF but also other errors can be returned.
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func (l *Lexer) Err() error {
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if l.err != nil {
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return l.err
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}
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return l.r.Err()
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}
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// Text returns the textual representation of a token. This excludes delimiters and additional leading/trailing characters.
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func (l *Lexer) Text() []byte {
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return l.text
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}
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// AttrVal returns the attribute value when an AttributeToken was returned from Next.
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func (l *Lexer) AttrVal() []byte {
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return l.attrVal
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}
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// Next returns the next Token. It returns ErrorToken when an error was encountered. Using Err() one can retrieve the error message.
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func (l *Lexer) Next() (TokenType, []byte) {
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l.text = nil
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var c byte
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if l.inTag {
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l.attrVal = nil
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for { // before attribute name state
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if c = l.r.Peek(0); c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' {
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l.r.Move(1)
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continue
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}
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break
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}
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if c == 0 && l.r.Err() != nil {
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return ErrorToken, nil
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} else if c != '>' && (c != '/' || l.r.Peek(1) != '>') {
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return AttributeToken, l.shiftAttribute()
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}
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l.r.Skip()
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l.inTag = false
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if c == '/' {
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l.r.Move(2)
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return StartTagVoidToken, l.r.Shift()
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}
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l.r.Move(1)
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return StartTagCloseToken, l.r.Shift()
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}
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if l.rawTag != 0 {
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if rawText := l.shiftRawText(); len(rawText) > 0 {
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l.text = rawText
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l.rawTag = 0
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return TextToken, rawText
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}
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l.rawTag = 0
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}
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for {
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c = l.r.Peek(0)
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if c == '<' {
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c = l.r.Peek(1)
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isEndTag := c == '/' && l.r.Peek(2) != '>' && (l.r.Peek(2) != 0 || l.r.PeekErr(2) == nil)
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if l.r.Pos() > 0 {
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if isEndTag || 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '!' || c == '?' {
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// return currently buffered texttoken so that we can return tag next iteration
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l.text = l.r.Shift()
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return TextToken, l.text
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}
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} else if isEndTag {
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l.r.Move(2)
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// only endtags that are not followed by > or EOF arrive here
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if c = l.r.Peek(0); !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
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return CommentToken, l.shiftBogusComment()
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}
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return EndTagToken, l.shiftEndTag()
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} else if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' {
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l.r.Move(1)
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l.inTag = true
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return l.shiftStartTag()
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} else if c == '!' {
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l.r.Move(2)
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return l.readMarkup()
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} else if c == '?' {
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l.r.Move(1)
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return CommentToken, l.shiftBogusComment()
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}
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} else if c == 0 && l.r.Err() != nil {
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if l.r.Pos() > 0 {
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l.text = l.r.Shift()
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return TextToken, l.text
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}
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return ErrorToken, nil
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}
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l.r.Move(1)
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}
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}
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////////////////////////////////////////////////////////////////
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// The following functions follow the specifications at https://html.spec.whatwg.org/multipage/parsing.html
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func (l *Lexer) shiftRawText() []byte {
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if l.rawTag == Plaintext {
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for {
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if l.r.Peek(0) == 0 && l.r.Err() != nil {
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return l.r.Shift()
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}
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l.r.Move(1)
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}
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} else { // RCDATA, RAWTEXT and SCRIPT
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for {
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c := l.r.Peek(0)
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if c == '<' {
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if l.r.Peek(1) == '/' {
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mark := l.r.Pos()
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l.r.Move(2)
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for {
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if c = l.r.Peek(0); !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
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break
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}
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l.r.Move(1)
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}
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if h := ToHash(parse.ToLower(parse.Copy(l.r.Lexeme()[mark+2:]))); h == l.rawTag { // copy so that ToLower doesn't change the case of the underlying slice
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l.r.Rewind(mark)
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return l.r.Shift()
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}
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} else if l.rawTag == Script && l.r.Peek(1) == '!' && l.r.Peek(2) == '-' && l.r.Peek(3) == '-' {
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l.r.Move(4)
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inScript := false
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for {
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c := l.r.Peek(0)
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if c == '-' && l.r.Peek(1) == '-' && l.r.Peek(2) == '>' {
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l.r.Move(3)
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break
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} else if c == '<' {
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isEnd := l.r.Peek(1) == '/'
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if isEnd {
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l.r.Move(2)
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} else {
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l.r.Move(1)
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}
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mark := l.r.Pos()
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for {
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if c = l.r.Peek(0); !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
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break
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}
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l.r.Move(1)
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}
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if h := ToHash(parse.ToLower(parse.Copy(l.r.Lexeme()[mark:]))); h == Script { // copy so that ToLower doesn't change the case of the underlying slice
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if !isEnd {
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inScript = true
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} else {
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if !inScript {
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l.r.Rewind(mark - 2)
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return l.r.Shift()
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}
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inScript = false
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}
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}
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} else if c == 0 && l.r.Err() != nil {
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return l.r.Shift()
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} else {
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l.r.Move(1)
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}
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}
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} else {
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l.r.Move(1)
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}
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} else if c == 0 && l.r.Err() != nil {
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return l.r.Shift()
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} else {
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l.r.Move(1)
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}
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}
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}
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}
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func (l *Lexer) readMarkup() (TokenType, []byte) {
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if l.at('-', '-') {
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l.r.Move(2)
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for {
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if l.r.Peek(0) == 0 && l.r.Err() != nil {
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l.text = l.r.Lexeme()[4:]
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return CommentToken, l.r.Shift()
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} else if l.at('-', '-', '>') {
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l.text = l.r.Lexeme()[4:]
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l.r.Move(3)
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return CommentToken, l.r.Shift()
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} else if l.at('-', '-', '!', '>') {
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l.text = l.r.Lexeme()[4:]
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l.r.Move(4)
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return CommentToken, l.r.Shift()
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}
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l.r.Move(1)
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}
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} else if l.at('[', 'C', 'D', 'A', 'T', 'A', '[') {
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l.r.Move(7)
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for {
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if l.r.Peek(0) == 0 && l.r.Err() != nil {
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l.text = l.r.Lexeme()[9:]
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return TextToken, l.r.Shift()
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} else if l.at(']', ']', '>') {
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l.text = l.r.Lexeme()[9:]
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l.r.Move(3)
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return TextToken, l.r.Shift()
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}
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l.r.Move(1)
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}
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} else {
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if l.atCaseInsensitive('d', 'o', 'c', 't', 'y', 'p', 'e') {
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l.r.Move(7)
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if l.r.Peek(0) == ' ' {
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l.r.Move(1)
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}
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for {
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if c := l.r.Peek(0); c == '>' || c == 0 && l.r.Err() != nil {
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l.text = l.r.Lexeme()[9:]
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if c == '>' {
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l.r.Move(1)
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}
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return DoctypeToken, l.r.Shift()
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}
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l.r.Move(1)
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}
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}
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}
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return CommentToken, l.shiftBogusComment()
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}
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func (l *Lexer) shiftBogusComment() []byte {
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for {
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c := l.r.Peek(0)
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if c == '>' {
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l.text = l.r.Lexeme()[2:]
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l.r.Move(1)
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return l.r.Shift()
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} else if c == 0 && l.r.Err() != nil {
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l.text = l.r.Lexeme()[2:]
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return l.r.Shift()
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}
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l.r.Move(1)
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}
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}
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func (l *Lexer) shiftStartTag() (TokenType, []byte) {
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for {
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if c := l.r.Peek(0); c == ' ' || c == '>' || c == '/' && l.r.Peek(1) == '>' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == 0 && l.r.Err() != nil {
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break
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}
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l.r.Move(1)
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}
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l.text = parse.ToLower(l.r.Lexeme()[1:])
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if h := ToHash(l.text); h == Textarea || h == Title || h == Style || h == Xmp || h == Iframe || h == Script || h == Plaintext || h == Svg || h == Math {
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if h == Svg || h == Math {
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data := l.shiftXML(h)
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if l.err != nil {
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return ErrorToken, nil
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}
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l.inTag = false
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if h == Svg {
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return SvgToken, data
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}
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return MathToken, data
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}
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l.rawTag = h
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}
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return StartTagToken, l.r.Shift()
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}
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func (l *Lexer) shiftAttribute() []byte {
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nameStart := l.r.Pos()
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var c byte
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for { // attribute name state
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if c = l.r.Peek(0); c == ' ' || c == '=' || c == '>' || c == '/' && l.r.Peek(1) == '>' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == 0 && l.r.Err() != nil {
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break
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}
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l.r.Move(1)
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}
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nameEnd := l.r.Pos()
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for { // after attribute name state
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if c = l.r.Peek(0); c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' {
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l.r.Move(1)
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continue
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}
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break
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}
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if c == '=' {
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l.r.Move(1)
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for { // before attribute value state
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if c = l.r.Peek(0); c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' {
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l.r.Move(1)
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continue
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}
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break
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}
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attrPos := l.r.Pos()
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delim := c
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if delim == '"' || delim == '\'' { // attribute value single- and double-quoted state
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l.r.Move(1)
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for {
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c := l.r.Peek(0)
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if c == delim {
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l.r.Move(1)
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break
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} else if c == 0 && l.r.Err() != nil {
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break
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}
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l.r.Move(1)
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}
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} else { // attribute value unquoted state
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for {
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if c := l.r.Peek(0); c == ' ' || c == '>' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == 0 && l.r.Err() != nil {
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break
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}
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l.r.Move(1)
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}
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}
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l.attrVal = l.r.Lexeme()[attrPos:]
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} else {
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l.r.Rewind(nameEnd)
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l.attrVal = nil
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}
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l.text = parse.ToLower(l.r.Lexeme()[nameStart:nameEnd])
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return l.r.Shift()
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}
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func (l *Lexer) shiftEndTag() []byte {
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for {
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c := l.r.Peek(0)
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if c == '>' {
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l.text = l.r.Lexeme()[2:]
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l.r.Move(1)
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break
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} else if c == 0 && l.r.Err() != nil {
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l.text = l.r.Lexeme()[2:]
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break
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}
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l.r.Move(1)
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}
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end := len(l.text)
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for end > 0 {
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if c := l.text[end-1]; c == ' ' || c == '\t' || c == '\n' || c == '\r' {
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end--
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continue
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}
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break
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}
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l.text = l.text[:end]
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return parse.ToLower(l.r.Shift())
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}
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// shiftXML parses the content of a svg or math tag according to the XML 1.1 specifications, including the tag itself.
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// So far we have already parsed `<svg` or `<math`.
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func (l *Lexer) shiftXML(rawTag Hash) []byte {
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inQuote := false
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for {
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c := l.r.Peek(0)
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if c == '"' {
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inQuote = !inQuote
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l.r.Move(1)
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} else if c == '<' && !inQuote && l.r.Peek(1) == '/' {
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mark := l.r.Pos()
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l.r.Move(2)
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for {
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if c = l.r.Peek(0); !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
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break
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}
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l.r.Move(1)
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}
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if h := ToHash(parse.ToLower(parse.Copy(l.r.Lexeme()[mark+2:]))); h == rawTag { // copy so that ToLower doesn't change the case of the underlying slice
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break
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}
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} else if c == 0 {
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if l.r.Err() == nil {
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l.err = parse.NewErrorLexer(l.r, "HTML parse error: unexpected NULL character")
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}
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return l.r.Shift()
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} else {
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l.r.Move(1)
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}
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}
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for {
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c := l.r.Peek(0)
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if c == '>' {
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l.r.Move(1)
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break
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} else if c == 0 {
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if l.r.Err() == nil {
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l.err = parse.NewErrorLexer(l.r, "HTML parse error: unexpected NULL character")
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}
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return l.r.Shift()
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}
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l.r.Move(1)
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}
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return l.r.Shift()
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}
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////////////////////////////////////////////////////////////////
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func (l *Lexer) at(b ...byte) bool {
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for i, c := range b {
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if l.r.Peek(i) != c {
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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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func (l *Lexer) atCaseInsensitive(b ...byte) bool {
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for i, c := range b {
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if l.r.Peek(i) != c && (l.r.Peek(i)+('a'-'A')) != c {
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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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