vue3-core/packages/compiler-core/src/parser/Tokenizer.ts

import {
  EntityDecoder,
  DecodingMode,
  htmlDecodeTree,
  xmlDecodeTree
} from 'entities/lib/decode.js'

const enum CharCodes {
  Tab = 0x9, // "\t"
  NewLine = 0xa, // "\n"
  FormFeed = 0xc, // "\f"
  CarriageReturn = 0xd, // "\r"
  Space = 0x20, // " "
  ExclamationMark = 0x21, // "!"
  Number = 0x23, // "#"
  Amp = 0x26, // "&"
  SingleQuote = 0x27, // "'"
  DoubleQuote = 0x22, // '"'
  Dash = 0x2d, // "-"
  Slash = 0x2f, // "/"
  Zero = 0x30, // "0"
  Nine = 0x39, // "9"
  Semi = 0x3b, // ";"
  Lt = 0x3c, // "<"
  Eq = 0x3d, // "="
  Gt = 0x3e, // ">"
  Questionmark = 0x3f, // "?"
  UpperA = 0x41, // "A"
  LowerA = 0x61, // "a"
  UpperF = 0x46, // "F"
  LowerF = 0x66, // "f"
  UpperZ = 0x5a, // "Z"
  LowerZ = 0x7a, // "z"
  LowerX = 0x78, // "x"
  OpeningSquareBracket = 0x5b // "["
}

/** All the states the tokenizer can be in. */
const enum State {
  Text = 1,
  BeforeTagName, // After <
  InTagName,
  InSelfClosingTag,
  BeforeClosingTagName,
  InClosingTagName,
  AfterClosingTagName,

  // Attributes
  BeforeAttributeName,
  InAttributeName,
  AfterAttributeName,
  BeforeAttributeValue,
  InAttributeValueDq, // "
  InAttributeValueSq, // '
  InAttributeValueNq,

  // Declarations
  BeforeDeclaration, // !
  InDeclaration,

  // Processing instructions
  InProcessingInstruction, // ?

  // Comments & CDATA
  BeforeComment,
  CDATASequence,
  InSpecialComment,
  InCommentLike,

  // Special tags
  BeforeSpecialS, // Decide if we deal with `<script` or `<style`
  SpecialStartSequence,
  InSpecialTag,

  InEntity
}

function isWhitespace(c: number): boolean {
  return (
    c === CharCodes.Space ||
    c === CharCodes.NewLine ||
    c === CharCodes.Tab ||
    c === CharCodes.FormFeed ||
    c === CharCodes.CarriageReturn
  )
}

function isEndOfTagSection(c: number): boolean {
  return c === CharCodes.Slash || c === CharCodes.Gt || isWhitespace(c)
}

function isASCIIAlpha(c: number): boolean {
  return (
    (c >= CharCodes.LowerA && c <= CharCodes.LowerZ) ||
    (c >= CharCodes.UpperA && c <= CharCodes.UpperZ)
  )
}

export enum QuoteType {
  NoValue = 0,
  Unquoted = 1,
  Single = 2,
  Double = 3
}

export interface Callbacks {
  onattribdata(start: number, endIndex: number): void
  onattribentity(codepoint: number): void
  onattribend(quote: QuoteType, endIndex: number): void
  onattribname(start: number, endIndex: number): void
  oncdata(start: number, endIndex: number, endOffset: number): void
  onclosetag(start: number, endIndex: number): void
  oncomment(start: number, endIndex: number, endOffset: number): void
  ondeclaration(start: number, endIndex: number): void
  onend(): void
  onopentagend(endIndex: number): void
  onopentagname(start: number, endIndex: number): void
  onprocessinginstruction(start: number, endIndex: number): void
  onselfclosingtag(endIndex: number): void
  ontext(start: number, endIndex: number): void
  ontextentity(codepoint: number, endIndex: number): void
}

/**
 * Sequences used to match longer strings.
 *
 * We don't have `Script`, `Style`, or `Title` here. Instead, we re-use the *End
 * sequences with an increased offset.
 */
const Sequences = {
  Cdata: new Uint8Array([0x43, 0x44, 0x41, 0x54, 0x41, 0x5b]), // CDATA[
  CdataEnd: new Uint8Array([0x5d, 0x5d, 0x3e]), // ]]>
  CommentEnd: new Uint8Array([0x2d, 0x2d, 0x3e]), // `-->`
  ScriptEnd: new Uint8Array([0x3c, 0x2f, 0x73, 0x63, 0x72, 0x69, 0x70, 0x74]), // `</script`
  StyleEnd: new Uint8Array([0x3c, 0x2f, 0x73, 0x74, 0x79, 0x6c, 0x65]), // `</style`
  TitleEnd: new Uint8Array([0x3c, 0x2f, 0x74, 0x69, 0x74, 0x6c, 0x65]) // `</title`
}

export default class Tokenizer {
  /** The current state the tokenizer is in. */
  private state = State.Text
  /** The read buffer. */
  private buffer = ''
  /** The beginning of the section that is currently being read. */
  private sectionStart = 0
  /** The index within the buffer that we are currently looking at. */
  private index = 0
  /** The start of the last entity. */
  private entityStart = 0
  /** Some behavior, eg. when decoding entities, is done while we are in another state. This keeps track of the other state type. */
  private baseState = State.Text
  /** For special parsing behavior inside of script and style tags. */
  private isSpecial = false
  /** Indicates whether the tokenizer has been paused. */
  public running = true
  /** The offset of the current buffer. */
  private offset = 0

  private readonly xmlMode: boolean
  private readonly decodeEntities: boolean
  private readonly entityDecoder: EntityDecoder

  constructor(
    {
      xmlMode = false,
      decodeEntities = true
    }: { xmlMode?: boolean; decodeEntities?: boolean },
    private readonly cbs: Callbacks
  ) {
    this.xmlMode = xmlMode
    this.decodeEntities = decodeEntities
    this.entityDecoder = new EntityDecoder(
      xmlMode ? xmlDecodeTree : htmlDecodeTree,
      (cp, consumed) => this.emitCodePoint(cp, consumed)
    )
  }

  public reset(): void {
    this.state = State.Text
    this.buffer = ''
    this.sectionStart = 0
    this.index = 0
    this.baseState = State.Text
    this.currentSequence = undefined!
    this.running = true
    this.offset = 0
  }

  public write(chunk: string): void {
    this.offset += this.buffer.length
    this.buffer = chunk
    this.parse()
  }

  public end(): void {
    if (this.running) this.finish()
  }

  public pause(): void {
    this.running = false
  }

  public resume(): void {
    this.running = true
    if (this.index < this.buffer.length + this.offset) {
      this.parse()
    }
  }

  private stateText(c: number): void {
    if (
      c === CharCodes.Lt ||
      (!this.decodeEntities && this.fastForwardTo(CharCodes.Lt))
    ) {
      if (this.index > this.sectionStart) {
        this.cbs.ontext(this.sectionStart, this.index)
      }
      this.state = State.BeforeTagName
      this.sectionStart = this.index
    } else if (this.decodeEntities && c === CharCodes.Amp) {
      this.startEntity()
    }
  }

  private currentSequence: Uint8Array = undefined!
  private sequenceIndex = 0
  private stateSpecialStartSequence(c: number): void {
    const isEnd = this.sequenceIndex === this.currentSequence.length
    const isMatch = isEnd
      ? // If we are at the end of the sequence, make sure the tag name has ended
        isEndOfTagSection(c)
      : // Otherwise, do a case-insensitive comparison
        (c | 0x20) === this.currentSequence[this.sequenceIndex]

    if (!isMatch) {
      this.isSpecial = false
    } else if (!isEnd) {
      this.sequenceIndex++
      return
    }

    this.sequenceIndex = 0
    this.state = State.InTagName
    this.stateInTagName(c)
  }

  /** Look for an end tag. For <title> tags, also decode entities. */
  private stateInSpecialTag(c: number): void {
    if (this.sequenceIndex === this.currentSequence.length) {
      if (c === CharCodes.Gt || isWhitespace(c)) {
        const endOfText = this.index - this.currentSequence.length

        if (this.sectionStart < endOfText) {
          // Spoof the index so that reported locations match up.
          const actualIndex = this.index
          this.index = endOfText
          this.cbs.ontext(this.sectionStart, endOfText)
          this.index = actualIndex
        }

        this.isSpecial = false
        this.sectionStart = endOfText + 2 // Skip over the `</`
        this.stateInClosingTagName(c)
        return // We are done; skip the rest of the function.
      }

      this.sequenceIndex = 0
    }

    if ((c | 0x20) === this.currentSequence[this.sequenceIndex]) {
      this.sequenceIndex += 1
    } else if (this.sequenceIndex === 0) {
      if (this.currentSequence === Sequences.TitleEnd) {
        // We have to parse entities in <title> tags.
        if (this.decodeEntities && c === CharCodes.Amp) {
          this.startEntity()
        }
      } else if (this.fastForwardTo(CharCodes.Lt)) {
        // Outside of <title> tags, we can fast-forward.
        this.sequenceIndex = 1
      }
    } else {
      // If we see a `<`, set the sequence index to 1; useful for eg. `<</script>`.
      this.sequenceIndex = Number(c === CharCodes.Lt)
    }
  }

  private stateCDATASequence(c: number): void {
    if (c === Sequences.Cdata[this.sequenceIndex]) {
      if (++this.sequenceIndex === Sequences.Cdata.length) {
        this.state = State.InCommentLike
        this.currentSequence = Sequences.CdataEnd
        this.sequenceIndex = 0
        this.sectionStart = this.index + 1
      }
    } else {
      this.sequenceIndex = 0
      this.state = State.InDeclaration
      this.stateInDeclaration(c) // Reconsume the character
    }
  }

  /**
   * When we wait for one specific character, we can speed things up
   * by skipping through the buffer until we find it.
   *
   * @returns Whether the character was found.
   */
  private fastForwardTo(c: number): boolean {
    while (++this.index < this.buffer.length + this.offset) {
      if (this.buffer.charCodeAt(this.index - this.offset) === c) {
        return true
      }
    }

    /*
     * We increment the index at the end of the `parse` loop,
     * so set it to `buffer.length - 1` here.
     *
     * TODO: Refactor `parse` to increment index before calling states.
     */
    this.index = this.buffer.length + this.offset - 1

    return false
  }

  /**
   * Comments and CDATA end with `-->` and `]]>`.
   *
   * Their common qualities are:
   * - Their end sequences have a distinct character they start with.
   * - That character is then repeated, so we have to check multiple repeats.
   * - All characters but the start character of the sequence can be skipped.
   */
  private stateInCommentLike(c: number): void {
    if (c === this.currentSequence[this.sequenceIndex]) {
      if (++this.sequenceIndex === this.currentSequence.length) {
        if (this.currentSequence === Sequences.CdataEnd) {
          this.cbs.oncdata(this.sectionStart, this.index, 2)
        } else {
          this.cbs.oncomment(this.sectionStart, this.index, 2)
        }

        this.sequenceIndex = 0
        this.sectionStart = this.index + 1
        this.state = State.Text
      }
    } else if (this.sequenceIndex === 0) {
      // Fast-forward to the first character of the sequence
      if (this.fastForwardTo(this.currentSequence[0])) {
        this.sequenceIndex = 1
      }
    } else if (c !== this.currentSequence[this.sequenceIndex - 1]) {
      // Allow long sequences, eg. --->, ]]]>
      this.sequenceIndex = 0
    }
  }

  /**
   * HTML only allows ASCII alpha characters (a-z and A-Z) at the beginning of a tag name.
   *
   * XML allows a lot more characters here (@see https://www.w3.org/TR/REC-xml/#NT-NameStartChar).
   * We allow anything that wouldn't end the tag.
   */
  private isTagStartChar(c: number) {
    return this.xmlMode ? !isEndOfTagSection(c) : isASCIIAlpha(c)
  }

  private startSpecial(sequence: Uint8Array, offset: number) {
    this.isSpecial = true
    this.currentSequence = sequence
    this.sequenceIndex = offset
    this.state = State.SpecialStartSequence
  }

  private stateBeforeTagName(c: number): void {
    if (c === CharCodes.ExclamationMark) {
      this.state = State.BeforeDeclaration
      this.sectionStart = this.index + 1
    } else if (c === CharCodes.Questionmark) {
      this.state = State.InProcessingInstruction
      this.sectionStart = this.index + 1
    } else if (this.isTagStartChar(c)) {
      const lower = c | 0x20
      this.sectionStart = this.index
      if (!this.xmlMode && lower === Sequences.TitleEnd[2]) {
        this.startSpecial(Sequences.TitleEnd, 3)
      } else {
        this.state =
          !this.xmlMode && lower === Sequences.ScriptEnd[2]
            ? State.BeforeSpecialS
            : State.InTagName
      }
    } else if (c === CharCodes.Slash) {
      this.state = State.BeforeClosingTagName
    } else {
      this.state = State.Text
      this.stateText(c)
    }
  }
  private stateInTagName(c: number): void {
    if (isEndOfTagSection(c)) {
      this.cbs.onopentagname(this.sectionStart, this.index)
      this.sectionStart = -1
      this.state = State.BeforeAttributeName
      this.stateBeforeAttributeName(c)
    }
  }
  private stateBeforeClosingTagName(c: number): void {
    if (isWhitespace(c)) {
      // Ignore
    } else if (c === CharCodes.Gt) {
      this.state = State.Text
    } else {
      this.state = this.isTagStartChar(c)
        ? State.InClosingTagName
        : State.InSpecialComment
      this.sectionStart = this.index
    }
  }
  private stateInClosingTagName(c: number): void {
    if (c === CharCodes.Gt || isWhitespace(c)) {
      this.cbs.onclosetag(this.sectionStart, this.index)
      this.sectionStart = -1
      this.state = State.AfterClosingTagName
      this.stateAfterClosingTagName(c)
    }
  }
  private stateAfterClosingTagName(c: number): void {
    // Skip everything until ">"
    if (c === CharCodes.Gt || this.fastForwardTo(CharCodes.Gt)) {
      this.state = State.Text
      this.sectionStart = this.index + 1
    }
  }
  private stateBeforeAttributeName(c: number): void {
    if (c === CharCodes.Gt) {
      this.cbs.onopentagend(this.index)
      if (this.isSpecial) {
        this.state = State.InSpecialTag
        this.sequenceIndex = 0
      } else {
        this.state = State.Text
      }
      this.sectionStart = this.index + 1
    } else if (c === CharCodes.Slash) {
      this.state = State.InSelfClosingTag
    } else if (!isWhitespace(c)) {
      this.state = State.InAttributeName
      this.sectionStart = this.index
    }
  }
  private stateInSelfClosingTag(c: number): void {
    if (c === CharCodes.Gt) {
      this.cbs.onselfclosingtag(this.index)
      this.state = State.Text
      this.sectionStart = this.index + 1
      this.isSpecial = false // Reset special state, in case of self-closing special tags
    } else if (!isWhitespace(c)) {
      this.state = State.BeforeAttributeName
      this.stateBeforeAttributeName(c)
    }
  }
  private stateInAttributeName(c: number): void {
    if (c === CharCodes.Eq || isEndOfTagSection(c)) {
      this.cbs.onattribname(this.sectionStart, this.index)
      this.sectionStart = this.index
      this.state = State.AfterAttributeName
      this.stateAfterAttributeName(c)
    }
  }
  private stateAfterAttributeName(c: number): void {
    if (c === CharCodes.Eq) {
      this.state = State.BeforeAttributeValue
    } else if (c === CharCodes.Slash || c === CharCodes.Gt) {
      this.cbs.onattribend(QuoteType.NoValue, this.sectionStart)
      this.sectionStart = -1
      this.state = State.BeforeAttributeName
      this.stateBeforeAttributeName(c)
    } else if (!isWhitespace(c)) {
      this.cbs.onattribend(QuoteType.NoValue, this.sectionStart)
      this.state = State.InAttributeName
      this.sectionStart = this.index
    }
  }
  private stateBeforeAttributeValue(c: number): void {
    if (c === CharCodes.DoubleQuote) {
      this.state = State.InAttributeValueDq
      this.sectionStart = this.index + 1
    } else if (c === CharCodes.SingleQuote) {
      this.state = State.InAttributeValueSq
      this.sectionStart = this.index + 1
    } else if (!isWhitespace(c)) {
      this.sectionStart = this.index
      this.state = State.InAttributeValueNq
      this.stateInAttributeValueNoQuotes(c) // Reconsume token
    }
  }
  private handleInAttributeValue(c: number, quote: number) {
    if (c === quote || (!this.decodeEntities && this.fastForwardTo(quote))) {
      this.cbs.onattribdata(this.sectionStart, this.index)
      this.sectionStart = -1
      this.cbs.onattribend(
        quote === CharCodes.DoubleQuote ? QuoteType.Double : QuoteType.Single,
        this.index + 1
      )
      this.state = State.BeforeAttributeName
    } else if (this.decodeEntities && c === CharCodes.Amp) {
      this.startEntity()
    }
  }
  private stateInAttributeValueDoubleQuotes(c: number): void {
    this.handleInAttributeValue(c, CharCodes.DoubleQuote)
  }
  private stateInAttributeValueSingleQuotes(c: number): void {
    this.handleInAttributeValue(c, CharCodes.SingleQuote)
  }
  private stateInAttributeValueNoQuotes(c: number): void {
    if (isWhitespace(c) || c === CharCodes.Gt) {
      this.cbs.onattribdata(this.sectionStart, this.index)
      this.sectionStart = -1
      this.cbs.onattribend(QuoteType.Unquoted, this.index)
      this.state = State.BeforeAttributeName
      this.stateBeforeAttributeName(c)
    } else if (this.decodeEntities && c === CharCodes.Amp) {
      this.startEntity()
    }
  }
  private stateBeforeDeclaration(c: number): void {
    if (c === CharCodes.OpeningSquareBracket) {
      this.state = State.CDATASequence
      this.sequenceIndex = 0
    } else {
      this.state =
        c === CharCodes.Dash ? State.BeforeComment : State.InDeclaration
    }
  }
  private stateInDeclaration(c: number): void {
    if (c === CharCodes.Gt || this.fastForwardTo(CharCodes.Gt)) {
      this.cbs.ondeclaration(this.sectionStart, this.index)
      this.state = State.Text
      this.sectionStart = this.index + 1
    }
  }
  private stateInProcessingInstruction(c: number): void {
    if (c === CharCodes.Gt || this.fastForwardTo(CharCodes.Gt)) {
      this.cbs.onprocessinginstruction(this.sectionStart, this.index)
      this.state = State.Text
      this.sectionStart = this.index + 1
    }
  }
  private stateBeforeComment(c: number): void {
    if (c === CharCodes.Dash) {
      this.state = State.InCommentLike
      this.currentSequence = Sequences.CommentEnd
      // Allow short comments (eg. <!-->)
      this.sequenceIndex = 2
      this.sectionStart = this.index + 1
    } else {
      this.state = State.InDeclaration
    }
  }
  private stateInSpecialComment(c: number): void {
    if (c === CharCodes.Gt || this.fastForwardTo(CharCodes.Gt)) {
      this.cbs.oncomment(this.sectionStart, this.index, 0)
      this.state = State.Text
      this.sectionStart = this.index + 1
    }
  }
  private stateBeforeSpecialS(c: number): void {
    const lower = c | 0x20
    if (lower === Sequences.ScriptEnd[3]) {
      this.startSpecial(Sequences.ScriptEnd, 4)
    } else if (lower === Sequences.StyleEnd[3]) {
      this.startSpecial(Sequences.StyleEnd, 4)
    } else {
      this.state = State.InTagName
      this.stateInTagName(c) // Consume the token again
    }
  }

  private startEntity() {
    this.baseState = this.state
    this.state = State.InEntity
    this.entityStart = this.index
    this.entityDecoder.startEntity(
      this.xmlMode
        ? DecodingMode.Strict
        : this.baseState === State.Text || this.baseState === State.InSpecialTag
        ? DecodingMode.Legacy
        : DecodingMode.Attribute
    )
  }

  private stateInEntity(): void {
    const length = this.entityDecoder.write(
      this.buffer,
      this.index - this.offset
    )

    // If `length` is positive, we are done with the entity.
    if (length >= 0) {
      this.state = this.baseState

      if (length === 0) {
        this.index = this.entityStart
      }
    } else {
      // Mark buffer as consumed.
      this.index = this.offset + this.buffer.length - 1
    }
  }

  /**
   * Remove data that has already been consumed from the buffer.
   */
  private cleanup() {
    // If we are inside of text or attributes, emit what we already have.
    if (this.running && this.sectionStart !== this.index) {
      if (
        this.state === State.Text ||
        (this.state === State.InSpecialTag && this.sequenceIndex === 0)
      ) {
        this.cbs.ontext(this.sectionStart, this.index)
        this.sectionStart = this.index
      } else if (
        this.state === State.InAttributeValueDq ||
        this.state === State.InAttributeValueSq ||
        this.state === State.InAttributeValueNq
      ) {
        this.cbs.onattribdata(this.sectionStart, this.index)
        this.sectionStart = this.index
      }
    }
  }

  private shouldContinue() {
    return this.index < this.buffer.length + this.offset && this.running
  }

  /**
   * Iterates through the buffer, calling the function corresponding to the current state.
   *
   * States that are more likely to be hit are higher up, as a performance improvement.
   */
  private parse() {
    while (this.shouldContinue()) {
      const c = this.buffer.charCodeAt(this.index - this.offset)
      switch (this.state) {
        case State.Text: {
          this.stateText(c)
          break
        }
        case State.SpecialStartSequence: {
          this.stateSpecialStartSequence(c)
          break
        }
        case State.InSpecialTag: {
          this.stateInSpecialTag(c)
          break
        }
        case State.CDATASequence: {
          this.stateCDATASequence(c)
          break
        }
        case State.InAttributeValueDq: {
          this.stateInAttributeValueDoubleQuotes(c)
          break
        }
        case State.InAttributeName: {
          this.stateInAttributeName(c)
          break
        }
        case State.InCommentLike: {
          this.stateInCommentLike(c)
          break
        }
        case State.InSpecialComment: {
          this.stateInSpecialComment(c)
          break
        }
        case State.BeforeAttributeName: {
          this.stateBeforeAttributeName(c)
          break
        }
        case State.InTagName: {
          this.stateInTagName(c)
          break
        }
        case State.InClosingTagName: {
          this.stateInClosingTagName(c)
          break
        }
        case State.BeforeTagName: {
          this.stateBeforeTagName(c)
          break
        }
        case State.AfterAttributeName: {
          this.stateAfterAttributeName(c)
          break
        }
        case State.InAttributeValueSq: {
          this.stateInAttributeValueSingleQuotes(c)
          break
        }
        case State.BeforeAttributeValue: {
          this.stateBeforeAttributeValue(c)
          break
        }
        case State.BeforeClosingTagName: {
          this.stateBeforeClosingTagName(c)
          break
        }
        case State.AfterClosingTagName: {
          this.stateAfterClosingTagName(c)
          break
        }
        case State.BeforeSpecialS: {
          this.stateBeforeSpecialS(c)
          break
        }
        case State.InAttributeValueNq: {
          this.stateInAttributeValueNoQuotes(c)
          break
        }
        case State.InSelfClosingTag: {
          this.stateInSelfClosingTag(c)
          break
        }
        case State.InDeclaration: {
          this.stateInDeclaration(c)
          break
        }
        case State.BeforeDeclaration: {
          this.stateBeforeDeclaration(c)
          break
        }
        case State.BeforeComment: {
          this.stateBeforeComment(c)
          break
        }
        case State.InProcessingInstruction: {
          this.stateInProcessingInstruction(c)
          break
        }
        case State.InEntity: {
          this.stateInEntity()
          break
        }
      }
      this.index++
    }
    this.cleanup()
  }

  private finish() {
    if (this.state === State.InEntity) {
      this.entityDecoder.end()
      this.state = this.baseState
    }

    this.handleTrailingData()

    this.cbs.onend()
  }

  /** Handle any trailing data. */
  private handleTrailingData() {
    const endIndex = this.buffer.length + this.offset

    // If there is no remaining data, we are done.
    if (this.sectionStart >= endIndex) {
      return
    }

    if (this.state === State.InCommentLike) {
      if (this.currentSequence === Sequences.CdataEnd) {
        this.cbs.oncdata(this.sectionStart, endIndex, 0)
      } else {
        this.cbs.oncomment(this.sectionStart, endIndex, 0)
      }
    } else if (
      this.state === State.InTagName ||
      this.state === State.BeforeAttributeName ||
      this.state === State.BeforeAttributeValue ||
      this.state === State.AfterAttributeName ||
      this.state === State.InAttributeName ||
      this.state === State.InAttributeValueSq ||
      this.state === State.InAttributeValueDq ||
      this.state === State.InAttributeValueNq ||
      this.state === State.InClosingTagName
    ) {
      /*
       * If we are currently in an opening or closing tag, us not calling the
       * respective callback signals that the tag should be ignored.
       */
    } else {
      this.cbs.ontext(this.sectionStart, endIndex)
    }
  }

  private emitCodePoint(cp: number, consumed: number): void {
    if (
      this.baseState !== State.Text &&
      this.baseState !== State.InSpecialTag
    ) {
      if (this.sectionStart < this.entityStart) {
        this.cbs.onattribdata(this.sectionStart, this.entityStart)
      }
      this.sectionStart = this.entityStart + consumed
      this.index = this.sectionStart - 1

      this.cbs.onattribentity(cp)
    } else {
      if (this.sectionStart < this.entityStart) {
        this.cbs.ontext(this.sectionStart, this.entityStart)
      }
      this.sectionStart = this.entityStart + consumed
      this.index = this.sectionStart - 1

      this.cbs.ontextentity(cp, this.sectionStart)
    }
  }
}