escape-dataurl.ts

// https://github.com/evanw/esbuild/blob/main/internal/helpers/dataurl.go

  const CharCode = {
    Tab: 9,
    LineFeed: 10,
    CarriageReturn: 13,
    Space: 32,
    Hash: 35,
    PercentSign: 37,
  }

  function isHex(c: number) {
    return c >= '0'.charCodeAt(0) && c <= '9'.charCodeAt(0) || c >= 'A'.charCodeAt(0) && c <= 'F'.charCodeAt(0) || c >= 'a'.charCodeAt(0) && c <= 'f'.charCodeAt(0)
  }

  function escape(text: string) {
    const hex = '0123456789ABCDEF'
    const n = text.length
    let result = ''

    // Spaces can be safely emitted for usage like `url()`, however it should always be escaped at the end
    let trailingStart = n
    for (; trailingStart > 0; trailingStart--) {
      const c = text.charCodeAt(trailingStart - 1)

      if (c > CharCode.Space || c === CharCode.Tab || c === CharCode.LineFeed || c === CharCode.CarriageReturn)
        break
    }

    let runStart = 0
    for (let i = 0; i < n; i++) {
      const c = text.charCodeAt(i)

      if (c === CharCode.Tab || c === CharCode.LineFeed || c === CharCode.CarriageReturn || c === CharCode.Hash
        || i >= trailingStart
        || (c === CharCode.PercentSign && i + 2 < n && isHex(text.charCodeAt(i + 1)) && isHex(text.charCodeAt(i + 2)))
      ) {
        if (runStart < i)
          result += text.slice(runStart, i)

        result += `%${hex[c >> 4]}${hex[c & 15]}`
        runStart = i + 1
      }
    }

    if (runStart < n)
      result += text.slice(runStart)

    return result
  }