Function parseMIMEType

deps/undici/src/lib/web/fetch/data-url.js:219–388

@param {string} input

(input)

// https://mimesniff.spec.whatwg.org/#parse-a-mime-type
/** @param {string} input */
function parseMIMEType (input) {
  // 1. Remove any leading and trailing HTTP whitespace
  // from input.
  input = removeHTTPWhitespace(input, true, true)

  // 2. Let position be a position variable for input,
  // initially pointing at the start of input.
  const position = { position: 0 }

  // 3. Let type be the result of collecting a sequence
  // of code points that are not U+002F (/) from
  // input, given position.
  const type = collectASequenceOfCodePointsFast(
    '/',
    input,
    position
  )

  // 4. If type is the empty string or does not solely
  // contain HTTP token code points, then return failure.
  // https://mimesniff.spec.whatwg.org/#http-token-code-point
  if (type.length === 0 || !HTTP_TOKEN_CODEPOINTS.test(type)) {
    return 'failure'
  }

  // 5. If position is past the end of input, then return
  // failure
  if (position.position >= input.length) {
    return 'failure'
  }

  // 6. Advance position by 1. (This skips past U+002F (/).)
  position.position++

  // 7. Let subtype be the result of collecting a sequence of
  // code points that are not U+003B (;) from input, given
  // position.
  let subtype = collectASequenceOfCodePointsFast(
    ';',
    input,
    position
  )

  // 8. Remove any trailing HTTP whitespace from subtype.
  subtype = removeHTTPWhitespace(subtype, false, true)

  // 9. If subtype is the empty string or does not solely
  // contain HTTP token code points, then return failure.
  if (subtype.length === 0 || !HTTP_TOKEN_CODEPOINTS.test(subtype)) {
    return 'failure'
  }

  const typeLowercase = type.toLowerCase()
  const subtypeLowercase = subtype.toLowerCase()

  // 10. Let mimeType be a new MIME type record whose type
  // is type, in ASCII lowercase, and subtype is subtype,
  // in ASCII lowercase.