Function multipartFormDataParser

deps/undici/src/lib/web/fetch/formdata-parser.js:64–201

* @see https://andreubotella.github.io/multipart-form-data/#multipart-form-data-parser * @param {Buffer} input * @param {ReturnType } mimeType

(input, mimeType)

 * @param {ReturnType<import('./data-url')['parseMIMEType']>} mimeType
 */
function multipartFormDataParser (input, mimeType) {
  // 1. Assert: mimeType’s essence is "multipart/form-data".
  assert(mimeType !== 'failure' && mimeType.essence === 'multipart/form-data')

  const boundaryString = mimeType.parameters.get('boundary')

  // 2. If mimeType’s parameters["boundary"] does not exist, return failure.
  //    Otherwise, let boundary be the result of UTF-8 decoding mimeType’s
  //    parameters["boundary"].
  if (boundaryString === undefined) {
    throw parsingError('missing boundary in content-type header')
  }

  const boundary = Buffer.from(`--${boundaryString}`, 'utf8')

  // 3. Let entry list be an empty entry list.
  const entryList = []

  // 4. Let position be a pointer to a byte in input, initially pointing at
  //    the first byte.
  const position = { position: 0 }

  // Note: Per RFC 2046 Section 5.1.1, we must ignore anything before the
  // first boundary delimiter line (preamble). Search for the first boundary.
  const firstBoundaryIndex = input.indexOf(boundary)

  if (firstBoundaryIndex === -1) {
    throw parsingError('no boundary found in multipart body')
  }

  // Start parsing from the first boundary, ignoring any preamble
  position.position = firstBoundaryIndex

  // 5. While true:
  while (true) {
    // 5.1. If position points to a sequence of bytes starting with 0x2D 0x2D
    //      (`--`) followed by boundary, advance position by 2 + the length of
    //      boundary. Otherwise, return failure.
    // Note: boundary is padded with 2 dashes already, no need to add 2.
    if (input.subarray(position.position, position.position + boundary.length).equals(boundary)) {
      position.position += boundary.length
    } else {
      throw parsingError('expected a value starting with -- and the boundary')
    }

    // 5.2. If position points to the sequence of bytes 0x2D 0x2D 0x0D 0x0A
    //      (`--` followed by CR LF) followed by the end of input, return entry list.
    // Note: Per RFC 2046 Section 5.1.1, we must ignore anything after the
    // final boundary delimiter (epilogue). Check for -- or --CRLF and return
    // regardless of what follows.
    if (bufferStartsWith(input, dd, position)) {
      // Found closing boundary delimiter (--), ignore any epilogue
      return entryList
    }

    // 5.3. If position does not point to a sequence of bytes starting with 0x0D
    //      0x0A (CR LF), return failure.
    if (input[position.position] !== 0x0d || input[position.position + 1] !== 0x0a) {