Function buildNgHeaderString

lib/internal/http2/util.js:766–851

* Builds an NgHeader string + header count value, validating the header key * format, rejecting illegal header configurations, and marking sensitive headers * that should not be indexed en route. This takes either a flat map of * raw headers ([k1, v1, k2, v2]) or a header object ({ k1: v1, k2: [v

(arrayOrMap,
                             validatePseudoHeaderValue,
                             strictSingleValueFields)

 * @returns {[string, number]}
 */
function buildNgHeaderString(arrayOrMap,
                             validatePseudoHeaderValue,
                             strictSingleValueFields) {
  let headers = '';
  let pseudoHeaders = '';
  let count = 0;

  const singles = new SafeSet();
  const sensitiveHeaders = arrayOrMap[kSensitiveHeaders] || emptyArray;
  const neverIndex = sensitiveHeaders.map((v) => v.toLowerCase());

  function processHeader(key, value) {
    key = key.toLowerCase();
    const isStrictSingleValueField = strictSingleValueFields &&
      kSingleValueFields.has(key);
    let isArray = ArrayIsArray(value);
    if (isArray) {
      switch (value.length) {
        case 0:
          return;
        case 1:
          value = String(value[0]);
          isArray = false;
          break;
        default:
          if (isStrictSingleValueField)
            throw new ERR_HTTP2_HEADER_SINGLE_VALUE(key);
      }
    } else {
      value = String(value);
    }
    if (isStrictSingleValueField) {
      if (singles.has(key))
        throw new ERR_HTTP2_HEADER_SINGLE_VALUE(key);
      singles.add(key);
    }
    const flags = neverIndex.includes(key) ?
      kNeverIndexFlag :
      kNoHeaderFlags;
    if (key[0] === ':') {
      const err = validatePseudoHeaderValue(key);
      if (err !== undefined)
        throw err;
      pseudoHeaders += `${key}\0${value}\0${flags}`;
      count++;
      return;
    }
    if (!checkIsHttpToken(key)) {
      throw new ERR_INVALID_HTTP_TOKEN('Header name', key);
    }
    if (isIllegalConnectionSpecificHeader(key, value)) {
      throw new ERR_HTTP2_INVALID_CONNECTION_HEADERS(key);
    }
    if (isArray) {
      for (let j = 0; j < value.length; ++j) {
        const val = String(value[j]);
        headers += `${key}\0${val}\0${flags}`;
      }