Function realpathSync

lib/fs.js:3234–3367

* Returns the resolved pathname. * @param {string | Buffer | URL} p * @param {string | { encoding?: string | null; }} [options] * @returns {string | Buffer}

(p, options)

 * @returns {string | Buffer}
 */
function realpathSync(p, options) {
  const h = vfsState.handlers;
  if (h !== null) {
    const result = h.realpathSync(p, options);
    if (result !== undefined) return result;
  }
  options = getOptions(options);
  p = toPathIfFileURL(p);
  if (typeof p !== 'string') {
    p += '';
  }
  validatePath(p);
  p = pathModule.resolve(p);

  const cache = options[realpathCacheKey];
  const maybeCachedResult = cache?.get(p);
  if (maybeCachedResult) {
    return maybeCachedResult;
  }

  const seenLinks = new SafeMap();
  const knownHard = new SafeSet();
  const original = p;

  // Current character position in p
  let pos;
  // The partial path so far, including a trailing slash if any
  let current;
  // The partial path without a trailing slash (except when pointing at a root)
  let base;
  // The partial path scanned in the previous round, with slash
  let previous;

  // Skip over roots
  current = base = splitRoot(p);
  pos = current.length;

  // On windows, check that the root exists. On unix there is no need.
  if (isWindows) {
    const out = binding.lstat(base, false, undefined, true /* throwIfNoEntry */);
    if (out === undefined) {
      return;
    }
    knownHard.add(base);
  }

  // Walk down the path, swapping out linked path parts for their real
  // values
  // NB: p.length changes.
  while (pos < p.length) {
    // find the next part
    const result = nextPart(p, pos);
    previous = current;
    if (result === -1) {
      const last = StringPrototypeSlice(p, pos);
      current += last;
      base = previous + last;
      pos = p.length;