Function readSync

lib/fs.js:849–897

* Synchronously reads the file from the * specified `fd` (file descriptor). * @param {number} fd * @param {Buffer | TypedArray | DataView} buffer * @param {number | { * offset?: number; * length?: number; * position?: number | bigint | null; * }} [offsetOrOptions] * @param {number}

(fd, buffer, offsetOrOptions, length, position)

 * @returns {number}
 */
function readSync(fd, buffer, offsetOrOptions, length, position) {
  validateBuffer(buffer);

  let offset = offsetOrOptions;
  if (arguments.length <= 3 || typeof offsetOrOptions === 'object') {
    if (offsetOrOptions !== undefined) {
      validateObject(offsetOrOptions, 'options', kValidateObjectAllowNullable);
    }

    ({
      offset = 0,
      length = buffer.byteLength - offset,
      position = null,
    } = offsetOrOptions ?? kEmptyObject);
  }

  if (offset === undefined) {
    offset = 0;
  } else {
    validateInteger(offset, 'offset', 0);
  }

  length |= 0;

  if (position == null) {
    position = -1;
  } else {
    validatePosition(position, 'position', length);
  }

  if (length === 0) {
    return 0;
  }

  if (buffer.byteLength === 0) {
    throw new ERR_INVALID_ARG_VALUE('buffer', buffer,
                                    'is empty and cannot be written');
  }

  validateOffsetLengthRead(offset, length, buffer.byteLength);

  const h = vfsState.handlers;
  if (h !== null) {
    const result = h.readSync(fd, buffer, offset, length, position);
    if (result !== undefined) return result;
  }

  return binding.read(fd, buffer, offset, length, position);
}

/**
 * Reads file from the specified `fd` (file descriptor)