Function read

lib/fs.js:747–830

* Reads 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} length * @param {num

(fd, buffer, offsetOrOptions, length, position, callback)

 * @returns {void}
 */
function read(fd, buffer, offsetOrOptions, length, position, callback) {
  fd = getValidatedFd(fd);
  let offset = offsetOrOptions;
  let params = null;
  if (arguments.length <= 4) {
    if (arguments.length === 4) {
      // This is fs.read(fd, buffer, options, callback)
      validateObject(offsetOrOptions, 'options', kValidateObjectAllowNullable);
      callback = length;
      params = offsetOrOptions;
    } else if (arguments.length === 3) {
      // This is fs.read(fd, bufferOrParams, callback)
      if (!isArrayBufferView(buffer)) {
        // This is fs.read(fd, params, callback)
        params = buffer;
        ({ buffer = Buffer.alloc(16384) } = params ?? kEmptyObject);
      }
      callback = offsetOrOptions;
    } else {
      // This is fs.read(fd, callback)
      callback = buffer;
      buffer = Buffer.alloc(16384);
    }

    if (params !== undefined) {
      validateObject(params, 'options', kValidateObjectAllowNullable);
    }
    ({
      offset = 0,
      length = buffer?.byteLength - offset,
      position = null,
    } = params ?? kEmptyObject);
  }

  validateBuffer(buffer);
  validateFunction(callback, 'cb');

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

  length |= 0;

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

  if (length === 0) {
    return process.nextTick(function tick() {
      callback(null, 0, buffer);
    });
  }

  if (buffer.byteLength === 0) {