nodejs/lib/internal/streams/state.js

'use strict';

const {
  MathFloor,
  NumberIsInteger,
} = primordials;

const { ERR_INVALID_ARG_VALUE } = require('internal/errors').codes;

function highWaterMarkFrom(options, isDuplex, duplexKey) {
  return options.highWaterMark != null ? options.highWaterMark :
    isDuplex ? options[duplexKey] : null;
}

function getDefaultHighWaterMark(objectMode) {
  return objectMode ? 16 : 16 * 1024;
}

function getHighWaterMark(state, options, duplexKey, isDuplex) {
  const hwm = highWaterMarkFrom(options, isDuplex, duplexKey);
  if (hwm != null) {
    if (!NumberIsInteger(hwm) || hwm < 0) {
      const name = isDuplex ? `options.${duplexKey}` : 'options.highWaterMark';
      throw new ERR_INVALID_ARG_VALUE(name, hwm);
    }
    return MathFloor(hwm);
  }

  // Default value
  return getDefaultHighWaterMark(state.objectMode);
}

module.exports = {
  getHighWaterMark,
  getDefaultHighWaterMark,
};