code: function howMuchToRead(n, state) {
    if (n <= 0 || state.length === 0 && state.ended) return 0;
    if (state.objectMode) return 1;
    if (n !== n) {
      // Only flow one buffer at a time
      if (state.flowing && state.length) return state.buffer.head.data.length;else return state.length;
    }
    // If we're asking for more than the current hwm, then raise the hwm.
    if (n > state.highWaterMark) state.highWaterMark = computeNewHighWaterMark(n);
    if (n <= state.length) return n;
    // Don't have enough
    if (!state.ended) {
      state.needReadable = true;
      return 0;
    }
    return state.length;
  }
docs: This function is designed to be inlinable, so please take care when making changes to the function body.