stringToCharCode_(str) {
    let code = 0;
    for (let i = 0; i < str.length; i += 1) {
      code |= str.charCodeAt(i) << ((str.length - i - 1) * 8);
    }
    return code;
  }
Convert a string to char code.

@param {string} str
@return {number}
@private