whole_func_string: function $checksum(byte) {
      checksum += toHex(byte);
      if (++offset < 20) return $checksum;
      var actual = sha1sum.digest();
      if (checksum !== actual) throw new Error("Checksum mismatch: " + actual + " != " + checksum);
    }
func_code_string: function $checksum(byte) {
      checksum += toHex(byte);
      if (++offset < 20) return $checksum;
      var actual = sha1sum.digest();
      if (checksum !== actual) throw new Error("Checksum mismatch: " + actual + " != " + checksum);
    }
func_documentation_string: 20 byte checksum