freeze option in EOS smart contract

class sample : eosio::contract{
    public:
    sample(account_name account) :eosio::contract(account),_global(_self, _self){}

    void freeze(uint64_t frozen) {
        require_auth(_self);
        _global.set(global_item{frozen}, N(global));
    }

    // any public actions 
    void action(...) {
        eosio_assert(isFrozen() != 1, "Contract is frozen!");
        ...
    }

    private:
    
    struct global_item {
        uint64_t frozen; 
    };
    typedef singleton<N(global), global_item> global_table;
    global_table _global;

    uint64_t isFrozen() {
        return _global.get().frozen;
    }
}